Question

1 complete summary table a - 1 in the appendix, filling in the characteristics of flatworms in the appropriate row.
2 a true coelom is completely lined with:
a. epidermis
b. cilia
c. gastrodermis
d. mesoderm
e. flagella
3 contrast the nervous system seen in planaria (dugesia) with that seen in hydra.
4 distinguish between the processes of egestion (or defecation) and excretion, using the flatworm as a model for both processes.
5 define cephalization and discuss its significance.
6 what is the evolutionary advantage for bilaterally symmetrical, motile animals such as flatworms to have a concentration of nervous tissue and sensory organs located at their anterior end?

Explanation:

1. Without access to Appendix Table A - 1, can't complete it. Research flatworm characteristics like body structure, feeding, etc. for filling.
2. A true coelom is lined by mesoderm. Mesoderm gives rise to various structures and is an important embryonic germ - layer in higher animals.
3. Planaria have a more complex nervous system with a brain and nerve cords, while Hydra has a nerve net which is a simpler, diffuse system without a central brain.
4. Egestion is the elimination of undigested food (feces) from the digestive tract, while excretion is the removal of metabolic waste products like ammonia from the body. In flatworms, egestion occurs through the single - opening digestive tract, and excretion is via flame cells.
5. Cephalization is the concentration of sensory organs and nervous tissue in the anterior end of an organism. It is significant as it allows for better perception of the environment in the direction of movement, leading to more efficient foraging, predator avoidance, etc.
6. For bilaterally symmetrical, motile animals like flatworms, having a concentration of nervous tissue and sensory organs at the anterior end allows them to sense the environment ahead as they move forward, enabling them to detect food, danger, and suitable habitats more effectively.

Answer:

1. No answer due to lack of Appendix table.
2. d. mesoderm
3. Planaria have a brain and nerve cords; Hydra has a nerve net.
4. Egestion is undigested food removal; excretion is metabolic waste removal. In flatworms, egestion via single - opening digestive tract, excretion via flame cells.
5. Cephalization is concentration of sensory and nervous tissue at anterior end. Significance: better environmental perception in direction of movement.
6. Allows for better sensing of the environment ahead during movement for food, danger detection, etc.