Download Animal Reproduction and Fertilization

GLE 6 – Compare the life cycles of a variety of
organisms, including non-flowering and flowering
plants, reptiles, birds, amphibians, and mammals.
GLE 14 – Differentiate between sexual and asexual
reproduction.
How Do Animals
Reproduce?

Animals undergo either asexual or sexual reproduction to make
more of their own kind or species.
Asexual Reproduction
  Budding
 In this form of
asexual
reproduction, an
offspring grows
out of the body of
the parent.
 Hydras exhibit
this type of
reproduction.
Asexual Reproduction

 Regeneration
 In regeneration, if a piece of
a parent is detached, it can
grow and develop into a
completely new individual.
 Echinoderms and
worms exhibit this type of
reproduction.
Sexual Reproduction

 The sex cells of two parent organisms join together to
produce a new organism that has DNA that differs
from both parents.
 All vertebrate classes (fish, amphibians, reptiles,
birds, and mammals) and most invertebrates
reproduce sexually.
 Some worms, mollusks, and fish may produce both
eggs and sperm. Individuals of these species will
usually fertilize the eggs of another individual.
Asexual vs. Sexual

Asexual Reproduction
 Advantage - One parent
can quickly produce
many identical offspring.
 Disadvantage - The
offspring have the same
DNA as the parent and
may not survive changes
in the environment.
Sexual Reproduction
 Advantage - The
offspring may have
characteristics that help
them survive changes in
the environment.
 Disadvantage - Parents
must find a mate, and the
development of offspring
takes a longer time.

Sponges Reproductive
Cycle –

 Sponges have life cycles
that alternate between
asexual and sexual
reproduction.
 They reproduce
asexually through
budding.
 A sponge produces both
sperm cells and egg cells.
A larva develops after a
sponge egg is fertilized.
Cnidarians Reproductive
Cycle –

 Cnidarians alternate
between two body forms: a
polyp that looks like an
upright vase and a medusa
that looks like an open
umbrella.
 Some polyps reproduce
asexually by budding or by
pulling apart.
 Adult medusas reproduce
sexually by releasing sperm
and eggs into the water.
How Do External and Internal
Fertilization Differ?

External Fertilization
 The joining of an egg and a
sperm outside the female’s
body
 Occurs outside the body for
many fish, amphibians, and
aquatic invertebrates
 Takes place in water to
prevent the eggs and sperm
from drying out
 Female releases eggs into the
water
 Male releases the sperm
nearby
Internal Fertilization
 The joining of an egg and a sperm
inside of the female’s body
 Occurs in most invertebrates,
many fish, amphibians, reptiles,
birds, and mammals
 Many fish, amphibians, reptiles,
and birds lay fertilized eggs
outside the parent’s body and the
offspring continue to develop
inside the eggs
 In mammals, the fertilized egg
develops inside the female. The
length of time between
fertilization and birth is the
gestation period.
Development and
Growth

Where Do Embryos
Develop?

The growing offspring, or embryo, may develop inside or outside
of the parent’s body.
Egg-Laying Animals

 Most animals without backbones
(including worms and insects) lay
eggs. Many fish, reptiles, and birds
lay eggs too.
 A few mammals lay eggs too. Egglaying mammals are called
monotremes. The duck-billed
platypus and four species of
anteaters lay eggs.
 The contents of the egg provide
nutrients for the developing embryo.
 The eggs of land vertebrates are
called amniotic eggs. Amniotic eggs
have a shell which allows the
offspring to grow and develop
without drying out.
Egg-Retaining Animals

 In some fish, amphibians, and
reptiles, an embryo develops
inside an egg that is kept
inside the parent’s body.
 The embryo gets its nutrients
from the yolk, just like in the
egg-laying animals.
 The parent’s body provides
extra protection for the eggs.
 The egg hatches either before
or after being released from
the parents body.
 Sharks, guppies, and garter
snakes retain their eggs.
Placental Mammals

 In most mammals, the embryo
develops inside the mother’s body
until its body systems can function
on their own.
 The mother provides the embryo
with everything it needs during
development through an organ
called the placenta.
 Blood carrying food and oxygen
from the mother flow to the
placenta and then to the embryo.
 Blood carrying wastes and carbon
dioxide from the embryo flow to the
placenta and then to the mother.
 The mother’s blood does not mix
with the embryo’s blood.
How Do Young Animals
Develop?

Young animals undergo changes in their bodies between birth and
maturity, when they are able to reproduce.
Crustaceans

 Three stages: egg, larvae, adult
 Most crustaceans begin their
lives as tiny, swimming larvae.
 The larvae do not resemble the
adult.
 Through metamorphosis,
larvae change into adults.
Insects – See handout.

Complete Metamorphosis
Incomplete Metamorphosis
 Four Stages: egg, larva,  Three stages: egg,
pupa, adult
nymph, and adult
Amphibians

 The term “amphibian” means
double life - one life in the
water and one life on land.
 Adult frogs reproduce sexually.
 Eggs are fertilized outside of the
female’s body.
 A tadpole (larva) hatches from
an egg, lives in water, and
breathes with gills.
 Legs develop.
 Tail shortens and lungs
develop.
 Tail is absorbed and
development is complete.
 Adult frog breathes with lungs
and can live on land.
How Do Animals Care
for Their Young?

Most amphibians and reptiles do not provide parental care, while
birds and mammals typically care for their offspring.
No Parental Care

 Most fish, amphibians, and
reptiles do not care for their
offspring
 Reptiles will bury their eggs for
protection. When their offspring
hatch they will be in an area that
provides shelter and food.
 Fish and amphibian eggs are not
protected by a shell and they are
not hidden from predators.
 The offspring must be able to
care for themselves from the
time birth.
 Most of the offspring is eaten by
predators.
Parental Care

Birds
Mammals
 Most bird species lay their
eggs in a nest and keep the
eggs warm until they hatch.
 Some hatchlings can move
around and find food right
after they hatch.
 Other hatchlings are
helpless and must be fed by
their parent.
 Parent birds feed and care
for their young until they
are able to take care of
themselves.
 Young mammals are
usually quite helpless
for a long time after
they are born.
 One or both parents
may continue to care
for their offspring until
the young animals are
independent.