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TL;DR: There is a dearth of actual experimental evidence. However: there is at least one study that confirmed the process ([STUDY #7] - Myxococcus xanthus; by Fiegna and Velicer, 2003). Another study experimentally confirmed higher extinction risk as well ([STUDY #8] - Paul F. Doherty's study of dimorphic bird species an [STUDY #9] - Denson K. McLain). ...

Squamates Extant venomous snakes do have venomous ancestors. Fry et al. (2006) reported on finding venom toxins more broadly within Reptilia, beyond the well-known venomous snakes and the helodermatid lizards. They show that varanid and iguanid lizards also have venom toxins. The same group of authors (Fry et al., 2009) then reported on the use of venom ...

Assuming that gravity was essentially the same (other answers to this question notwithstanding), very large dinosaurs were dealing with the same forces that they would today. There are two clades of dinosaurs in which gigantism evolved, Sauropoda (quadrupdeal sauropods) and Theropoda (including T. rex). Each "solved" the problem of large size in different ...

In general the answer is always the same: you construct a phylogenetic tree. In order to locate different species on this tree in relation to each other, you use various features to compare which species are more similar to each other than others. The best way of doing this is by comparing their DNA sequence, especially orthologous genes (i.e. genes common ...

Many of them looked like little rodents. However, several distinct mammalian lineages were already present, including Monotremes, marsupials and placental mammals. Throughout the whole mesozoic era, mammals were already quite diversified! Also, even though most of the mammals that survived the K/T boundary were rather small, there were already some larger ...

This is a question I have often heard and there is no one certain answer to it. There are several scientific hypothesis about the methabolism of dinosaurs, but none of them has been ever proved or completely disproved. Arts of methabolism First of all, the term "cold-blooded" and "hot-blooded" are not scientific. In biology the organisms are classified ...

Extending Konrad Rudolph's answer, research has been conducted into reconstructing the phylogenetic tree via protein sequence data of the T. rex (one of the latest living dinosaurs): C. L. Organ et al, Molecular Phylogenetics of Mastodon and Tyrannosaurus rex, Science 320 (2008), p. 499. They use a variety of standard methods for the phylogenetic ...

You are talking about the mitochondrial eve and the chromosome Y adam. At some point there must be just one pair, though historically the evidence can be lost if there is a near complete extinction event. Current evidence for eve points to SE Africa.

A recent genetic analysis suggests that they were probably bigger that we thought before : http://www.newscientist.com/article/dn22343-mammals-ancestor-was-not-as-puny-as-we-thought.html