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Text

Just as in humans, sex organ

Just as in humans, sex organ is organized by penis and vagina

How is sex mating formed in plants

Once pollen gets transferred to the stigma the male gametes from pollen grains release and fuse with the egg in the ovule to form a zygote. This process of fusion of gametes is called fertilization. The zygote thus formed, divides and develops into an embryo, and later into a seed. The ovary develops into a fruit.

12.5: Mating Systems in Plants

Biology LibreTexts

https://bio.libretexts.org › ... › 12: Sex Strategies

4 Mar 2024

Asexual Reproduction

Many plants are facultatively sexual rather than obligately sexual. Asexual reproduction is a type of reproduction where the offspring comes from one parent only, thus, inheriting the characteristics of the parent. Asexual reproduction in plants occurs in two fundamental forms vegetative reproduction and agamospermy.1 Vegetative reproduction involves a vegetative piece of the original plant producing new individuals by budding, tillering, etc. and is distinguished from apomixis, which is a replacement of sexual reproduction, and in some cases involves seeds. Apomixis occurs in many plant species such as dandelions (Taraxacum species) and also in some non-plant organisms. For apomixis and similar processes in non-plant organisms, see parthenogenesis.

Natural vegetative reproduction is a process mostly found in perennial plants, and typically involves structural modifications of the stem or roots and in a few species leaves. Most plant species that employ vegetative reproduction do so as a means to perennialize the plants, allowing them to survive from one season to the next and often facilitating their expansion in size. A plant that persists in a location through vegetative reproduction of individuals constitutes a clonal colony. A single ramet, or apparent individual, of a clonal colony is genetically identical to all others in the same colony. The distance that a plant can move during vegetative reproduction is limited, though some plants can produce ramets from branching rhizomes or stolons that cover a wide area, often in only a few growing seasons. In a sense, this process is not one of reproduction but one of survival and expansion of biomass of the individual. When an individual organism increases in size via cell multiplication and remains intact, the process is called vegetative growth. However, in vegetative reproduction, the new plants that result are new individuals in almost every respect except genetic. A major disadvantage of vegetative reproduction, is the transmission of pathogens from parent to offspring. It is uncommon for pathogens to be transmitted from the plant to its seeds (in sexual reproduction or in apomixis), though there are occasions when it occurs.2

Seeds generated by apomixis are a means of asexual reproduction, involving the formation and dispersal of seeds that do not originate from the fertilization of the embryos. Hawkweeds (Hieracium), dandelions (Taraxacum), some species of Citrus and Kentucky blue grass (Poa pratensis) all use this form of asexual reproduction. Pseudogamy occurs in some plants that have apomictic seeds, where pollination is often needed to initiate embryo growth, though the pollen contributes no genetic material to the developing offspring.3 Other forms of apomixis occur in plants also, including the generation of a plantlet in replacement of a seed or the generation of bulbils instead of flowers, where new cloned individuals are produced.

Sexual Reproduction

Sexual reproduction involves two fundamental processes: meiosis, which rearranges the genes and reduces the number of chromosomes, and fertilisation, which restores the chromosome to a complete diploid number. In between these two processes, different types of plants and algae vary, but many of them, including all land plants, undergo alternation of generations, with two different multicellular structures (phases), a gametophyte and a sporophyte.

In mosses and liverworts, the gametophyte is relatively large, and the sporophyte is a much smaller structure that is never separated from the gametophyte. In ferns, gymnosperms, and flowering plants (angiosperms), the gametophytes are relatively small and the sporophyte is much larger. In gymnosperms and flowering plants the megagametophyte is contained within the ovule (that may develop into a seed) and the microgametophyte is contained within a pollen grain.

In the evolution of early plants, abiotic means, including water and much later, wind, transported sperm for reproduction. The first plants were aquatic, and released sperm freely into the water to be carried with the currents. Ancestral land plants like liverworts and mosses have motile sperm that swam in a thin film of water or were splashed in water droplets. As taller and more complex plants evolved, modifications in the alternation of generations evolved. In the Paleozoic era progymnosperms reproduced by using spores dispersed on the wind and many gymnosperms and some angiosperms still rely on wind for gamete dispersal. The seed plants including seed ferns, conifers and cordaites have pollen grains that contain the male gametes for protection of the sperm during the process of transfer from the male to female parts. Angiosperms, or flowering plants, are the most derived and most abundant plant species and they rely on flowers producing pollen and ovules for reproduction.

Self-Fertilization and Self-Incompatibility

Many species of plants, particularly those which produce both staminate and pistillate flowers or produce ‘perfect’ bisexual flowers, also have the ability to reproduce sexually with themselves. This is advantageous particularly if pollination services are unreliable or unpredictable, as it ensures the plant still has some fitness. Self-pollination is a form of pollination in which pollen from the same plant arrives at the stigma of a flower (in flowering plants) or at the ovule (in gymnosperms). The term selfing that is often used as a synonym, is not limited to self-pollination, but also applies to other types of self-fertilization. Plants may either be obligately self-fertilizing, or facultatively so. In facultatively selfing plants, there may be mechanisms which delay selfing, such as stamens that are initially reflexed but move to come into contact with the stigma. About 42% of flowering plants exhibit a mixed mating system in nature.4 In the most common kind of system, individual plants produce a single flower type and fruits may contain self-pollinated, out-crossed or a mixture of progeny types. Another mixed mating system is referred to as dimorphic cleistogamy. In this system a single plant produces both open, potentially out-crossed and closed, obligately self-pollinated cleistogamous flowers.5

Still other species are self-incompatible, and will reject their own pollen grains if they land on their own stigmatic surface. These plants are obligately outcrossing, and must successfully sexually reproduce with another member of their species. In plants with SI, when a pollen grain produced in a plant reaches a stigma of the same plant or another plant with a matching allele or genotype, the process of pollen germination, pollen-tube growth, ovule fertilization, or embryo development is inhibited, and consequently no seeds are produced. SI is one of the most important means of preventing inbreeding and promoting the generation of new genotypes in plants and it is considered one of the causes of the spread and success of angiosperms on the earth.

Outcrossing Fertilization

Plants that use insects or other animals to move pollen from one flower to the next have developed greatly modified flower parts to attract pollinators and to facilitate the movement of pollen from one flower to the insect and from the insect back to the next flower. Flowers of wind-pollinated plants tend to lack petals and or sepals; typically large amounts of pollen are produced and pollination often occurs early in the growing season before leaves can interfere with the dispersal of the pollen. Many trees and all grasses and sedges are wind-pollinated.

Plants have a number of different means to attract pollinators including color, scent, heat, nectar glands, edible pollen and flower shape. Along with modifications involving the above structures two other conditions play a very important role in the sexual reproduction of flowering plants, the first is the timing of flowering and the other is the size or number of flowers produced. Often plant species have a few large, very showy flowers while others produce many small flowers, often flowers are collected together into large inflorescences to maximize their visual effect, becoming more noticeable to passing pollinators. Flowers are attraction strategies and sexual expressions are functional strategies used to produce the next generation of plants, with pollinators and plants having co-evolved, often to some extraordinary degrees, very often rendering mutual benefit. Specialization can be advantageous because it results in more consistent pollination services. As a result, the specialized pollinator and plant can exert strong selective pressure on each other, leading to coevolution. Examples of this include the coevolution between figs and fig wasps, or yucca and yucca moths, wherein the yucca moths are both the obligate pollinators and the antagonistic herbivores of yucca. Another visually striking example is the co-evolution of long floral corollas and long beaks or proboscii in pollinators 12.5.1A+B

In plants, sex is organised through pollen, but in fish, the most mysterious kind of sex is organised. Male fish release semen into the water and female fish eat it.

Translate Hindi

जैसे मनुष्य में सेक्स निवारण पेनिस और वेजाइना द्वारा संगठित होता है

पौधों में सेक्स संगम कैसे बनता है

एक बार जब पराग वर्तिकाग्र में स्थानांतरित हो जाता है, तो पराग कणों से नर युग्मक मुक्त हो जाते हैं और बीजांड में अंडे के साथ जुड़कर युग्मनज बनाते हैं। युग्मकों के संलयन की इस प्रक्रिया को निषेचन कहा जाता है। इस प्रकार बनने वाला युग्मनज विभाजित होकर भ्रूण में विकसित होता है और बाद में बीज में बदल जाता है। अंडाशय फल में विकसित होता है।

12.5: पौधों में संभोग प्रणाली

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https://bio.libretexts.org › ... › 12: सेक्स रणनीतियाँ

4 मार्च 2024

अलैंगिक प्रजनन

कई पौधे अनिवार्य रूप से यौन के बजाय कल्पित रूप से यौन होते हैं। अलैंगिक प्रजनन एक प्रकार का प्रजनन है जहाँ संतान केवल एक माता-पिता से आती है, इस प्रकार, माता-पिता की विशेषताओं को विरासत में लेती है। पौधों में अलैंगिक प्रजनन दो मौलिक रूपों में होता है: कायिक प्रजनन और अगामोस्पर्मी। 1 कायिक प्रजनन में मूल पौधे का एक कायिक भाग शामिल होता है जो कलिकायन, टिलरिंग आदि द्वारा नए व्यक्तियों का उत्पादन करता है और यह अपोमिक्सिस से अलग होता है, जो लैंगिक प्रजनन का प्रतिस्थापन है और कुछ मामलों में इसमें बीज शामिल होते हैं। अपोमिक्सिस कई पौधों की प्रजातियों जैसे सिंहपर्णी (टारैक्सैकम प्रजाति) और कुछ गैर-पौधे जीवों में भी होता है। गैर-पौधे जीवों में अपोमिक्सिस और इसी तरह की प्रक्रियाओं के लिए, अनिषेकजनन देखें।

प्राकृतिक कायिक प्रजनन एक ऐसी प्रक्रिया है जो ज्यादातर बारहमासी पौधों में पाई जाती है और इसमें आमतौर पर तने या जड़ों और कुछ प्रजातियों के पत्तों में संरचनात्मक संशोधन शामिल होते हैं। अधिकांश पौधों की प्रजातियां जो कायिक प्रजनन का उपयोग करती हैं, वे पौधों को बारहमासी बनाने के साधन के रूप में ऐसा करती हैं, क्लोनल कॉलोनी का एक एकल रेमेट या स्पष्ट व्यक्ति आनुवंशिक रूप से उसी कॉलोनी के अन्य सभी के समान होता है। वानस्पतिक प्रजनन के दौरान एक पौधा जिस दूरी तक जा सकता है, वह सीमित होती है, हालांकि कुछ पौधे शाखाओं वाले प्रकंदों या स्टोलन से रेमेट का उत्पादन कर सकते हैं जो अक्सर केवल कुछ ही बढ़ते मौसमों में एक विस्तृत क्षेत्र को कवर करते हैं। एक अर्थ में, यह प्रक्रिया प्रजनन की नहीं बल्कि जीवित रहने और व्यक्ति के बायोमास के विस्तार की है। ��ब एक व्यक्तिगत जीव कोशिका गुणन के माध्यम से आकार में बढ़ता है और बरकरार रहता है, तो इस प्रक्रिया को वनस्पति वृद्धि कहा जाता है। हालाँकि, वनस्पति प्रजनन में, परिणामस्वरूप जो नए पौधे बनते हैं, वे आनुवंशिक को छोड़कर लगभग हर मामले में नए व्यक्ति होते हैं। वनस्पति प्रजनन का एक बड़ा नुकसान माता-पिता से संतानों में रोगजनकों का संचरण है। पौधों से उसके बीजों में रोगाणुओं का संचार होना असामान्य है (यौन प्रजनन या अपोमिक्सिस में), हालांकि ऐसे मौके भी आते हैं जब ऐसा होता है।2 अपोमिक्सिस द्वारा उत्पन्न बीज अलैंगिक प्रजनन का एक साधन है, जिसमें ऐसे बीजों का निर्माण और फैलाव शामिल होता है जो भ्रूण के निषेचन से उत्पन्न नहीं होते हैं। हॉकवीड्स (हिरासियम), डंडेलियन (टारैक्सैकम), साइट्रस की कुछ प्रजातियाँ और केंटकी ब्लू ग्रास (पोआ प्रेटेंसिस) सभी अलैंगिक प्रजनन के इस रूप का उपयोग करते हैं। स्यूडोगैमी कुछ पौधों में होती है जिनमें अपोमिक्सटिक बीज होते हैं, जहाँ भ्रूण के विकास को आरंभ करने के लिए अक्सर परागण की आवश्यकता होती है, हालाँकि पराग विकासशील संतानों में कोई आनुवंशिक सामग्री नहीं देता है।3 पौधों में अपोमिक्सिस के अन्य रूप भी होते हैं, जिसमें बीज के स्थान पर पौधे का निर्माण या फूलों के बजाय बल्बिल का निर्माण शामिल है, जहाँ नए क्लोन किए गए व्यक्ति उत्पन्न होते हैं। यौन प्रजनन

