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Summary Reproductive Animal Strategies - Life Sciences
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Summarised notes on Matric Reproductive Animal Strategies from the Mind Action series Life Science textbook.
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Reproductive Animal StrategiesGoal of each species
Reproductive effort: Produce the maximum number of surviving offspring while using the least amount of
energy
reproductive strategies have developed to enable species to breed successfully and then survive to reproductive
age
Courtship
Behaviour and/or signals designed to attract another animal for mating and breeding
Simple strategies
Chemical (pheromones), visual or auditory stimuli are used to find mates
- Insects: some females produce species-specific pheromones that attract males eg: moths
- Frogs: Male frogs sing a species-specific song at breeding ground (water) to attract females
- Birds:Males sing a species-specific song to attract females and then must impress and sexually
stimulate her often by special plumage
Complex Strategies
Unique to each species
Females usually favour large, more elaborate physical features and high energy active males
Helps reinforce pair bonding and promises healthier offspring
- Birds: blue cranes’ have a complex and extended series of cells as well as an elaborate dance by males
- Springbok: annual rut (period of sexual excitement): They defend territories with loud grunts, attack
vegetation and deposit urine and dung in a ritualised display to attract females. Timely reproduction
in spring before the rainy season to ensure mothers are in good condition and young are born when
there is enough food. These favourable conditions are all a result of rutting strategy
How courtship maximises reproduction of healthy offspring
- Ensure strongest males and females find suitable mates
- Sexual behaviour is timed so both are ready for mating at the same time
- Energy expenditure usually by male, so female conserves it for breeding
External vs internal fertilisation
External fertilisation
In water in most aquatic vertebrates
Not ideal as:
, - Wasteful as many eggs are produced but most are eaten
- Fertilisation is not certain
How it can maximise reproduction
- Huge numbers of eggs and sperm released to increase probability of fertilisation
- Courtship rituals eg fish swim side by side when releasing eggs and sperm to ensure fertilisation occurs
Requires a lot of energy
Internal fertilisation
In terrestrial vertebrates
Male gametes released directly into body of female (mating or copulation) and fertilize eggs inside body
- Birds and reptiles: use a cloaca (single opening in lower abdomen) male and female line up their
cloacae for transfer of sperm
- Mammals: males have a penis to introduce sperm into female (copulation) ensures sperm is transferred
without any environmental conditions interfering
How it can maximise reproduction
- Fertilisation is more certain as gametes are placed as close together as possible therefore fewer are
needed
Uses less energy and therefore can be used for other purposes to maximise reproduction
Ovipary, ovovivipary and vivipary
Describe the moment at which the future offspring separates from a parent and indicate:
- Where embryos develop
- How embryo and foetus are nourished
Ovipary
Eggs develop outside of the parent (may fertilise externally or internally)
Egg yolk is the only food developing embryos receive until they hatch
How ovipary in aquatic environments maximises reproduction
- LArge numbers of eggs with a small yolk needed as eggs are vulnerable to predation
Requires high amount of energy from female however less needed for parental care
SA Example: Catsharks lay eggs aka mermaids purses, empty shells usually found on shores
How ovipary in land environments maximises reproduction
- Few eggs produced thus saving energy that goes into:
- Producing eggs with nutrient rich yolk and protein-rich abdomen, allowing fully formed
animal at hatching
- Protection and incubation of eggs
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