Reproduction - Paper 1 Flashcards
What is fertilisation? (Plants)
When a pollen grain lands on the stigma of a flower of the correct species, a pollen tube begins to grow. It grows through the style until it reaches an ovule inside the ovary. The nucleus of the pollen then passes along the pollen tube and fuses (joins) with the nucleus of the ovule. This process is called fertilisation.
Why is self-pollination avoided?
Cross-pollination helps with genetic variation so that changes in the environment do not affect the species. Self-pollination inhibits this, and is therefore avoided
How do plants avoid self pollination?
- They have their stamen above the stigma so that pollen can be blown away easily.
- the stigma matures after the stamen, so that the stamen of the plant has already gone when the stigma is matured,
What are characteristics of insect pollinated flowers?
- brightly coloured
- have a nectary + scent
- have a sticky and small stigma
- have only a few anthers
- pollen has barbs to hook onto pollinators
- e.g roses, tulips, lily, sunflower
What are the characteristics of wind pollinated flowers?
- petals are small or don’t exist because they aren’t needed and could get in the way
- no nectary or scent
- large and feathery stigma on outside of flower to catch pollen
- many exposed anthers so that pollen can easily be blown away
- produce a lot of pollen, which are small and light to easily be carried in the wind
What is the difference between self-pollination and cross-pollination?
Cross pollination is when the pollen from one plant pollinates another plant, self pollination is when a flower pollinates itself by accident.
What is the micropyle?
It is where the pollen tube entered the ovule
What is meant by the term germination?
Germination is when a new plant grows from a seed. The testa splits and a root and shoot emerge.
What happens during germination?
- water enters the seed through the micropyle and activates enzymes
- the water also softens the testa to allow it to split
- the enzymes break the starch in the cotyledon down into maltose and then glucose. This glucose is then used in respiration to provide energy for growth.
- the radicle grows first, so that it can get water
- then the plumule grows…
What is meant by the term dry mass?
The mass of an object when completely dried, without any water
Explain what a graph showing the dry mass of a seed during germination would look like and why
- the graph line would start high, then curve down and then steadily grow again
- the graph line would start high because the seed starts full of starch and stores, because it needs this energy as it cannot yet photosynthesise
- the graph line curves down because the seed loses stores because it is using up energy to grow
- the graph line steadily grows because the plant is growing and increasing in mass as it photosynthesises
How is pollination different to fertilisation?
Pollination is the transfer of pollen from the anther to the stigma, whereas fertilisation is when the male and female gametes fuse
What are three conditions which are essential for germination to take place?
water, oxygen and warmth
Draw and label a diagram of the male reproductive system
Include:
Bladder, sperm duct, glands, urethra, penis, scrotum, testes
