Scribd
Upload
64 views2 pages

Reproduction: Types of Fertilisation

This document discusses two types of fertilization: external and internal. External fertilization occurs outside the body, as seen in fish and amphibians where eggs and sperm are released into water and join. Internal fertilization evolved for terrestrial animals, allowing copulation to bring gametes together inside the female reproductive tract. This protects the fertilized egg from dangers outside and allows for fewer but larger offspring. The document provides examples of different animal groups that use internal fertilization, such as cartilaginous fish, reptiles, birds, and mammals.

Uploaded by

Kate
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
64 views2 pages

Reproduction: Types of Fertilisation

This document discusses two types of fertilization: external and internal. External fertilization occurs outside the body, as seen in fish and amphibians where eggs and sperm are released into water and join. Internal fertilization evolved for terrestrial animals, allowing copulation to bring gametes together inside the female reproductive tract. This protects the fertilized egg from dangers outside and allows for fewer but larger offspring. The document provides examples of different animal groups that use internal fertilization, such as cartilaginous fish, reptiles, birds, and mammals.

Uploaded by

Kate
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
You are on page 1/ 2

Reproduction

Types of Fertilisation

Process of bringing together the male and female sex cells


(gametes)
Process can be classified as internal or external reproduction

External Fertilisation
Fertilisation occurs outside the body.
This occurs in marine environments where the female releases
large amounts of eggs into the water. The male the releases
sperm in the same area.
A risk is that gametes will be dispersed quickly so the egg and
sperm must be released close together at the same time.
Fish have a relatively short reproductive period.
Most offspring are eaten or destroyed by microbes.
From bony fish to amphibians:
Bony fish carry out external fertisation.

Amphibians often has the reproductive part of the life cycle in water.
Example: the male frog grabs the female and releases sperm (in
fluid) at the same time the female releases eggs into the water.

Internal Fertilisation
External fertilisation for terrestrial animals is not an option.
Gametes would dry out.
Terrestrial animals had to evolve a way of bringing the gametes
together internally.
Copulation is where the male inserts sperm into the female
reproductive tract.
As the fertilised egg is not at risk of predation, dispersal or
dehydration, far fewer embryos are needed, so the female
produces fewer eggs.
Who does internal fertilization?
Cartilaginous fish e.g. sharks, rays

The male has a modified pelvic fin to insert sperm into the female.

Reptiles:
Reptiles have internal fertilisation, and then the eggs are laid and
continue to develop before hatching.
Male reptiles have a penis to insert the sperm.

Birds:
Male birds do not have a penis.
In the female glands along the oviducts produce a protein (egg
white) and calcium carbonate to make the shell.
The egg is fertilised internally but then laid and incubated for
several weeks.
Mammals:
Mammals need the sperm to be inserted into the female
reproductive tract for fertilisation to occur.
Mammals produce very few eggs and can have long or short
reproductive cycles.
The extent of embryonic develop varies between mammals.

You might also like