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Crabs evolved at least five times from separate groups of crustaceans (2021)

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101–110 of 138 posts

Re: Crabs evolved at least five times from separate groups of crustaceans (2021)

#101
Feet: our ancestors had hands at the end of their legs, yet some non-primate have feet that have similarities with ours.

https://en.m.wikipedia.org/wiki/Comparative_foot_morphology

> The paw of the dog, the hoof of the horse, the manus (forefoot) and pes (hindfoot) of the elephant, and the foot of the human all share some common features of structure, organization and function.

Re: Crabs evolved at least five times from separate groups of crustaceans (2021)

#102
post #80

Earlier quoted context omitted.

I wasn't aware of that some time ago, it's a fascinating insight. I got a lightbulb (going wtf/dark actually!) when watching cartoon or something with triceratops. They looked so much like rhinos. But had eggs. I had trouble reconciling it with evolution. They were so far ancestor-wise but so close physically-looking wise. Convergent evolution is very interesting. It suggests aliens may not be that different from us…

My understanding is that eggs and no-eggs are not as different as might be expected. After all, the no-eggs still have eggs but, just, don't lay the eggs or let us make French toast, custards, or omelets! Maybe a key issue would be the amazing placenta. But maybe the egg animals are not so far from having a placenta because they still DO have to be willing to accept the male sperm without killing it, and part of what…

Hookup culture and milt are probably not a match waiting to be made in (seven minute underwater) heaven.

Re: Crabs evolved at least five times from separate groups of crustaceans (2021)

#104
post #90

Earlier quoted context omitted.

If the habitat was the bottleneck, we could learn about a convergence point that tells us about possible non-Earth life. "Whatever the advantages are, they do not apply in all habitats because some groups have also lost carcinization; one modern example being the frog crab."

Fun fact: life has terraformed the Earth (pun fully intended) into what it is today: - Photosynthesis created and maintains the current composition of the athmosphere. By removing too much CO2, it likely also contributed to several ice ages. - Early life sequestered almost all the iron in the primordial Earth's sea into sediments, which turned into iron ores. - We take the presence of such a basic thing as soil for a…

I agree, but the first peak of atmospheric oxygen was more deadly than your description https://en.wikipedia.org/wiki/Great_Oxidation_Event

Re: Crabs evolved at least five times from separate groups of crustaceans (2021)

#106
post #17

Earlier quoted context omitted.

The teeth are already there. A few gradually longer ones makes obvious sense to be a better predator, giving them an evolutionary advantage.

Then why aren't they still around? Why don't they evolve again?

Probably climate change and humans.

Re: Crabs evolved at least five times from separate groups of crustaceans (2021)

#107
post #47

Earlier quoted context omitted.

Not exactly what you’re asking but whales used to be land mammals. > It is believed that modern-day whales evolved from land-based animals about 55 million years ago. These land-based mammals are believed to be hoofed mammals, sharing a common ancestry with even-toed ungulates such as the cow and the deer. > Evolution of Whales Whales started their journey as all other organisms have, as single-celled bacteria. An ev…

Which one of these was also the common ancestor of the hippopotamus?

According to wiki it's the third last item in their list, Artiodactyls pakicetus:

https://en.m.wikipedia.org/wiki/Pakicetus

> the closest living non-cetacean relative being the hippopotamus.

Re: Crabs evolved at least five times from separate groups of crustaceans (2021)

#108

Earlier quoted context omitted.

> I mean just the basic concept of survival of the fittest, which doesn't require deep understanding of biology. Even that can be tricky for some people, since it requires people to think about fitness in a holistic way. But laypeople are culturally primed to think of athleticism. When talking to people skeptical of evolution, this sort of confusion comes up a lot. A lot of "If evolution makes things stronger then wh…

This. And, still biological, “why have some places selected for greater disability like deafness, or seeming disadvantages like below average height?” I don’t want to give too much weight to the “universal” concept, but it’s easy to imagine similar questions about why certain pockets of culture are places where seemingly disadvantaged traits thrive. “Fit” is probably something better explained literally for an introd…

I'm not sure if I'm misunderstanding your comment, but some animals that live all their life in caves and some parasites are blind or have lost their eyes completely.

Re: Crabs evolved at least five times from separate groups of crustaceans (2021)

#110

Earlier quoted context omitted.

There was a recent article on here about how species that looked alike were not necessarily related and is was more common to have physically dissimilar but geographically close species that were evolutionary relatives. One of the points was that convergent evolution was more common than people thought. These stories appear to support the convergent evolution assertion

Curious if that applies to humans as well. I’m from S Asia and well.. I do have my distinct looks that I share with my family and community, that are different from other communities. Are humans like that as well? I am aware of the migration theories and people crossing ice bridges and all that, but did people evolve in different areas and then spread out after settling their original area?

Another good example of convergent evolution in humans is adaptation to high altitudes. Andean, Tibetan, and Ethiopian populations all separately evolved distinct mechanisms to thrive in relatively hypoxic environments [0].

[0] https://royalsocietypublishing.org/doi/10.1098/rstb.2018.023...

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