#tomoyasu / interactions.

[plaguecest]

skeptic mha is a laptop / computer objectum. send post

[goodheartt]

tag drop pt. 9

[drujiko]

𝗠𝗲𝗲𝘁 𝘁𝗵𝗲 𝗔𝗱𝗺𝗶𝗻

✨// Howdy, this account is ran by Jester! A majority of what I post will be canon compliant, but I'll be filling in some information with my own headcanons. Admin is an adult!

𝗥𝘂𝗹𝗲𝘀 𝗮𝗻𝗱 𝗚𝘂𝗶𝗱𝗲𝗹𝗶𝗻𝗲𝘀

For a majority of my rules, please see the list posted by @marbled-magician! If you're wanting to interact with the doctor, I ask that you read over these and the ones I have added below.

While Ujiko is a controversial character within the show, the admin does not condone or approve of his actions. Harassments or death threats will not be tolerated and will result in a block.

Please don't vent in the asks. I understand that it's easy to do with a fictional character, but there is a real human behind the screen.

This blog will, for the most part, be pg-13. References to Nomus, Nomu creations, death, etc. will be used. Canon back stories such as Tomura Shigaraki's and All For One's will be referenced. This account is not spoiler free.

He'll be interacting with villains, ocs, and heroes. However, his responses will be in character! So he may be uninterested, mean, or backhanded depending on what has been said. If you want to plot something out, message me!

𝗖𝗼𝗻𝗻𝗲𝗰𝘁𝗶𝗼𝗻𝘀 𝗨𝗻𝗱𝗲𝗿 𝗖𝘂𝘁

𝗔𝗹𝗹 𝗙𝗼𝗿 𝗢𝗻𝗲

𝗟𝗲𝗮𝗴𝘂𝗲 𝗼𝗳 𝗩𝗶𝗹𝗹𝗮𝗶𝗻𝘀/𝗣𝗮𝗿𝗮𝗻𝗼𝗿𝗺𝗮𝗹 𝗟𝗶𝗯𝗲𝗿𝗮𝘁𝗶𝗼𝗻 𝗙𝗿𝗼𝗻𝘁

Tomura Shigaraki - @dusty-handyman

Himiko Toga - @little-sis-toga

Kurogiri - @mistdad

Touya Todoroki (Dabi) - @endeavorsbiggesthater

Atushiro Sako (Mr. Compress) - @marbled-magician

Shuichi Iguchi (Spinner) - @spinner-the-gecko

Jin Bubaigawara (Twice) - @duality-in-spandex

Kenji Hikiishi (Magne) - @magnetic-sister

Mustard - @must4rdmha

Goto Imasuj (Muscular) - @bl00dymerder

Lady Nagant - @the-lovely-lady-nagant

Kagero Okuta (Giran) -

𝗦𝗵𝗶𝗲 𝗛𝗮𝘀𝘀𝗮𝗶𝗸𝗮𝗶

Kai Chisaki (Overhaul) - @kaichisaki-rp

Hari Kurono (Chronostasis) - @kurono-stasis

Shin Nemoto - @shinnemoto-rp

𝗠𝗲𝘁𝗮 𝗟𝗶𝗯𝗲𝗿𝗮𝘁𝗶𝗼𝗻 𝗔𝗿𝗺𝘆

Rikiya Yotsubashi (Re-Destro) - @theliberat0r

Geten - @geten-iceman

Koku Hanabata (Trumpet) - @inciting-trumpet

Chitose Kizuki (Curious) - @yourcur1ousrep0rt3r

Tomoyasu Chikazoku (Skeptic) - @skeptic-inc

𝗣𝗿𝗼-𝗵𝗲𝗿𝗼𝗲𝘀

𝗢𝗿𝗶𝗴𝗶𝗻𝗮𝗹 𝗖𝗵𝗮𝗿𝗮𝗰𝘁𝗲𝗿𝘀

Getaway - @just-getaway

Kageno - @kagenoakirp

Yumiko - @yumikoshigarakirp

Static - @static-volt

Carmine & Rockstar - @teamdesertflower

Morrigan Taggart - @nightshcderp

[byjovewhataspend]

alr so like what's ur headcannons on skeptic/tomoyasu like ships things he likes don't like I'm just curious lol

if i like a character ill ship him with almost everyone So tomoyasu/anyone-you-can-think-of-an-excuse-to-put-him-nearby

