Identify which clade contains a polytomy in the phylogeny...

Identify which clade contains a polytomy in the phylogeny below. Note that the taxa on the right correspond to the clades in the phylogeny on the left. Placentals Marsupials Monotremes Birds Crocodiles Lizards + Snakes Tuatara Turtles Frogs Salamanders Caecilians Lungfishes Coelacanth Teleosts Gars Bowfins Sturgeons Bichir Sharks + Skates Chimaeras Lampreys Hagfishes Mammals Reptiles (including birds) Amphibians Lobe-finned fishes Ray-finned fishes Cartilaginous fishes Agnathans AMNIOTA TETRAPODA SARCOPTERYGII OSTEICHTHYES GNATHOSTOMATA amphibians ray-finned fishes reptiles + birds mammals all of these groups contain a polytomy

Transcript

00:01 Hi, in today's video we will discuss about this cladogram given in the patient and identify which species of these cladogram is showing polytomy.

00:10 What is a cladogram? cladogram can be outlined as a graphical representation or a representation of ancestral relationship of species.

00:23 That means how species are ancestrally related and who are their common ancestors can be predicted or analyzed using a cladogram.

00:33 The question is asking which species is showing polytomy in this cladogram.

00:39 Polytomy is a simultaneous speciation of two or more species.

00:49 That means when two or more species undergo the process of speciation simultaneously, then it is known as polytomy.

00:57 So, in polytomy, the inter node of cladogram shows two or more common descendants or immediate descendants of this species.

01:08 For example, let's talk about mammals.

01:11 In mammals, placental, marsupil and monotrains, they have common ancestors.

01:18 And this inter node is representing the speciation of these three different species.

01:24 So, it is showing the polytomy.

01:27 Let's discuss the option and find out which species is showing polytomy or not.

01:33 So first option is saying amphibians.

01:37 We need to find out whether amphibians of this cladogram is showing polytomy or not.

01:42 So, amphibians include frog, salamanders and cesareans.

01:47 So yes, they are showing polytomy because, as you can see, these have this common internode, from which they all have been arised.

01:57 So it is the correct option.

01:59 Because yes amphibians are showing poly tommy in this cladogram...

Question

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