Mating and fertilisation in mammals Flashcards
(25 cards)
How do mammals reproduce?
They reproduce sexually through internal fertilisation.
What is internal fertilisation?
Where the male sexual organ is pushed into the female and ejaculation takes place inside.
How does internal fertilisation increase the chance of successful fertilisation?
The sperm are introduced directly into the reproductive tract without contact to air.
What usually precedes mating for mammals?
Courtship behaviours.
What is the primary function of courtship behaviours?
To attract a mate to breed with.
What are the many functions of courtship behaviours?
- Attract a mate;
- Same species;
- Different sex;
- Sexually mature;
- Heightens sexual responsiveness;
- Pair bond.
What is a pair bond?
A close relationship between partners which keep them together while young are brought up, or for life.
How is a pair bond formed?
Formed through courtship behaviours.
What are pheromones?
Chemicals used by females to attract mates and signal they are in oestrus and able to conceive (sexually mature).
What may female mammals do when they are oestrus (sexually mature)?
Release pheromones which attract potential mates and signal they are ready to breed.
Do sexual pheromones occur in humans?
Yes, they may occur but their role is debated heavily.
What is copulation?
Sexual Intercourse.
Successful courtship rituals are likely to lead to what?
Copulation and fertilisation.
In mammals, fertilisation of oocytes by sperm cells must take place deep in the female’s body. How is this achieved?
The males have a penis which can become erect for insertion in the female’s vagina.
How does erection of the penis occur?
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.
How do most mammals copulate?
Most mammals have the males stand and enter the female from behind.
Which mammals copulate face-to-face and what significance does this have?
Whales, humans, orang-utans, gorillas and chimpanzees. This is thought to play an important role in the formation of long-term pair-bonds.
How does ejaculation occur?
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.
How long does it take for human sperm to fertilise an oocyte?
A human sperm has to spend at least 7 hours in the female before they can fertilise an oocyte.
What must occur within the female to allow fertilisation?
Capacitation.
What is capacitation?
The functional maturation of the sperm.
What happens to the sperm after capacitation?
They are able to swim more vigorously and release chemicals to penetrate the oocyte.
How is a sperm cell drawn to its destination?
Through uterine contractions and the movement of cilia in the oviduct.
How does a sperm cell maintain its nutrition when inside the female?
Fructose from within the semen and then by the nutrients of vaginal secretions.
