REPRODUCTIVE STRTEGIES IN ANIMALS

1

• Sexual reproduction involves the fusion of motile
  (male) and stationary (female) gametes.
• Asexual reproduction involves reproduction of
  organisms from parts or the whole parent body
  form

2

• Advantages and disadvantages of metamorphosis
• Advantages include less competition between
  young and parents (more food, shelter, etc. is
  available) young raised in a more hospitable
  environment young face different predator
  pressures than adults protected even if one
  habitat become inhospitable adults unable to
  cannibalize young and greater specialization for
  each life stage.
• Disadvantages include little parental protection
  for young difficulty in finding appropriate,
  unpolluted, adjacent habitats and possibility of
  accidentally mating with close relative.

3
REPRODUCTIVE STRATEGIES IN ANIMALS
4
COURTSHIP

• Definition
• Rituals and actions performed to attract the
  mate.
• Courtship rituals include the following actions
• Displaying beauty e.g. male peacock feathers
• Fighting skills, e.g. lions, elephants
• Performing intricate dances, touching or
  vocalisation e.g. fiddler crab
• Bringing food e.g. Pels fishing owl

5
Performing intricate dances
6
Displaying beauty e.g. male peacock feathers
7
Courtship rituals
8
Courtship rituals
9
INTERNAL FERTILISATION

• The sperm cell from the male is transferred into
  the female by copulation (sexual intercourse).
• The sperm cell then fuses with the egg cell
  inside the body of the female.
• Examples terrestrial mammals, birds, and
  insects.
• Advantages
• Ensures that the sperm cell comes into contact
  with the egg
• Protected from predators
• Removed from harsh environments
• Disadvantages
• Fewer eggs are produced .
• The animal must have an organ to insert the
  sperm cells.

10
Internal Fertilization Terrestrial vertebrates
clasp each other tightly during copulation, the
act by which the male deposits his sperm into the
females reproductive tract. For the giant
Galápagos tortoises pictured here, mating may
take hours and is initiated by the male, who
bangs his shell against that of the female to get
her attention. These animals mate in the spring.
11
EXTERNAL FERTILISATION

• The sperm cell fuses with the egg cell outside
  the body of the female.
• The sperm cells are discharged (released)
  directly into water.
• Examples are aquatic animals like frogs, sponges,
  jellyfish, worms and fish
• Advantages
• No additional energy is needed for parental care
  or formation of a protective layer.
• No need for a male to have a special organ to
  insert the sperm into the females body.
• Chances of fertilisation are enhanced by
  courtship display by fish.
• Does not need much energy.
• Disadvantages
• Chances are very slim for a sperm
• cell to meet the egg of same species.

12
A mass of amphibian eggs, appearing as small
black spots, is contained within a gelatinous
mass while they incubate in a freshwater pond.
Eggs deposited in this fashion receive little or
no parental protection and will soon hatch into
small, wriggling tadpoles.
13
Shark Egg Case with Embryos These two dogfish egg
cases show the developing embryos inside. Each
egg case contains enough yolk to sustain the
nutritional needs of the embryo until it hatches.
The outer covering of the egg case is a tough,
horny material. Each of the corners of the egg
case is drawn out into a long coiled filament, or
tendril, that wraps around rocks, kelps, or other
materials on the sea floor, preventing the egg
case from being carried away by currents and
exposed to possible predation
14
TYPES OF REPRODUCTIONOVIPARITY /EGG-LAYING

• Refers to egg laying animals
• Eggs are protected by a hard shell , while others
  are protected by a jelly like layer after
  fertilisation.
• Development does not occur inside the body
• The development of an organism is completed
  inside the egg after it has been laid
• Examples Frogs, insects, birds, and marine
  mammals
• Advantages
• Eggs and sperm cells are produced in large
  numbers to increase chances of survival to
  adulthood.
• Much energy is invested for parental care.
• Parental care ensures survival to adulthood.
• Disadvantages
• Mortality rate is high.

15
OVOVIVIPARITY

• Refers to animals that do not lay eggs , but keep
  them in their bodies until they hatch.
• The body temperature is necessary for them to
  hatch.
• There is no connection between the embryo and the
  mother.
• Examples Sharks , lizards cockroaches and some
  snakes
• ADVANTAGES
• The young one is protected from cold and
  predators to ensure survival
• The young one can develop to a fairly large size
  before birth

16
Common Lizard The common lizard is the most
northerly occurring lizard and can be found
within the Arctic circle. It does not lay eggs
but gives birth to fully formed young
17
VIVIPARITY

• Refers to animals that give birth to live young
  ones.
• There is a connection between the developing
  foetus and the mother.
• Examples Human beings, whales and kangaroos.
• Advantages
• The temperature is regulated by the mother
• The mother provides nutrition for the young one
• Mortality rate is lower
• Disadvantages
• Number of off springs produced is few.
• More energy is used to provide parental care.

