Exam 22: Chaetognaths, Echinoderms, and Hemichordates

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The ___________ ___________ was formerly thought to be a notochord.

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buccal diverticulum

Outline the phylogeny and adaptive diversification of the hemichordates and discuss the latest data of small subunit rRNA supporting a deuterostome phylogeny for this group.

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Hemichordates are a group of marine invertebrates that are closely related to chordates, which include vertebrates. The phylogeny of hemichordates has been a topic of interest for researchers, as it provides insights into the evolutionary history of deuterostomes, a major group of animals that includes vertebrates.

The phylogeny of hemichordates is characterized by their adaptive diversification into three main classes: Enteropneusta (acorn worms), Pterobranchia, and Planctosphaeroidea. These classes exhibit a wide range of body plans and ecological adaptations, reflecting their diverse evolutionary history.

Recent data from small subunit rRNA sequences have provided support for a deuterostome phylogeny for hemichordates. This molecular evidence suggests that hemichordates share a common ancestor with echinoderms, another group of deuterostomes that includes sea stars and sea urchins. This finding is consistent with morphological and developmental similarities between hemichordates and echinoderms, such as the presence of gill slits and a tripartite body plan during embryonic development.

Overall, the phylogeny and adaptive diversification of hemichordates provide valuable insights into the evolutionary history of deuterostomes. The latest data from small subunit rRNA sequences support a deuterostome phylogeny for this group, shedding light on their evolutionary relationships with other major animal groups.

________ ________ is a connective tissue that allows echinoderms to hold certain postures for long periods without straining muscles.

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Catch collagen

The hemichordates and echinoderms apparently form a sister group to the ________________.

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The Class Enteropneusta are also known as __________________.

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The ancestor of the echinoderms had _____________ symmetry.

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The echinoids

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Hemichordates live

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The grooves that run along the oral side of the arms of sea stars are called ________________ grooves.

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The ossicles are penetrated by a meshwork of spaces filled with fibers and dermal cells; the meshwork is _____________ and is unique to echinoderms.

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Pedicellariae are

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Brittle stars differ from sea stars by

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The madreporite of sea cucumbers is located in the ________________.

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The designation of hemichordates as primitive chordates in 1885 by Bateson has proved

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Deuterostome characteristics

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Unique characteristics of echinoderms include all of the following EXCEPT

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Echinoderm evolution is controversial but most zoologists agree that ___________ are related and form one clade.

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Describe the human response to the impact of sea star predators in oyster beds and include how the remedy for eliminating sea stars does not also eliminate the oysters.

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The function of the papulae in the sea star is

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Water enters the water vascular system of a sea star through a porous plate on the aboral surface called the

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