Reproductive strategies in some animals

• Reproduction is the process of making new individuals of the same species (ensures continued survival of a species)
• Goal is to produced the maximum number of offspring whilst using the least amount of energy (reproductive effort)
• Reproductive strategies refers to the structural, functional and behavioral mechanisms or adaptations that improve the chances of successful fertilisation or survival of offspring
• strategy-genetically determined behaviour.
• Courtship is the behaviour or signals designed to attract another animal for mating and breeding
• different forms of courtship are simple and complex
• simple strategies include chemical, visual or auditory stimuli used to attract mates.
• Complex strategies are unique to each species.

  Females favor males that are larger, have more elaborate physical features, display more energy in courtship
• Complex strategy South African example:

  Springbok have a period of sexual excitement. Males defend territories with loud grunts, attack vegetation with horns.

  Young are born after 6months in the spring. This ensures mothers are in good condition and young are born when theres enough food
• How will courtship maximise reproduction?

  Ensures that suitable mates are found- females can choose better males allowing for healthier offspring, males and females are ready for mating at the same time, energy expenditure is on the part of the males so females save energy for breeding
• Simple strategy South African example:

  Most frogs have to return to water for mating and breeding(breeding ground). Males sing(croak, grunt) to attract females(each species has its own song)
• Fertilisation is the fusion of the nucleus of the egg and sperm.
• External fertilisation is fertilisation that takes place outside the body, usually in water.
• How does external fertilisation maximise reproduction?

  Many eggs and sperm produced resulting in more fertilised eggs.

  Courship rituals bring males and females together.
• External fertilisation South African example:

  Males frogs shed millions of sperm and female frogs shed 2000 - 3000 eggs which increases the possibility of fertilisation.

  Enough offspring grow into adults from the large number of eggs fertilised. Fish swim side by side when releasing eggs and sperm to ensure that the gametes are close to each other for fertilisation to occur.
• Internal fertilisation is fertilisation that occurs inside the body of one or both parents.
• cloaca is the single opening in the lower abdomen used birds and reptiles for mating
• once in inside the female the sperm swim to the egg in fluid-seminal fluid(from male) and mucous membrane fluids(from female)
• How does internal fertilisation maximise reproduction?


  Makes fertilisation more certain as gametes are as close together as possible hence less gamete production require. Energy is saved which is then used for other aspects of reproductio like parental care
• Internal fertilisation South African example:

  When lioness is ready, lion will try to grip her neck before getting support(mounting). Copulation is complete few thrusts after mounting
• Ovipary, ovovivipary and vivipart are reproductive strategies that decribe the moment at which the future offspring separates from a parent.
• Ovipary- eggs(internal/ external fertilisation) develop outside parent body.
• How does ovipary in aquatic environments?

  Many eggs are produced to ensure that some survive predation and sharks have egg cases, which well protect the developing embryo, containing the embryo and yolk supply, which provide nutrition for developing embryo
• Ovipary acquatic South African example:

  Cat sharks
• How does ovipary in land environment maximise reproduction

  Fewer eggs are produced, have a shell protecting the embryo from dehydration, pathogens and physical danger and have a nutrient-rich yolk to ensure better survival.
• Ovipary land South African example: Birds
• Ovovivipary - eggs kept inside the females body until they hatch
• How does ovovivipary maximise reproduction?

  Energy is conserved as fewer eggs are produce. Eggs are protected from predation and cold temperatures within the female body. Young are born fully developed enhancing chance of survival as they can get their own food and more easily escape predators
• Ovovivipary South African example:

  The ragged-tooth sharks embryo initially feeds on their own supply of yolk then eventually fertilised eggs and on other developing embryos( intro-uterine cannibalism)
• Vivipary- Eggs dont have protective shell. the egg develops into a embryo then foetus within the mothers body.
• How does vivipary maximise reproduction?

  Fewer eggs produced so energy is conserved to nourish the embryo via the placenta. Energy is also available for parental care. Embryo and foetus are protected within the mothers body. This greatly increases the chances of offspring surviving and reaching reproductive age.
• Vivipary South African example:

  Hammerhead sharks whose female joins with young via the yolk sac that forms a connection with the mothers oviduct tissue - young receive nourishment.
• Amniotic egg- Types of eggs produced by birds, reptiles and egg-laying mammals.
• What are amniotic eggs?

  An evolutionary adaption of terrestrial animals. Eggs have an extra-embryonic membrane(allantois, chorion, yolk sac, and amnion
• How does amniotic egg maximise reproduction?

  The membranes enables embryos to develop more quickly and to a greater extent prior to hatching. Frees animals from dependancy on bodies of water for reproduction
• Amniotic egg South African example:

  reptiles, birds and mammals.
• Parental care- patten of behaviour in which parent spends time or energy to improve the surviva, condition and futre reproductive success of offspring
• Parental care can be found in exothermic(fish, amphibians and reptiles) and endothermic(birds and mammals)
• Pre-natal care- guarding eggs, building nests, incubating and placental nourishment
• post-natal care- providing food, protection, teaching offspring