PP4_Diversity_of_reproductive_strategies.ppt

Reproductive strategies

1. KNOWLEDGE AREA:
Life Processes in Plants and
Animals
TOPIC 2.1: Reproduction in
Vertebrates
Diversity of Reproductive
Strategies

3. Fertilization is the fusion of the egg and
sperm to form a diploid zygote.
There are 2 types of fertilization.
This is the…
1.External fertilization
2.Internal fertilization
We shall look at each of these types of fertilization.

4. External Fertilization:
External fertilization is fertilization
that occurs outside the female body.
This means that the sperm fuses with the egg
outside the body.
No physical contact is necessary between the 2
parents.
Water is a required for external fertilization.

5. The Importance of Water during External
Fertilization
Water is needed for 2 reasons.
These are…
1.Keeps the eggs moist, thus preventing them from
drying out.
2.Medium in which sperms swim towards the egg.

6. Disadvantage of External
Fertilization:
Many of the sperms
produced may not reach
the eggs. This is overcome
because the organisms
produces a large number
of sperms in the hope that
at least some of them
reach the egg.
Some examples of animals
that undergo external
fertilization are frogs and
fish.

7. TERM:
Fertilization
DEFINITION:
Process during which the
sperm fuses with the egg to
produce a diploid zygote
USE IN SENTENCE:
Fertilization results in the
formation of a zygote.

8. TERM:
External fertilization
DEFINITION:
Process during which the
sperm fuses with the egg
outside the female’s body.
USE IN SENTENCE:
During external fertilization
all the sperms may not
reach the egg.

9. Internal Fertilization:
This is process where the
sperm fuses with the egg
inside the female body.
This means that the male
deposits sperm inside the
female reproductive organs.
It also means that
fertilization occurs inside the
female body.
No water is required for
internal fertilization.
This makes it an adaptation
for terrestrial life.

10. A smaller quantity of sperms are produced since
the chances of success are greater.
Examples of organisms that undergo internal
fertilization are birds and mammals, including
humans.

11. TERM:
Internal fertilization
DEFINITION:
Process during the sperm
fuses with the egg inside
the female’s reproductive
organs.
USE IN SENTENCE:
Internal fertilization is a
more certain process.

12. Ovipary
This is a method of
reproduction in which
eggs are laid and
development of these
eggs occur outside the
mother’s body.
These eggs can be
fertilized internally or can
be fertilized outside the
mother’s body, after they
have been laid.
The egg will hatch into a
young animal.

13. Disadvantages of Ovipary:
Eggs may be eaten by predators.
This can be avoided if there is parental care, that
is the eggs are protected by the parents.
Most invertebrates and many vertebrates
reproduce in this way.
Some examples are frogs and hens.

14. TERM:
Ovipary
DEFINITION:
a method of reproduction
in which eggs are laid and
development of these eggs
occur outside the mother’s
body.
USE IN SENTENCE:
Lizards and turtles are
examples of animals that
undergo ovipary
reproduction.

15. Vivipary:
This is the type of
reproduction in which
the young develops
inside the mother’s
uterus after internal
fertilization.
During development the
young receive nutirents
from the mother’s blood
via the placenta.
When the young are
born active.

16. Advantage of Vivipary Development.
Internal fertilization occurs, thus increases the
chances of fertilization.
Development occurs within the mother’s body
ensuring protection of the developing young.
The young are born well developed and are therefore
less prone to being attacked.
If parental care is present then the chances of
survival of the young are even further increased.
Mammals are example of vivipary organisms.

17. TERM:
Vivipary
DEFINITION:
the type of reproduction in
which the young develops
inside the mother’s uterus
after internal fertilization.
USE IN SENTENCE:
A rat is an example of an
animal that shows vivipary
reproduction.

18. Ovovivipary
This is a type of reproduction in which eggs are
produced but the eggs develop within the
mother’s body and they may hatch within the
mother’s body.
So we can say that the young are born alive.
The young get their nutrition from the egg and
not from the mother.
 

19. Advantages of Ovovivipary:
Internal fertilization increases the chance of
successful fertilization.
Therefore there is a greater chance of offspring being
produced.
The young are well developed when born therefore
their chances of survival increases because they will
be able to evade their predators.
Some fish, retiles and invertebrates are examples of
organisms that undergo ovovivipary reproduction.

20. TERM:
Ovovivipary
DEFINITION:
Refers to a type of
reproduction in which eggs
develop within the
mother’s body and hatch
inside the mothers body
before being born.
USE IN SENTENCE:
Organisms that undergo
ovovivipary reproduction
have a greater chance of
survival than organisms
that undergo ovipary
reproduction.

