asexual reproduction in plants

1. REPRODUCTI
ON IN
ANIMALS

2. Lesson 1: Sexual Reproduction in ANIMALS
Animals cannot live forever. Like humans, animals
also need to reproduce. They have also their own
reproductive system that makes them able to do such
life processes. Most of them perform sexual
reproduction involving male and female animals. In
this way, extinction is prevented, and diversity is
maintained in nature. Producing new animals may
mean food supply to other organisms. It may also
signal the continuous existence of certain species.

3. Lesson 1: Sexual Reproduction in ANIMALS
Animals have the means to increase their number
through reproduction. This is to preserve their species
and to help in keeping the natural balance as they
interact with other animals. Different animals have
unique modes of reproduction. It can be noticed that
some animals can reproduce in large numbers like
insects, pigs, dogs, and frogs while some animals can
not. On the other hand, those big animals generally
reproduce in fewer number.

4. Sexual and Asexual Reproduction
Reproduction is the creation of new individual from
existing individuals. It is important for the perpetuation of
spcies whose life span is finite. There are two ways in which
organisms reproduce – sexual and asexual reproduction.
Asexual Reproduction involves one parent. The
offspring that is produced is genetically identical to the
parent. It involves regular body cells and the process is
quicker than sexual reproduction. In a stable
environment, it creates a large thriving population but
faces a massive die-off if conditions change. The
offspring that is produced has limited ability to adapt.

5. Characteristics of Asexual Reproduction
Following are the important features of
asexual reproduction:
• Single parent involved.
• No fertilization or gamete formation takes place.
• This process of reproduction occurs in a very short
time.
• The organisms multiply and grow rapidly.
• The offspring is genetically similar.

6. Advantages of Asexual Reproduction
Following are the advantages of asexual reproduction:
• Mates are not required.
• The process of reproduction is rapid.
• An enormous number of organisms can be produced in very less time.
• Positive genetic influences pass on to successive generations.
• It occurs in various environments.
Disadvantages of Asexual Reproduction
The major disadvantages of asexual reproduction are:
• Lack of diversity. Since the offspring are genetically identical to the parent, they
are more susceptible to the same diseases and nutrient deficiencies as the parent.
All the negative mutations persist for generations.
• Since only one organism is involved, the diversity among the organisms is limited.
• They are unable to adapt to the changing environment.
• A single change in the environment would eliminate the entire species.

7. Asexual Reproduction Examples
Following are the examples of asexual reproduction:
• Bacterium undergoes binary fission in which the cell
divides into two along with the nucleus.
• Blackworms or mud worms reproduce through
fragmentation.
• Hydras and starfish reproduce through fragmentation
• Budding of yeast
• Organisms such as copperheads undergo parthenogenesis.

13. Fertilization
In higher form of animals, sexual reproduction is
involved. This is by the union of the egg cell
from a female animal and the sperm cell from the
male animal. The joining together of two
different sex cells is called fertilization. When the
egg become fertilized, a new individual called
zygote develops. Fertilization may be external or
internal.

14. It occurs inside the body of a female.
The number of gametes produced is less. The
male gametes are deposited in the body of the
female.
It needs to have protection for developing egg
cells.
The fertilized egg or embryo is protected from
predation and harsh environment.
It has a higher survival rate.
Examples include reptiles, birds, and
mammals.
External Fertilization Internal Fertilization
It occurs outside the body of a female.
A large numer of gametes are located in
the surrounding medium where
fertilization ntakes place.
It is usually happens in a wet
environment.
Eggs are exposed to the environment.
It has a lower survival rate.
Examples include bony fishes and
amphibians.
The table below show a comparison of internal and external fertilization.

17. Amphibians are small vertebrates that need water, or a moist
environment, to survive. The species in this group include frogs,
toads, salamanders, and newts. All can breathe and absorb water
through their very thin skin. Amphibians also have special skin
glands that produce useful proteins.
Reptiles are air-breathing, cold-blooded vertebrates that have scaly
bodies rather than hair or feathers; most reptile species are egg-
laying, though certain “squamates” — lizards, snakes and worm-
lizards — give birth to live young.
Mammal – a class of warm-blooded vertebrate animals that have, in
the female, milk-secreting organs for feeding the young. The class
includes human beings, apes, many four-legged animals, whales,
dolphins, and bats.

18. The method of internal fertilization includes oviparity,
ovoviviparity, and viviparity.
Egg-laying mammals are called oviparous. Eggs are
developed and hatched outside the body of an animals. All
birds, lizards, chicken, most fish, reptiles and insects are
oviparous.
Ovoviviparous animals have eggs that are retained in the
female but the embryo obtains its nourishments from the
egg’s yolks. The egg hatch within the body. Examples are
rattlesnakes, some reptiles and fish.
Viviparous animals are born alive. Most mammals are like
humans, cats, dogs and horses are viviparous.

19. Lesson 2: Reproduction and Life Cycle of common
animals
Most animals reproduce sexually. Sexual fertilization may be
external like in frogs and fish. It may also be internal like in dogs, cat,
butterflies, mosquitoes and others.
Insect population is an example of a successful reproduction. They
undergo a cycle through the environment that is sometimes hostile to them.
It happens when the egg cells are fertilized inside the body of a
female animals through union with the male’s sperm cells. Most insects go
through a process called metamorphosis.
- a metamorphosis is a dramatic change that some animals and
insects go through during their life cycles. The change is dramatic,
and the baby stage looks very different from the adult stage.

20. The release of fish eggs and their fertilization is called
spawning. The females lay eggs and the males fertilize
them by releasing their seed over the eggs. A fish seed is
called milt or soft roe. Most fish species spawn in the
same ground. Oftentimes, only a few individual grow to
maturity out of hundreds and thousands of eggs laid.
When the eggs are hatched, the larvae spend the first part
of their life as zooplankton. They are transported by sea
currents to places where they grow into adults.
Reproduction in Fish

22. All frogs reproduce sexually. They lay eggs in
water and the eggs hatch into tadpoles that grows into
frog. All frogs hatch from eggs. Egg fertilization happens
outside the female’s body instead of inside. The female
releases her egg cells and the male releases his sperm cell
at the same time. The female releases as few as one or as
many as several hundred eggs.
The life cycle of the frog starts from eggs to
tadpoles. Tadpoles will develop rear legs first and then
the front legs. It will become a froglet and then eventually
an adult frog.
Reproduction and Life Cyle of Frog

23. Tadpoles can
be vegetarians
or omnivores
and they are
voracious
eaters since
they need a lot
of energy to
complete their
metamorphosi
s into frogs.