Draw a phylogeny of deuterostomes, indicating the most likely relationships among chordates, hem

Draw a phylogeny of deuterostomes, indicating the most...

Key Concepts

Echinoderms

Echinoderms are a phylum of marine animals distinguished by their radial symmetry, a unique water vascular system, and a calcified endoskeleton. This group includes organisms such as starfish and sea urchins, and their study helps elucidate evolutionary strategies adapted to marine environments, establishing their relationship within the deuterostome lineage.

Deuterostomes

Deuterostomes are a major clade of animals characterized by their embryonic development, where the first opening (the blastopore) develops into the anus rather than the mouth. This group includes diverse phyla such as chordates, hemichordates, and echinoderms. Understanding deuterostomes is crucial for tracing the evolutionary relationships and developmental patterns that distinguish these organisms from protostomes.

Phylogenetic Tree

A phylogenetic tree is a diagram that represents the evolutionary relationships among different species or groups by illustrating their common ancestry and divergence through branching patterns. These trees help scientists visualize the connections between various organisms, infer their shared characteristics, and understand how evolutionary processes have shaped biodiversity over time.

Chordates

Chordates are animals that, at some stage in their development, possess key features such as a notochord, a dorsal hollow nerve cord, and pharyngeal slits. This diverse group encompasses organisms ranging from simple invertebrate chordates to complex vertebrates, and its study is essential for understanding the evolution of complex body plans and the development of key vertebrate features.

Hemichordates

Hemichordates are a group of marine invertebrates that provide important insights into the evolution of chordates due to their shared characteristics and developmental similarities. They possess a body divided into distinct regions and exhibit features that bridge the gap between simpler invertebrates and more complex chordates, offering clues into the evolutionary transitions among deuterostomes.

Transcript

00:02 Have you ever picked up a serotonin to do it very carefully? they do have a lot of spines coming out of their skin.

00:09 Syrians are echinoderms, which means spiny skin.

00:13 And if you look at a serotonerms or other typical echinoderms like c -stars, sandalers, sea cucumbers, they all have radial symmetry.

00:22 They're roundish.

00:23 They have a top and the bottom, but no right of the left side.

00:26 And then there's chordates, which are all of the vertebrates, like lions and tigers and bears and dogs and cats and and some inverticordaes like sea squirts which are the tunicates so they're a very different phyla you find econa dermata and file in cordata but i want to tell you why they are actually more closely related than they are to other phyla so echiniderms and chordates are more closely related to each other than like you look at echinoderms even though they are radially symmetrical, they have a round structure, they are not very close related to other radially symmetrical animals.

01:12 And if you look at the characteristics that they share versus the characteristics that they each have, one of the reasons right off the bat that you can see why they are more closely related than sea stars or sea urchins are to, say, jellyfish, is that they both have a complete digestive tract, whereas jellyfish have a single cavity, gastrovasculative cavity, the urchins, and chordates, ehandress, and cordates, both have a complete digestive tract with a mouth and anus being two separate openings.

01:53 On the other hand, we have the surgeons which have radio symmetry, cordates which have bilateral symmetry, but the radio symmetry that you see in econiderms is different from radio symmetry that you see in jellyfish.

02:11 And the reason, and other nigerians, and the reason for that is that se surgeons have radio symmetry that's called penta radial symmetry.

02:21 They have five points to their symmetry.

02:24 And also they evolved, they developed from bilaterally symmetrical larva.

02:30 So because they are bilaterally symmetrical at the beginning of their life, their life history, their life cycle, and then they transformed being radio and they're more stationary adults.

02:42 They are technically radially symmetrical, but they are classified closer to other bilaterally symmetrical animals.

02:52 One of the most important features that they share that's going to end up giving them a lot of similarities that they're both deuterostomes.

03:03 Both the echiniderms and the coordinates are both deuterostomes.

03:10 So we want to see they are both deuterostomes.

03:13 And that makes them more close related to each other than two other phylo within animals.

03:19 To show you what a deuterostom is, look at this circle that we have here.

03:26 If this circle was a hollow ball of cells called a flascula.

03:37 So the circle is a hollow ball of cells called a blastula.

03:41 What happens as an organism like a chordate or any kind of derm develop is that part of this flashula will start to indent.

03:52 And then it will indent some more.

03:55 And they will indent some more...

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