Which of the following combinations of phylum and...

Which of the following combinations of phylum and description is correct?
(A) Echinodermata-radial symmetry as a larva, coelom
(B) Nematoda-roundworms, internal skeleton
(C) Platyhelminthes-flatworms, gastrovascular cavity, no body cavity
(D) Porifera-gastrovascular cavity, coelom

Key Concepts

Gastrovascular Cavity

A gastrovascular cavity is a central digestive compartment that functions in both digestion and the distribution of nutrients. Found in some animal groups, it typically has a single opening that serves as both the mouth and the anus. This structure is important in the classification and functional biology of groups that lack a more complex digestive and circulatory system.

Body Cavity Organization

Body cavity organization, including the presence of a true coelom or its absence, is critical in animal classification. A coelom, a fluid-filled cavity entirely lined by mesoderm, provides space for the development and movement of internal organs. In contrast, the absence of a coelom (acoelomate) or a less fully developed cavity (pseudocoelomate) represents different evolutionary adaptations among phyla.

Animal Phyla Classification

This concept involves organizing animals into groups based on fundamental anatomical and developmental traits. It provides a systematic framework to compare and contrast characteristics such as body symmetry, presence or absence of body cavities, and other morphological features, which are essential for understanding evolutionary relationships.

Body Symmetry

Body symmetry refers to the arrangement of an organism's body parts relative to a central point or axis. Generally, animals exhibit either bilateral symmetry, where the body can be divided into mirror-image halves, or radial symmetry, where parts are arranged around a central axis. This concept helps explain how different organisms interact with their environment and perform various biological functions.

Transcript

00:02 Okay, in this problem, we're looking at different invertebrate phyla.

00:07 So we have a phylum, and then we have some type of characteristic, and we have to see if that characteristic matches up with the phylum.

00:19 Does that phylum have the correct characteristics? our first is an echinoderm.

00:34 That is c -star, brittle star, sea urchins.

00:39 So write that example there, so you can have that in your head.

00:44 The characteristics that are said are here is radio symmetry and a sealum, which is the body cavity, so that body cavity is in between the intestinal track and the body wall.

01:08 And radialarians do have a sealum, and we might think that they have radio symmetry.

01:20 A lot of them, you know, have a central area, maybe arms coming out from them.

01:27 But the larvae actually have bilateral symmetry.

01:32 And things in the c -star, like the madriporite, which is an opening on top of the c -star, is not centered.

01:39 So they do not pose complete radial symmetry along with c -cucumber, which is in this group, which does not display radio symmetry.

01:55 Okay.

01:56 Our next first group is our nematodes, nematoda.

02:10 And so those are roundworms.

02:12 That's one of the characteristics.

02:14 And that is correct.

02:22 That group, that common name because of how they look, they are round worms.

02:27 The next characteristic they describe is an internal skeleton.

02:42 These are invertebrate animals.

02:47 They do not have an internal skeleton.

02:51 They actually, nematodes.

02:52 Have a cuticle, that they molt their dicesones that they have on the outside.

03:05 So they have no exoskeleton...

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