These notes are for IEB Grade 12 Life Sciences. They include information on sexual and asexual reproduction in plants including pollination, fertilisation and seed formation, reproductive strategies (r and K method) in animals, courtship behaviors and fertilisation methods.
- 2 parents
- Genetic material combines (offspring different from parents)
- Gametes are created in the gonads through meiosis
o Haploid ovum or sperm
- Gametes combine to create a diploid zygote
- There is large genetic variation within populations
o This increases the chance of survival in changing environments
- Can result in speciation
- The chance is inheriting “bad” genes is reduced
o Negative mutations are possible
- There are fewer offspring per parent
o It takes longer to produce games as it requires large amounts of energy
o Special organs need to be created to produce gametes (flowers)
- Agents are needed to disperse pollen and seeds
Asexual reproduction
- One parent needed
- All offspring have the same genetic material
o “Clones” of parent
- Creation of offspring through mitosis
o No gametes required
- Large numbers of offspring can be created in favourable conditions
o This is due to the low energy expenditure
- Offspring are well suited to environmental conditions
o React the same as the parent plant
o When conditions change they struggle to adapt
- If the parent plant is strong the offspring will be strong
o If the parent plant is weak, offspring are weak
- Lots of offspring can mean overpopulation
o There is an increase in competition
, Reproduction in Plants and Animals
Reproductive organs
Dicotyledonous plants
Angiosperms are flowering plants
- Their sexual organs are flowers
o Eggs = Ova
o Sperm = Pollen
There are 4 whorls in dicotyledonous plants
- Calyx, Corolla, Androeceium,
Gynoecium
Calyx
Outermost whorl
- Small green sepals which protect the flower in bud
Corolla
Brightly coloured petals (fused together)
- Attract insects fro easier pollination
Androecium (male)
Stamens
- Attached inside the petals
- A long filament and lobed anther
o The pollen is formed in the anther
Gynoecium (female)
Stigma, style and ovary
- Stigma: Sticky and receives pollen
- Style: Long and thin, where pollen tube grows
- Ovary: 2 locules with ovules
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