1. Reproduction and Development
How Animals Reproduce
Sexual Reproduction
Asexual Reproduction
Animal Development

2. How Animals Reproduce Reproduction in animals is either
sexual or asexual
Reproduction is characterized by
certain adaptations
Eggs are an important adaptation in
reproduction for many animal groups

3. Sexual Reproduction In sexual reproduction, sperm
from a male unite with one or
more eggs produced by a female
in a process called fertilization
In animal groups, fertilization
may be external or internal

4. External Fertilization
Many animal species may produce one
or many new individuals at one time
Water-inhabiting animals may
produce huge numbers of eggs and
sperm at one time.
These organisms depend on water to
carry out fertilization

5. During External fertilization, the female releases eggs into the water
During External fertilization, the female releases eggs into the water. The male then releases sperm, which swim to the eggs

6. Internal Fertilization
A female produces one or more
eggs that are kept in the body
The male deposits sperm in a
fluid into the female’s body
The sperm swim to and unite with
the eggs.

7. that undergo development in the female’s body generally produce
Organisms that have fertilized eggs
that undergo development in the
female’s body generally produce
smaller numbers of offspring.
Organisms that undergo internal
fertilization are not restricted to
living in or near water to accomplish
fertilization

8. Asexual Reproduction Asexual reproduction is the
production of a new organism from
just one parent
No eggs or sperm are exchanged
Asexual reproduction occurs in manly
invertebrates

9. Two types of Asexual Reproduction
Budding– a new organism breaks
off from the parent
Regeneration– regrowth of a new
organism from a portion of the
original body.

10. Animal Development Development of a fertilized egg into an
adult varies in the animal world.
Birds and mammals have young that
look very similar to the adult form of
their species
Some animals at first look nothing like
their parents and undergo extensive
changes in their form

11. Metamorphosis Metamorphosis is the change in
form that organisms undergo in
their life cycle
Organisms change form completely as
they grow from egg to adult
Two types of metamorphosis are known
in insect life cycles
Complete metamorphosis
Incomplete metamorphosis

12. Complete Metamorphosis in Butterflies
Stage 1 Egg
Stage 2 Larva
Stage 3 Pupa
Stage 4 Adult

13. Stage 1 Egg Complete metamorphosis begins about seven days after
an egg is fertilized.
The caterpillar egg develops
into a larva

14. Stage 2 Larva The larva chews the egg case open and stretches out.
In fact the larva can eat several
times its body weight in one day.
As it grows, the larva molts—its
exoskeleton splits and a new one
forms
Just before its last molt, the mature
larva attaches itself to a twig or leaf

15. In the pupa stage the caterpillar
spins a covering from a silken
thread it produces.
During this time, chemicals
called hormones cause vast
changes to take place that
result in a complete change in
form inside the pupa

16. In the adult stage, the insect splits open its covering and emerges.
The adult insect—a butterfly—unfolds its wings and flutters them, thus pumping blood into its veins

17. Survival During Development
Animals evolve a variety of adaptations to survive to adulthood
Some of these adaptations involve:
Reproducing in large numbers
Shells
Internal development

18. Reproducing in large numbers
Animals that develop through the process of metamorphosis seem to reproduce in large numbers.

19. Shells
Birds and reptiles reproduce in smaller numbers. These species have adapted ways to protect their young as they develop outside the female’s body.
After fertilization, a protective shell forms around an egg.
The shell keeps the egg from drying out.

20. Internal Development Most mammals develop within the female’s body.
Internal development provides protection for the embryo.