Mating and fertilisation in mammals

Question 1

How do mammals reproduce?

Answer 1

They reproduce sexually through internal fertilisation.

Question 2

What is internal fertilisation?

Answer 2

Where the male sexual organ is pushed into the female and ejaculation takes place inside.

Question 3

How does internal fertilisation increase the chance of successful fertilisation?

Answer 3

The sperm are introduced directly into the reproductive tract without contact to air.

Question 4

What usually precedes mating for mammals?

Answer 4

Courtship behaviours.

Question 5

What is the primary function of courtship behaviours?

Answer 5

To attract a mate to breed with.

Question 6

What are the many functions of courtship behaviours?

Answer 6

• Attract a mate;
• Same species;
• Different sex;
• Sexually mature;
• Heightens sexual responsiveness;
• Pair bond.

Question 7

What is a pair bond?

Answer 7

A close relationship between partners which keep them together while young are brought up, or for life.

Question 8

How is a pair bond formed?

Answer 8

Formed through courtship behaviours.

Question 9

What are pheromones?

Answer 9

Chemicals used by females to attract mates and signal they are in oestrus and able to conceive (sexually mature).

Question 10

What may female mammals do when they are oestrus (sexually mature)?

Answer 10

Release pheromones which attract potential mates and signal they are ready to breed.

Question 11

Do sexual pheromones occur in humans?

Answer 11

Yes, they may occur but their role is debated heavily.

Question 12

What is copulation?

Answer 12

Sexual Intercourse.

Question 13

Successful courtship rituals are likely to lead to what?

Answer 13

Copulation and fertilisation.

Question 14

In mammals, fertilisation of oocytes by sperm cells must take place deep in the female’s body. How is this achieved?

Answer 14

The males have a penis which can become erect for insertion in the female’s vagina.

Question 15

How does erection of the penis occur?

Answer 15

Hydraulic action - the penis becomes gorged with blood which acts as a hydrostatic skeleton.
In most mammals they also have a bone in the penis called the ‘os penis’ to provide extra support.

Question 16

How do most mammals copulate?

Answer 16

Most mammals have the males stand and enter the female from behind.

Question 17

Which mammals copulate face-to-face and what significance does this have?

Answer 17

Whales, humans, orang-utans, gorillas and chimpanzees. This is thought to play an important role in the formation of long-term pair-bonds.

Question 18

How does ejaculation occur?

Answer 18

Sperm is forced from the accessory glands into the vas deferens, the bladder sphincter closes, preventing urine from entering the urethra, sperm is expelled from the epididymis into the vas deferens and the urethra propels semen out of hte penis.

Question 19

How long does it take for human sperm to fertilise an oocyte?

Answer 19

A human sperm has to spend at least 7 hours in the female before they can fertilise an oocyte.

Question 20

What must occur within the female to allow fertilisation?

Answer 20

Capacitation.

Question 21

What is capacitation?

Answer 21

The functional maturation of the sperm.

Question 22

What happens to the sperm after capacitation?

Answer 22

They are able to swim more vigorously and release chemicals to penetrate the oocyte.

Question 23

How is a sperm cell drawn to its destination?

Answer 23

Through uterine contractions and the movement of cilia in the oviduct.

Question 24

How does a sperm cell maintain its nutrition when inside the female?

Answer 24

Fructose from within the semen and then by the nutrients of vaginal secretions.

Question 25

How many sperm cells start the journey into an oocyte, how many reach a cell and how many fuse with it?

Answer 25

Millions of cells start the journey to the oocyte in the oviduct, and several hundred may crowd around the cell, but only one will eventually fuse with it.