Faves: Deku -- they are very similiar people-- screaming obsessive stalkers that care very much about other people (in their own way) and are inspired to violence (in their own way) because of that. + i feel like the PLF would have a high likelihood to recognize and acknowledge how the lack of bodily autonomy granted in a hero-based society greatly harms quirkless people. i have a whole headcanon about young skeptic using his unusually overpowered quirk to protect kids that got bullied, which was PRIMARILY heteromorph/mutant types but probably also included like the 1or 2 quirkless kids in his school. i like to imagine a scenario either of 'they went to school together' or 'deku never got OFA and so ended up getting picked up by the Meta Liberaton Army (pre-LoV) and them either helping/sponsoring him to become the first quirkless hero (because it helps their narrative) OR a non-of-that-happened au where he graduates highschool and joins and quickly becomes skeps right-hand-arm, his confidant, his silly rabbit (They just both rant at eachother nonstop and neither ever gets tired of listening to the other even though it sounds liek arguing. they both stalk eachother to show affection)

(also like, dont kid yourself, if izuku hadnt been able to be a hero he wouldve turned to doling out justice on his own somehow. Viglante, sure, but also totally susceptible to a group that trains people in secret to defend themselves and others in an unfair system)

These below are set in FangusFungs au about a Swamp Creature skep. my first thought was 'deku would get involved in that'

Tokoyami-- i like to imagine a post-series situation where Pro Hero Tokoyami sees and recognizes Tomoyasu, who was previously a HIGHLY visible GOTH individual in the public eye that was outspoken about heteromorph rights. hard to imagine young tokoyami not admiring him, at least distantly, so meeting up with him again as an adult would change things a lot. i could see them getting together <3 it would be really cute

HANABATA: obviously. come one. goth dilf powercouple. theyve known eachother for ages and are fully on the same side. the smooth-talking trumpet with his charm and handsome face versus skeptic whos so angry about the coffee machine being on the fritz that hes popping a vein in his forehead. whats not to love here?

Shigaraki: come on... like obviously

(featured below, my PR MANAGER SKEP au. basically when the league defeated the MLA and became the PLF they decided to turn their substantial political power onto the idea of rehavilitating their image and making them figureheads! managed to get skeptic off for his crimes andturning people to their cause and to their side)

also Dabi, since they are (COUGH) basically the only ones to interact... but this is the only art i have for that

aaaand present mic! they look alike and both have loud self-aggrandizing annoying personalities, are both alt-fashion guys with long hair, and they both scream a lot. theyd either get along SO WELL or theyd hate eachother (i cant show you the art ive made for this, its all porn)

as far as my personal headcanons (the ones above notwithstanding... i think hes technically a mutant! but hes the TYPE of mutant where its minimal enough that in almost any room he will never be the MOST visibly mutated. he has spent his life Very Aware that the only reason he isnt discriminated against is because other people are discriminated against HARDER. that if every super-visibly mutated person on the world disappeared (like the CRC group wants) then the focus would go to people with tails, then people with animal ears, and then people like him. He has known he was just Lucky since he was 5 and he never forgot that, and thats why as a grown adult (in his.. what? 30s? 40s? i like him to be about 37-42 in canon but if you told me he was 26 id believe you) he would still have such strong opinions and focus specifically on people with visible mutations and the struggles they have

like.. whether the MLA/PLF went about their dreams for liberation the right way (no) you can't deny that they DID care! i also headcanon that if the whole LOV thing hadn't happened they never wouldve started this war, that they had a 60+ year plan they were only 15 years into tops that was focused on changing laws and changing the media narratives first and foremost. so in any 'the league didnt happen' au you can easily say they were working above-board (though personally i think they were all the types to still be murdering and making up blackmail stuff for political opponents AND/OR known mutant-haters)

[saiibeo]

FEEL / @uncxntrxllable 'damn.' questions for muses status: accepting ! !

how does your character react to a persons touch? a random stranger’s? a loved one’s? a friend’s?

ooooo okay so I really love this one a whole lot. i was babbling about this to a friend not long ago, but corvus has a big thing about touch in their language. they don't like being touched by strangers. that's a whole set of trust issues that has so much i couldn't unpack here. with strangers they can range from being playful, friendly, and seemingly upbeat to being cold, merciless, and downright being a bitch. but regardless of that, either way, they never let anyone they don't know touch them. it's something only people they grow to genuinely trust can do.

