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Grade 12 IEB Life science/biology strand 2: (2.3) Reproductive animal strategies summary $4.50   Add to cart

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Grade 12 IEB Life science/biology strand 2: (2.3) Reproductive animal strategies summary

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This aesthetic, in-depth, neatly typed document summarises 2.3 of strand 2 of the IEB grade 12 mind action series textbook: Reproductive animal strategies. it includes the full 2.3 reproductive animal strategies syllabus as well as additional class and research notes.

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  • November 29, 2022
  • 7
  • 2022/2023
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By: karelconradie • 1 year ago

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REPRODUCTIVE ANIMAL STRATEGIES
Reproduction: Production of a new generation of organisms from existing generation



Goal of species: To produce the maximum number of surviving o spring while using least amount of

energy = reproductive e ort

• Unique reproductive strategies ensure maximum reproductive success = successful breeding &

survival to reproductive age



1) Courtship:

Behaviour/signals designed to attract another animal for mating & breeding

• Simple strategies: chemical, visual or auditory stimuli

. - Species speci c pheromones eg. moths

- Singing (species speci c) eg. frogs

- Species speci c song & colours eg. birds

• Complex strategies:

- Females favour larger, energetic males

- Blue crane's courtship displays: complex calls & elaborate dances

- Springbok: Annual rut (period of sexual excitement), results in breeding taking place if conditions

are favourable

- Courtship feeding (birds)

• Courtship maximises reproduction:

- Ensures male & females are suitable mates

- Ensures males & females are ready for mating at the same time

- Energy expenditure usually by male; female conserves energy for breeding. Therefore strong,

healthy o spring are produced



2) External vs. internal fertilisation:

• External fertilisation: takes place in water & occurs in most aquatic vertebrates eg. sh, frogs

, . - Wasteful (huge number of eggs produced & most get eaten)

- Fertilisation is not certain

- Huge number of eggs and sperm are released into water

- Courtship rituals



• Internal fertilisation: Occurs in terrestrial vertebrates eg. reptiles, birds, mammals

. - Most birds & reptiles mate using cloaca

- Males have penis to insert sperm into female (copulation)

- More certain (Gametes are closer together and fewer gametes are needed)

- Energy saved in producing fewer gametes



3) Ovipary, Ovovivipary and vivipary:

• Reproductive strategies that describe that moment at which future o spring separates from

parent:

• Where embryos develop

• How embryo & foetus are nourished



• Ovipary: eg. catshark & snakes

. - Egg develops outside of body (fertilised internally or externally)

- Egg yolk is the only food embryos receive

- Most sh & amphibians (aquatic)

- birds and most reptiles (land)



• Ovovivipary: eg. ragged-tooth shark

. - Fertilised egg kept inside female until hatching (therefore o spring are born 'live')

- Embryo gets food from yolk in egg

- Some sh & reptiles

- Fewer eggs produced (mother's expenditure is less)

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