ILT Development of the Toad

Question 1

Ventral

Answer 1

• towards the belly/front

* away from the vertebral column

Question 2

Dorsal

Answer 2

• back

* towards the vertebral column

Question 3

Posterior

Answer 3

Towards the tail

Question 4

Anterior

Answer 4

Towards the head

Question 5

Longitudinal section

Answer 5

A section cut parallel to the long axis of the structure

Question 6

Transverse section

Answer 6

A section cut at right angles to the long axis of the structure

Question 7

Oblique section

Answer 7

A section cut at an angle to the longitudinal axis

Question 8

What are the 2 hemispheres of a fertilised egg?

Answer 8

Animal - rich with black/brown pigment

Vegetal - where yolk is concentrated

Question 9

What happens in the cleavage process?

Answer 9

It is the first phase of embryonic development

• single-celled cells gets carved into a large number of cells calls blastomeres

Question 10

What happens in the late stages of cleavage?

Answer 10

• At the end of cleavage the embryo is known as a blastula
• it consists of a ball of cells several layers thick with an internal cavity called the blastocoel
• blastocoel is closer to the animal than to the vegetal pole

Question 11

Gastrulation

Answer 11

• The beginnings of gastrulation is marked by the appearance of a pigmented slit - blastopore
• as gastrulation proceeds the blastopore is transformed form a slit, to crescent to a circle
• blastocoel destroyed to form the archenteron

Question 12

What does the ectoderm give rise to?

Answer 12

• It is the outer layer of pigmented cells

* gives rise to the nervous system and the epidermis of the skin

Question 13

What does the mesoderm give rise to?

Answer 13

• it lies just below the ectoderm

* gives rise to skeletal muscle, cardiac muscle, smooth muscle of the digestive and respiratory tract

Question 14

What does the endoderm give rise to?

Answer 14

• lines the archenteron (Cavity)

* epithelial cells of the digestive tract and the liver and pancreas