यौन प्रजनन में दो मूलभूत प्रक्रियाएँ शामिल हैं: अर्धसूत्रीविभाजन, जो जीन को पुनर्व्यवस्थित करता है और गुणसूत्रों की संख्या को कम करता है, और निषेचन, जो गुणसूत्र को पूर्ण द्विगुणित संख्या में पुनर्स्थापित करता है। इन दो प्रक्रियाओं के बीच, विभिन्न प्रकार के पौधे और शैवाल भिन्न होते हैं, लेकिन उनमें से कई, जिनमें सभी भूमि पौधे शामिल हैं, दो अलग-अलग बहुकोशिकीय संरचनाओं (चरणों), एक गैमेटोफाइट और एक स्पोरोफाइट के साथ पीढ़ियों के परिवर्तन से गुजरते हैं।

मॉस और लिवरवॉर्ट्स में, गैमेटोफाइट अपेक्षाकृत बड़ा होता है, और स्पोरोफाइट एक बहुत छोटी संरचना होती है जिसे कभी भी गैमेटोफाइट से अलग नहीं किया जाता है। फ़र्न, जिम्नोस्पर्म और फूल वाले पौधों (एंजियोस्पर्म) में, गैमेटोफाइट अपेक्षाकृत छोटे होते हैं और स्पोरोफाइट बहुत बड़ा होता है। जिम्नोस्पर्म और फूल वाले पौधों में मेगागैमेटोफाइट बीजांड के भीतर होता है (जो बीज में विकसित हो सकता है) और माइक्रोगैमेटोफाइट पराग कण के भीतर होता है।

प्रारंभिक पौधों के विकास में, अजैविक साधनों, जिसमें पानी और बहुत बाद में हवा शामिल है, ने प्रजनन के लिए शुक्राणुओं का परिवहन किया। पहले पौधे जलीय थे, और धाराओं के साथ ले जाने के लिए पानी में स्वतंत्र रूप से शुक्राणु छोड़ते थे। लिवरवॉर्ट और मॉस जैसे पैतृक भूमि पौधों में गतिशील शुक्राणु होते हैं जो पानी की एक पतली परत में तैरते थे या पानी की बूंदों में छींटे होते थे। जैसे-जैसे लम्बे और अधिक जटिल पौधे विकसित हुए, पीढ़ियों के परिवर्तन में संशोधन विकसित हुए। पैलियोज़ोइक युग में प्रोजिम्नोस्पर्म हवा में फैले बीजाणुओं का उपयोग करके प्रजनन करते थे और कई जिम्नोस्पर्म और कुछ एंजियोस्पर्म अभी भी युग्मक फैलाव के लिए हवा पर निर्भर हैं। बीज वाले पौधों में बीज फ़र्न, कोनिफ़र और कॉर्डाइट्स में पराग कण होते हैं जिनमें नर युग्मक होते हैं जो नर से मादा भागों में स्थानांतरण की प्रक्रिया के दौरान शुक्राणु की सुरक्षा करते हैं। एंजियोस्पर्म, या फूल वाले पौधे, सबसे अधिक व्युत्पन्न और सबसे प्रचुर मात्रा में पाए जाने वाले पौधे हैं और वे प्रजनन के लिए पराग और बीजांड पैदा करने वाले फूलों पर निर्भर हैं। स्व-निषेचन और स्व-असंगतता

पौधों की कई प्रजातियाँ, खास तौर पर वे जो पुंकेसर और स्त्रीकेसर दोनों तरह के फूल पैदा करती हैं या ‘परफेक्ट’ उभयलिंगी फूल पैदा करती हैं, उनमें खुद के साथ यौन प्रजनन करने की क्षमता भी होती है। यह खास तौर पर फायदेमंद है अगर परागण सेवाएँ अविश्वसनीय या अप्रत्याशित हैं, क्योंकि यह सुनिश्चित करता है कि पौधे में अभी भी कुछ योग्यता है। स्व-परागण परागण का एक रूप है जिसमें एक ही पौधे से पराग फूल के कलंक (फूल वाले पौधों में) या बीजांड (जिम्नोस्पर्म में) पर पहुँचता है। स्व-परागण शब्द जिसे अक्सर पर्यायवाची के रूप में इस्तेमाल किया जाता है, केवल स्व-परागण तक सीमित नहीं है, बल्कि अन्य प्रकार के स्व-निषेचन पर भी लागू होता है। पौधे या तो अनिवार्य रूप से स्व-निषेचन कर सकते हैं, या फिर स्वेच्छा से। स्वेच्छा से स्व-निषेचन करने वाले पौधों में, ऐसे तंत्र हो सकते हैं जो स्व-निषेचन में देरी करते हैं, जैसे कि पुंकेसर जो शुरू में प्रतिवर्तित होते हैं लेकिन कलंक के संपर्क में आने के लिए आगे बढ़ते हैं। प्रकृति में लगभग 42% फूल वाले पौधे मिश्रित प्रजनन प्रणाली प्रदर्शित करते हैं।4 सबसे आम प्रकार की प्रणाली में, अलग-अलग पौधे एक ही प्रकार के फूल उत्पन्न करते हैं और फलों में स्व-परागण, बाह्य-संकरण या संतति प्रकारों का मिश्रण हो सकता है। एक अन्य मिश्रित प्रजनन प्रणाली को द्विरूपी क्लिस्टोगैमी कहा जाता है। इस प्रणाली में एक ही पौधा खुले, संभावित रूप से बाह्य-संकरण और बंद, अनिवार्य रूप से स्व-परागण वाले क्लिस्टोगैमस फूल दोनों उत्पन्न करता है।5

अभी भी अन्य प्रजातियाँ स्व-असंगत हैं, और यदि वे अपने स्वयं के वर्तिकाग्र सतह पर उतरते हैं तो वे अपने स्वयं के पराग कणों को अस्वीकार कर देंगे। ये पौधे अनिवार्य रूप से बाह्य-संकरण कर रहे हैं, और उन्हें अपनी प्रजाति के किसी अन्य सदस्य के साथ सफलतापूर्वक यौन प्रजनन करना चाहिए। SI वाले पौधों में, जब किसी पौधे में उत्पादित पराग कण समान पौधे या मिलान करने वाले एलील या जीनोटाइप वाले किसी अन्य पौधे के वर्तिकाग्र तक पहुँचता है, तो पराग अंकुरण, पराग-नलिका वृद्धि, बीजांड निषेचन या भ्रूण विकास की प्रक्रिया बाधित होती है, और परिणामस्वरूप कोई बीज उत्पन्न नहीं होता है। एसआई पौधों में अंतःप्रजनन को रोकने और नए जीनोटाइप की पीढ़ी को बढ़ावा देने के सबसे महत्वपूर्ण साधनों में से एक है और इसे पृथ्वी पर एंजियोस्पर्म के प्रसार और सफलता के कारणों में से एक माना जाता है।

आउटक्रॉसिंग फर्टिलाइजेशन

पौधे जो एक फूल से दूसरे फूल में पराग ले जाने के लिए कीटों या अन्य जानवरों का उपयोग करते हैं, उन्होंने परागणकों को आकर्षित करने और एक फूल से कीट तक और कीट से अगले फूल तक पराग की आवाजाही को सुविधाजनक बनाने के लिए बहुत संशोधित फूल भागों का विकास किया है। पवन-परागण वाले पौधों के फूलों में पंखुड़ियों और या बाह्यदलों की कमी होती है; आम तौर पर बड़ी मात्रा में पराग का उत्पादन होता है और परागण अक्सर बढ़ते मौसम की शुरुआत में होता है इससे पहले कि पत्तियाँ पराग के फैलाव में बाधा डाल सकें। कई पेड़ और सभी घास और सेज पवन-परागण हैं।

पौधों के पास परागणकर्ताओं को आकर्षित करने के लिए कई अलग-अलग तरीके हैं, जिनमें रंग, गंध, गर्मी, अमृत ग्रंथियाँ, खाद्य पराग और फूल का आकार शामिल हैं। उपरोक्त संरचनाओं से जुड़े संशोधनों के साथ-साथ दो अन्य स्थितियाँ फूल वाले पौधों के यौन प्रजनन में बहुत महत्वपूर्ण भूमिका निभाती हैं, पहला है फूल आने का समय और दूसरा है उत्पादित फूलों का आकार या संख्या। अक्सर पौधों की प्रजातियों में कुछ बड़े, बहुत ही आकर्षक फूल होते हैं जबकि अन्य कई छोटे फूल पैदा करते हैं, अक्सर फूलों को उनके दृश्य प्रभाव को अधिकतम करने के लिए बड़े पुष्पक्रमों में एक ��ाथ इकट्ठा किया जाता है, जो परागणकर्ताओं के लिए अधिक ध्यान देने योग्य बन जाते हैं। फूल आकर्षण रणनीतियाँ हैं और यौन अभिव्यक्तियाँ कार्यात्मक रणनीतियाँ हैं जिनका उपयोग पौधों की अगली पीढ़ी का उत्पादन करने के लिए किया जाता है, जिसमें परागणकर्ता और पौधे सह-विकसित होते हैं, अक्सर कुछ असाधारण डिग्री तक, बहुत बार पारस्परिक लाभ प्रदान करते हैं। विशेषज्ञता फायदेमंद हो सकती है क्योंकि इससे अधिक सुसंगत परागण सेवाएँ मिलती हैं। नतीजतन, विशिष्ट परागणकर्ता और पौधे एक-दूसरे पर मजबूत चयनात्मक दबाव डाल सकते हैं, जिससे सह-विकास होता है। इसके उदाहरणों में अंजीर और अंजीर ततैया, या युक्का और युक्का पतंगों के बीच सह-विकास शामिल है, जिसमें युक्का पतंगे अनिवार्य परागणकर्ता और युक्का के विरोधी शाकाहारी दोनों हैं। एक और दृष्टिगत रूप से आकर्षक उदाहरण परागणकर्ताओं में लंबे पुष्प कोरोला और लंबी चोंच या सूंड का सह-विकास है 12.5.1A+B

