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7

the production of liquids to nourish offspring has evolved separately in several lineages, mammals have simply taken it further than any other group. it is pretty easy to see how it could evolve, any way of providing even trace nutrients or nourishment to young will have an advantage in organisms that are already engaged in child rearing. it means exposing ...


6

Blue coloration in animals is caused by structural color rather than blue pigments. In the case of vervet monkeys and other mammals studied this is due to collagen fibers in the skin being arranged with a regular spacing that results in blue wavelengths constructively interfering while other wavelengths destructively interfere1. This "news" article in ...


4

Update 2 (interpreting "faster" in terms of efficiency because it seems easier to measure) The question has been updated but I still don't see a reference for insects being more efficient than mammals. Therefore I investigated this and did not find convincing evidence that it is the case. Granted, the means of measuring efficiency are not necessarily ...


4

Petrides, 1950, writes: Male skunks have tiny nipples which are considerably smaller than those of juvenile females. and also: Female skunks which had bred could easily be distinguished from those which had not by differences in the size of the teats So it sounds like the mere presence of teats is not sufficient to sex skunks, but the size is ...


4

Secondary ectothermy has been suggested in living crocodylians by Seymour et al. (2004). Their rationale is based on: Presence of a 4 chambered heart (otherwise only found in endotherms) Post-cardiac shunting via the foramen of Panizza and "cog-tooth" valve, which develop secondarily in crocodylians Lung structure and ventilation during locomotion Thus ...


2

There is no evolutionary "ratchet" that prevents a life form from evolving "backwards". However, it is statistically unlikely because it would pretty much require all of the environmental factors that changed during the transition from "cold blooded" to "warm-blooded" to change back in the reverse order, because all of those factors contributed to the ...


2

Mammals and reptiles aren't considered amphibians, because amniotes are not hypothesized to descend from Amphibia. That is to say that Amphibia did not evolve into Amniota. They are sister clades (actually Reptiliomorpha in the Tree of Life tree below).


2

Some named groups are not monophyletic (see this post for definition if needed). Fishes do not represent a monophyletic group. Groups like "fishes" are completely awful to define but everyone would agree that no, humans are not fish! Now, it is important to understand for many terms, there might have a scientific and a popular definition of the term. For ...


2

The best article I found was this one. In it it says among other things that: Kanzi, an unusually intelligent Bonobo chimp trained at Georgia State University, was remarkable in that he learned to use around 200 symbols on a portable electronic symbol board, a computer with buttons in the shape of absolute arbitrary symbols rather than manual signs. ...


1

I think you are confused about what erect limbs means, monotremes have erect hindlimbs. Erect is not the same as pillar erect (which is exceedingly rare) Just because a limb is bent or a joint can rotate does not mean it is not an erect limb. More importantly terms like semi-erect don't actually mean much, it is a weak gradation not discrete categories. ...


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