Question

(1) The echinoderms share a set of common features, but the evolution of the various classes suggests a malleable body plan. Consider the following echinoderms representing 3 different classes: (a) a stalked sea lily, (b) a sea star, and (c) sea cucumber. For each of these 3 organisms, discuss (i) the location and function of the tube feet, (ii) the mode of feeding, (iii) the organization and use of the skeletal elements, and (iv) the organization and use of connective tissue. In your answer be sure to explain how differences among these classes are associated with different life styles. Organize your essay by writing a short paragraph for each of the three organisms.

(2)(a) Compare and contrast mechanisms of feeding and respiration among the following four taxa of invertebrates: crinoids, enteropneusts, pterobranchs, and ascidians. Be sure to discuss the key structures involved in feeding and gas exchange, and how they function in each group. (b) To what extent do similarities in form and function in part A reflect homology versus homoplasy? Explain your answer

Answer 1

Q.1 . Answer:- Tube feet in stalked sea lilies is located in a deep groove in the tegmen portion and it's function is --- locomotary organ and also function to collect food particle and fold the food particle and bring it to the food groove.

Tube feet in sea star is located in the grooves along the arms. It's function is ---- to perform respiration , it also serve as one of the locomotary organ and helps in feeding process .

Tube feet in sea cucumber is present in grooves along the arms . Tubefeets are used in movement or locomotary purpose and feeding purpose.

The mode of nutrition in sea lilies is both heterotrophic ( as they eat planktons) and saprotrophic ( as they also eat detritus) . They use tube feet to intake food particle into food groove .

The mode of nutrition of sea star is hetrotrophic as they eat small aquatic animals. Sea star push out it's one stomach among two inside out to make food soupy and swallow food particle by stomach. It also take help of water vascular system in it's feeding .

The mode of nutrition in sea cucumber is heterotrophic ( they feed on plankton , algae, aquatic invertebrates) and also saprotrophic ( dead organisms so called scavenger) . Sea cucumber take up position by adjusting their tentacles according to food size to catch food particles and then send it too food groove for further digestion.

The skeleton system of sealilies comprised of calcium carbonate rich skeleton and overall skeletal branched network is knkown as stereom.

The endoskeleton and internal skeleton together forms the skeleton system of sea star , which are rich in calcium carbonate . The plates which are arranged in the skeleton system are called ossicle . spines and granules are two types of forms of endoskeleton system.

The skeleton system of sea cucumber is limited to internal skeleton made of calcium carbonate rich ossicles. These ossicles are smaller in size and are present under the skin.

Skeleton system of all three species provide rigidity and support to body system and also help in locomotion.

Sea lilies , sea cucumber and sea star contain contractile connective tissue. The muscles contain ligaments and inside the ligaments there seems to be distribution of collagen fibril and microfibril and neuron like cell process . There is non fixed order or orientation in the distribution of neuron like cell process in between these fibrils , they are randomly situated and the cell bodies accomplished with this cell processes are present in the minute opening of ossicles and are linked with Nervous system . Connective tissue are used in locomotary purpose or movement of organ.