पौधों में यौनक्रिया फिरभी पराग द्वारा तो संगठित होता है

मगर मछलियों में सबसे ज्यादा रहस्यमय यौनक्रिया संगठित होता है

पुरुष मछली पानी में वीर्य वहा देते है और नारी मछली वीर्य खा जाते है

#nasa #google #youtube #facebook

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botanyone · 5 months

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A Universal Theory of Sex

A Universal Theory of Sex https://ift.tt/7AG5Kh0 Sexual reproduction in plants and animals presents an evolutionary enigma. It is genetically risky, time-consuming, and error-prone – possibly leading to reduced fitness. And yet, at least 99% of all plants and animals reproduce sexually. This commonality raises the question of whether universal evolutionary pressures exist to select for and maintain sexual reproduction. Elvira Hörandl argues in a review paper in Annals of Botany that the need for DNA repair may be the basis for the near universally of sex in the plant and animal kingdoms. And she uses land plants as a tool to make her case. “Land plants are of special interest for this question because, on the one hand, sexual reproduction is predominant, similar to animals; on the other hand, some theories developed for animals are not readily applicable to plants because autotrophic organisms have different physiological constraints.” The key process in sexual reproduction is meiosis, defined as the pairing and recombination of corresponding parental chromosomes. During this process, parental DNA is fused to create genetic variation in offspring. The new genetic combinations can be advantageous, neutral, or even detrimental to fitness if well-adapted genes are broken up. Hörandl argues that plants don’t need meiosis to achieve advantageous genetic combinations — polyploidy can be used instead. In plants, many species are polyploid, i.e., have multiple genomes, and individual genetic variation is correspondingly high. This built-in genetic diversity confers the necessary ‘phenotypic plasticity’ for plants to respond to environmental stressors such as light, heat, drought, and salt. In this context, asexual reproduction, where plants reproduce without meiosis, can make sense as a reproductive strategy. However, while many plants do reproduce asexually, Hörandl shows that many of those species run both sexual and asexual reproductive pathways in parallel in the same plant in a flexible manner and do not rely solely on asexual forms of reproduction. And so, the question becomes, if polyploidy and asexual reproduction are enough to create the necessary genetic diversity for fitness, why then do plants bother with sexual reproduction? Hörandl suggests that ‘DNA restoration theory’ provides the answer. DNA restoration theory posits that the major function of meiosis is to repair damaged DNA and remove negative mutations in each generation. In that light, genetic recombination is not the end goal of sexual reproduction but is instead a by-product of a DNA repair mechanism. DNA needs repair because it is continuously damaged by mitochondrial respiration as well as by photosynthesis in plants. Hörandl writes that: “In the long term, asexual reproduction without any recombination would result in genomic decay owing to the accumulation of deleterious mutations, specifically in small populations, finally leading to extinction of the asexual lineage.” Indeed, sexual reproduction, and consequently meiosis, is triggered in plants grown in DNA damage-inducing, stressful environments. Hörandl notes that only “…a little bit of sex (a mean of ~6 % recombined offspring in three progenies) is sufficient to avoid accumulation of mutations over generations.” Consequently, species may have evolved the ability to reproduce sexually in order to repair and maintain their DNA. READ THE ARTICLE Hörandl, E. (2024) “Apomixis and the paradox of sex in plants,” Annals of Botany, p. mcae044. Available at: https://doi.org/10.1093/aob/mcae044. The post A Universal Theory of Sex appeared first on Botany One. via Botany One https://botany.one/ April 26, 2024 at 08:24PM

#Botany #Plant Science #Botany One

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ecobiohub · 3 years

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What is Apomixis and What is its Importance in Plants?

In this tutorial, we have discussed “What is apomixis and what is its Importance in plants?” What is Apomixis The formation of new individuals through the normal process of sexual reproduction by the meiotic formation of gametes and their subsequent fusion during fertilisation is called amphimixis. The formation of new individuals through asexual reproduction without the formation and fusion of…

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#apomixis #apomixis definition #apomixis meaning #apomixis means #what is apomixis

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is-the-snake-video-cute · 2 years

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how does parthenogenesis work? I knew asexual reproduction was a thing for stuff like plants and bacteria and some invertebrates but I didn't know it could happen in bigger animals like reptiles

Great question! It's kinda complicated, especially among vertebrates, but here's the lowdown.

Normally, reproduction requires an egg cell and a sperm cell, right? Reptiles have what is called apomixis parthenogenesis. This means that egg cells split by mitosis, resulting in diploid cells. "Diploid" means that the cells have two sets of chromosomes, and in reproductive cells, that means they have everything they need to produce a viable embryo! (Human reproductive cells are the opposite, they're haploid cells, meaning they only have one set of chromosomes.)

It's important to note that parthenogenesis can only occur in animals that have egg cells that contain instructions for gene expression. It can't happen in humans, for example, because our egg cells require functional gene instructions from sperm cells to form properly. Parthenogenesis up to the mitosis stage can occur in humans, but it can't ever produce viable embryos.

So, basically: egg cell splits, copies all the chromosomes it needs from the parent, and forms into a viable embryo. Hatchlings produced via parthenogenesis are usually exact clones of the parent, and will usually all be female in lizards or all male in snakes thanks to how reptile chromosomes work (with the exceptions being with weirdness in snakes since they have a ZW chromosome system ((where ZZ is male and ZW is female)); there's a female boa constrictor who reproduced through parthenogenesis and the hatchlings were WW females! Check out this article, it's wild).

#not a rating #snake anatomy #parthenogenesis

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wherethebirdsings · 3 years

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parthenogenesis in vertebrates

a couple of days ago i saw this post on instagram (tldr; SEA aquarium zebra sharks conceived without a father, hatched from unfertilised eggs.) my memory of what i learned in school about this was hazy at best (lol), so i did some research, and here's what i found :D

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parthenogenesis. rooted in the Greek words parthenos - meaning virgin, and genesis - meaning origin. for multicellular eukaryotes, it refers to the production of offspring from unfertilised sex cells.

such asexual repro is common in plants, but much less so in animals. when it does occur, it's usually in invertebrates (eg. rotifers, marine clams, insects like aphids, and those of the order Hymenoptera.)

if we're talking vertebrate groups, parthenogenesis has been found in reptiles, birds, bony fish and 6 sp of sharks + rays. but it is very rare :0

the first case of parthenogenesis in zebra sharks was recorded in 2016, in an aquarium in Australia.

parthenogenesis in diploid organisms happens in 1 of 2 ways.

→ automixis, where haploid gametes are produced through meiosis, then fused back together to form a diploid zygote. the offspring is genetically different from its mother & siblings.

→ apomixis, where a diploid gamete is produced through mitosis-like cell division, forming a diploid egg(?) cell. offspring is thus genetically identical to its mother.

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here's the cool thing: parthenogenesis can be either obligate or facultative. species that are facultatively parthenogenic (let's call it FP) are able to switch between sexual and asexual repro. such reproductive flexibility may increase organisms' adaptability & fitness :)

this paper found that switching to parthenogenesis in (predominantly sexually-reproducing) vertebrates could be a response to the removal of potential mates. after all, most records of FP have been in isolated, captive females (like our aquarium-dwelling zebra shark.)

however, we will need more conclusive data to confirm this correlation. so if you're wondering why a vertebrate might wake up one day and choose parthenogenesis - as of now, no one knows.

picture: wikimedia commons

references: britannica, nat geo, dudgeon et al. (2017), evolution 2nd ed. (carl t. bergstrom)

#parthenogenesis #animals #i google stuff

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sciencespies · 3 years

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Baby shark born in all-female tank could be the first 'virgin birth' for its species

https://sciencespies.com/nature/baby-shark-born-in-all-female-tank-could-be-the-first-virgin-birth-for-its-species/

Baby shark born in all-female tank could be the first 'virgin birth' for its species

Scientists say a rare shark “virgin birth” may be the first of its kind after a baby shark was born in an all-female tank in an Italian aquarium.

The baby smoothhound shark, named Ispera, which means hope in Sardianian, was born at the Acquario di Cala Gonone in Sardinia, Italy, according to Italian outlet AGI.

Its mother had spent ten years living in a tank with one other female, the outlet said, and scientists suspect the newborn could be the first documented case of shark parthenogenesis in that species.

Parthenogenesis is a rare phenomenon where an egg develops into an embryo without being fertilized by a sperm.

The process has been observed in more than 80 vertebrate species, according to Live Science, including sharks, fish, and reptiles.

“About 15 species of sharks and rays are known to do this,” Demian Chapman, director of the sharks and rays conservation program at Mote Marine Laboratory & Aquarium in Florida, told Live Science.

He added that while sharks probably had the ability to do it, it was difficult to document in the wild.

Chapman told Live Science that in the wild, parthenogenesis might be the last resort for females that cannot find a mate in situations of low population density.

The response can also be triggered in captive sharks who are separated from males for long periods of time, he said.

There are two different types of parthenogenesis, according to National Geographic.

One is apomixis, a type of cloning most common in plants.

The other, documented in sharks, is automixis, which involves the slight shuffling of the mother’s genes to create offspring similar to the mother but not exact clones.

Researcher Christine Dudgeon from the University of Queensland in Australia told Live Science how parthenogenesis worked.

“Rather than combining with a sperm cell to make an embryo, [the egg cell] combines with a polar body, which is essentially another cell that is produced at the same time that the egg cell is produced and has the complementary DNA,” Dudgeon told Live Science.

“Parthenogenesis is essentially a form of inbreeding, as the genetic diversity of the offspring is greatly reduced,” Dudgeon added.

As a result, parthenogenesis offspring could have a reduced chance of survival, she said.

Marine biologists at the Italian aquarium have sent DNA samples to a laboratory to confirm that Ispera was born through parthenogenesis, the New York Post reported.

This article was originally published by Business Insider.

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megabadbunny · 7 years

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Rose x Ten, post GitF-au/fixit; angst, fluff, romance, more angst, and possibly some smut later, but this part (and all parts on ff.net) is sfw (minor exception for brief language). And a huge thank you to everyone who left a comment encouraging me to continue, as well as everyone who didn’t completely lose patience with me--this chapter is dedicated to you lovely peaches!!! <3 <3 <3

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Minuet, Part IV

The next day, the Doctor’s behavior can only be described as jumpy.

“And here we have the great lakes of Therran Vox!” he announces, throwing open the TARDIS doors to reveal a bleach-bright vision of sparkling water and dazzling white sky. “Not to be confused with Academy-Award-winning actress Charlize Theron, mind, nor the lakes of TheronnEx, though much of the plant life is certainly related, evolutionarily speaking.”

The Doctor plucks three umbrellas from their resting-place against the TARDIS wall, tossing one to Rose and Mickey each in turn before stepping out of the TARDIS with an umbrella of his own. “Something like third cousins, maybe third cousins once removed, maybe twice,” he continues. “Bit hard to know for certain, sort of tricky trying to gauge that sort of thing when your generations span centuries and solar systems. Speaking of reproduction, did you know that the Therranian water lily is one of the few angiosperms in the known universe that can reproduce via spores? Well, they don’t technically reproduce via spores, per se, but their pollen has been known to hitch a ride on them a time or two. Sort of like a botanical hitchhiker, only on a semi-mesoscopic scale. And when you’re talking spores and pollen able to withstand the vaccums of space, well, that sort of explains the galaxy-hopping, doesn’t it? Though the waterlilies on TheronnEx have a sort of unfortunate expired meat smell about them…”

Rose stretches and yawns, ignoring the Doctor’s prattling in favor of taking in the sights all around her. She’s surrounded on all sides by an intricate network of perfectly round lakes, connected only by slim strips of grassy land. Reflecting the world above—everything from willowy trees to the pearl-white sky to the metallic towerlike structures reaching high up, up, up into the swollen candyfloss clouds—the lakes glimmer and sparkle like a collection of mirrors, glasslike and silver and still. Stepping closer to one of the lakes, Rose inspects a tree by its banks, whose slender roots creep gently into the water. Her eyes travel over the trunk, which stretches high into the morning air, lifting its canopy of paper-thin roots far above the water surface. It doesn’t take an architect to observe the similarity between the trees and the tower structures, whose engineers clearly looked to the willows for inspiration in constructing both the complex, interwoven-strut foundations of the towers as well as their observation decks spreading up above. Rose jumps as a handful of water droplets fall across her upturned face, just before a light drizzle descends all around, tiny water droplets singing through the air before they land with a series of dainty plops and splashes. Their touch on the grass releases a mild fragrance into the air, something delightfully fruitlike and soft.

