More Reproduction Flashcards
What are the roles of oestrogen and progesterone in the menstrual cycle.
Oestrogen causes the uterus lining to thicken, stops FSH and releases LH.
Progesterone maintains the uterus lining and stops LH.
Insect pollinated
Contain large, colourful, scented petals.
Contains nectaries
Pollen grains have sticky or spiky outer walls
Stigmas are small and held inside the flower
Produce small amounts of pollen
Pollen is heavy
Wind pollinated
Small petals (don’t get in the way when wind blows the pollen)
Green/tiny petals
No scent
No nectaries
Many anthers which are often large and hang outside the flower so pollen is easily dispersed.
Stigmas are large and feathery to trap pollen.
Hang outside the flower.
Produce large amounts of pollen
Pollen is lightweight
What stimulates the development of secondary sexual characteristics
Oestrogen and testosterone
Sexual
Requires fertilisation
Two gametes needed
Two parents needed
Variation in offspring
Asexual
Does not require fertilisation
No gametes
Cells divide by mitosis
One parent
Genetically identical offspring
Stigma
Female
The part of the carpel where pollen lands during pollination
Ovary
Sits at the base of the carpel and protects the female gamete from the dry air outside
Ovule
Contains an egg sac that surrounds the egg cell
Female gametes
Sepal
Protects the flower in the bud
Anthers
Contain cells which produce the male gamete
Filament
Joins the anther to the rest of the flower
Nectary
Makes nectar and attracts insects
Pollen
The male gamete
Mitosis
Division of body cells
Meiosis
Division of gametes
Fertilisation
Happens in the Fallopian tube and involves the fusion of a male and female gamete which produces a zygote. This then becomes an embryo by mitosis.
An egg cell is large so that
It can store a lot of carbohydrates for energy
What carries speed from the testes to the penis
The sperm duct
What fluid surrounds the baba
Amniotic fluid
When does reproduction in plants occur?
When the male nucleus from the pollen grain fuses with the female egg in the egg sac
What stimulates the pollen tube to grow?
The pollen grain landing on the stigma
How does the pollen tube grow through the style
It used enzymes to break through the style and then enters the ovule
The growth of the pollen tube leads to…
Fertilisation
Fertilisation leads to….
Seed formation.
After fertilisation
Ovule
Ovary
Ovule-seed
Ovary-fruit
Steps of seed formation
1- zygote transforms into an embryo with a small root and shoot.
2-the other parts of the ovule then become cotyledons
3- the ovule will become the seed coat (testa)
4- the ovary will become the fruit coat
Micropropagation
The culture of explants in the lab to produce many clones of a single plant. (Artificial cloning)
Size and examples and other names for explants
Cuttings
0.5-1mm
Tips of shoots/roots
Micropropagation stages
1- explants is scraped from the parent plant.
2-cut and trim to shape
3-explants are placed in agar growth medium containing nutrients and auxins.
4- samples develop into tiny plantletes
5- plant legs are planted into compost
Advantages
Less likely to contain viruses
Good for research cos identical
Easier to produce plants that are difficult to grow from seeds
Guarednteed production of identical plants with desirable characteristics
Fast, requires small space
Disadvantages
Something goes wrong, can’t tell till too late then loads of dodgy plants
Interferes with nature
Reduces genetic variation and therefore increases vulnerability to change
What happens during pollination in plants
The pollen grains from the anther transfer to the stigma
Why does pollination happen
So that the male gametes can reach the female gametes
asexual reproduction
involves no fertilisation between male and female gametes. Offspring are genetically identical to their parents
Can you think of 3 organisms that reproduce asexuaslly?
bacteria
types of fungi
strawberries
steps of plant fertilisation
Pollen is transferred from one flower to another either by wind or insects
Pollen lands on stigma and grows a pollen tube down through the style and towards the ovary
The nucleus of the pollen grain passes down the tube and fertilises the egg cell inside the ovule
The fertilised egg develops into an embryo; the ovary forms the fruit and the ovule forms the seed
