3.OVIPARY, OVOVIVIPARY, VIVIPARY – terms used to describe what happens when future offspring separates from parent

1. 3.OVIPARY, OVOVIVIPARY, VIVIPARY – terms used to describe what happens when future offspring separates from parent • OVIPARY – eggs are released and develop outside body of female, fertilisation internal or external, egg yolk only nutrition. • OVOVIVIPARY – Internal fertilisation, egg shell soft, eggs hatch inside body, appears to be born alive, egg yolk nutrition, mother for protection. • VIVIPARY – fertilisation internal, no egg shell, nutrition via placenta. Lorraine Kuun, July 2011

2. OVIPARY in aquatic conditions • Most fish, amphibians and lower aquatic forms. • Needs large numbers of eggs. • Larval stage self-sufficient; don’t compete with parents – use different food sources. • Eggs and larvae easily dispersed. Lorraine Kuun, July 2011

3. OVIPARY in terrestrial (land) environments – maximising reproduction • Invertebrates produce large numbers of eggs to ensure survival (no or little parental care). • Protective shell prevents embryo from drying out. • Fewer eggs in e.g. birds and reptiles – energy can be used for more food in egg (yolk and albumin), hatching and protection, parental care. • Development of amnion important factor in success. Lorraine Kuun, July 2011

4. Hard shell good protection for developing embryo; prevents embryo from drying out. Lorraine Kuun, July 2011

5. Shark egg pouch with yolk clearly visible Lorraine Kuun, July 2011

6. OVOVIVIPARY – how is reproduction maximised? • Fewer eggs needed – higher survival rate of offspring. • Developing embryo much less vulnerable to predators. • Developing embryo not subject to environmental changes e.g. temperature. • Young born fully developed, can feed and escape predators more easily. • Occurs in some invertebrates, fish and reptiles. Lorraine Kuun, July 2011

7. Dogfish embryo with yolk sac Lorraine Kuun, July 2011

8. Lorraine Kuun, July 2011

9. Young puff adder being “born alive” after hatching inside mother; note position of cloaca. Lorraine Kuun, July 2011

10. VIVIPARY maximising reproduction • Occurs in placental mammals, some sharks and scorpions • Fertilisation internal, no shell • Placenta responsible for nutrition – young born alive • 1. fewer eggs necessary • 2. energy available for nourishment and protection of embryo, as well as parental care Lorraine Kuun, July 2011

11. Lorraine Kuun, July 2011

12. 4. Precocial vs. Altricial development PRECOCIAL • Young hatch or born when almost fully developed • Open eyes, hair or down • Active or mobile • Not confined to nests • Energy goes into prenatal development ALTRICIAL • Born or hatched when not well-developed • Often naked, lacking hair or down • Cannot walk or fly • Confined to nest or burrow • Energy goes into parental care after birth Lorraine Kuun, July 2011

13. PRECOCIAL ANIMALS • Ground-nesting birds e.g. Penguins, domestic poultry, ostriches • Large mammals e.g. Elephants, species of antelope, horses etc • Allows young to fend for itself, feed and stay warm • Stay with herd for protection against predators • Learn from older individuals in herds • OFFSPRING HAS GOOD CHANCE OF SURVIVAL Lorraine Kuun, July 2011

14. Left: Penguin chick and Above: foal, both mobile soon after birth Lorraine Kuun, July 2011

15. ALTRICIAL ANIMALS • Small animals that produce big litters e.g. mice, rats, cats, dogs • Tree-nesting birds that have nests away from predation • Humans (see human reproduction) • Altricial species need parental care for a long time – usually female that does the caring, male sometimes involved. • Birds usually have mouth-lining or gape-edge • Mammals small and immature brains Lorraine Kuun, July 2011

16. Altricial bird – see mouth-lining that attracts mother Lorraine Kuun, July 2011

17. Mice survive in broods, cared for by mother (left); Kittens born weak and totally dependent on mother (below) Lorraine Kuun, July 2011

18. 5. The Amniotic egg • Adaptation of later vertebrates; can lay eggs in terrestrial environment. • Amniotic egg has fluid-filled, extra-embryonic membranes that prevents embryo from drying out. • Earlier vertebrates lay eggs in water; need to return to water/live in water to reproduce. • Amniotic egg lessens dependence on water for reproduction. Lorraine Kuun, July 2011

19. The Amniotic egg • Fertilisation is internal. • Extra-embryonic (not part of embryo) membranes only develop after fertilisation. • Membranes are: • Amnion • Allantois • Yolk sac • Chorion Major evolutionary development; allowed first reptiles to colonise land! Lorraine Kuun, July 2011

20. The Amniotic egg Lorraine Kuun, July 2011

21. How does the amniotic egg maximise reproduction? • The fluid-filled amnion surrounds and protects the embryo, especially against dehydration and shock. • Allantois acts as reservoir for nitrogenous waste in birds and reptiles. • Yolk sac holds nutritious food for development of embryo. • Chorion surrounds all other membranes: in birds it allows for gaseous exchange; in mammals it forms the placenta (taking over functions of allantois and yolk sac, amongst others (see human reproduction). Lorraine Kuun, July 2011

22. Amniotic egg as seen in human embryonic development Lorraine Kuun, July 2011

23. 6. Parental care • Any pattern of behaviour in which parent spends time or energy to improve the 1survival, 2condition and 3future reproductive success of offspring. • Care can be given at any stage: • Prenatal – guarding eggs, building nests, carrying broods, incubating eggs and placental nourishing. • Post-natal – providing food, protecting offspring, teaching offspring. Lorraine Kuun, July 2011

24. Little or no parental care • Little or no parental care means a low reproductive effort. • Reproductive energy put into producing masses of eggs. • High mortality rate amongst eggs as well as young. • Few individuals survive to reproductive age. • E.g. Most fish, amphibians, insects, most reptiles Lorraine Kuun, July 2011

25. When parental care is given • Few eggs or young produced. • Low mortality rate amongst eggs or young. • High reproductive effort. • Reproductive energy goes into parental care after birth (post-natal). • Most offspring survive to reproductive age. • E.g. Mammals, birds, some reptiles, exceptions amongst fish and Arthropods. Lorraine Kuun, July 2011

26. Right: chicken laying egg, mother feeding young Left: Midwife toad

27. Ovovivipary type of parental care Left: Male seahorse with young emerging from breeding pouch Lorraine Kuun, July 2011

28. Lorraine Kuun, July 2011