It’s absolutely wonderful, a proper exotic alien planet, and Rose lifts her face completely toward the sky, eyes closed as the rain peppers kisses on her cheeks. God, she’s missed this.

Without even thinking about it, Rose reaches for the Doctor’s hand, but he sets off at a brisk pace before her hand can do anything more than brush against his, blathering on about para-symbiotic relationships and rhizomes and apomixis and god knows what else.

(Scratch that earlier thought—he’s ridiculously jumpy.)

“Is this normal?” Mickey asks under his breath.

Rose watches the Doctor as he wanders off, chattering loudly to no one in particular, and she tries to ignore the sick feeling bubbling up in her chest, the hurt aching in her gut. It’s just because she didn’t sleep well last night, she reasons. For all that she had dreamed of being back aboard the TARDIS, snuggling into her bed replete with plush foam and soft blankets and squishy pillows, she slept absolutely dreadfully. Probably she’d just got used to the hard and unforgiving beds back at the palace; certainly the lack of sleep can’t be blamed on anything else. Or anyone, for that matter.

Great fat rain droplets smack against her head like a dozen tiny missiles and Rose wipes water out of her face, deploying her umbrella with a sigh. “No,” she replies. “This is new.”

“Did something happen last night?”

“No. Nothing happened.”

Rose knows Mickey doesn’t believe her, would be able to tell by his suspicious silence even if she couldn’t see the eyebrow arching off his forehead, but mercifully, he doesn’t press for more. Instead, he proffers his arm to Rose, standing ramrod-straight like he’s posing for a school formal photo. He would look a little silly even if his umbrella wasn’t covered in bright yellow smiley faces.

“C’mon, babe,” he says in response to her questioning look. “Let’s go for a stroll and you can tell me all about your adventures back in fancypants France.”

Rose smiles despite herself. “Are you sure you’d rather hear about that than whatever thrilling greenhouse trivia the Doctor’s throwing our way?”

“Nah, we’ll just make sure to toss a few uh-huh’s and oh how fascinating’s his way every once in a while.”

Threading her arm through his, Rose laughs.

“…and here it is!” announces the Doctor, several thousand steps and two grumpy and wet-shoed humans later. The trail stops at an impressive, five-meter tall wall, rainbow-bismuth-colored and extending as far as the eye can see in either direction; the Doctor presents it all with a flourish of his umbrella. “The main attraction, the big to-do, the pièce de résistance—the grand Temple of the High Chauncery, perfect for viewing Therran Vox’s universe-renowned celebration of transient luminous events!”

He turns to Rose and Mickey with a wide grin, only to be met by a pair of identical blank stares. “Oh, come on,” says the Doctor, undeterred. “Mickey, you must have heard me mention the High Chauncery’s luminous wassail at least once!”

“Pretty sure I’ve never heard any of those words in my life,” Mickey replies flatly.

“So what’s a transient luminous event?” asks Rose. “I mean, luminous—that means light, right?”

“Right you are,” the Doctor replies, and is Rose just imagining it, or does he meet her gaze even less than usual? “The term refers to electrical phenomena produced during a thunderstorm.”

“So, lightning,” says Mickey, unimpressed.

“Well, yes, if you want to be reductive,” the Doctor responds, rolling his eyes. “But it’s not just lightning, it’s spectacular lightning. Like I said, phenomenal. Lots of worlds experience it, Earth included, but on most planets the events flash by so quickly, so high in the atmosphere, that you can’t observe them with the naked eye. That’s what makes the storms on Therran Vox so special; the chemical composition of the atmosphere here makes for an event that’s far more visible. You can catch the light show in all its glory, from front-row seats! Nothing quite like it in the universe, but why would I tell you when I can just show you?”

He raps his knuckles against the gate wall and a small round window opens in the metallic surface, a liquid movement like oil springing away from soap. A humanoid face appears on the other side, her eyes a fascinating multicolor, her forehead bedecked in rows of ornamental dots.

“Invitation?” the owner of the face inquires.

The Doctor produces the psychic paper from his jacket-pocket. “Sir Doctor and his traveling companions, Dame Tyler and Majordomo Smith of the Powell Estate,” he says rather grandly, “here to view some of the universe’s finest luminescent theatre!”

“Of course, your Grace,” replies the gatekeeper, peering at the psychic paper through the rain. She turns around and issues a curt nod to her comrade (another humanoid, another set of ornamental dots), and the window in the wall slowly opens up, widening by inches into a round doorway.

“Your timing is most fortuitous, sir—all of the other guests have already arrived, and we’re closing the outer shield any moment now,” the gatekeeper continues. “Per your itinerary, the first ritual doesn’t take place until the morning, but that gives you the evening to settle in and enjoy the first stirrings of the storm. In the meantime, Votary Uruud here will give you a quick tour through the Temple before showing you to your quarters, and we’re happy to take your luggage for you as well—”

“Sorry, sorry,” says the Doctor, his eyebrow arching in confusion. “Our quarters?”

“Our luggage?” asks Mickey under his breath.

“Yes, Sir Doctor, your quarters. For the duration of the event.”

The Doctor blinks. “The duration of the event,” he repeats, his eyebrow arching further.

“For the month, sir.”

The Doctor’s eyebrow has now arched so high it’s in danger of disappearing into his hairline. “Right,” he says. “The month-long ritual. The month-long ritual storm celebration. The month-long ritual storm celebration for which we are totally, completely, and utterly prepared. With luggage and toiletries and things. For a month.” He tugs on one ear. “Except—”

“Oh, silly us!” Rose interrupts, throwing her hands up in mock-surprise. “We left all of our things back at our ship!”

“Yes, quite!” the Doctor agrees. “So we’ll just run back and grab it all, shall we?”

Rose and Mickey nod vigorously.

Glancing at each of them, the gatekeeper’s face wrinkles in concern. “Forgive my impudence, your Graces, but it’s too late to turn back now. You won’t reach your ship before the Allstorm arrives.”

“The Allstorm?” Mickey asks, incredulous even as rain dodges his umbrella to splatter against his cheek. Rose elbows him in the ribs and he clears his throat. “I mean, of course, the Allstorm!” he laughs nervously. “I know what that is. Sure, why not?”

“Thanks for the warning, but we’ll take our chances,” says the Doctor. “Bit of rain will do us more good than harm.”

“Please, your Graces, I must protest—the blessed High Chauncery is a generous man and will supply you with all that you could need. You mustn’t remain outdoors any longer, it’s not safe—”

No sooner has the Doctor turned to leave than a great bolt of lightning splits open the sky, followed by a blast of thunder so violent it shakes the ground beneath everyone’s feet, their ears ringing after. Looking skyward, Rose can’t help but notice that the formerly friendly-looking clouds appear significantly more ominous now, less fluffy-pink and more threatening-red and heavy with rain. They cluster overhead, slowly blocking out the sun, and Rose watches as the world is painted crimson around them. She suddenly thinks of Sunday school, of pharaohs and plagues and endless night, of storms that send blood pouring from the skies and swelling in the rivers. She shudders.

Another barrage of thunder strikes, so loud Rose can feel it in her bones, rattling her teeth. The Doctor heaves an impatient sigh. “Our quarters it is, then,” he says reluctantly.

The gatekeeper beams at him. “Oh, very good, sir. Thank you, sir. Welcome to the High Chauncery’s Temple of the Allstorm!”

While the storm rages overhead, its searing white lightning and murderous clouds all-too-visible through a ceiling that, to all appearances, seems to be made of a thick stained glass, Votary Uruud leads the Doctor, Rose, and Mickey on a tour of the opulent beauty that is the Temple. They show the party through a marble-lined courtyard into a veranda replete with columns and overflowing in ornamental greenery and other Votaries carrying a generous surplus of niblets on trays. Mickey and Rose inspect the food eagerly, sampling things spicy and salty, sugary and sweet; Rose tries not to notice how the Doctor, strangely, avoids all of the niblets altogether. The veranda opens to a garden lush with flora of every color imaginable, vibrant vermillion and stunning cobalt and brilliant fuschia and everything in-between. Some of the flowers bloom as large as dinner plates, others as small as thimbles, and Rose watches in fascination as each of them slowly turn their faces toward the sky, almost as if they’re looking for the storm, like they can sense it.

“They’re lumosynthetic,” the Doctor murmurs to Rose. “They’ve evolved to feed off light from any source, even lightning in a storm. You should see them when the real storm starts.”

She nods in response, and wonders at how he doesn’t lean in nearly as close as usual, how he draws away so much quicker.

The garden leads to a chamber of swimming pools nearly identical to the perfectly round lakes outside, save that their water glows with the otherworldy light of bioluminescent algae. At Uruud’s gentle urging, Rose and Mickey each dip a hand into the water and delight at the glow that dances across their skin, lingering in a smattering of ghostly footprints several moments after leaving the pool.

In addition to the wonders that call the Temple home, Rose, Mickey, and the Doctor also encounter other guests as they dutifully follow Uruud, people of all shapes and shades and sizes, everyone from other Therrans to bird-people with special goggles to fish-people with special suits to upright rhinoceri and even a group of New Earth’s cat folk, though thankfully, Rose notes, none of them appear to be nuns. Almost all of the Therrans bear the same dots on their faces as Uruud and the gatekeeper, all in different numbers and configurations. One such woman, a gorgeous figure clad in a semisheer gold and scarlet gown with facial markings to match, watches them from the safety of her richly-clad party, her eyes lingering on the Doctor long after he walks by.

(Half a year ago, Rose would have threaded her arm through the Doctor’s and shot the woman a dagger-filled glance until she drew back in surprise, would have done it without even thinking. Now she just bites her lip and silently wishes for the woman to slip on a banana-peel.)

As they pass through the menagerie afterward, peering through latticework enclosures at a host of incredible creatures (winged lizards and scaled mammoths and jewel-skinned snakes, oh my), Rose starts to notice the walls around them—wide as they are, and as full as the space is between them, it’s sort of difficult to tell, but she could almost swear they were curved. In fact, she thinks, stepping closer so she can fit her palm to one wall’s smooth surface, she would be willing to bet that all the rooms in the Temple are built this way, round-walled and circular like the lakes outside.

“It’s like a ripple,” she realizes aloud when the party reaches the entertainment library, whose walls are lined with curving shelves that are not packed with books or movies so much as hundreds upon hundreds of glowing white orbs.

“Beg pardon?” asks Votary Uruud with a polite small.

“The Temple. It’s built like a ripple, isn’t it?”

Uruud’s smile brightens into something genuine then. “It is indeed, your Grace!”

“You’re not wrong,” says the Doctor thoughtfully. “The Temple is made up of a series of concentric rings, each split into different chambers for different purposes. The deeper into the Temple you go, the smaller and more important the chambers become—entertainment and feasting and grand ritual gives way to spaces of study, sleep, work, and personal worship.”

He pauses for a moment, musing. “And with the glass ceiling exposing everything to the gods above, I’d imagine you’re right—from a bird’s-eye view, the structure would look just like a ripple. Well-spotted, Rose.”

