Chapter 9: Reproduction in humans

Question 1

Asexual reproduction

Answer 1

Only needs one parent,

Since there is only one parent, there is no fusion of gametes and no mixing of genetic information.

As a result, the offspring are genetically identical to the parent and to each other: in other words, they are clones.

Question 2

Four stages of sexual reproduction

Answer 2

1. Gametes (sperm and ova) are produced
2. The male gamate (sperm) is transferred to the female gamete (ovum)
3. Fertilisation must occur - sperm fuses with the ovum
4. The sygote formed develops into the new individual

Question 3

Gametes

Answer 3

The cells from each parent that combine to form the zygote are called gametes. In humans, the male gamete is called sperm, and the female gamete is called an egg.

When the gametes join they form a cell called a zygote.

Human sperm and eggs contain 23 chromosomes. Human zygotes contain 46 chromosomes.

Question 4

Haploid

Answer 4

All gametes are haploid.

Haploid: having half the normal number of chromosomes

Question 5

Key definitions…

Answer 5

Gamete – cell with half the normal number of chromosomes, and only used for sexual reproduction

Zygote – cell formed when two gametes combine

Fertilisation – term to describe the joining of two gametes

Haploid – having half the normal number of chromosomes

Diploid – having the normal number of chromosomes

Question 6

Mitosis and Meiosis

Answer 6

Mitosis is the type of cell division used for growth, repair and asexual reproduction. Mitosis occurs wherever new cells are needed. It produces two cells that are identical to each other, and the parent cell.

In mitosis each chromosome is copied exactly.

Meiosis is a different kind of cell division. It is used to produce male and female gametes.

Question 7

Sperm

Answer 7

specialised for swimming…a tail-like flagellum

Question 8

External vs internal fertilisation

Answer 8

most fish release sperm into water…

…most mammals & birds ejaculate into bodies of females (Guy, did you know that??)

Question 9

Fertilisation

Answer 9

At fertilisation, the nuclei of the sperm and an egg join to form the zygote. The zygote contains 23 pairs of chromosomes - 23 single chromosomes from the sperm, and 23 single chromosomes from the egg, thereby creating the correct number of 46 chromosomes for all body cells. It also means the zygote contains a complete set of chromosomes from each parent.

Question 10

Meiosios -> Fertilisation -> Mitosis

Answer 10

Question 11

Male & female reproductive system

(WARNING: CONTAINS IMAGES OF THE WILLY WONKER AND THE NOO-NOO)

Answer 11

Question 12

Amnion

Answer 12

a membrane that encloses the developing embryo…

….this secretes amniotic fluid which protects the baby from jolts and bumps

Question 13

Fetus

Answer 13

when the embryo becomes recognisably human

Question 14

3 stages of birth

Answer 14

1. Dilation of cervix
2. Delivery of the baby
3. Delivery of the afterbirth

Question 15

Menstrual cycle

Answer 15

The menstrual cycle in women is a recurring process, taking around 28 days.

During the process, the lining of the uterus - womb - is prepared for pregnancy, and if pregnancy does not happen, the lining is then shed at menstruation.

Question 16

FSH

Answer 16

FSH

The hormone FSH is secreted by the pituitary gland. FSH makes two things happen:

it causes an egg to mature in an ovary

it stimulates the ovaries to release the hormone oestrogen

Question 17

Oestrogen

Answer 17

The hormone oestrogen is secreted by the ovaries. Oestrogen makes two things happen:

it stops FSH being produced - so that only one egg matures in a cycle

it stimulates the pituitary gland to release the hormone LH

Question 18

LH

Answer 18

The hormone LH causes the mature egg to be released from the ovary.

Question 19

Progesterone

Answer 19

Progesterone is a hormone secreted by ovaries. It maintains the lining of the uterus during the middle part of the menstrual cycle and during pregnancy.