2.3.4 Fertilisation Flashcards
What is fertilisation?
It is the term used to describe the exact moment when the nuclei of the male and female gametes fuse
What happens to the number of chromosomes at fertilisation?
The full number of chromosomes are restored, forming a zygote
Where is the sperm deposited in mammal fertilisation?
The sperm is deposited near the entrance of the cervix
What is the acrosome reaction?
The acrosome reaction occurs when the sperm makes contact with the zona pellucida.
- Digestive enzymes are released from the acrosome
- These digest the zona pellucida, making way for the sperm
What is the cortical reaction?
Happens when the sperm fuses with the cell membrane
- Cortical granules are released, making the zona pellucida thicker and impenetrable to other sperm
Where does fertilisation in plants occur?
In the embryo sac
What is the first stage of plant fertilisation?
The pollen grain lands on the stomata, absorbing water and splitting open
What happens after the pollen grain has split open?
A pollen tube grows out of the pollen grain and down the style
What is the role of the tube nucleus?
It makes enzymes that digest the surrounding cells, making way for the tube
What happens once the tube reaches the ovary?
The tube nucleus disintegrates and the two male nuclei burst into the embryo sac. One of the nuclei fuses with the egg nucleus, forming a zygote
What does the second male nucleus do?
It fuses with two other nuclei and produces a large nucleus, which divides and becomes a food store for the mature seed
What type of fertilisation happens to plants?
Double fertilisation, due to the two male nuclei fusing with female nuclei