“Your Graces are most observant,” says Uruud, beaming at each of them in turn. “Although few are as resplendent as the High Chauncery’s Temple, each of the Allstorm Temples is inspired by the form of water in honor of They Who Provide.”

“Who’s that? Like a bunch of gods?” Mickey asks, interest piqued.

“They are one god,” Uruud replies, and then, continuing in much the same fashion as someone reciting an oft-spoken Bible verse, “for just as our gods cannot be tamed by earthly will, neither can man nor woman tame the form of water.”

Confused, Rose and Mickey both turn to the Doctor. “They Who Provide is the genderless water god,” he explains. “Our hosts don’t really adhere to a binary the same way you lot tend to. Gender isn’t assigned at birth, but rather chosen at the coming-of-age. You choose one or the other, or both, or neither, and you can change it at any time.”

“So which one did you choose?” Mickey asks Uruud. “If that’s not a rude question or anything,” he adds hurriedly.

“I follow in the footsteps of They Who Provide,” replies Uruud, bowing their head in deference.

“So, like, do you have a special party for it, or something? Like a bar mitzvah?”

Uruud laughs, quickly sobering after. “Forgive me, your Graces! I’m merely surprised—even though the Temple receives a great many honored guests for each Allstorm, most of them seem to prefer the delights of our leisure chambers and pleasure rituals rather than inquire after our ways. Storm bless them, but…”

“Let me guess,” Rose cuts in with a grin. “They’re all either snooty prigs, entitled prats, or insufferable know-it-alls who love telling you how to do your job?”

“Oh, I would never dare besmirch the name of our honored guests,” replies Uruud, the very picture of politeness even as a spark of mirth twinkles in their eyes. “But I also wouldn’t dare argue with the wise words of such an honored guest, either.”

“Of course not,” Rose replies, tapping the side of her nose.

A chirping sound fills the air then, and Uruud lifts their wrist to check their watch (or at least Rose assumes it’s a watch, though she imagines they probably call it a timekeeper or something fancy like that). “And now, your Graces, I must assume my other duties for the evening,” says Uruud. “However, I would be happy to show you to your quarters first!”

They rap their knuckles on a blank patch of wall, just like the Doctor did earlier, and just like before, a round doorway opens up, widening like a mouth. Uruud steps through, Mickey following after; the Doctor pauses, however, so Rose does as well. She watches him as he stares up through the ceiling, his hands tucked in his pockets, his brow wrinkled in deep consideration.

Rose draws a deep breath. All right. They’re alone, now. Just the two of them. No big deal. They can still be normal. Right?

“Penny for your thoughts?” Rose prompts.

The Doctor’s eyes narrow at a particularly bright arc of lightning dancing overhead. “I’m still mulling over what the gatekeeper said. For the duration of the event, for the month. But I checked and double-checked the TARDIS chronometer before we stepped out, and this is the wrong time of year for the Allstorm, I’m sure of it. I wanted to show you two the sights, to be sure, but this isn’t quite what I had in mind. It’s like trying to buy a dog and receiving a coyote instead. I wouldn’t have brought us here if I’d known…”

Sighing, he shakes his head. “At any rate, why would so many people willingly lock themselves up in one building for an entire month? Spectacular lightning-show or no, that’s a dreadfully long time to be cooped up in the same building.”

“Well, Uruud mentioned other stuff too, pleasure rituals and whatnot,” Rose points out. An unfortunate thought pops into her head and her eyes widen in alarm. “Oh god, that’s not like a fertility ritual or forced-mating thing, is it?”

“What? No!” laughs the Doctor. “It’s just regular ol’ fun, sanctioned by the god of your choice. Feasts and plays and weddings and galas and drinking a little too much of the holy libations, that sort of thing. An Allstorm is always an excuse for celebration.”

“Even if it’s taking place at the wrong time?”

“Even if.” The Doctor quiets then, suddenly thoughtful. “Still, though. An entire month? Granted, it’s been a few decades since my last visit. Not to mention, they don’t call it the Allstorm for nothing—it covers the whole planet, wrapping all of Therran Vox in a brilliant display of water and light. But you’re talking about something that lasts a few days, a week, tops. Certainly not a whole month!”

“Well, I’m sure Uruud would be happy to tell us more about it, if we asked,” Rose suggests. “Maybe it’s a one-off thing, or—I don’t know, maybe things are just different now.”

The Doctor’s gaze shifts to her, and Rose could swear a shadow flickered across his face for just the briefest second. If she didn’t know any better, she would say it looked a little like sadness. Or worse, resignation.

“Yep,” he says, his voice clipped even as he smiles. “You’re probably right.”

Rose frowns. It feels like something just happened, like she just said the wrong word and the Doctor shuttered the gates after, but she can’t put her finger on it, and the Doctor hardly seems in the mood to help. He brushes past her without another word, following after Mickey and Uruud through the round doorway, hands firmly tucked in his pockets.

Worrying her lower lip between her teeth, Rose lingers for a moment after, wondering. Guilt and frustration bubble up in her gut, churning in equal measure. Is this just how it’s going to be between them, now? Awkward and distant and stiff, and forever?

(How the hell is she supposed to fix this?)

“My sincerest apologies,” says Uruud, frowning as they peruse the screen of their wristwatch. The light from the screen bathes their face in a gentle blue, highlighting their dots in stark relief. “I’m so sorry, but I cannot seem to find your names in the database. I can only think the electrical interference from the Allstorm is affecting our information network…”

“Oh, it’s no worries,” replies the Doctor with a breezy wave of the hand. “Just chuck a few rooms our way, any rooms will do.”

“Of course, sir. I have two rooms available; will that suit the needs of your party?”

“If you need additional space,” calls a soft voice behind them, smooth and silken, “I would be delighted to share.”

Rose and the Doctor turn to see the red-and-gold woman from before, her immaculately-painted crimson mouth spread in a beatific smile, and god, she’s even more beautiful up close. Voluminous black hair, eyes as blue as lapis, features that couldn’t be more perfect if they’d been chiseled by a master sculptor; Rose can’t blame the woman for being so beautiful, or showcasing it so well (how can she, when even she can’t tear her eyes away?), but the self-assurance she projects, the confidence in her gait as she strolls up to their party, looking the Doctor up and down, makes something burn in Rose’s chest, twisting and growling like a tiny little green-eyed beast. This, Rose thinks, is a woman who has received everything she has ever wanted, and has no doubts now that anything else she wants will soon be hers as well.

And then there’s the fact that the Doctor hasn’t said anything to rebuff her, and Rose fumes, and worries, and wonders if—

"He’s taken,” she blurts out.

In her periphery, Rose sees the Doctor glance her way, his expression unreadable. The woman, however, offers her an imperious look that she knows all too well. Her gaze travels over Rose, appraising. Rose is suddenly very aware of what she must look like right now, all damp jeans and dripping umbrella and shoes squelching with mud. But she didn’t spend half a year in the French court for nothing; she draws herself up to her full height, chin up, and looks the woman square in the eye, offering a sly smile.

“Thank you for your kind offer, but I’m afraid we can’t accept,” Rose says, the words falling into place like the dials on a slot machine. “See, he’s married—”

“To Mickey!” the Doctor interrupts with a mad grin.

Now it’s Rose’s turn to stare.

What?

The Doctor just beams at the noblewoman, his smile gigawatt-bright. Rose turns to Mickey for help, for a dose of sanity, for anything, but he can’t offer anything useful; he’s too busy looking surprised.

“Ah, it feels like it was just yesterday,” the Doctor says wistfully, looping an arm around Mickey’s shoulders. “Quite possibly because it was just yesterday. It’s all still very new, you see. Bit of a whirlwind affair. Almost completely unexpected. But the heart wants what the heart wants. Isn’t that right, Peaches?”

“Erm,” says Mickey.

“And we thought, what better place to honeymoon than Therran Vox during the Allstorm?” continues the Doctor. “I wanted a trip to Barcelona, personally, but I just can’t say no to this face.” He tenderly pinches Mickey’s chin and Mickey looks very much like he wouldn’t mind being swallowed up by the floor right about now. “He’s a dreadful romantic, my Mickey.”

“Peaches?” Mickey asks, voice faint.

“We’re still figuring out the pet names,” the Doctor whispers conspiratorially to the noblewoman, and Rose fights the urge to roll her eyes, or stomp her foot, or maybe to scream. “Like I said, it’s all very new. But we’re very much in love, isn’t that right?”

Mickey shoots Rose an uncertain look, and the Doctor tightens his arm around Mickey’s shoulders until he yelps in surprise. “So in love, right, darling?”

“So in love it’s almost unbelievable,” Mickey replies through a teeth-gritted smile.

“So in conclusion, my dove and I would be more than happy to share a room,” the Doctor finishes.

“Very good, sir,” replies Uruud, relief washing over their face. “Now, if you’ll just follow me, we’ll get you settled in!”

“Anyway, thanks again for the generous offer!” the Doctor calls back to the red-and-gold woman as he follows Uruud down the corridor. Mickey trails after the two of them in something of a daze, as if he still can’t quite believe what’s going on. Rose can’t say she blames him. She’s having a little trouble processing it all herself.

(So is she just supposed to pretend that everything is normal, then, except when the Doctor starts to feel flighty? Five and a half months she waits for him, she waits, and at the end of it he’ll shout and then fall silent and then act all remorseful, he’ll insult Rose and then apologize and then, out of nowhere, apropos of nothing, grab her and kiss her, not six hours after he was ready to jump through that window and leave her and Mickey stranded, not six hours after he was kissing another woman? And then after all that, the mood swings and the almost-confessions and the bullshit refusal to discuss anything that truly matters, and now he’s the one pushing her away? And what, is Rose just supposed to accept it, roll with the punches, fall in line like a good little tin soldier? She’s just supposed to stand there and take it?)

The guilt from earlier subsides, a tide drawing back to reveal a shore littered in broken shells and bits of glass and something black and sticky, an oil spill slowly staining the sand.

“Rose?” Mickey calls from down the corridor, stopping to wait for her.

Hands balled into fists, Rose follows after them, wondering how her day could possibly get any worse.

***

Next Part (forthcoming)

***

#ficandchips #tenrose #ten/rose #tenxrose #gitf fixit #post-gitf #angst #angst with a happy ending #(ultimately - though it might take them a minute to get there ;)#also sweet baby jesus has it seriously been six months since my last update for this story???#my godddddd #i'm so sorry i hope all my readers are still alive and well and flourishing #<3 <3 <3 <3 <3 <3 <3 <3 <3 <3 #but for reals it feels so good to get this posted #ahhh #relief

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breyesbioblog · 4 years

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Plants and their Soilmates

In the previous blog I talked about reproduction in microorganisms in this blog I'll talk about how plants reproduce with their “soilmates”. Plants are one of the most important parts of our ecosystem, we rely on plants for food and oxygen we breathe. Since plants are so essential to us why not learn about how they reproduce and maintain their population despite the growing population of the organisms that need them to survive.

Like those I mentioned in the previous blog, plants can also reproduce using asexual and sexual modes of reproduction. Asexual reproduction can be categorized into artificial sexual reproduction and natural asexual reproduction. In artificial sexual reproduction, humans will have to involved to mediate the processes which in turn allows to further increase the rates of propagation as well as create new varieties, examples of artificial sexual reproductions are grafting, cutting, laying, and micropropagation. On the other hand natural asexual reproduction, the plants have specialized stems to grow into new individuals, it's like budding but they don’t get separated unless an external force makes them so. Examples of these specialized stems are tubers for potatoes, rhizomes for ginger, bulbs for onions, corms for gabi, stolons for grass, and apomixis which means a plant can produce seeds even without fertilization.

