Reproduction

Question 1

The four stages of fertilization:

Answer 1

Gametes are produced.

The sperm is transferred to the ovum.

The fusion of gametes - fertilization occurs.

A zygote is formed which divides by mitosis to develop into a new individual.

Question 2

Define chromatids:

Answer 2

One of the two (thread-like) copies of a replicated chromosome.
Each chromatid contains an exact copy of the double helix of DNA.

Question 3

What happens in the two stages of meiosis?

Answer 3

• Chromosomes pair up in homologous pairs. One chromosome from each homologous pair separates into each of the two new daughter cells
• Chromatids of each chromosome separate and each chromatid goes into each of the new daughter cells

Question 4

Structure of sperm:

Answer 4

Head: enzyme sac, nucleus

Midpiece: mitochondria

Tail: like a flagellum for propulsion

The cytoplasm of the ovum contains stores of energy and materials so that the fertilized egg can start dividing and developing into an embryo

Question 5

The stages of fertilization-:

Answer 5

• Sperm approaches the egg
• Penetrates through the cell membrane
• Nucleus of sperm fuses with the nucleus of the ovum (The fertilization membrane that prevents any more sperm from penetrating)

Question 6

Define ovulation:

Answer 6

The release of an egg from a follicle in the ovary

Question 7

The course of the sperm:

Answer 7

Testes ➡ Sperm duct ➡ Seminal vesicle (semen - provides nutrients and a medium for swimming) ➡ urethra ➡ vagina

Question 8

The course of the ovum:

Answer 8

Follicle rupture ➡ ovary ➡ Fallopian tube ➡ uterus ➡ zygote ➡ embryo…

Question 9

The function of the placenta:

Answer 9

An organ that contains the blood vessels of the embryo in close proximity to the blood vessels of the mother. Allows the exchange of gases, nutrients, and waste products. (+antibodies)

Secretes progesterone that helps maintain the pregnancy and prevents the embryo from being aborted.

Maintains the position of the embryo in the uterus

Question 10

The functions of the umbilical artery and umbilical vein:

Answer 10

Umbilical artery: carries deoxygenated blood and waste products from the fetus to the placenta

Question 11

Structure of the placenta:

Answer 11

Umbilical cord: umbilical artery and umbilical vein ➡ chorionic villi ➡ membrane: separates the mother and fetus’ blood ➡ pool of the mother’s blood

Question 12

How is the embryo protected in the womb?

Answer 12

The embryo is enclosed in a membrane called the amnion that secretes amniotic fluid, which acts as a shock absorber and protects the embryo from sudden movements and bumps

Question 13

The stages of the birth process:

Answer 13

Dilation of the cervix: muscles of the uterus contract to tear the amnion

Delivery of the baby: strong muscle contractions of the uterus push the baby’s head through the cervix then the vagina

Delivery of the afterbirth: uterus continues to contract and pushes the placenta out, together with the membranes that surrounded the body

Question 14

Two hormones involved in breastfeeding:

Answer 14

Prolactin influences the production of milk

Oxytocin stimulates the release of the milk

Question 15

Changes in the mother’s diet when breastfeeding:

Answer 15

The energy intake has to increase by 25% together with an increase in the intake of protein, calcium, and vitamins

Question 16

The advantages of breastfeeding:

Answer 16

• Very healthy
• Contains antibodies
• Emotional bond

Question 17

Developments involved in puberty:

Answer 17

• Production of gametes
• Development of secondary sexual characteristics
• Reproduction can occur

Question 18

The functions of FSH and LH in males:

Answer 18

FSH: stimulate sperm production

LH: stimulates the production of testosterone

Question 19

The average age for puberty:

Answer 19

Females: 11-14
Males: 13-16

Question 20

The function of the menstrual cycle:

Answer 20

Control the development of the lining of the uterus so if the egg is fertilized then the uterus would be ready to receive it.

If not fertilized, it is lost through the body as the flow of menstrual blood and the cells of the lining

Question 21

Methods of contraception:

Answer 21

Natural methods:

• Avoid intercourse
• Intercourse during the “safe period” (unreliable)
• Withdrawal before ejaculation (unreliable)

Barrier methods:

• Condom and femidom (protects against STDs)
• Cap with the spermicidal cream

IUDs: prevent the fertilized egg from implanting. Some contain progesterone which thickens the mucus in the cervix

Hormonal methods (contraceptive pill):

• Combined pill: estrogen and progesterone (preventing the production of FSH and LH)
• Mini-pill: progesterone thickens the mucus in the cervix

Sterilization:

• Vasectomy
• Tubal ligation

Question 22

Possible fertility treatments:

Answer 22

• Surgical procedures due to a blocked oviduct or a cyst in the ovary
• Hormonal treatments: FSH
• Artificial insemination (Healthy sperm is placed in the woman’s uterus at the time of ovulation to increase chances of fertilization)
• In-vitro fertilization: Fertilisation occurs in a Petri dish. After a few days of monitoring the growth of the embryo, it is implanted into the woman’s uterus to continue its growth

Question 23

Reasons for infertility:

Answer 23

• Low sperm count
• Eggs may not develop properly (not ovulating properly)
• Blocked oviduct or a cyst on the ovary
• Not producing enough FSH to start egg development in the ovary

Question 24

Growth spurts:

Answer 24

Periods of rapid growth and development.

The infant growth spurt (4-10, the rate of growth decreases but more slowly)
Adolescent growth spurt