Post by Admin on Oct 4, 2016 19:10:46 GMT
Sexual reproduction involves two sex cells joining together during fertilisation. A gamete is a sex cell.
Asexual reproduction means that new individuals are formed from only one parent. In asexual reproduction, the offspring are identical to the parent. An example of asexual reproduction in plants is when strawberry plants form runners. These runners produce new and identical plants.
In sexual reproduction, the offspring have a combination of features inherited from each parent. The flower is the reproductive part of the plant.
Parts of a flower:
Sepals - Protect the flower when it is a bud.
Petals - Protect reproductive parts and sometimes attract insects.
Carpel - The female part of the flower, it produces the female gamete (the egg)
Stamen - The male part of the flower, it produces the male gamete (in the pollen grain)
Structure of the carpel:
Stigma - Landing place for pollen grains.
Style - Connects stigma to ovary.
Ovary - Contains one or more ovules.
Ovule - Produces an egg
Egg - The nucleus of the egg is the female sex cell.
Structure of the stamen:
Filament - Supports the anther
Anther - Produces pollen grains
Pollen - The nucleus of the pollen is the male sex cell.
Pollination is the transfer of pollen from a stamen to a carpel.
Wind:
Petals are small, green and have no scent or nectar.
Huge number of small pollen grains formed
Stamens are large and hang outside the petals.
Stigmas are large and feathery and outside the petals.
Examples include grasses and oak trees
Insect:
Petals are large, colourful, scented and make nectar.
Small number of large pollen grains formed
Stamens are small and are enclosed by the petals
Stigmas are rounded and inside the petals
Examples include buttercups and roses
Fertilisation is the joining of the male and female gametes to form a zygote. The pollen grain forms a pollen tube which grows down to the ovule. The male gamete passes down the pollen tube and combines with the female gamete in the ovule. After fertilisation, the following events occur:
- The ovule becomes the seed
- A coat called a testa forms around the seed
- The zygote grows to form an embryo
The embryo consists of a radicle (roots) and plumule (shoots)
- The ovary swells with food to form a fruit which surrounds and protects the seed.
Dispersal is the carrying of the seed as far as possible from the parent plant. The benefit of dispersal is that the seedlings do not have to compete for light, space, water or minerals) with the parent plant.
Water dispersal - Coconuts
Self dispersal - Pea pod
Wind dispersal - Dandelion & Sycamore
Animal dispersal - Strawberry & Goosegrass
Germination is the growth of a seed to form a new plant. The main conditions for germination are water, oxygen and a suitable temperature. The main events in germination are:
- The seed absorbs water from the soil
- The food supply in the seed is used to allow the radicle and plumule to grow
- The radicle bursts out through the testa, followed by the plumule.
- Once the first leaves form above the soil, the seedling starts to make it's own food.
The stages in plant sexual reproduction are:
Pollination -> Fertilisation -> Dispersal -> Germination.
Asexual reproduction means that new individuals are formed from only one parent. In asexual reproduction, the offspring are identical to the parent. An example of asexual reproduction in plants is when strawberry plants form runners. These runners produce new and identical plants.
In sexual reproduction, the offspring have a combination of features inherited from each parent. The flower is the reproductive part of the plant.
Parts of a flower:
Sepals - Protect the flower when it is a bud.
Petals - Protect reproductive parts and sometimes attract insects.
Carpel - The female part of the flower, it produces the female gamete (the egg)
Stamen - The male part of the flower, it produces the male gamete (in the pollen grain)
Structure of the carpel:
Stigma - Landing place for pollen grains.
Style - Connects stigma to ovary.
Ovary - Contains one or more ovules.
Ovule - Produces an egg
Egg - The nucleus of the egg is the female sex cell.
Structure of the stamen:
Filament - Supports the anther
Anther - Produces pollen grains
Pollen - The nucleus of the pollen is the male sex cell.
Pollination is the transfer of pollen from a stamen to a carpel.
Wind:
Petals are small, green and have no scent or nectar.
Huge number of small pollen grains formed
Stamens are large and hang outside the petals.
Stigmas are large and feathery and outside the petals.
Examples include grasses and oak trees
Insect:
Petals are large, colourful, scented and make nectar.
Small number of large pollen grains formed
Stamens are small and are enclosed by the petals
Stigmas are rounded and inside the petals
Examples include buttercups and roses
Fertilisation is the joining of the male and female gametes to form a zygote. The pollen grain forms a pollen tube which grows down to the ovule. The male gamete passes down the pollen tube and combines with the female gamete in the ovule. After fertilisation, the following events occur:
- The ovule becomes the seed
- A coat called a testa forms around the seed
- The zygote grows to form an embryo
The embryo consists of a radicle (roots) and plumule (shoots)
- The ovary swells with food to form a fruit which surrounds and protects the seed.
Dispersal is the carrying of the seed as far as possible from the parent plant. The benefit of dispersal is that the seedlings do not have to compete for light, space, water or minerals) with the parent plant.
Water dispersal - Coconuts
Self dispersal - Pea pod
Wind dispersal - Dandelion & Sycamore
Animal dispersal - Strawberry & Goosegrass
Germination is the growth of a seed to form a new plant. The main conditions for germination are water, oxygen and a suitable temperature. The main events in germination are:
- The seed absorbs water from the soil
- The food supply in the seed is used to allow the radicle and plumule to grow
- The radicle bursts out through the testa, followed by the plumule.
- Once the first leaves form above the soil, the seedling starts to make it's own food.
The stages in plant sexual reproduction are:
Pollination -> Fertilisation -> Dispersal -> Germination.