Moving on to sexual reproduction, just like what I said in the last blog sexual reproduction allows the diversity of genes among the species that can help them survive or adapt to the environment it is living in. when you see a flower you wouldn’t think it was tool plants use to reproduce will you? Flowers produce seeds, and seeds are very essential for the survival of plants that reproduce using sexual means, they are also used as nourishment of young plants. Some plants have evolved to have their seeds be covered by the mature ovaries of flowers called fruit, which is eaten by some animals and helps disperse the seed. Through pollination, plants are able to reproduce over distances with the assistance of insects and other animals, and for the wind-pollinated counterpart. As pollen reaches another plant, their egg cells are fertilized and grow into seeds.

#science #blog #plants

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tser · 7 years

Photo

This caresheet was originally written in ‘97, and was the first caresheet I ever wrote. Here is an updated version that isn’t formatted like a defunct Geocities site mirror. Most of this information is based on personal experience, with some gleaned from websites, books, and information from those who keep snails raised for food.

Note that this primarily applies to temperate species of terrestrial slugs and snails. It is US-centric since that is where I live. It does not apply to Giant African Land Snails, which are popular pets in other countries but illegal here in the US. For care and keeping of Giant African Land Snails, I suggest finding a species-specific caresheet!

Please note that keeping slugs and snails is not legal everywhere. Some are classed as pest animals and require a permit. Others only require a permit for sales, breeding, or transporting over state lines. Please check your local laws and be a responsible pet keeper.

Also a trigger warning: This caresheet will refer to h*rm*phr*d*tism, which, though a biologically acceptable way of describing slug reproduction, may be triggering for some people for whom it is used as a slur.

Supplies:

Waterproof enclosure

Substrate; optional drainage layer material

Organically raised plants, if desired

Rocks, branches, moss (or hamster tubes, plastic houses) and other cage "furniture"

A clean, new mister bottle

Distilled or dechlorinated water

Veggies and other food

Slug Anatomy

Slugs and snails are molluscs of the class gastropod (”stomach foot”). Snail generally refers to gastropods which can full retract into their shells; slugs are those which have no shell, an internal shell, or a very reduced shell.

They sense their world through two sets of tentacles, which they can retract. The mantle covers their genitals and anus. They ripple along using contractions of their foot.

Their pneumostome, a large opening on the side of their mantle, is how they breathe.

All slugs and snails produce a mucous which helps keep them moist and clean. They shed debris behind them in their mucous, leaving a trail which varies by species.

Slugs and snails do not have teeth. Instead they have a rasp-like radula, which they scrape away at food with.

Many slug and snail species are simultaneous hermaphroditic, able to produce both sperm and eggs at the same time. Some species are able to self-fertilize (apomixis), creating offspring without another present, and this should be kept in mind when keeping them as pets.

Housing

The home for your slug or snail should be escape proof, large, watertight, and have ventilation. For a single, small slug (1" or under), a large canning jar (1 gallon or more) will work for a short time, but they should be moved to something better as soon as possible.

Slugs and snails, as omnivorous detrivores, are high bioload animals. They eat a lot and poop a lot. This means that they need more space than it might seem by size.

Do not overcrowd your slugs and snails! It will make them sick and die.

Ideal is a small aquarium or “critter keeper” style plastic enclosure. The perfect size for a couple small slugs or snails would be five or ten gallons (banana slugs and other large species need a lot of space and a 10 gallon minimum).

Another option is a plastic storage tub with holes for ventilation. The lid should be very secure with clips or similar security.

For an aquarium, you should use a tight-fitting screen lid, preferably with locks or clips to hold it in place. Ideally, use the integrated sliding style screen lids. Do not underestimate a slug’s strength or ability to escape!

Slugs are surprisingly strong for their size, and remarkably squishy, they just sort of push their way out of things. A hole the size of a hole punch is easy for even large slugs to escape through!

Snails are not as likely to escape through holes because their shells get in the way, but can still push open insecure lids.

A secure lid will also to keep your pet safe from outside forces.

Any holes for ventilation should be very small or covered in mesh. The typical hole created by a soldering iron or drill, typical for keeping animals in plastic tubs, may be large enough for many slugs to escape through, and hot glue should be used to attach fiberglass screen over these holes.

If you intend to allow your slugs to breed, you will need the very finest mesh or even fabric to keep your baby slugs from escaping.

Parameters

Temperate terrestrial slugs and snails like cooler temperatures. 60-75 degrees, depending on where you got your slug or snail, is a good bet. Hot, dry weather will cause slugs and snails to die, or to go into estivation (inactivity during hot weather, sort of a summer version of hibernation). Too cold will make them hibernate. If you find your slug contracted, buried, and surrounded by mucous, it may be estivating or hibernating.

They need humidity on the higher side. 50% humidity with humid hides and micro-climates is generally good. Higher spikes (such as when misting) are fine.

Substrate

An ideal substrate for terrestrial slugs and snails is moisture retentive and resistant to decay, as slugs need high humidity enclosures.

A good option for substrate is Atlanta Botanical Gardens (ABG) Mix. You can purchase this from terrarium stores, or mix your own using recipes found online. Another option are other pre-mixed substrates safe for reptiles and invertebrates available from vivarium supply stores, such as The BioDude’s Terra Fauna, or NEHerp’s Vivarium Substrates 1 or 2. There are many other recipes online for bioactive humid vivariums.

Be sure the substrate you use is free of fertilizers, pesticides and herbicides. Do not use potting soil, even organic. Even organic substrate often has fertilizers, rewetting agents, and other natural additives which may cause problems in a terrarium. If you use soil from outside, it is generally best to sterilize it by baking it in the oven first.

Simple substrates are also appropriate for slugs, but may need to be replaced more often. Coco fiber (Eco Earth), coco chips, long fiber sphagnum moss, and cypress mulch (Forest Floor) are all safe for slugs and maintain the humidity they need.

Do not use pine or cedar shavings. It is toxic to slugs.

Aspen does not hold up in the humidity necessary for slugs.

Planted Vivs for Slugs

Planting a slug’s enclosure is optional, and difficult to maintain due to the voraciousness of slugs.

If you would like to do a traditional terrarium with plantings, first put a drainage layer (approximately two inches) in the terrarium. This helps protect the roots from getting too wet and rotting. Options for a drainage layer include LECA, NEHerp’s LDL, or Hydroballs. Gravel is another option (such as aquarium gravel) but is very heavy. Over the drainage layer, place a layer of fiberglass screen to keep the substrate from mixing into the drainage layer.

Over this, place several inches of substrate.

Choose plants appropriate to the humidity and light level of your enclosure. Choose only organically raised plants -- remember, pesticides are specifically designed to kill slugs. When planting, bare root the plant, removing all potting soil that came with the plant, and rinse the plants well. For tougher plants, you may want to soak them for 15 minutes in clean water, then give them a two to three minute soak in diluted bleach, then rinse them extremely well. This will remove any possible pests you might introduce to your terrarium.

Keep in mind that your slugs and snails will likely nibble all but the toughest plants, and they may need to be replaced. Tough plants that slugs seem to ignore (mostly) include leathery ferns and bromeliads.

Since you may need to replace them often, you may choose to sink them into the soil in pots, rather than plant them directly. This makes them easy to remove and replace.

Bioactive

Bioactive is a good choice for slugs, since they are high waste animals. If you would like to go bioactive with slugs, you will need to use a mixed vivarium substrate. A drainage layer is optional but may be helpful.

Clean up crew appropriate to a slug enclosure includes springtails and various species of isopod. Keep in mind that isopods may prey on slug and snail eggs.

Springtails are amazing at keeping down mold in humid habitats and I highly recommend them.

I suggest doing more research into bioactive if you wish to keep your slug in this manner.

Habitat Decor

Decor for your slugs doesn’t need to look natural! This is Squelchie’s enclosure. This includes two hamster hides, one of which is stuffed with damp sphagnum moss.

Decor is important for your slug to self-regulate its moisture needs, and find places to hide.

You can decorate with rocks, branches and flat pieces of bark. Wood that holds up well in humid enclosures includes ghostwood, manzanita, Malaysian driftwood, mopani, and cork bark. Do not use raw pine or cedar.

You need not be limited to naturalistic decor, however. Hamster tubes and hides or brightly colored plastic containers make slug mazes, balconies and alleys! Half buried new terra cotta flower pots or plastic flower pots are cheap and effective choices. Glassware is also a good and safe choice. Ceramics work very well but glazes should be food safe, and avoid copper glazes and metal lusters. Make sure that the containers are new or thoroughly cleaned so they do not have any soap residue.

You can also use fake plastic or silk plants (also sold at pet stores), an easier and less chompable choice than natural plants.

Anything you choose should be appropriate for a humid habitat.

It's fairly important to have at least one hide; an enclosed plastic container, a flat piece of wood or cork bark, or something similar that the slug or snail can hide under. For snails, cork flats should be elevated at one end by a rock or another piece of wood to accommodate their shell. Natural and artificial hides in the reptile sections at pet stores are quite suitable, as well as plastic rodent hides (which are far less suitable for hamsters than they are for slugs). Slugs and snails hide for safety and moisture regulation.

One very useful natural addition to your terrarium is moss. Sphagnum or terrarium moss at the pet store in the reptile and amphibian section works well. This helps keep the moisture in the terrarium, and create humid micro-climates. Leaf litter, such as oak or magnolia, is also useful, as it helps retain moisture in the substrate.

Water

Use dechlorinated, distilled, or R/O water. The treatment chemicals in tap water, such as chlorine and chloramine, can kill slugs and snails.

If you choose to treat water with a dechlorinator I recommend Prime or AquaSafe.

Slugs and snails need to be kept humid and can dry out easily. You should mist the enclosure daily. Their substrate should be kept damp but not wet.

Don't put any water dishes or pools in your terrarium. Although its unlikely the slugs would drown (but possible), it's unnecessary, and quickly gets filthy. Slugs and snails get moisture from the food they eat and from water collecting on the sides when you regularly mist the habitat.

If you want to go all out, an alternative to the mister bottle is a misting set up, such as the Mist King, ReptiRain, or Monsoon system, sold for reptiles and amphibians. It will mist your slug on a timer, freeing you from the chore.

Feeding

Squelchie about to eat some cucumber out of their ceramic dish.

Feed either on a clean flat rock (or slate tile), or a small dish (ceramic, glass, or resin are all appropriate). Slugs often leave a mess where they eat, and this is for cleaning ease.

Feeding your slug is fairly simple and actually quite fun. Slugs and snails should be fed organic produce. Pesticides are designed specifically to kill slugs! If you can’t purchase all organic, it is best to follow these guidelines in choosing which fruits and vegetables are safer when conventionally grown. Conventionally grown vegetables should be peeled, if possible, as well as washed, before giving them to your slugs. Wash all food, organic or conventionally grown, carefully before giving it to your slugs or snails.

Try all sorts of vegetables, fruits, and plants on your slug or snail. Slugs and snails seem most partial to soft fruits and vegetables such as cucumber, summer squash, and zucchini (sliced); leafy greens like lettuce, mustard greens, and dandelion greens; and fruit like strawberries and peaches. Ornamental plants like hostas, oxalis, and similar are also an option. Different species have different preferences; it’s best to experiment.

Commercial invertebrate food is also an option for feeding slugs. Repashy’s Bug Burger is usually accepted by slugs. Ken’s Premium Veggie Sticks with Calcium are a great choice, especially for snails.

Slugs can also eat small amounts of high protein food like fish food or dog food. Some species need more protein in their diet than others. (Some species are entirely predatory; be sure to look up the species you wish to keep.)

Commercial food should be supplemented with a variety of fresh food.