i'm gonna take this as not only reacting because there isn't much to say on that note, but i'm also adding in the way they are about touching other people.

now i will say there are instances of acquaintances being allowed to touch them, especially being on the same 'team' as someone so to speak. a good example of that being in a recent thread tomoyasu(skepticxsm) in their villain verse. being merely poked in the forehead, they had no negative reaction. when a stranger does touch them though they can become incredibly hostile if not having already dodged the touch out of sheer reflex. they do tend to go easier on those who touch out of habit because they understand it's not always done with any intention and sometimes people do it mindlessly. that hostility is a hell of a lot worse if they don't like someone though and they absolutely will make sure it's known.

now, when corvus trusts someone they do an entire 180. in their attitude and in the way that their touch differs and how it's incorporated in the way they communicate. if someone is a friend to them, they will go from not even letting their shoulder brush theirs to actually doing it on purpose either playfully or a 'hey i'm here'. they will often put their hand on the others shoulder while trying to get by them, poke at them randomly in passing, or even quickly give a gently squeeze to their bicep as an act of affection. it's a lot of things they don't even notice doing. they feel rather elated when someone they trust proceeds to do the same as they also see it as a worldless 'i trust you'.

for loved ones it depends on the type. familial, if we take their twin brother crane for example(in verse where they actually can interact with him of course), they're always doing things like throwing their arm around him, ruffling his hair, swift kisses to the cheek after annoying him. in general they're much more comfortable and even when he's agitated with them they have so much trust put into the fact that he would never hurt them that they aren't afraid to even give affection when he's in that state (minus if he tells them not to, in which case of course they respect that). their affection tends to be more than what friends get for those they feel familial connections to. i'd say basil(prismpowa) is a good example of this because he's one of their best friends. they feel that type of familial connection to basil and very easily they give him affection like random platonic kisses, hugs, and in terms even cuddling this poor guy like they're a koala.

for lovers it can actually look a lot different once they're used to it. i think at first romantic affection would make them feel strange because I can confidentially say that corvus has never had a serious romantic relationship in any of their verses for a variety of reasons, so it takes time for them to get used to the steadiness of being with someone and that includes being touched more differently than what they're used to. however, once they are used to it they revel in any chance they get to have affection from the other and proceed to do the same mindless touching they do with everyone else they trust. basically once that trust is gained they'll always say 'i'm here' or 'i love you' without even realizing it. and i think that's odd, but it's one of my favorite things about them. someone who seems like they'd break a hand before allowing someone to even poke them having one of their love languages be physical.

[evoldir]

Fwd: Graduate Position: MiamiU.EcolEvolution

Begin forwarded message: > From: evoldir@evol.biology.mcmaster.ca > Subject: Graduate Position: MiamiU.EcolEvolution > Date: 2 October 2024 at 07:46:21 BST > To: rdmpage@gmail.com > > > The Department of Biology at Miami University is seeking to recruit > students for our Master’s and PhD programs. > > https://ift.tt/FLujsSP > > We have a strong core group of faculty working in ecology and evolution > creating a great community for our students, supported by modern facilities > in microscopy, genomics, and a research field station in Oxford Ohio. > Additional facilities for ecological and botanical research include the > Herbarium in Oxford and The Conservatory at the nearby Hamilton campus. Our > departmental program covers all levels of organization within biology. > > The Department provides guaranteed support through teaching assistantships > (which include tuition waivers), as well as through faculty research grants > when available. Miami is located in Oxford Ohio, a college town with ample > outdoor opportunities and a vibrant downtown. Miami currently enrolls > approximately 2,300 graduate students and 20,500 undergraduates. > > > > Faculty with interests in ecology and evolution that are actively > recruiting students are below. We encourage prospective students to email > potential mentors before applying > > Dean Castillo - Evolutionary genetics of reproduction, mating behaviors, > and speciation. https://ift.tt/UlWOPrs ( > castild@miamioh.edu) > > Deidra Jacobsen - Ecology and evolution of plant-insect interactions > > (jacobsd8@miamioh.edu) > > Lesley Knoll - Freshwater ecology; aquatic ecosystem function (e.g., > anoxia, nutrient fluxes) and structure (e.g., phytoplankton composition, > toxic cyanobacteria) responses to environmental change (knolllb@miamioh.edu) > > Richard Moore - Evolution of plant sexual reproduction; plant conservation > genetics > > (moorerc@miamioh.edu) > > Yoshi Tomoyasu- developmental and evolution of insect wings > > https://ift.tt/udAeO0n (tomoyay@miamioh.edu) > > Zheng Li - genome evolution with impacts on phenotype evolution and > biodiversity > > (liz7@miamioh.edu) > > "Castillo, Dean"

