Invertebrates

Question 1

Define an animal

Answer 1

A multicellular, heterotrophic eukaryote with tissues that develop from embryonic layers

Question 2

What is the term used for an animal lifecycle

Answer 2

Diploid dominiant

Question 3

Give details on the 5 stages in animal development

Answer 3

1. Gametogenesis - Production of gametes
2. Fertilisation - Fusion of gametes to form diploid zygote
3. Cleavage - Rounds of mitosis to form the blastula
4. Gastrulation - Differentiation of cells into tissues
5. Organogenesis - Formation of organs and organ systems

Question 4

What is a blastula and what is the inside called

Answer 4

A hallow ball of cells - Blastocoel

Question 5

What is determinate and indeterminate cleavage

Answer 5

Determinate - fate of the cells is predetermined - they are given different properties
Indeterminate - cells are complete copies of the zygote - totipotent

Question 6

What is the gastrula

Answer 6

Multilayered and multidimensional structure formed by the folding of blastula into blastocoel - opening is called the blastopore

Question 7

What are phlyogenetic tree A and B based on and what is the disagreement

Answer 7

A - based on morphological and developmental characteristics
B - Based on molecular studies
A divides bilaterans into 2 clades whereas B divides bilaterans in to 3 clades

Question 8

What is special about sponges

Answer 8

Basal animals that lack symmetry and true tissue and only have 1 germ layer - Parazoans

Question 9

What are the 2 phylum that exhibit radial symmetry

Answer 9

Cnidarians and Ctenophores

Question 10

Body plan of a radially symmetrical animal

Answer 10

Oral and aboral surface

Question 11

Body plan of a bilaterally symmetrical animal

Answer 11

Dorsal, Ventral, Anterior and posterior

Question 12

What is the major evolutionary trend of bilaterally symmetrical animals

Answer 12

Cephalisation - Concentration of nervous tissue towards one end of the organism

Question 13

What do the 3 germ layers each give rise to

Answer 13

Ectoderm - Epidermis and CNS
Endoderm - Lining of digestive tract and organs derived from it
Mesoderm - Muscle

Question 14

Name for animals with 2 or 3 germ layers

Answer 14

Diploblastic and Triploblastic

Question 15

What does the coelom separate

Answer 15

The digestive tract from the outerbody wall - Endo from ecto

Question 16

What is an acoelomate body

Answer 16

A solid body with no cavity between gut and body wall

Question 17

What is a pseudocoelomate body

Answer 17

A body with a fluid filled cavity partiallylined with tissue derived from the mesoderm

Question 18

What is a coelomate body

Answer 18

A body with a fluid filled cavity completely lined with tissue derived from mesoderm

Question 19

What are the 3 advantages of a coelom

Answer 19

1. Prevents internal injury
2. Acts as a hydrostatic skeleton against which muscles can act
3. Allows internal organs to grow and move independently of outer body wall

Question 20

What is the difference between radial and spiral cleavage

Answer 20

Spiral - Resulting cells are not located exactly on top of each other and are at a slight angle
Radial - Resulting cells are located exactly on top of each other

Question 21

4 main differences between protostomes and deuterostomes

Answer 21

P - Spiral cleavage, determinate cleavage, mouth is formed from the blastopore and coelom is formed by Schizocoelous development
D - Radial cleavage, indeterminate cleavage, anus is formed from the blastopore and coelom is formed by Enterocoelous development