Reproduction 2: Oogenesis and Mating

Question 1

Define oogenesis

Answer 1

The process of egg formation

Question 2

Describe the 4 stages of oogensis

Answer 2

1. Primary oocyte (diploid) Meiosis
2. Secondary oocyte (diploid) and first polar body
3. Ovum (haploid) and polar bodies
4. Ovum (haploid)

Question 3

How many ovums come from the primary oocyte? what is this different from?

Answer 3

The primary oocyte = 1 ovum

In contrast to the 4 sperm cells from a primary spermocyte

Question 4

Describe oogeneis in mammals

Answer 4

• Oogenesis within a follicle (1 ova with cells to norish)
• 400,000 follicles at birth but ovulation starts in puberty
• Starts in puberty
• 1 per month
• Follicle ruptures, oocyte enters Fallopian tube for fertilisation
• If not fertilised, degenerates and prepared uterus lining (thick, vascular endometrium lining) sloughs away

Question 5

In mammals, what happens if the egg is not fertilised?

Answer 5

The egg degenerates and the prepared (thick vascular) uterus lining sloughs away

Question 6

Describe oogenesis in fruit flies

Answer 6

• Oogenesis from distal to proximal
• Start in larval stage
• Eggs produced in a few days
• <100 per day
• Released into uterus for fertilisation
• Egg laid whether fertilised or not
• Oviparous (no pregnancy)

Question 7

When does fruit fly oogenesis begin?

Answer 7

Larval stage

Question 8

When does mammal oogenesis begin?

Answer 8

puberty

Question 9

Which 2 hormones help to control oogenesis?

Answer 9

LH and FSH

Question 10

How does FSH control oogenesis?

Answer 10

stimulates development of follicles and secretion of oestrogen

Question 11

How does LH control oogenesis?

Answer 11

stimulates maturation of follicles and release of ova at ovulation

Question 12

What is the role of oestrogen?

Answer 12

enhances growth of follicles, grows endometrium

Question 13

What is the role of progestrone?

Answer 13

grows and maintains endometrium for pregnancy, secretes nutrients for embryo

Question 14

How long is the menstrual cycle in humans?

Answer 14

28 days

Question 15

What does external gamete release require and why?

Answer 15

Requires water → males and females shed gametes into water

Question 16

What are 3 problems of external gamete release

Answer 16

• Can’t control delivery
• Requires huge numbers of gametes (due to problem of delivery)
• Predation of eggs

Question 17

What is indirect fertilisation?

Answer 17

Male deposits sperm ‘packet’ (spermatophore) and female picks it up

Question 18

What is direct fertilisation also known as?

Answer 18

Copulation

Question 19

What is direct fertilisation?

Answer 19

Where sperm is transferred directly into a female (often by intromittent organ)

Question 20

What is a hermaphrodite? Give an example

Answer 20

Individual has both ‘male’ and ‘female’ reproductive parts
E.g slugs

Question 21

Describe how hermaphrodites ferilise

Answer 21

• Partners exchange sperm and use that to fertilise their own eggs
• Generally not self fertilising
• Eggs more expensive than sperm

Question 22

Give an example of an organism that uses traumatic insemination

Answer 22

Bed bugs: Females lack gential openings, male pierces membrane and places sperm into the females haemocoel

Question 23

What is sexual canibalism? Give some examples

Answer 23

Female kills mate during or after copulation
e.g spiders, preying mantis, amphipods