Reproduction

Question 1

Define sexual reproduction

Answer 1

A form of reproduction which involves gametes (sex cells). It produces genetically varied offspring and involves mitosis and meiosis.

Question 2

Define asexual reproduction

Answer 2

A form of reproduction that doesn’t involve gametes. It produces genetically identical offspring (clones) and only involves mitosis.

Question 3

What is the difference between mitosis and meiosis

Answer 3

By mitosis, a cell splits to create two identical copies of the original cell. In meiosis cells split to form new cells with half the usual number of chromosomes, to produce gametes for sexual reproduction

Question 4

Where are human gametes produced and what are they called

Answer 4

The male gamete is called the sperm and is produced in the testes. The female gamete is called the ova and are produced in the ovaries.

Question 5

Name one difference between the sperm and egg cell

Answer 5

Either:

• The sperm cell has a tail-like flagellum, helping it move around in liquids.
• The ova is much bigger than the sperm cell

Question 6

Name three parts of the male reproductive system

Answer 6

Any three from:

• Scrotum
• Foreskin
• Testis
• Urethra
• Sperm duct
• Penis
• Prostate gland

Question 7

Name three parts of the female reproductive system

Answer 7

Any three from:

• Oviduct
• Ovary
• Uterus
• Cervix
• Vagina
• Urethra

Question 8

Name and define the types of fertilisation, and give an example of a species who does this type of fertilisation.

Answer 8

External fertilisation, when the sperm and ova fuse outside of the body. Species example can be fish

Internal fertilisation, when the sperm and ova fuse inside the body. Species example can be any type of mammal or bird.

Question 9

What are the risks of external fertilisation

Answer 9

External fertilization requires the presence of water to carry the sperm to the egg. That means animals with external fertilization must return to water to lay their eggs and fertilize them there. If the water current is too strong, it may carry the sperms away from the eggs, leaving many eggs unfertilized.

Question 10

How does the sperm fertilise the ova

Answer 10

When the sperm reaches the ovum, its nucleus enters the ovum and fuses with the ovum’s nucleus.

Question 11

How many chromosomes does each human gamete have?

Answer 11

Each human gamete has 23 chromosomes.

Question 12

List the order in which a fertilised egg develops in with these four words:
Gamete, embryo, fetus, zygote

Answer 12

1. Gamete
2. Zygote
3. Embryo
4. Fetus

Question 13

How do sperm each the ova

Answer 13

The sperm is carried into the sperm duct, mixes with a fluid and becomes semen. This is ejaculated from the penis into the vagina. The sperm cells then swim towards the oviducts. If an ovum is present, fertilisation may occur.

Question 14

Where do the ova come from

Answer 14

The ova comes from the ovaries. One ovum is released from an alternating ovary each month.

Question 15

How does the ova become an embryo

Answer 15

When the ovum is fertilised, it becomes a zygote. The zygote will travel down the oviducts, whilst turning into an embryo via mitosis, where the cells split identically into two, then four, then eight and so on before becoming an embryo

Question 16

How does the embryo become a fetus

Answer 16

The embryo exits the oviducts and reaches the uterus. The uterus lining is thick in order to support the developing embryo and stop it aborting, thanks to the hormone progesterone. Mitosis keeps occurring until the embryo looks human, which is when it’s referred to as a fetus

Question 17

What happens in the womb during pregnancy

Answer 17

Any of these things:

• The amnion membrane encloses itself around the fetus. This membrane then produces amniotic fluid, protecting the fetus against jolts and bumps, keeps the baby warm and stops the baby from drying out.
• The umbilical cord connects the fetus to a placenta. This anchors the embryo in the uterus, as well as allowing gas and nutrient exchange between the mum and the baby

Question 18

How do oxygen and nutrients enter the body

Answer 18

The mother’s artery supplies oxygen and nutrients via diffusion into the placenta. They then go through the fetal vein in the umbilical cord to the developing embryo/fetus.

Question 19

How do carbon dioxide and other waste materials exit the fetus/embryo

Answer 19

The fetal artery, located in the umbilical cord, carries CO2 and urea to the placenta. They then diffuse through a membrane into the mother’s artery, via capillaries. The capillaries lead into the vein, where the waste is then excreted from the body.

Question 20

List a reason as to why the mother’s circulatory system isn’t directly connected to the baby’s circulatory system.

Answer 20

Either:

• The baby’s blood type may be different to the mothers. This means that the white blood cells will attack the embryo’s blood, eventually killing the embryo/fetus (as they see the embryo/fetus’ blood as a foreign body)
• The blood pressure of the mother will be far greater than the embryo/fetus’, which means that if they were connected then the blood will spray into the embryo/fetus’ tissues, deforming and possibly breaking them, which can kill the embryo/fetus.

Question 21

Name two hormones in females which affect their reproductive system.

Answer 21

Oestrogen - lining of the uterus becomes repaired and thickened after menstruation, released is triggered by the hypothalamus.
Progesterone - secreted from the placenta during pregnancy and the corpus luteum during menstration.