Animal Organization

Question 1

What are the different grades of organization? Which phylum shows which?

Answer 1

1. Protoplasmic grade- unicellular
2. Celllular grade- differentiated cells NOT organized.
3. Cell-tissue grade- cells organized to perform common functions (muscle, nerve, etc). Diploblastic and Triploblastic organization.

Question 2

What are the different types of symmetry and what each symmetry is good for? Which phylum shows which?

Answer 2

1. Asymmetry- most protists and many sponges
2. Spherical- any plane passing through the center divides the body into similar halves. Good for floating, rolling- many protists
3. Radial- more than 2 planes passing through the longitudinal; similar halves. Allows interaction w/ environment in all directions. Good for sedentary (sessile) lifestyles- corals.
4. Bilateral- a single plane divides the body into two halves- right and left. Specialized for directional movement. head with sensory and feeding structures- cephalization.

Question 3

What is meant by diplo and triploblastic? Which phylum shows which?

Answer 3

• Diploblastic- two embryonic layers. Ectoderm and endoderm. Mitotic divisions called cleavage divide zygote into a cluster of cells called blastula. The ectoderm cells are arranged around a central fluid filled cavity called blastocoel. Endoderm is formed by invagination of one side of blastula.- Cnidaria
• Triploblastic- 3 germ layers, 3rd layer is called mesoderm (produced from endoderm and comes to lie between the ecto and endoderm)- animals

Question 4

What is a complete and incomplete gut? Which phylum shows which?

Answer 4

Incomplete Gut- Only opens at blastopore- Flatworms (opening is both mouth and anus)
Complete Gut- Cavity invaginates further to develop a second opening at the other end (one opening is mouth, the other is anus)

Question 5

What is a coelom? What is it good for?

Answer 5

A fluid filled space in which internal organs can be suspended and separated from the body wall.
Good for:
1. space for organs
2. more surface for diffusion and therefore facilitates increase in body size.
3. storage area.
4. hydrostatic skeleton-flexible support allowing change of shape and movement.

Question 6

What are the different types of coelom? Which phylum shows which?

Answer 6

1. Acoelomate Plan- Mesoderm fills blastocoel
2. Pseudocoelomate Plan- Mesoderm lines one side of blastocoel
3. Schizocoelous Plan- Band of mesoderm surrounds gut and then splits open
4. Enterocoelous Plan- Mesodermal pouches surround gut

Question 7

What is the defining feature that distinguishes protostomes from deuterostomes? Which phylum shows which?

Answer 7

Protostome- 1st opening is the mouth, 2nd is the anus (Flatworms, Arthropods)
Deuterostomes- 1st opening is the anus, 2nd is the mouth (Fish)

Question 8

What are the main derivatives of each of the germ layers?

Answer 8

Ectoderm- Outer epithelium of body and derivatives (hair, nails, epithelial glands, lining of mouth, etc)
- Neural tube (brain, spinal cord, motor nerves)
- Neural crest- Sensory ganglia and nerves, adrenal medulla, sympathetic ganglia, skull, gill arches, dentine of teeth
Mesoderm- circulatory system- blood, bone marrow, endothelium of blood vessels, lymphatics
Somites- skeletal muscle, bone and cartilage of skeleton (except skull), dermis, connective tissues
Organs of urogenital system- Ureter, kidney, gonads, reproductive ducts
Endoderm- Liver, Pancreas

Question 9

What are the costs and benefits of being bigger? How have animals solved the problems that come with being big?

Answer 9

Benefits- less surface area, Buffers against environmental fluctuations, uses metabolic energy more efficiently
Costs- More volume, Makes it difficult for cells located deep within the body to respire or get nutrition
Solutions: increase surface area by folding or flattening the body to get close to the surface (flatworms), develop internal transport system (Annelids, Chrodates)