18
A placental mammal, the female cat gives birth to
young that have developed inside its body. Nine
weeks after fertilization, hormones stimulate the
cats uterus to contract and expel the kittens.
Here, one kitten has already been born. The next
can be seen emerging from the birth canal of the
mother, shrouded in the amniotic sac that
encloses each developing kitten in the womb. When
the membrane breaks, the young animal takes its
first breath of air. The mother licks the newborn
kitten clean and dry and chews through the
umbilical cord still connecting it to the
placenta. Another kitten is born within half an
hour, by which time the first two, blind but not
helpless, have smelled and felt their way to
their mothers belly to begin feeding. The
placenta, or afterbirth, follows the last kitten.
19
AMNIOTIC EGG

• This is the egg laid by reptiles, birds and some
  mammals.
• The embryo develops inside the amnion and is
  protected by many membranes and hard shell.
• Amniotic fluid protects the embryo from drying
  out.
• It feeds from the yolk.
• The allantois removes metabolic wastes.
• The chorion supplies oxygen, food and water.
• Advantages
• They are resistant to dryness
• Oviporous mammals can move to environments
• Is protected by a number of membranes.
• This complicated structure can allow animals to
  evolve into bigger forms, and better protect
  themselves.

20
Amniotic Egg A critical evolutionary development
for terrestrial animals is the reptilian amniotic
egg, now also characteristic of birds and some
mammals. The developing embryo, protected from
drying out, can survive out of water and in a
variety of habitats. The yolk provides it with
food, and the albumen supplies water and
nutrients. Wastes are released to the allantois,
an extension of the embryonic gut. Oxygen
diffuses easily through the thin outer shell of
the egg its passage to the embryo is regulated
by the chorion.
21
TYPES OF DEVELOPMENTSPRECOCIAL DEVELOPMENT

• Young ones are relatively mature and are able to
  move around after they are born or hatch.
• Their eyes are open, and have good eyesight
• They can go out to search food for themselves.
• Have strong skeleton, and their body is either
  covered by feathers (birds) or hair(mammals).
• Birds need their parents to keep them warm, but
  this lasts for a short period.
• Mammals can regulate their body temperature.
• Examples birds, cattle, sheep, antelopes,
  buffalo, elephants, hippos and giraffe.

22
(No Transcript)
23
Snake Giving Birth Most snakes hatch from eggs
that have been laid outside the mother's body,
but among some snake species, females bear live
young, as shown here. This method of reproduction
may be beneficial to snakes that live in cold
climates, because the pregnant female can bask in
the sun to keep her developing offspring warm.
24
ALTRICIAL DEVELOPMENT

• Young ones are unable to move after birth and are
  helpless.
• They do not have feathers (birds) and blind.
• They need to be fed and kept warm.

Helpless at Birth Although this two-month-old
parma wallaby joey successfully completed a blind
journey from its mothers birth canal to her
pouch without help, it would not survive without
her.
25
(No Transcript)
26
PARENTAL CARE

• Refers to looking after young ones through
  feeding, keeping them warm, protecting them from
  the predators.
• Such animals give rise to few offsprings

27

• Metamorphosis
• biological process by which an animal physically
  develops after birth or hatching, involving a
  conspicuous and relatively abrupt change in the
  animal's form or structure through cell growth
  and differentiation.
• Metamorphosis usually proceeds in distinct
  stages, starting with larva or nymph, optionally
  passing through pupa, and ending as adult

28

• Because development is not the same in all
  insects, it is convenient to group them into
  major categories according to the pattern of
  structural changes complete and incomplete
  metamorphosis

29
Complete metamorphosis is characteristic of
beetles, butterflies and moths, flies, and wasps.
Their life cycle includes four stages egg,
larva, pupa , and adult. The larva differs
greatly from the adult. It is wingless, and its
form and habits are suited for growth and
development rather than reproduction
30
.
In insects (e.g., grasshoppers, termites, true
bugs) there is a incomplete metamorphosis that
consists of an egg, nymph, and adult. The nymph,
or immature insect, resembles the adult in form
and eating habits, differing in size, body
proportions, and colour pattern
31
(No Transcript)
32
.

• Advantages and disadvantages of metamorphosis
• Advantages include less competition between
  young and parents (more food, shelter, etc. is
  available) young raised in a more hospitable
  environment young face different predator
  pressures than adults protected even if one
  habitat become inhospitable adults unable to
  cannibalize young and greater specialization for
  each life stage.
• Disadvantages include little parental protection
  for young difficulty in finding appropriate,
  unpolluted, adjacent habitats and possibility of
  accidentally mating with close relative