[dabihaul666]

chikazoku “emily the strange lookin ass” tomoyasu

[villain-sympathizer]

Hi! Can you possibly do something for Redestro & skeptic with a shy SO?

Fluff/smut. Go wild. 🥹

HELL YES i can anon 💕💕💕

i'll stick to fluff for now since i have more content ideas for that!

────── ･ ｡ﾟ: *.☽ .* : ｡ﾟ･ ──────

[Contents: Mentions of social anxiety; Skeptic being a meanie butt at first but he becomes a softie]

»»—— ReDestro + Skeptic with a shy S/O ——««

He's so patient, despite what people would think considering his Quirk. He can never hide his irritation because his stress markings would give him away, regardless if he's still smiling and light hearted.

However, with his S/O, you'll never see his markings grow, even if they're purposefully trying to make him mad. Why? Because he loves them! I absolutely see one of his main love languages being acts of service, so no matter the task, it never bothers him.

If their shyness gets in the way of doing tasks, such as making a phone call or approaching someone for directions, he'll do it without hesitation. Eventually he'll start to do these things automatically, as if it were instinct.

If his S/O ever thinks of themself as a burden for needing so much help on basic social interactions, he'll remind them that he's absolutely more than willing and happy to do these things. Why? Because it's for them. The entire dynamic between them is basically just that quote from Euripedes by Anne Carson:

"Pylades: I'll take care of you. Orestes: It's rotten work. Pylades: Not to me. Not if it's you."

You bet your ass if anyone makes fun of his S/O's shyness, or does that bullshit 'Speak up, quit being shy/quiet', Rikiya is shutting them tf down in the most passive-aggressive business-like style. ESPECIALLY if it's a business partner, because I know damn well Rikiya is the kind of guy to bring his S/O everywhere. Hell, if it was rude enough, he would just drop ties with that person right then and there, all with a sweet little smile on his face.

Is willing to work with them to help improve their shyness! If they want, that is. Coming from my experience with social anxiety, it's insanely fuckin' tough to work through that, but it always helps to have people I'm comfortable with to be there with me incase I mess up. And that's exactly the role Rikiya will happily play if they want.

Absolutely will give quiet claps and praise whenever they accomplish something on their own. He's their personal cheerleader and will never stop being a personal cheerleader.

────── ･ ｡ﾟ: *.☽ .* : ｡ﾟ･ ──────

Okay, it's obvious that Tomoyasu is totally the type of person to get fed up with people who are shy. The pauses, the stuttering, the rambling, the mumbling - they're all likely his biggest pet peeves.

However, that viewpoint changes the moment he finds himself attached to someone.

When he first met his S/O, he likely acted like how most assholes would with someone who was shy: "What? Speak up and cease your mumbling, you measly worm, I haven't got all day." Or "For the love of Destro, will you just get to the point already? And quit your stuttering, it's embarrassing."

But all that starts to change, slowly but surely, when he comes to like that person. Now it's: "Sorry, what was that? I was distracted." (He was not, but it likely makes them feel less guilty), "Louder please, [Name]." and "I'm not going to bite, [Name]. Now just tell me what it is you need to say."

It was shocking to the rest of the PLF, to say the least, to see Tomo grow kinder to someone. That was the obvious sign that he had some sort of feelings for them, because Tomo never changes, especially not for someone else.

One he and his S/O are together, it's an absolutely drastic change. While his words went from downright mean, to a little rude but considerate, now suddenly morphed to being completely soft and understanding towards them. It gave his subordinates whiplash from how his demeanor would instantly change the moment his S/O was involved.

"If I see even ONE more mistake from any of you brain-dead troglodytes, I'll be sure this weeks paycheck runs you into the fucking GROUND- Oh, hello dear, I'm glad to see you." Followed by a kiss to their head, and absolutely floored looks from his workers.

