1.4.4 gametes

Question 1

gametes

Answer 1

Gametes are sex cells and they are haploid. This means they have only one set of chromosomes, compared to all other cells in the body which are diploid and have two.
Sperm is the male gamete, and the egg is the the female gamete.
In fertilisation, a sperm and egg fuse to produce a diploid zygote, which divides to become an embryo.

Question 2

sperm cell

Answer 2

Sperm cells are highly specialised for their function.
Sperm cells must swim towards the egg, and to do this they have a tail. The tail moves with energy provided by mitochondria in the midpiece of the sperm.
The genetic material is contained in the head of the sperm cell, inside a nucleus. The head of the sperm is the only part to enter the egg of a female.
The head is covered by acrosome, which releases enzymes to break down the zona pellucida (the egg’s outer membrane).
Sperm cells are very small, so males can make many of them to increase the chance of fertilisation.

Question 3

egg cells

Answer 3

Egg cells are much bigger than sperm cells. Females produce less eggs than males produce sperm, but more is invested in each egg.
The cytoplasm of the egg cell is high in nutrients which are used when the embryo is growing.
The outer membrane of the egg is called the zona pellucida. The zona pellucida must be penetrated by a sperm in order for the egg to be fertilised.
Once a sperm has entered the egg, the zona pellucida plays a role in preventing polyspermy, where more than one sperm fertilises the egg.