Topic 16 Flashcards
Asexual reproduction
The process used to produce genetically identical offspring from one parent (bacteria and many plants reproduce like this)
Advantages of asexual reproduction
- lots of offspring produced quickly
- no neet to attract mate, so less energy needed
- all offspring are genetically identical to parents so creates a consistent product
- crop plants can be grown asexually from cuttings, maturing quicker, harvested sooner
Disadvantages of asexual reproduction
- no genetic variation between offspring, organisms unlikley to adapt to changes in environment
- overpopulation may occur if too many offspring produced
Sexual reproduction
The process used to produces offspring that genetically distinct fron each other. It involves the fusion of thr nuclei of 2 gametes to form a zygote
Advantages of sexual reproduction
- produces genetic variation
- diversity can lead to natural selection
- selective breeding used to crop production and quality
Disadvantages of sexual reproduction
- it takes more time and energy so less offspring is produced in a lifetime and havento attract male
- two parents needed to can be a problem if organism is isolated
The stamen
- produced male gametes (anther and filament)
- anther: contains pollen grains that help produce male gametes
- filament- hold up anther
The carpel
- carpel produces female gametes (stigma,style and ovary)
- stigma: end bit that pollen grains attach to
- style: supports the stigma and connects it to ovary
- ovary: contains female gametes inside ovules
Pollination
The transfer of pollen from an anther to a stigma
Self-pollination
When pollen is transferred from an anther to a stigma on either the same flower or a different flower on the same plant
cross pollination
When pollen is transferred from an anther to a stigma on a flower from a different plant of the same species
Cross pollination and self pollination effects on plant population
. Self-pollinating plants don’t rely on pollinators- easier for the plant to spread to locations where there aren’t pollinators available.
• Cross-pollinating plants rely on pollinators to transfer pollen grains elsewhere.
Cross-pollination produces more variation - more likely to be able to adapt and survive any changes in the environment.
• Self-pollination produces less variation because the gene pool is smaller -less likely to be able to adapt to changes in the environment
Adapting to insect pollination
1) large brightly coloured petals to attract insects to the anthers and stigmas inside.
2) scented flowers and nectaries to attract insects.
3) stigma is sticky so that any pollen picked up by insects on other plants will stick to the stigma.
Insect-pollinated plants make big, sticky pollen grains - the grains stick to insects as they go from plant to plant.
Wind pollination
1) Small, dull petals
2) No nectaries or strong scents
3) Long filaments that hang the anthers outside the flower, so that a lot of the pollen gets blown away by the wind.
4) A large and feathery stigma to catch pollen as it’s carried past by the wind -stigma often hangs outside the flower too.
Wind-pollinated plants have lots of small, light pollen grains - these grains can easily be carried to other plants by the wind.
Process of fertilisation
• A pollen grain lands on the stigma of a flower, usually with help from insects or the wind
A pollen tube grows out of the pollen grain and down through the style to the ovary and into the ovule.
A nucleus from the male gamete moves down the tube to join with a female gamete in the ovule. Fertilisation is when the two nuclei fuse together to make a zygote. This divides by mitosis to form an embryo.
• Each ovule containing a fertilised female gamete forms a seed, which can then grow into a new plant.
Germination conditions
• Water - to activate the enzymes that break down the food reserves in the seed.
• Oxygen
- for respiration which transfers the energy from food for growth.
• A suitable temperature - for the enzymes inside the seed to work. This depends on what type of seed it is.
Urethra
A tube which carries sperm through the penis during ejaculation. Urine also passes through the urethra to exit the body
Urethra
A tube which carries sperm through the penis during ejaculation. Urine also passes through the urethra to exit the body
