Presentation on theme: "OVIPARY, OVOVIVIPARY, VIVIPARY"— Presentation transcript:
1 OVIPARY, OVOVIVIPARY, VIVIPARY Introduction:Result of fertilisation is a diploid zygote (called egg)Three different reproductive strategies in vertebrateswhich are based on the relationships betweenzygote and parents / female (protection, nutritionand development of embryo) are called ovipary,ovovivipary and vivipary.
2 Ovipary OVIPARY: The fertilised eggs develop and hatch outside the mother's body.The female releases her fertilised eggs into the environment (outside the body of female).The fertilised egg / zygote is enclosed by a protective shell.Egg yolk provides nutrition for the embryo.Fertilisation can be internal or external
3 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.External fertilisation.Fertilised eggs and larvae easily dispersed by sea currents.
4 OVIPARY in terrestrial (land) environments – maximising reproduction Protective shell (leathery shell in case of reptiles) prevents embryo from drying out. Shell of embryo of birds is hard and brittle (breaks easily).Fewer eggs in e.g. birds and reptiles – energy can be used for more food in large egg (yolk and albumin), hatching and protection, parental care.Female reptile makes a hole in soil to lay her eggs in it. The sun incubates them. Birds: Parent(s) sit on the eggs to keep them warm. Birds feed young one’s.Young reptiles are very vulnerable to predators.Development of amnion important factor in success. See the amniotic egg.
5 Hard shell good protection for developing embryo; prevents embryo from drying out.
6 (ovo+vivi+parity (a noun), egg-live-birthing) OVOVIVIPARYOVOVIVIPARY refers to the development of a fertilised egg enclosed with a soft shell that is retained (kept) in the mother's body. The young hatch within the mother's body and are then born. The developing young obtain nutrients from the yolk of theegg. Parents take no part in feeding the embryo.Ovovivipary occurs in some insects, some fish and somereptiles. Specific examples puff adder, Cape chameleon. Internal fertilisation, egg shell is soft, eggs hatch inside body,appears to be born alive, egg yolk nutrition, mother forprotection.(ovo+vivi+parity (a noun), egg-live-birthing)
7 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 fish and reptiles.
9 Young puff adder being “born alive” after hatching inside mother; note position of cloaca.Lorraine Kuun, July 2011
10 VIVIPARYVivipary refers to the development of the embryo in the female’s body uses nutrients from her body.Internal fertilisation, no egg shell, covered bymembranesNutrition via placenta from the mother tothe embryo. Waste is also passing throughthe placenta from the embryo to the mother.Young one’s have parental care. Study the detailduring human reproduction.
11 VIVIPARY maximising reproduction Occurs in placental mammals, some sharks and scorpionsFertilisation internal, no shellPlacenta responsible for nutrition – young born alivefewer eggs necessaryenergy available for nourishment and protection of embryo, as well as parental care
14 Some differences Ovipary Ovovivipary Vivipary Internal and external fertilisationInternal fertilisationFertilised eggs laid outside the body some examples enclosed by a leathery or calcareous shellFertilised eggs kept inside the body enclosed by a soft shellZygote, embryo and foetus develop in the uterus -protected by membranesEmbryo gets it’s food from the yolkGets it’s food from mother via the umbilical cordEgg hatches outside of the bodyEgg hatches inside the body just before birthLive young bornWith or without parental careParental care