Chapter 18 and 19

Question 1

What are the different types of symmetry?

Answer 1

Radial Symmetry - An arrangement of body parts of an organism like pieces of a pie around an imaginary central axis

Bilateral Symmetry - An arrangement of body parts such that an organism can be divided equally by a single cut passing longitudinally through it. A bilaterally symmetric organism has mirror-image right and left sides.

Question 2

What are the different surfaces of an animal?

Answer 2

Anterior - Pertaining to the front, or head, of a bilaterally symmetric animal

Posterior - Pertaining to the rear, or tail, of a bilaterally symmetric animal

Dorsal surface - Pertaining to the back of a bilaterally symmetric animal

Ventral Surface - Pertaining to the underside, or bottom, of a bilaterally symmetric animal

Question 3

What is a protostome?

Answer 3

A mode of animal development in which the first opening formed during gastrulation becomes the mouth.
Eg. flatworms, molluscs, annelids, nematode

Question 4

What is a deuterostome?

Answer 4

A mode of animal development in which the first opening formed during gastrulation becomes the anus, and the mouth forms from a second opening.
Eg. Echinoderms, chordates

Question 5

What are characteristics of the phylum Cnidaria?

Answer 5

• characterized by radial symmetry
• characterized by bodies arising from only two tissue layers
• two types of body forms
  a. Polyp
  b. Medusa
• carnivorous
• have cnidocytes, that function in defense and in capturing prey
• gastrovascular cavity

Question 6

What are the two types of Cnidaria body forms?

Answer 6

Polyp - a columnar, hydra-like body, tentacles projecting from one end, their mouth is on top of the body, at the hub of their radiating tentacles. Also, polyps are mostly stationary.
Eg. Hydras, sea anemones

Medusa - an umbrella-like body form, fringe tentacles around the lower edge, their mouth is in the center of the undersurface. It leads into a multifunctional compartment called the gastrovascular cavity, where food is digested. Also, Medusae move freely about in the water.
Eg. Marine jelly

Question 7

What is a gastrovascular cavity?

Answer 7

A central compartment with a single opening, the mouth; functions in both digestion and nutrient distribution. It may also function in circulation, body support, waste disposal, my gas exchange.

Question 8

What are cnidocytes?

Answer 8

A specialized cell for which the phylum Cnidaria is named; consists of a capsule containing a fine coiled thread, which, when discharged, functions in defense and prey capture.

Question 9

What are characteristics of the phylum Porifera?

Answer 9

• some are radially symmetric, but most lack body symmetry
• no nerves or muscles
• body consists of two layers, separated by a gelatinous region
• ## suspension feeders

Question 10

What are choanocytes and amoebocytes?

Answer 10

Choanocytes - a flagellated collar cell found in sponges, that traps food particles around the base of its flagellum, and also help to sweep water through the sponges body.

Amoebocytes - an amoeba-like cell that moves by pseudopod is and is found in most animals. Depending on the species, it may digest and distribute food, dispose of wastes, form skeletal fibers, fight infections, and change into other cell types.