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Phylogenetic comparative methods (PCMs) use information on the historical relationships of lineages (phylogenies) to test evolutionary hypotheses.The comparative method has a long history in evolutionary biology; indeed, Charles Darwin used differences and similarities between species as a major source of evidence in The Origin of Species.
A protist is any eukaryotic organism (that is, an organism whose cells contain a cell nucleus) that is not an animal, plant, or fungus.While it is likely that protists share a common ancestor, the last eukaryotic common ancestor, [1] the exclusion of other eukaryotes means that protists do not form a natural group, or clade.
The holozoan protists play a crucial role in understanding the evolutionary steps leading to the emergence of multicellular animals from single-celled ancestors. Recent genomic studies have shed light on the evolutionary relationships between the various holozoan lineages , revealing insights into the origins of multicellularity .
Protists are distributed across all major groups of eukaryotes, including those that contain multicellular algae, green plants, animals, and fungi. If photosynthetic and fungal protists are distinguished from protozoa, they appear as shown in the phylogenetic tree of eukaryotic groups.
The resemblance between the crocodilians and phytosaurs in particular is quite striking; even to the point of having evolved the graduation between narrow- and broad-snouted forms, due to differences in diet between particular species in both groups. [88] Death adders strongly resemble true vipers, but are elapids. [89]
As a result, these amitochondriate protists were separated from the protist kingdom, giving rise to the, at the same time, superkingdom and kingdom Archezoa. This superkingdom was opposed to the Metakaryota superkingdom, grouping together the five other eukaryotic kingdoms (Animalia, Protozoa, Fungi, Plantae and Chromista).
An intermediate stage between spindle and cilium would be a non-swimming appendage made of microtubules with a function subject to natural selection, such as increasing surface area, helping the protozoan remain suspended in water, increasing the chances of bumping into bacteria to eat, or serving as a stalk attaching the cell to a solid substrate.
Animals and fungi are also more closely related to amoebas than to plants, and plants are more closely related to the SAR supergroup of protists than to animals or fungi. [citation needed] Animals and fungi are both heterotrophs, unlike plants, and while fungi are sessile like plants, there are also sessile animals.