Chapter 32

Question 1

What is the development of animals in order?

Answer 1

1. Zygote
2. Multiplies many times and creates “Eight cell stage” and Cleavage is formed (spiral cleavage in protostomes and radial in deuterostomes)
3. Blastula (hollow inside surrounded by cells)
4. Gastrulation occurs and starts to create a hole in the middle.
5. Blastopore is formed = hole in the blastula

Question 2

How is a protostome developed?

Answer 2

• Blastopore becomes the mouth of the organism
• Cleavage in the eight cell stage is not aligned (spiral)
• determinate (already know what tissue to make)

Question 3

How is a Deuterostome developed?

Answer 3

• Blastopore becomes the Anus
• Cleavage in the eight cell stage is aligned (radial)
• indeterminate

Question 4

What are the 3 different germ layers?

Answer 4

Ectoderm, Mesoderm, Endoderm

Question 5

What are the functions of each of the 3 germ layers?

Answer 5

Ectoderm: the germ layer covering the surface of the embryo, gives rise to the outer covering of the animal and to some phyla the central nervous system.
Mesoderm: fills the space between the ectoderm and endoderm.
Endoderm: the innermost germ layer, lines the pouch that forms during gastrulation and gives rise to the lining of the digestive tract.

Question 6

What is an Eucoelomate?

Answer 6

A Eucoelomate are animals that have a true coelom, a body cavity completely lined by tissue derived from mesoderm. (earth worms, annelids etc.)

Question 7

What is a Pseudocoelomate?

Answer 7

A Pseudocoelomate are animals that have a body cavity lined by tissue derived from mesoderm and by tissue derived from endoderm. Seems like it has a true coelom but have part of its cavity covered by mesoderm. (Roundworms)

Question 8

What is an Acoelomate?

Answer 8

No cavities (platyhelminthese)