1. Define sessile. Name an invertebrate with a sessile adult stage. 2. Describe the skeleton of a sponge. 3. Sponges have specialized cells called collar cells. Describe how collar cells are...

1. Define sessile. Name an invertebrate with a sessile adult stage.

2. Describe the skeleton of a sponge.

3. Sponges have specialized cells called collar cells. Describe how collar cells are specialized for the functions they serve.

4. What is a nematocyst? What is its function.

5. How do coral reefs form?

6.Describe specialized feeding structures of parasitic platyhelminths.

7.How do free-living nematodes contribute to the carbon cycle?

8.Describe the basic body plan of a mollusk.

9. What are gills? What is their function?

10. What is the difference between an open and a closed circulatory system?

11. What is a radula? What is it used for?

12. Define regeneration.

13. Identify distinguishing traits of most arthropods. 14. What is molting? Why does it occur?

15. Name three arthropod head appendages and state their functions.

16. Describe two structures that allow arthropods to breathe air.

17. List several traits that characterize insects.

Expert Answers
paepin eNotes educator| Certified Educator

1. Define sessile. Name an invertebrate with a sessile adult stage.
Sessile refers to an immobile organism. A sessile organism is fixed in one place and cannot move. Sponges are examples of organisms that are sessile at the adult stage.

2. Describe the skeleton of a sponge.
Sponges are members of the phylum Porifera, which have pores and channels for water flow. If you were to touch the hard outer skeleton of a sponge, it would feel a bit like a bone - that's because it is made up of calcium carbonate. It's important to note that a sponge's skeleton is an exoskeleton.

3. Sponges have specialized cells called collar cells. Describe how collar cells are specialized for the functions they serve.
A sponge's collar cells (or choanocytes) help circulate water through the organism and trap food for the sponge. Choanocytes have a round cell body and a whip-like tail - this structure allows them to perform the important functions the sponge needs for survival.

4. What is a nematocyst? What is its function?
A nematocyst is a type of cnidae, which means they are found in organisms that are part of the Cnidarian phylum. Jellyfish and corals are examples of organisms that are part of the cnidarian family. The unique function of a nematocyst is its ability to sting.

5. How do coral reefs form?
When coral reproduce, a pool of coral larvae float through the water and attach to nearby surfaces. Successful coral larvae will land on immobile objects (such as rocks). As coral grows, it expands and covers an entire surface. If you consider what might happen in a place where a large amount of successful coral has taken root, you can see how plenty of coral can grow in a single place. The resulting neighborhood of coral is what makes up a reef.

6.Describe specialized feeding structures of parasitic platyhelminthes.
Parasitic platyhelminthes (also known as flatworms) have a hook-like structure on their mouths, which allow them to successfully attach to their host.

7.How do free-living nematodes contribute to the carbon cycle?
Nematodes, or round worms, break down organic matter in the soil. The nutrients from the breakdown process reenter the ecosystem, thus contributing to the carbon cycle.

8.Describe the basic body plan of a mollusk.
Snails, squid, and clams are all different types of mollusks. Although there are different organisms that make up the Mollusca phylum - and even though these organisms look quite different - there are a few body parts that unite these animals. In fact, all mollusks have a foot, mantle cavity, shell, gills, and a digestive tract.

9. What are gills? What is their function?
Gills are specialized respiratory organs that allow animals to breathe in water by extracting oxygen.

10. What is the difference between an open and a closed circulatory system?
A closed circulatory system completely encapsulates an organisms blood in arteries, veins, capillaries, and organs. In contrast, an open circulatory system pumps blood into body cavities to surround organs that can diffuse blood between cells.

11. What is a radula? What is it used for?
A radula is a tongue-like structure used by mollusks to scrape food off of surrounding surfaces.

12. Define regeneration.
Regeneration is a process of regrowth that allows some organisms to be resilient to damage. Starfish, for example, can regenerate damaged extremities.

13. Identify distinguishing traits of most arthropods.
Arthropods have an exoskeleton, a body organized into segments, and paired appendages.

14. What is molting? Why does it occur?
Molting (in arthropods) allows an organism to shed an old exoskeleton and create a new exoskeleton. This process allows organisms to grow - in fact, arthropods only grow through this process.

15. Name three arthropod head appendages and state their functions.
Arthropods have antennae (for sensing), compound eyes (for vision), and mandibles and maxilla (for eating).

16. Describe two structures that allow arthropods to breathe air.
Arthropods that live in water have gills. Arthropods that live on land inhale air through tubes called tracheae.

17. List several traits that characterize insects.
Insects have six legs, wings, an exoskeleton, and segmented bodies.