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)
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)