21. An amniotic egg is one
that has 4 membranes.
These membranes
surround the embryo as
shown in the diagram
alongside.
Therefore they are
called extra-
embryonic
membranes.
Most amniotic eggs are
covered by a shell. An Amniotic Egg

22. The 4 membranes are…
1.Amnion
2.Chorion
3.Allantois
4.Yolk sac
Try and locate each of
these membranes on
the diagram.
Lets look at each
membrane in some
detail…
An Amniotic Egg

23. 1.The Amnion…
This is the outer most
membrane.
It forms a cavity called
the amniotic cavity.
A fluid called the
amniotic fluid is found
in the amniotic cavity.
The amniotic fluids
provides cushioning
against mechanical
shock.
An Amniotic Egg

24. 2.The Chorion:
This membrane plays
an important role in
gaseous exchange.
It allows oxygen to
pass though to the
embryo and carbon
dioxide to pass from
the embryo.
Both oxygen and
carbon dioxide enter
and leave through the
shell. An Amniotic Egg

25. 3.The Allantois:
It has 2 functions…
1.It plays a role in
gaseous exchange.
2.It stores wastes
made by the
embryo.
An Amniotic Egg

26. 4.The Yolk Sac:
It contains the
yolk.
The yolk is a
source of food for
the embryo.
An Amniotic Egg

27. The egg shells are important because they reduce
dehydration.
This enables these animals to live in a wide range
of terrestrial habitats, when compared to
amphibians.
Mammal’s eggs do not have egg shells.
The egg shells are not necessary because the
embryo’s develop within the mother’s body.
Therefore dehydration is avoided.

28. We will now look at the development within birds.
Their young undergo 2 different methods of
development.
These are…
1.Precocial development and
2.Altricial development
The type of development that occurs in bird
species depends on…
1.The availability of food
2.Predators in the environment
Now lets look at each type of development.

29. 1.Precocial Development
Birds that show this type of development
originally lived in a type of environment that
had a lot of food but had many predators.
The female birds produce eggs with a lot of
energy because they have a lot of available
food.
The greater amount of food allows for more
time and more energy for greater
development within the egg.
Therefore the birds that hatch from these eggs
are well developed.

30. They show the following
characteristics…
1.When they hatch their
eyes are open.
2.Their bodies are
covered with soft
feathers called down.
3.They are able to move
soon after they hatch.
4.They are able to feed
themselves.
5.They are independent
of their parents.
Birds show precocial
development

31. This development ensures that the young are
able to leave the nest soon after hatching.
They are also able to avoid their predators to a
certain extent.
They are able to do this because of the
developments discussed above.
Duck’s and geese show precocial development.

32. 2.Altricial Development…
Birds that show this type of development
originally lived in an environment that did not
have many predators and had little food.
Therefore the eggs produced did not have as
much energy as those of the precocial species.
Therefore there is less energy for development
within the egg.
Therefore the development of birds with this
type of development is poor.

33. These birds show the
following
characteristics…
1.Their eyes are closed
when they hatch.
2.Their bodies do not
have down feathers.
3.They are not able to
move soon after they
hatch.
Altricial Development

34. 4.They are not able to feed themselves when
they are newly hatched.
5.They depend on their parents.
From the characteristics we can see that these
animals are not well developed.
Therefore they will have to spend more time in
their nests.

35. They stay in the nests until they are able to fly,
walk or swim.
Therefore the parents have to protect and hide
their nests, to prevent their entire brood from
being eaten by predators.
Examples of birds that show this type of
development are songbirds and bats.
But some mammals also show altricial
development.

36. TERM:
Precocial development
DEFINITION:
Refers to birds that are
hatched with eyes open,
covered with down, and
leave the nest within two
days.
USE IN SENTENCE:
Birds with precocial
development have a
greater chance of survival
soon after hatching.

37. TERM:
Altricial Development
DEFINITION:
Refers to birds that are
hatched with eyes closed,
with little or no down,
incapable of departing
from the nest, and fed by
the parents.
USE IN SENTENCE:
Birds with altricial
development need the care
and protection of their
parents when they hatch.

38. In-between Species:
However not all birds fall into either the precocial
or altricial development.
Some species have a mixture of both types of
development.
For example when some birds hatch their eyes
are open and they have down feathers (precocial
characteristics) but they are unable to move
about or feed themselves (altricial
characteristics)
Therefore their parents need to feed them and
protect them, like hawks.

39. Other birds can have down feathers, but show
the characteristics of altricial development.

40. Parental care is also known as paternal investment.
It refers to the ways in which parents increase the
chances of survival of their offspring.
Here are some examples of parental care…
1.Building of Nests and Burrows
Most invertebrates and vertebrates build nests and
burrows for breeding.
For example the male weaver birds build nests and
the female examines the nest if it is not up to her
standards then she breaks the nest and he starts over
and this continues until the nest is safe and strong for
the eggs.