Slugs and especially snails must have a piece of cuttlebone (find it at your local petstore, in the bird section) to gnaw on and keep their shells strong. A calcium powder purchased at the pet store and sprinkled over the food is another option, and some people even feed them crushed tums.

Be careful not to overfeed.

Other Care and Cleaning

You will need to keep your slug's habitat clean or it will begin to smell rancid and also attract pests like fruit flies.

Do not use chemicals or soap the habitat or on decor. Soap and cleaning products will kill slugs.

Clean out uneaten food every day. Unless you have a bioactive vivarium with a false bottom or drainage layer, don't let the habitat develop standing water, or it will start to smell sour.

Rocks and many sticks and bark can be rinsed thoroughly in hot water and baked or boiled to sterilize.

A good choice for a cleaner for slug habitats is vinegar. It can be used diluted as a mild disinfectant. Simply rinse thoroughly afterwards.

In non-bioactive habitats, replace the substrate every month or so.

In bioactive enclosures with a large enough substrate area to support the inhabitants, with a healthy clean up crew, the clean up crew will keep the substrate fresh for years. However, these habitats are not maintenance free. You will still need to clean above-substrate decor of slime trails and waste weekly. Most CUC do not climb.

Slugs and snails absorb everything through their skin. Do not use hairsprays, spray cleaners, or other sprays around your slugs and snails (even in the same room).

Handling

Slugs and snails are delicate creatures. Even the snail's shell is fragile. Handle them gently, if at all, and always with freshly washed, clean hands that are wet with water, free of hand lotion or perfume. Do not attempt to peel them off furniture or the sides of their terrarium unless absolutely necessary. To peel them off, spray them with your misting bottle, then gently slide your hand under their heads and body. Do not grasp them by their shell or back and pull!

To remove slug slime from your hands, wait for it to dry, and rub it off with a dry cloth, then wash your hands. Adding water will often make the slime worse.

An alternative to touching the slug is using a piece of bark or large leaf to move them.

Wash your hands both before and after handling snails and slugs, as you would (hopefully) with any animal.

Breeding

I do not encourage breeding slugs and snails, because they have hundreds of babies that will be impossible to rehome, as well as difficult to provide the right environment for. However, I am including this information as slugs and snails do breed very readily, and a keeper may be faced with babies -- even if they only keep one slug or snail, in some cases.

Generally, breeding slugs and snails is as easy as putting together two of the same species, and providing an ideal habitat.

The first thing to keep in mind is that mating can be very hard on your slug or snail, and some (about a third) do not survive after laying eggs. Keep this in mind if you intend to keep more than one slug or snail together. Most of this information is gathered from breeding snails (which are kept in captivity and bred as a food source for humans) but much of it applies to slugs as well.

There is no guarantee your slugs or snails will breed, but if they do so it will generally happen when the conditions in their habitat mimic those of late spring and early summer in their native environment (temperature, humidity, and length of daylight).

Slugs and snails are often simultaneous hermaphrodites, meaning that each slug can both produce sperm and eggs. Because of this, any pair can breed. In some species, they are sequentional hermaphrodites, meaning that they will produce sperm in one mating, and receive sperm to fertilize eggs in another mating.

In certain species, such as banana slugs, apophallation is common. In these cases, the penis of one slug becomes trapped in the other, and they will chew their penis, or their mate’s, off. The slug can still mate as the egg producer in the future.

If you intend to breed your slugs or snails, they should have deep, loose soil to lay their eggs in (at least two inches deep). They dig holes and lay 30 - 90 eggs in them. Some lay in one hole, others dig several holes and distribute their eggs. The genital opening from which they lay their eggs is right behind their head. Slugs and snails will not be able to lay their eggs in soil that is too heavy (such as clay), or too dry. Soil should be 20 - 40% organic material, and 65 to 80 degrees Farenheit (preferably 70 F). Soil moisture levels should be high, about 80% humidity.

Eggs are usually laid within weeks of mating, though some species can store sperm for up to a year (which means that sometimes if you receive or catch a slug it may already be gravid). It can take them a day or more to lay their eggs, and sometimes they take a break between laying, up to several weeks. Eggs hatch anywhere from 10 to 30 days after laying (varying by species, temperature and other factors).

Baby snails especially need a good source of calcium! They need it to grow their shells. They can grow very fast so slugs and snails need plenty of food and calcium in their youth.

Keep in mind many slug and snail species have absolutely tiny offspring, which can get out of the tiniest holes. Mesh as fine as fabric may be necessary to keep them in.

To prevent reproduction, finding and destroying eggs is the easiest choice.

Finally, it may be legal to keep slugs and snails but not breed them. Be sure to look up your local laws on the subject.

Buying Slugs

One of the most common questions I get asked, especially in the winter, is where one can purchase terrestrial slugs and snails. There is no easy way to do so.

Selling and buying most terrestrial slugs and snails is regulated by the government. In order to buy or sell them in many states, you must have a USDA permit. If you do wish to apply for such a permit (and succeed in getting one), you can then purchase the land slugs and snails specified in your application from biological supply companies such as Carolina Biological Supply or Niles Biological Supply.

Alternately, you may be interested in keeping aquatic snails. Some breed too readily and become pests, but others, like nerite, apple, and mystery snails, are quite manageable. Most have no regulations attached to their purchase or sale, and many can be acquired at a local pet shop. Mystery snails even come in a variety of colors. If you are interested in purchasing and keeping an aquatic snail, Applesnail.net has excellent information on caring for them.

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beccatraceyaut-blog · 6 years

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Acetone transfer and Indian ink. With this I wanted to explore the idea of leaves. To me, the idea of leaves is shape. I used line and shape as my elements. These conventions are seen throughout my artwork as leaf skeletons, leaf cells, and leaves themselves show these. Leaves interest me as they’re like a human, showing the cellular processes of MRSCGREN. Movement can be seen in leaves as they move towards sunlight in order to complete photosynthesis and for warmth. They also move towards water, nutrients, and safety via growth. Respiration is completed (H2O+CO2 -> 02+C6H12O6), water and carbon dioxide is converted through sunlight to create glucose (food) and oxygen. Plants are sensitive as they react and sense changes to their environment. They react by growing towards light and against gravity. Carnivorous plants react when touched by an insect.

All living organisms are made up of multiple cells, plants are called multicellular organisms. Plants grow via cell division, and some keep growing until there are not enough nutrients. Cell division is called mitosis. Mitosis happens in steps. These steps are called prophase, prometaphase, metaphase, anaphase, telephase, and cytokinesis. During prophase, chromosomes become dense and therefore visible. Spindle fibres come from the centrosomes of the chromosomes and move towards opposite poles. During prometaphase chromosomes continue to condense. Kinetochores appear at the centromeres and mitotic spindle microtubules attach to these. During metaphase chromosomes line up at the metaphase plate (equator of the cell).

Each sister chromatid is attached to a spindle fibre coming from opposite sides of the cell. During anaphase, centromeres split into two. Sister chromatids (now chromosomes) are pulled towards opposite sides of the cells. Certain spindle fibres begin to elongate the cell. During telophase chromosomes arrive at either end of the cell (poles) and de-condense. Nuclear envelope material surrounds each set of chromosomes. The mitotic spindle breaks down and the spindle fibres continue to push the poles apart. During cytokinesis, the last phase, in plant cells, a cell plate, the parent of a new cell wall separates the daughter cells. This now means that cells have divided and the plant can now grow taller towards sunlight.

During reproduction, all living organisms, specifically plants, make similar copies of themselves. Plants can reproduce asexually or sexually. Sexual reproduction requires another parent plant. This process needs meiosis which rearranges genes and reduces the number or chromosomes, it also needs fertilisation which restores the chromosome to a complete diploid number. In between these processes, all land plants go through alternation of generations with two different multicellular structures, a gametophyte and a sporophyte. The gametophyte is the plant that is haploid, containing a single set of chromosomes in each cell. The gametophyte produces male or female gametes or both through mitosis.

The fusion of male and female gametes (fertilisation) produces a diploid zygote, which develops by mitotic cell divisions into a multicellular sporophyte. The mature sporophyte produces spores by meiosis, sometimes referred to as "reduction division" because the chromosome pairs are separated once again to form single sets. In ferns, gymnosperms, and flowering plants (angiosperms), the gametophytes are relatively small and the sporophyte is much larger. In gymnosperms and flowering plants the mega gametophyte is contained within the ovule (that may develop into a seed) and the micro gametophyte is contained within a pollen grain.

Plants are immobile, and cannot hunt for sexual partners for reproduction. In the evolution of early plants, abiotic factors including water and wind, transported sperm for reproduction. It is believed that insects fed on pollen, and plants thus evolved to use insects to actively carry pollen from one plant to the next. Flowering plants are the dominant plant form on land and they reproduce by sexual and asexual means. Often their most distinguishing feature is their reproductive organs, called flowers. Sexual reproduction in flowering plants involves the production of male and female gametes, the transfer of the male gametes to the female ovules in a process called pollination. After pollination occurs, fertilisation happens and the ovules grow into seeds within a fruit. After the seeds are ready for dispersal, the fruit ripens and by various means the seeds are freed from the fruit and after varying amounts of time and under specific conditions the seeds germinate and grow into the next generation.

In plants that use insects or other animals to move pollen from one flower to the next, plants have developed greatly modified flower parts to attract pollinators and to facilitate the movement of pollen from one flower to the insect and from the insect back to the next flower. Flowers of wind pollinated plants tend to lack petals and or sepals; typically large amounts of pollen are produced and pollination often occurs early in the growing season before leaves can interfere with the dispersal of the pollen. Many trees and all grasses and sedges are wind pollinated, as such they have no need for large fancy flowers.

Reproduction in which male and female gametes do not fuse, as they do in sexual reproduction. Asexual reproduction may occur through budding, fragmentation, fission, spore formation and vegetative propagation. Plants have two main types of asexual reproduction in which new plants are produced that are genetically identical clones of the parent individual. Vegetative reproduction involves a vegetative piece of the original plant (budding, tillering, etc.) and is distinguished from apomixis, which is a replacement for sexual reproduction, and in some cases involves seeds. Apomixis in many plant species and also in some non-plant organisms.

The next in MRSCGREN is excretion. Excretion means to get ride of waste material created by nutrition. In plants, excretion happens when there’s an accumulation of waste material in leaves and excreted when leaves fall. Green plants produce carbon dioxide and water as respiratory products. In green plants, the carbon dioxide released during respiration gets utilised during photosynthesis. Oxygen is a by product generated during photosynthesis, and exits through stomata, root cell walls, and other routes. Plants can get rid of excess water by transpiration and guttation.

It has been shown that the leaf acts as an 'excretophore' and, in addition to being a primary organ of photosynthesis, is also used as a method of excreting toxic wastes via diffusion. Other waste materials that are exuded by some plants — resin, saps, latex, etc. are forced from the interior of the plant by hydrostatic pressures inside the plant and by absorptive forces of plant cells. These latter processes do not need added energy, they act passively. However, during the pre-abscission phase, the metabolic levels of a leaf are high. Plants also excrete some waste substances into the soil around them.

The last in MRSCGREN is nutrition. Plants need nutrition for energy and growth. In green plants, they make their food from CO2 and water via photosynthesis. Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organisms' activities. This chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesised from carbon dioxide and water – hence the name photosynthesis, from the Greek “light", and “putting together". In most cases, oxygen is also released as a waste product. Most plants perform photosynthesis and are called photoautotrophs. Photosynthesis is largely responsible for producing and maintaining the oxygen content of the Earth's atmosphere, and supplies all of the organic compounds and most of the energy necessary for life on Earth. Which is a vital component to other animals, specifically humans.

