Fertilisation Flashcards
Define fertilisation.
The union of the male and female gametes to form a diploid zygote
What happens when a pollen grain lands on a stigma?
The pollen grain is stimulated to grow by sugars produced by the stigma
What stimulates the pollen grain to grow when it lands on a stigma?
Sugars produced by the stigma
What happens when the pollen grain has been stimulated to grow by the sugars produced by the stigma?
A pollen tube grows down through the style towards the ovule
What controls the growth of the pollen tube?
It is controlled by a nucleus (tube nucleus) which degenerates when the pollen tube reaches the micropyle (opening of the ovule)
What does the pollen tube grow towards?
The ovule
What happens to the tube nucleus when the pollen tube reaches the micropyle?
It degenerates
When does the tube nucleus degenerate?
When the pollen tube reaches the micropyle
How does the pollen tube know to grow to the ovule?
The pollen tube grows towards chemicals released from the ovule (chemotropism)
What is the function of the pollen tube?
It allows the male gametes of the flowering plant to move towards the egg without the need for external water (Adaptation towards life on land)
What is the main adaptation towards life on land for flowering plants?
(2)
The pollen tube
It allows the male gametes to move towards the egg without the need for external water
In relation to fertilisation, why are flowering plants said to be unique?
They have a double fertilisation
What passes through the pollen tube?
The two haploid male gamete nuclei
What creates the pollen tube?
The tube nucleus
What happens to the first haploid male gamete nucleus?
2
It joins with the egg nucleus to form a diploid zygote
This zygote will develop into an embryo (young plant)
