Reproduction Flashcards
Definition of sexual reproduction
The joining of two sex cells or gametes during during fertilisation
Two characters of sexual reproduction
- two parents needed
- offspring produced are genetically different to the parent
Two characteristics of asexual reproduction
- One parent needed
- offspring produced are genetically identical to the parent (eg bacteria, production of spores by fungi)
Three advantages of sexual reproduction
- introduces variation into a population
- species can adapt to new environments
- disease is less likely to affect all the individuals in a population
Two advantages of asexual reproduction
- population can increase rapidly
- can exploit a suitable habitat quickly
Two disadvantages of sexual reproduction
- time and energy needed to find a mate
- not possible for an isolated individual
Three disadvantages of asexual reproduction
- does not lead to variation in a species
- species may only be suited to one habitat
- disease may affect all the individuals in a population
Name a natural method for the reproduction of plants
Runners
Name an artificial method for the reproduction of plants
Cuttings
Explain how runners can be used in the asexual reproduction of plants.
- cells split off from the parent plant to grow a radicle (side branch) which forms plantlets
- this forms a plant that is genetically identical to the parent plant via asexual reproduction (cloning)
Explain how cuttings can be used in the asexual reproduction of plants.
- specific plant tissue is selected and sterilised
- tissue sample is taken and grown in a petri dish containing sterile nutrient agar gel
- the explant is treated with auxins to stimulate shoot + root development
- once root and shoot are developed, the cloned plant is then transferred to soil
define fertilisation
the fusion of a male and female gamete to produce a zygote that undergoes cell division and develops into an embryo
Describe the process of fertilisation in plants
- Digestive enzymes are produced by the tip of the pollen tube, enabling it to grow through the style and ovary tissues and reach the ovule.
- The pollen grain enters the ovule through a small gap, the micropyle , to reach the egg cell (the female gamete).
- The male nucleus/gamete is then able to travel down the pollen tube into the ovule, so that it can fuse with the egg cell (fertilisation).
The plant zygote becomes…
The seed
Petals (wind pollinated)
Scentless, inconspicuous or absent (replaced by another structure)
Nectar and scent (wind pollinated)
None
Stamen (wind pollinated)
Long filaments so anthers hang outside flower when ripe.
Pollen (wind pollinated)
Grains with smooth surface to help float through the air. Produced in large quantities.
Stigma (wind pollinated)
Often feathery and hangs outside flower to increase chance of catching pollen in the air.