And like ReDestro, he'll go off on anyone who makes fun of his S/O's shyness, going absolutely feral with rage sometimes.

There was a time where Dabi was poking fun at them, saying how they'd be more enjoyable to be around if they were bolder and less quiet, and clearly making them uncomfortable and upset.

Oh, Tomo had an absolute fit when he walked in to that. He needed to be physically restrained by ReDestro's quirk, yelling and spitting like a rabid cat at the burnt man, who honestly seemed pretty unnerved at the raw power Tomo can channel when he wants to. It wasn't until his S/O stood between them that he even begun to calm down.

After that, no one attempted to make even a lighthearted joke about them, not even when neither of them were in the room. Tomo has cameras and mics everywhere, after all.

[tonberry-yoda]

That Stupid Party - Tomoyasu Chikazoku (Skeptic)

Pairing - Tomoyasu Chikazoku (Skeptic) x f!reader

Warnings - none! just tomoyasu being extra hot lmao

Word Count - 792

Notes - this is one of my older writings and I wanted to post it here because I am a super big fan of it! Also, the first paragraph is in all italics, meaning that it takes place in the past. Enjoy!

“Tomoyasu, you wanna play?!” Tomoyasu gripped onto his cup and took a step back. “Oh… no thanks. I'm not really one to play… games like that.” “Come on, man!! We’re in college! Live a little before you become a boring adult!” “I-I'm okay. Thanks though.” “What? Never had your first kiss before? Spin the bottle is a perfect opportunity.” “I said I'm okay. I'm going to grab another drink.” He walked past another guy who wasn't playing and the entire circle was booing him, but there was nothing that was going to change his mind. Tomoyasu walked into the garage to dig around in the fridge for something to drink, but found a girl sitting on a bean bag, playing a guitar. They made direct eye contact and she smiled softly before getting back to playing. “You uh…” Tomoyasu grabbed another drink and turned around. “Wanna drink?” “I'm okay. Thanks though. What are they doing out there?” “Playing spin the bottle.” “Ugh. Gross.” “Tell me about it.” Tomoyasu slumped next to her and opted for a soda. “So, why are you here?” He turned to her, watching her hands strum the guitar. “My boyfriend lives here. He’s the one who hosted the party.” Tomoyasu hummed in response and turned back, laying his head on the couch behind him. “He's probably the only guy not playing spin the bottle.” “The blonde one?” “Yeah, that’s him.” “Doesn't he play football or something?” “Yeah. Pretty gross, right?” “I mean, I don't particularly like football, so yes.” “Tell me about it. If I have to go to one more game, I might throw up.” Tomoyasu giggled and clutched onto his soda, looking around the garage covered in fun decorations and a giant poster of All Might next to an All Might body pillow. “Is your boyfriend a fan of All Might?” She laughed out loud and ran up, hanging the guitar back where she found it and grabbed the pillow. “You see, this is my boyfriend’s house, but the garage is my little area, so this pillow is mine.” Tomoyasu laughed and caught the pillow when she threw it at him. “Where did you even get this?” “A friend gifted it to me. She still won't tell me where she bought it.” He threw it back and had a big smile on his face. “So, you a friend of my boyfriend?” “No, not really. I'm friends with someone who does know him, but I've never really interacted with him. He seems a little douchey. No offense.” “None taken. He's really one for hating on nerds. No offense.” “Oh, I don't find offense to being called a nerd. So… why is he dating you?” “I'm sorry?” He pointed down at her water bottle and her face went red. It was covered in video game stickers and underneath it was a folder full of her writing. “Uh… I don't really know actually.” She laid her head on the back of the beanbag and stared at the fairy lights on the ceiling. “Sounds to me that you don't really like him.” “I mean… I don't know. He's sweet, but he's definitely not the one, you know? I don't think we’re ever going to get married.” “Gotcha. Are you looking for the one?” “Mhm. It's my life goal.” She looked over at Tomoyasu, feeling her cheeks get warmer. “What about you?” “I don't really know yet. I'm a 5 at best, I don't really think there’s a girl looking for a 5.” “I think there’s a few. And you’re not a 5. You’re an 8 ½, 9 if you grow your hair out, 10 if you wore a turtleneck.”

