03 Animal Development

Question 1

What is cleavage?

Answer 1

cell division in the development of the embryo. Since the cell division occurs very quickly, the new cells don’t have time to grow bigger

Question 2

What are the new cells produced through cleavage called?

Answer 2

Blastromeres

Question 3

What’s a morula?

Answer 3

A solid ball of cells. An embryo containing 16-64 cells

Question 4

What’s a blastula?

Answer 4

a hollow ball of cells formed at the 128 cell stage

Question 5

What is visible in the blastula?

Answer 5

the blastocoel

Question 6

What poles does a developing blastula have?

Answer 6

animal pole and a vegetal pole

Question 7

Why is an egg’s yolk closer to the vegetal pole?

Answer 7

The cytoplasm towards the vegetal pole is denser with nutrients, and they become the embryo’s food source (the yolk).

Question 8

Why is the vegetal pole larger than the animal pole?

Answer 8

Because the yolk blocks cell division at the vegetal side, the cells divide more actively on the animal pole

Question 9

What does the vegetal pole give rise to?

Answer 9

The inside of the organism (intestines)

Question 10

What does the animal pole give rise to?

Answer 10

The outside of the organism (skin, nerves)

Question 11

What is gastrulation?

Answer 11

It occurs when a side of the hollow ball starts to move in to create a blastopore (indent)

Question 12

What does the blastopore expanding lead to?

Answer 12

forms the animal’s anus and digestive system

Question 13

What happens to the cells at gastrulation?

Answer 13

They start to differentiate to have different purposes

Question 14

Name the 3 embryonic germ layers

Answer 14

ectoderm, mesoderm, endoderm

Question 15

What does the ectoderm form?

Answer 15

Outer organs; skin cells, nervous system, sensory organs

Question 16

What does the mesoderm form?

Answer 16

Middle layer organs; muscle, kidney, circulatory system, reproductive system

Question 17

What does the endoderm form?

Answer 17

Inner organs; digestive system, lungs, thyloid

Question 18

Where does the neural fold form?

Answer 18

Along the back of the embryo

Question 19

What emerges from the neural fold area?

Answer 19

the notochord (pre-spine)

Question 20

A zygote is totipotent. What does that mean?

Answer 20

It’s able to rise to every type of cell in the human body

Question 21

Cells become more pluripotent after a while. What does this mean?

Answer 21

They are more restricted in what they can become.

Question 22

What can the final version of a cell do?

Answer 22

It can only read specific dna

Question 23

What is apoptosis?

Answer 23

programmed cell death, and it’s a major part of fetal development

Question 24

give 2 examples of apoptosis

Answer 24

removal of tissue, organ sculpting

Question 25

What are protostomes?

Answer 25

animals in which the mouth develops as the first opening in the digestive system

Question 26

What are deuterostomes?

Answer 26

Animals in which the first opening formed develops into the anus

Question 27

name differences in protostomes and deuterostomes

Answer 27

determination of cell types occurs earlier in protostomes and cleavage pattern/size is different. cell differentiation pattern is different for both

Question 28

Why do sea urchins develop in a symmetrical way?

Answer 28

Because their yolk is spread throughout the embryo (mammals too)

Question 29

How are the sizes of sea urchin cells?

Answer 29

They’re around the same size as others

Question 30

What are sea urchins surrounded by?

Answer 30

fertilisation membrane, from which the early embryo hatches

Question 31

Where does internal fertilisation occur?

Answer 31

In the female fallopian tube

Question 32

Once fertilised, where does the egg attach to?

Answer 32

The wall of the uterus

Question 33

Where does the embryo and foetus develop?

Answer 33

Inside the uterus in an amniotic sac filled with fluid

Question 34

What does a placenta do?

Answer 34

it allows the exchange of wastes, gases, nutrients with the mother