Section 3: a) (Human) Reproduction

Question 1

What are the main features of sexual reproduction?

Answer 1

~Involves the joining (fusion) of male and female gametes
~Involves two parents
~Leads to variation between the offspring
~Slower type of reproduction because a mate has to be found
~Type of reproduction which humans use to produce offspring

Question 2

What are the main features of asexual reproduction?

Answer 2

~No fusion of gametes
~Involves only one parent who can produce new life
~Does not lead to variation in the offspring (clones are produced)
~Faster type of reproduction because a mate does not have to be found
~Type of reproduction sometimes used by plants and insects but happens very often in bacteria or fungi

Question 3

Describe the differences between sexual and asexual reproduction.

Answer 3

Sexual reproduction involves the joining (fusion) of male and female gametes; the offspring inherit genes from two parents. Whereas, asexual reproduction does not involve the fertilisation of gametes; the offspring inherit genes from only one parent.
Sexual reproduction leads to variation between the offspring whereas asexual reproduction doesn’t lead to variation in the offspring (clones are produced). Sexual reproduction is the slower type of reproduction as a mate has to be found. Whereas, asexual reproduction is the faster type of reproduction as a mate doesn’t have to be found. Humans use sexual reproduction to produce offspring whereas bacteria & fungi often use asexual reproduction and plants & insects sometimes use it too.

Question 4

What are gametes?

Answer 4

Gametes are specialised cells for sexual reproduction. The male sex cell is called the sperm and the female sex cell is called the egg.

Question 5

What are some adaptations of a sperm cell?

Answer 5

~Long tail for swimming
~Head for getting into the female cell
~Nucleus: controls the sperm cell, carries DNA
~Contains enzymes so it can digest into the egg

Question 6

What is the function of a sperm cell?

Answer 6

To reach the female cell (egg) and fuse with it.

Question 7

Give two adaptations of an egg cell.

Answer 7

~Large

~Contains lots of cytoplasm

Question 8

What is the function of an egg cell?

Answer 8

To fuse with the male cell (sperm) and then to provide food for the new cell that has been formed.

Question 9

What does the egg do after one sperm nucleus has entered it?

Answer 9

It quickly forms a protective barrier/membrane to prevent other sperm from entering.

Question 10

What does fertilisation in sexual reproduction involve?

Answer 10

Fertilisation involves the fusion of a haploid sperm nucleus and a haploid egg nucleus in the fallopian tube to produce a diploid zygote.

Question 11

When the zygote undergoes cell division what does it develop into?

Answer 11

It develops into an embryo which is a ball of 64 cells.

Question 12

What is the name of the process when the embryo embeds itself into the thickened uterus lining?

Answer 12

Implantation

Question 13

How does the embryo get its nutrients for the first 3 months?

Answer 13

For the first 3 months, the embryo receives nutrients from the mother by diffusion through the uterus lining.

Question 14

How long does gestation occur?

Answer 14

It lasts for about 40 weeks, starting from the time of the woman’s last period. In this time, the fetus’ mass will increase by approximately 8 million times.

Question 15

What happens after 3 months?

Answer 15

The placenta has developed and the embryo is now a fetus where all its major organs can be identified.

Question 16

What is the placenta?

Answer 16

It is an organ which allows materials to constantly be exchanged between the mother and fetus. It develops from fetal tissues.

Question 17

What substances diffuse from the mother’s blood into the fetus?

Answer 17

Water, oxygen, minerals e.g. calcium, amino acids, glucose, vitamins.
(Alcohol and nicotine can also pass through)

Question 18

Give three reasons why it is important that the maternal and fetal blood do not mix.

Answer 18

1. The higher blood pressure of the mother could damage the fetus.
2. To prevent toxins and bacteria from passing from the maternal to the fetal blood.
3. The mother creates antibodies which reject the fetus and could damage it.

Question 19

Which substances diffuse from the fetus’ blood into the mother’s blood and why is it important they are removed?

Answer 19

Carbon dioxide and urea. They have to be removed as the fetus could reabsorb them; they are toxins.

Question 20

What is the amniotic sac and how does it protect the fetus?

Answer 20

The amniotic sac is a bag of fluid that the fetus develops inside and is contained in the amnion (the bag’s membrane). The fluid protects the fetus from damage and variations in temperature.

Question 21

What is the function of the oviduct?

Answer 21

It carries the ovum from the ovary to the uterus.

Question 22

What is the function of the ovary?

Answer 22

It produces ova and the hormone oestrogen.

Question 23

What is the function of the uterus?

Answer 23

It is where the embryo grows.

Question 24

What is the function of the vagina?

Answer 24

It is where the sperm are deposited.

Question 25

What is the function of the sperm tube/sperm duct?

Answer 25

It carries sperm from the testes to the urethra.

Question 26

What is the function of the urethra?

Answer 26

It carries sperm through the penis during ejaculation. Urine also passes through the urethra to exit the body.

Question 27

What is the function of the testes?

Answer 27

It produces sperm and the hormone testerone.

Question 28

What is the function of the penis?

Answer 28

It passes urine out of the body from the bladder and passes semen into the vagina of a woman during sexual intercourse.

Question 29

What are secondary sexual characteristics?

Answer 29

They are features that bodies have that identify them as either male or female.

Question 30

What are the two main purposes of secondary sexual characteristics?

Answer 30

So that the body is ready to reproduce and advertise that it is ready to reproduce to the opposite sex.

Question 31

What hormone controls the male secondary sexual characteristics and where is it made?

Answer 31

Testerone-made in the testes

Question 32

What hormone controls the female secondary sexual characteristics and where is it made?

Answer 32

Oestrogen-made in the ovaries

Question 33

What are the main male secondary sexual characteristics?

Answer 33

~Voice deepens
~Facial and body hair
~Start making sperm
~Penis and testicles enlarge

Question 34

What are the main female secondary sexual characteristics?

Answer 34

~Periods start
~Pubic hair
~Breasts and hips develop