“T-Tomoyasu, let me mmf-” He pressed his lips to hers again, nearly knocking her down the stairs. He pinned her against the wall and pulled away with a soft smile. “Let you what?” She put her hands on his chest and smiled back. “Tomo, let's get up the stairs first, okay?” He pouted and she locked her hands onto his turtleneck with a devilish smile. She pulled him up the stairs and he immediately pressed his lips to hers, leading them back to their room. He pulled away with a smack and cupped her cheek. “You still think you’re a 5, Tomo?” “A 6. At the most. You on the other hand, darling, you’re a 12.” “Oh, shut up, neither of those are-” He pulled her closer and kissed her bottom lip. “I'm so glad I found you at that stupid party.” Her eyes were shiny and he pulled her face closer before hugging her. He was so glad that his first kiss was at that party. And he was so glad it wasn't from that game of spin the bottle.

[tmoyasu-a]

please like and reblog if you’re interested in interacting with an unaffiliated tomoyasu chizakou (skeptic) from my hero academia! i’ll check you out and give a follow if i think we could write well together!

[s-kepsis]

                     LIKE // REBLOG                to interact with a brand new       CHIKAZOKU “SKEPTIC” TOMOYASU                        manipulated by                                 PIP

[tomochikazoku]

"THANKS, I EAT CHEESE" I'M- AHAHAHAHAHAHAHA

Damn.

Tomoyasu needed to get his head together. This was miserably embarrassing. During normal interactions, he was confident and taking charge. When it came to gracious comments that leaned dangerously close to flirting, he was at a loss. It was almost as if his brain would dump every social experience he had out the window and go on overdrive.

[saiibeo]

✏️

send in ✏️ and I’ll use this (improved) incorrect quote generator featuring both our muses! / @skepticxsm status: accepting ! !

Corvus: Can you pass the salt? Tomoyasu: Can you pass away? Corvus: Too much salt.

bonus because of them interacting with both in their villain verse:

Nia & Corvus:*Playing video games* Tomoyasu: You guys woke up at 5:30 in the morning just to play games? Nia: *silence* Corvus: *silence* Tomoyasu, finally figuring it out: ...You two never went to sleep, did you? Nia & Corvus in shame: Yeah...

[emmagreen1220-blog]

New Post has been published on Biology Dictionary

New Post has been published on https://biologydictionary.net/common-descent/

Common Descent

Common Descent Definition

Common descent is a term within evolutionary biology which refers to the common ancestry of a particular group of organisms. The process of common decent involves the formation of new species from an ancestral population. When a recent common ancestor is shared between two organisms, they are said to be closely related. In contrast, common descent can also be traced back to a universal common ancestor of all living organisms using molecular genetic methods. Such evolution from a universal common ancestor is thought to have involved several speciation events as a result of natural selection and other processes, such as geographical separation.

Theory of Common Descent

The theory of common descent states that all living organisms are descendants of a single ancestor. Thus, the Theory of Common Descent helps to explain why species living in different geographical regions exhibit different traits, some traits are highly conserved among broad animal classifications (e.g., vertebrates or tetrapods), seemly different species (e.g., birds and reptiles) share inherited physical and genetic traits, and successfully adapted organisms typically produce more offspring. While the Theory of Common Descent is primarily derived from the physical observation of various phenotypes (e.g., size, colour, beak shape, embryological development, etc.), modern advances in genetics and associated molecular techniques have been able to demonstrate that the process by which DNA is eventually translated into proteins is maintained among all lifeforms. Small changes in DNA between organisms have revealed a shared ancestry as well as insight into important changes that resulted in various speciation events. Phylogenetic trees and cladograms are often used to hypothesize the evolution of various organisms and shared common descent.

Examples of Common Descent

Human Chromosome 2

Compelling evidence of the shared common ancestry of humans with the great apes is the fusion event which occurred when two chromosomes common in apes fused to form chromosome 2 in humans (as illustrated below). This resulted in humans having only 23 pairs of chromosomes, while all other hominidae have 24 pairs. The great apes (e.g., chimpanzees, gorillas, and orangutans) have two chromosomes with almost identical DNA sequences as that found in chromosome 2 of humans. Further evidence of such a fusion event is the residual presence of telomeres and a centromere, which indicate that the genetic information was historically found on two separate chromosomes.