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violetcabin · 7 years

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Dandelion tea is good for circulation, vitamins and digestion. Make a delicate herbal tea with the flowers and a stronger, more pungent one with the leaves. Homemade wine can also be made from the flowers.

The name dandelion comes from the French word dent-de-lion, meaning “lion’s tooth.” In French they are called pissenlit – literally ‘bedpissers’, an homage to the plant’s diuretic properties.

Taraxacum is a large genus of flowering plants in the family Asteraceae, classification in the daisy family. Taraxacum species produce seeds asexually by apomixis, meaning the seeds can be produced without pollination. This is why dandelions are genetically identical to the parent plant.

#dandelion #original photography

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margdarsanme · 4 years

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NCERT Class 12 Biology Chapter 2 Sexual Reproduction in Flowering Plants

NCERT Class 12 Solutions for Biology Chapter 2 Sexual Reproduction in Flowering Plants

QUESTIONS FROM TEXTBOOK SOLVED

1. Name the parts of anangiosperm flower in which development of male and female gametophytes take place.Ans. Development of male gametophyte (micro- gametogenesis) occurs in pollen sac of anther up to 2 – celled stage. The female gametophyte develops (megagametogenesis) in the nucellus of ovule.

2. Differentiate between microsporogenesis and megasporogenesis. Which type of cell division occurs during these events? Name the structures formed at the end of these two events?Ans.Differences between microsporogenesis and megasporogenesis are as follows –

Each microspore mother cell and megaspore mother cell contain two sets of chromosomes and are therefore diploid. The diploid megaspore mother cell and microspore mother cell enlarges and undergo meiosis to produce, four haploid cells called megaspores and microspores respectively.The chromosome number is reduced by half and therefore megaspores and microspores are haploid.Microsporogenesis and megasporogenesis give rise to pollen grains and embryo sac respectively. Pollen grain is the male gametophyte and embryo sac represents the female gametophyte.

3. Arrange the following terms in- the correct developmental sequence : Pollen grain, sporogenous tissue, microspore tetrad, pollen mother cell, male gametes.Ans. Sporogenous tissue – pollen mother cell – microspore tetrad – pollen grains – male gametes.

4. With a neat, labelled diagram, describe the parts of a typical angiosperm ovule.Ans.A typical angiospermic ovule is a small structure which is formed in the ovary. Ovule first develops as a projection on the placenta and composed of multilayered cellular tissue called the nucellus. The hypodermal cell of die nucellus enlarges and transformed into megaspore mother cell. This cell undergoes meiosis to produce four haploid cells only one of which develops & forms embryo sac (female gametophyte). An ovule may be surrounded by one or two protective layers called integuments, leaving a small opening at one end termed as micropyle which acts as passage for the entry of the pollen tube into the ovule. Thus, a typical ovule consists of a fully developed embryo sac with the nucellus and integuments.

5. What is meant by monosporic development of female gametophyte?Ans. In many flowering plants, only one out of the four megaspores enlarges and develops into female gametophyte or embryo sac. The other three megaspores degenerate. This type of embryo sac formation is called as monosporic type of development.

6. With a neat diagram explain the 7-celled, 8- nucleate nature of the female gametophyte.Ans.Embryo sac (or female gametophyte) is formed by three successive mitotic divisions that take place in the nucleus of megaspore.The nucleus of the functional megaspore divides meiotically to form two nuclei which move to the opposite poles, forming the 2-nucleate embryo sac. Two more sequential mitotic nuclear divisions result in the formation of the 4-nucleate and later the 8-nucleate stages of the embryo sac. After the 8-nucleate stage, cell walls are laid down leading to the organisation of the typical female gametophyte or embryo sac. Six of the eight nuclei are grouped together at micropylar and chalazal end and form the egg apparatus and antipodals respectively. The large central cell left over with two polar nuclei. Thus, a typical female gametophyte consists of 7 cells with 8 nucleus.

7. What are chasmogamous flowers? Can cross-pollination occur in cleistogamous flowers? Give reasons for your answer.Ans. Chasmogamous flowers or open flowers in which anther and stigma are exposed for pollination. Cross-pollination cannot occur in cleistogamous flowers. These flowers remain closed thus causing only self-pollination. In cleistogamous flowers, anthers dehisce inside the closed flowers. So the pollen grains come in contact with stigma. Thus there is no chance of cross¬pollination, e.g., Oxalis, Viola.

8. Mention two strategies evolved to prevent self-pollination in flowers.Ans. Continued self-pollination decreases the vigour and vitality of a particular race. Thus, flowering plants have developed many devices to discourage self-pollination and to encourage cross-pollination.Dichogamy and self-sterility are.two most common devices that ensure cross-pollination. Dichogamy – Maturation of anther and stigma at different times in a bisexual flower prevent self-pollination.Self-sterility (or self-incompatibility) – Due to the presence of self-sterile gene in some flowers, pollen grains do not germinate on the stigma of that flowers. e.g.,- tobacco, potato.

9. What is self-incompatibility? Why does self-pollination not lead to seed formation in self-incompatible species?Ans. When the pollen grains of an anther do not germinate on the stigma of the same flower, then such a flower is called self-sterile or incompatible and such condition is known as self¬incompatibility or self-sterility.The transference of pollen grains shed from the anther to the stigma of the pistil is called pollination. This transference initiate the process of seed formation. Self-pollination is the transfer of pollen grain shed from the anther to stigma of pistil in the same flower. But in some flower self¬pollination does not lead to the formation of seed formation because of the presence of same sterile gene on pistil and pollen grain.

10. What is bagging technique? How is it useful in a plant breeding programme?Ans. It is the covering of emasculated flowers (removal of anthers in bud condition from a bisexual flower by a bag of butter paper or polythene in their bud condition i.e., before anthesis) to prevent contamination of its stigmas with unwanted pollens. When the stigmas of emasculated flowers mature the bags are removed, stigmas are dusted with pollen grains of desired male . plants by means of a presterilized brush and flowers are rebagged till fruit develop. This technique is mainly used in artificial hybridization. Plant breeders often use this technique to prevent the contamination of stigma of the flowers from unwanted pollen grains.

11. What b triple fusion? Where and how does it take place? Name the nuclei involved in triple fusion.Ans. Fusion of second male gamete with die two polar nuclei located in the central cell to form the triploid primary endosperm nucleus (PEN) is called triple fusion or vegetative fertilization. This process takes place in the embryo sac. After reaching the ovary, pollen tube enters into the embryo sac from the micropylar end. After penetration, the tip of the pollen tube ruptures releasing the two male gametes. The one male gamete fuses with the egg to form the diploid zygote. This process is called syngamy and the other male gamete fuses with the two polar nuclei to form the triploid primary endosperm & this process is known as triple fusion. These two events of fertilization constitute the process of double fertilization.

12. Why do you think the zygote is dormant for sometime in a fertiUsed ovule?Ans. The zygote after a period of rest develops into embryo. Most zygotes remain dormant till certain amount of endosperm forms. They do so, to provide assured nutrition to the developing embryo.

13. Differentiate between:(a)hy pocotyl and epicotyl;(b)coleoptile and coleorrhiza;(c)integument and testa;(d)perisperm and pericarp.Ans:

14. Why is apple called a false fruit? Which Part(s) of the flower forms the fruit?Ans. Botanically ripened ovary is called a true fruit. The fruits in which thalamus and other floral parts develop along with the ovary are called false fruits. For example – apple, strawberry, cashew etc. In apple the main edible portion of the fruit is the fleshy thalamus. Ovary forms the fruit after fertilization or without fertilization in parthenocarpic fruits.

15. What is meant by emasculation? When and why does a plant breeder employ this technique?Ans. Emasculation is the removal of stamens mainly the anthers from the flower buds before their dehiscence. This is mainly done to avoid self-pollination. Emasculation is one of the measures in the artificial hybridization. Plant breeders employed this technique to prevent the pollination within same flower or to pollinate stigmas with pollens of desired variety.

16. If one can induce parthenocarpy through the application of growth substances, which fruits would you select to induce parthenocarpy and why?Ans. Parthenocarpic fruits are seedless. They develop from ovary without fertilization. Banana, grapes, oranges, Pineapple, Guava, Watermelon, lemon are selected because these seedless of units are of high economic importance. The fruits in which seeds or seed part form edible portion (e.g.,Pomegranate) are not selected to induce parthenocarpy.

17. Explain the role of tapetum in the formation of pollen-grain wall.Ans. Tapetum is the innermost layer of the microsporangium. The tapetal cells are multinucleated and polyploid. They nourish the developing pollen grains. These cells contain ubisch bodies that help in the ornamentation of the microspores or pollen grains walls. The outer layer of the pollen grain is called exine and is made up of the sporopollenin secreted by the ubisch bodies of the tapetal cells. This compound provides spiny appearance to the exine of the pollen grains.

18. What is apomixis and what is its importance?Ans. Apomixis is a mode of asexual reproduction that produces seeds without fertilization, e.g.- some species of Asteraceae and Grasses. This method is important in hybrid seed industry. Hybrids are extensively cultivated for increasing productivity. But the main drawback is that the hybrid seeds are to be produce every year because the seeds of the hybrid plants da not maintain hybrid characters for longer period due to segregation of characters. This can be avoided if apomixis can be introduced in hybrid seeds. For this reason scientists are trying hard to identify genes for apomixis.

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maharamiko · 7 years

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Dendalion. Randa Tapak atau Dandelion adalah bagian dari Taraxacum, sebuah genus besar dalam keluarga Asteraceae. Nama Randa Tapak sendiri biasa digunakan untuk merujuk kepada sebuah tumbuhan yang memiliki "bunga" yang memiliki "bunga-bunga" kecil yang terbang ditiup angin. Asal asli dari tumbuhan ini adalah Eropa dan Asia, namun sudah menyebar ke segala tempat. Yang disebut sebagai bunga dari tumbuhan ini menjadi semacam jam hayati yang secara teratur melepaskan banyak bijinya. Biji-biji ini sesungguhnya adalah buahnya. Taraxacum (/təˈræksəkʊm/) is a large genus of flowering plants in the family Asteraceae which consists of species commonly known as dandelion. They are native to Eurasia and North America, but the two commonplace species worldwide, T. officinale and T. erythrospermum, were introduced from Europe and now propagate as wildflowers.[2] Both species are edible in their entirety.[3] The common name dandelion (/ˈdændɪlaɪ.ən/ DAN-di-ly-ən, from French dent-de-lion, meaning "lion's tooth") is given to members of the genus. Like other members of the Asteraceae family, they have very small flowers collected together into a composite flower head. Each single flower in a head is called a floret. Many Taraxacum species produce seeds asexually by apomixis, where the seeds are produced without pollination, resulting in offspring that are genetically identical to the parent plant. https://en.m.wikipedia.org/wiki/Taraxacum #nature #naturephotography #flora #park #gardens #garden #plants #greenlife #green #flower #flowers #instagood #instaart #macro_secrets #macro #macro_holic #indonesia_photography #indonesia_greatshots #colors #wind #fly #white #macrophotography #macro_highlight #instanusantara #instagram @macrophotoawards_com @macro_highlight @macro.indonesia @nusa_macro @macro_holic @macro_secrets @color_macro_world @macroan

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margdarsanme · 4 years

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NCERT Class 12 Biology Chapter 2 Sexual Reproduction in Flowering Plants

NCERT Class 12 Solutions for Biology Chapter 2 Sexual Reproduction in Flowering Plants

QUESTIONS FROM TEXTBOOK SOLVED

13. Differentiate between:(a)hy pocotyl and epicotyl;(b)coleoptile and coleorrhiza;(c)integument and testa;(d)perisperm and pericarp.Ans:

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