The document summarises external and internal fertilisation, ovipary, ovovipary and vivipary. Including the advantages and disadvantages of each, where energy is spent and types of parental care.
External Fertilisation is achieved outside the ● Sessile organisms can have a ● Sperm and eggs may drift apart
fertilisation female maximised reductive success (fail to reach egg)
● No energy spent on parental care ● Sperm and eggs may be
Eg: frogs, Only in aquatic organisms or protective shell formation destroyed or eaten
muscles, ● Uncontrolled environment (may
oysters, fish Egg and sperm are released not be beneficial to survival eg:
simultaneously in water high/low temperatures)
● Requires many sperm and
Water provides a medium to prevent many eggs to be produced
desiccation ● Low change of fertilisation
Eggs surrounded by jelly layer, contain
yolk, no parental care
Internal Fertilisation is achieved in the female ● Gametes not exposed to ● Involves courtship and finding a
fertilisation environment ∴ won’t dry out mate
Insemination is achieved by sperm ● Embryos safe from environment ● Longer gestation
Eg: mammals, being placed in the female's body so and predators (protected)
sharks, birds, eggs are fertilised inside ● Higher change of successful
reptiles fertilisation
Achieved through copulation ● Laid eggs have protective shell
● Parental care
Table of offspring development strategies:
, Explanation Advantages Disadvantages
Ovipary Egg laying organism Aquatic organisms: Aquatic organisms:
● Nourished by egg yolk ● Susceptible to predators
Eg: birds, Embryos develop in the egg outside ● Many eggs with small yolks ● No parental care
platypus, the parent
echidna, Land animals: (amniotic egg) Land organisms:
reptiles, Fertilised internally or externally ● Nourished by egg yolk (larger) ● Susceptible to predators
insects, ● Protective shell to prevent
frogs, fish desiccation
● Parental care
Ovovipary Kept inside then hatched internally ● Younger born fully developed ∴ can
(soft shell) escape predators and get their own
Eg:some food
sharks, Kept at a constant ideal temperature in ● Protected by mother while
garter the mother developing
snakes Mother provides gaseous exchange
Internal fertilisation
Vivipary Egg cells have no shell ● Regulated incubation temperature
● Protected by mother at embryo
Eg: Embryo develops in female and is stage
placental nourished by female (live-born young)
mammals,
some Internal fertilisation
sharks
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