Reproduction in vertebrates
Strategies
Strategy How it works? Advantages
External The sperm fertilizes the egg Water prevents the eggs from
Fertilisation outside the body of the female, drying out and allows the sperm
usually in water. to swim towards the egg.
Internal The male deposits its sperm Allows terrestrial animals to
Fertilisation inside the reproductive organs reproduce in a dry environment
of the female and fertilization without the need for water.
occurs inside the female’s Internal fertilization is more
reproductive organs certain than external fertilization.
Ovipary Eggs are laid and hatching Egg provides nutrition for the
takes place outside the developing embryo and protects
mother’s body. the embryo. A shelled egg frees
these animals from the need to
reproduce in water.
Vivipary The young develop inside the More efficient development of the
uterus of the mother after the embryo as nutrients are received
eggs are fertilised internally. for a longer period from the
mother’s blood through a
placenta. Embryo is protected in
the body of the mother.
Ovovivipary Young develop from eggs that Embryos obtain their nutrients
are fertilised internally and from the egg yolk. The eggs are
retained within the mother's protected from predators until
body after fertilisation until they hatching occurs.
hatch.
Amniote Egg Embryo protected by the shell Amniote egg protects embryo
of the egg; egg consists of from dehydration. Yolk sac
many extraembryonic provides nutrition, Allantois for
membranes that serve excretion, chorion for gas
different functions. exchange.
Precocial Hatchlings are quite well- Hatchlings are more prepared to
Development developed when they hatch – handle the challenges of the
eyes open, able to move, able environment; More independent
to feed. Brain size and
intelligence remains the same
throughout their lives.
Altricial Hatchlings are poorly- Parental care afforded to protect
Development developed when they hatch. the young from predators.
Unable to feed on their own,
cannot move. Brain size and
intelligence increases a lot
after hatching.
, Parental Care Parental care offered through Increases chances of survival of
building of nests, protecting the young.
the eggs, protecting the young,
teaching the young.
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