PROTOSTOME/ DEUTEROSTOME DIVIDE

Question 1

Key requirements for organisms to be LARGER

• basically why do organisms need a coelom?

Answer 1

• transport systems
• enlarged exchange surfaces
• internal spaces for organ movement

Question 2

Coelomate body plan

How many times has it evolved?

Answer 2

• thin walls of peritoneum separate mesenteries
• The coelom has exits to the outside of the body called
  coelomoducts, often modified for excretory or reproductive functions (kidneys, oviducts).
• organs suspended in coelomic fluid containing cells

2) at least twice after Bilateria

Question 3

The only phylum in the protostomes that does not have a coelom is (a) All (b) do.

Answer 3

PLATYHELMINTHES

DEUTEROSTOMES

Question 4

How does a coelom form?

Answer 4

1) dividing cells of the embryo form a hollow ball, the
blastula, surrounding a fluid-filled space, the blastocoel.

2) gastrulation creates layers
3) mouth formation differs between protostomes ( forms mesoderm from clumps of cells in blastocoel) and deuterostomes (second opening from outpockets of gut)

Question 5

no peritoneum in haeomcoel means

Answer 5

organs bathed directly in blood

Question 6

Describe the 3 protostome lineages

Answer 6

1) PLATYZOA (contains flatworms)
1. External cilia as larvae and adults.
2. Growth without moulting.
3. NOT with coelomic structures.
4. NOT segmented.

2) TROCHOZOA (mollusca and annelida)
1. External cilia as larvae and adults.
2. Growth without moulting
3. Often with coelomic structures in adult
4. Some segmented (annelids), some not (molluscs)

3) ECDYSOZOA (arthropods and nematodes)
1. NO external cilia as adults
2. NO ciliated larvae.
3. Grow by moulting (Ecdysis)
4. All have secondary haemocoels
5. Some segmented (arthropods), some not (nematodes)

Question 7

Function of coelomoducts

Answer 7

excretory or reproductive function

Question 8

What is peritoneum?

Answer 8

• the coelom is surrounded by mesoderm, with a special lining called the peritoneum

Question 9

___ ___ of nervous, digestive and excretory systems was adequate to fulfil requirements of small organisms or low complexity.

Answer 9

serial repetition

Question 10

What is a haeomocoel?

Answer 10

The cavity, between the organs of arthropods and molluscs, through which the blood etc. circulates.