41. 2.In the Care of Eggs…
In some species like fish the eggs are laid and left
with no parental care.
Some reptiles like lizards and snakes guard their
eggs after they hatch.
Other reptiles, like some snakes, incubate their
eggs.
Some organisms like the shark are ovoviviparous
and only release their eggs just before they are
hatched, this increases their chances of survival.
All mammals will provide food and protection for
their young until they are born. They are
viviparous.

42. 3.In provision of Food for Unborn or Un-hatched
Young.
The scarab beetles collect food and roll them into
small balls and leave them in the nest before the
eggs are hatched.
4.In Providing Food after Hatching or Birth…
In some birds the young are fed on similar food as
the adult.
In other insects and birds the young are fed with
partially digested food that is regurgitated by the
parents.

43. 5.In protecting the Young…
Some invertebrate larva the young take shelter
in some part of the parents body or beneath
one parent.
This protects the young from predators or
parasites.
The young of geese and swans stay with their
parents for at least 6 months for protection.

44. 6.In providing Social Assistance to Mature
Offspring
Many offspring stay close to the mother.
In this way the young learn from their mother’s
on how to interact with the other members of
the group.

45. Fertilization: process during which the sperm
fuses with the egg to produce a diploid zygote.
External fertilization: process during which the
sperm fuses with the egg outside the female’s
body.
Internal fertilization: process during the sperm
fuses with the egg inside the female’s
reproductive organs.
Ovipary: a method of reproduction in which eggs
are laid and development of these eggs occur
outside the mother’s body.

46. Vivipary: the type of reproduction in which the young
develops inside the mother’s uterus after internal
fertilization.
Ovovivipary: refers to a type of reproduction in which
eggs develop within the mother’s body and hatch
inside the mothers body before being born.
Precocial development: refers to birds that are
hatched with eyes open, covered with down, and
leave the nest within two days.
Altricial Development: refers to birds that are
hatched with eyes closed, with little or no down,
incapable of departing from the nest, and fed by the
parents.
Parental care: It refers to the ways in which parents
increase the chances of survival of their offspring.

47. 1.The type of development in birds where the
young are incapable of moving around after
hatching
A. Ovovivipary
B. Altricial
C. Precocial
D. Vivipary

48. 2.Method of reproduction in which the foetus is
nourished through an umbilical cord is…
A: Ovipary
B: Vivipary
C. Both A and B
D. Neither A nor B

49. 3.Which ONE of the following refers to
development in some birds where the eggs hatch
outside the body and the young are born
immobile and totally dependent on its parents?
A. Vivipary and precocial development
B. Ovipary and altricial development
C. Vivipary and altricial development
D. Ovipary and precocial development

50. 4.The method of reproduction in which the young
hatch from eggs outside the mother’s body…
A. Vivipary
B. Ovipary
C. Ovovivipary
D. None of the above

51. 5.The type of development in organisms where the
young are capable of moving around and feeding
themselves after hatching…
A. Altricial
B. Precocial
C. Both A and B
D. Neither A nor B

52. 6.The liquid that protects embryo against
mechanical shock…
A. Chorion
B. Allantois
C. Amnion
D. Yolk sac

53. 7.Allows for gaseous exchange only…
A. Chorion
B. Allantois
C. Amnion
D. Yolk sac

54. 8.Stores waste substances produced by the
embryo…
A. Chorion
B. Allantois
C. Amnion
D. Yolk sac

55. 9.Serves as food for the embryo …
A. Chorion
B. Allantois
C. Amnion
D. Yolk sac

56. 10.Reduces dehydration…
A. Chorion
B. Allantois
C. Egg shell
D. Yolk sac

57. 11.Fertilization that occurs within the female body…
A. Internal fertilization
B. External fertilization
C. Both A and B
D. None of the above

58. 12.Fertilization that occurs outside the female body…
A. Internal fertilization
B. External fertilization
C. Both A and B
D. None of the above

59. 13.Method of reproduction in which the young
develop from eggs that are internally fertilized
and retained within the mother’s body and hatch
after development…
A. Ovovivipary
B. Vivipary
C. Ovipary
D. None of the above

60. 14.Type of development in which the young has a
greater chance of survival immediately after
hatching…
A. Precocial
B. Altricial
C. Both A and B
D. None of the above

61. 15.Type of development in which the young has a
very slim chance of survival immediately after
hatching if the is no parental care is…
A. Precocial
B. Altricial
C. Both A and B
D. None of the above

62. 1.B
2.B
3.B
4.B
5.B
6.C
7.A
8.B
9.D
10.C
11.A
12.B
13.A
14.A
15.B