Endogenous Retroviruses

Endogenous retroviruses are residual DNA sequences found in the genomes of virtually all living organisms as a result of ancient viral infections. Since the retroviral sequences are incorporated into the DNA of the host organism, such sequences are inherited in the offspring. Since such infections are random events, as is the location in which the viral genome is inserted within the genome, the identification of the same retroviral sequences in multiple species is indicative of a shared ancestry. Such analyses of endogenous retroviruses often reveal speciation events (e.g., feline endogenous retroviruses reveal the separation between large and small cat species) and how closely related two species may be, as observed in the shared endogenous retroviruses between humans and other primate species.

The Presence of Atavisms

Atavisms are the appearance of a lost trait observed in an ancestral species that is not observed in more recent ancestors. Atavisms are an example of common descent as they provide evidence of the phenotypical or vestigial features that are often retained throughout evolution. Some examples, include the appearance of hind limbs in whales as evidence of a terrestrial ancestor, teeth exhibited by chickens, additional toes observed in modern horse species, and the back flippers of bottlenose dolphins. Atavisms tend to arise because the ancestral genes are not deleted from the genome, but rather silenced and then reactivated in later offspring.

Vestigial Structures

Similar to atavisms, vestigial structures are structures that are homologous to those found in ancestral species, but have become underdeveloped, non-functional, or degenerated in more recently evolved organisms. Such structures provide evidence of adaptations to a new environment, in which the ancestral organ or limb is no longer required, or has been modified to better suit a new purpose. There are an abundance of examples of vestigial structures observed in nature. Some examples include, the hind limbs and pelvic girdle observed in whales (as shown below) and snakes, non-functional wings exhibited by some insect species, non-functional wings of flightless bird species (e.g., ostriches), abdominal segments of barnacles, and the embryonic limb buds exhibited by several species lacking hind limbs (e.g., dolphins).

Pentadactyl Limbs

The presence of pentadactyl limbs is an example of a homologous trait exhibited by all tetrapods and is highly conserved throughout evolution, despite some modifications. Such limbs are first observed in the evolution from fishes to amphibians and consists of a single proximal, two distal, carpal, five metacarpal, and phalange bones. Although the overarching structure of the pentadactyl limbs is similar, various modifications have been made throughout evolution as adaptations to specific environments or lifestyles. Some examples include the modified pentadactyl wings of bats, the elongated forearms of primate species, the flippers of dolphin and whale species, and the modified digits of horses to form a hoof.

Fossil Evidence

The fossilized remains of various organisms combined with modern dating methods provides some of the most convincing evidence of common descent and evolutionary history. Fossilization occurs when the bones of a decaying animal become porous and the mineral salts in the surrounding earth infiltrate the bones, converting them to stone. Other methods include preservation in ice, imprinted remains (e.g., plants or footprints), tree resin, and peat. Since fossils are found in sedimentary rock, which is formed by layers of silt and mud, each layer corresponds to a specific geological period which can be dated. Thus, the extinction, evolution, and emergence of various species can be observed throughout history using the fossil record. Many extinct species are also observed in the fossil record, such as dinosaurs.

Biogeography

Biogeography presents compelling evidence of common descent by showcasing speciation and novel traits through adaptations to environmental pressures. One of the most famous examples is that of island biogeography and Charles Darwin’s observations of the beaks of finches residing on the Galapagos Islands. In these finches, the beaks had been adapted for the specific vegetation found on the island, resulting in deviation from the ancestral finches found on the mainland. Long term effects of geographical separation are also observed with the evolution of new species that are not found elsewhere in the world. An example of this is the presence of marsupial species on the continent of Australia, and the emergence of polar bears as a result of geographical isolation in the arctic.

Quiz

1. The presence of a tail during the early stages of human embryological development is an example of: A. Sequence homology B. Biogeography C. Activation of chromosome 2 D. Vestigial structure

Answer to Question #1

D is correct. Vestigial structures are features that remain from an ancestral form, but have subsequently lost a function or have an adapted function throughout evolution.

2. Recently, a bottlenose dolphin with four fins (two in the front and two in the back rather than only two in the front) was identified. This is an example of: A. Convergent evolution B. Pentadactyl limbs C. Activation of chromosome 2 D. An atavism

Answer to Question #2

D is correct. Atavisms are the appearance of an ancestral feature in an organism that are not present in more recent ancestors. This results from the conservation of genes for such features that become re-activated.

References

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