Lessons in Earth and Life Science for HumSS

1. WEEK 3
Prepared by: Eden J. Loredo

2. The animal kingdom is a diverse as
the plant kingdom, particularly in
terms of how they reproduce.
Majority of animals reproduce
sexually, but lower forms reproduce
via asexual reproduction.

3. ASEXUAL REPRODUCTION
The type of reproduction in animals that
occur with a single parent and produce
offspring by cell division or splitting of one
cell into two.
It is commonly found among protists,
cnidarians, and some complex animals.
The resulting offspring are identical to the
parents in terms of characteristics unless
mutations occurred.

4. ASEXUAL REPRODUCTION IN UNICELLULAR
Through the process of mitosis, unicellular or one-
celled organisms (amoeba or paramecium) can
reproduce ab exact copy of the parent in an asexual
process called fission.
Bipartition happens when
unicellular organisms split in two to
produce new life.

5. Advantage of Asexual Reproduction
It enables animals living in isolation to reproduce even without a
mate.
It can produce numerous offspring quickly.
It can help organism perpetuate and continue its species for
generations.

6. ASEXUAL REPRODUCTION IN MULTICELLULAR
INVERTEBRATES:
cnidarians, sponges,
flatworms, annelids,
echinoderms
⮚Cnidarians - hydras
reproduce by budding
wherein an outgrow bud
(small projections) arises
from the body of the
parent.

7. ASEXUAL REPRODUCTION IN MULTICELLULAR
INVERTEBRATES: cnidarians,
sponges, flatworms, annelids,
echinoderms
⮚Annelids – earthworms can
reproduce by regenerating parts
through fragmentation (a single
parent breaks into parts that give
rise to new individuals)
✔ Starfish
✔ Sponges
✔ planaria

8. ASEXUAL REPRODUCTION
PARTHOGENESIS – give rise to
the growth and development of
an embryo without fertilization.
⮚Insects – bees, aphids
⮚Crustaceans – water fleas,
crayfish
⮚Flatworms
⮚Snails
⮚Few reptiles
⮚Some fish species

9. • In honeybees, the queen bee only
mates once and stores sperm cells,
which will she will use to selectively
fertilize eggs.
• If there are no sperm cells released,
the eggs will develop
parthenogenically into male drones. If
the sperms are allowed to fertilized
the eggs, the eggs will develop either
into future female queens or female
workers.

10. SEXUAL REPRODUCTION
• Higher forms of animals reproduce through a process
involving gametes (sex cells) produced by the parents.
• Majority of the animals are dioecious (have separate sexes):
⮚Male – testes (produce male gametes – sperm)
⮚Female – ovaries (produce female gametes - egg)
⮚Hermaphrodites:
✔posses both male and female organs
✔Can either have its eggs fertilized by another
organism of its kind or on its own
✔Examples: simple vertebrates, earthworms, some
fish

11. THREE
FUNDAMENTAL
STEPS OF SEXUAL
REPRODUCTION
Gametogenesis –
production of
gametes

12. THREE
FUNDAMENTAL
STEPS OF SEXUAL
REPRODUCTION
Spawning or
mating –
bringing gametes
together

13. THREE
FUNDAMENTAL
STEPS OF SEXUAL
REPRODUCTION
Fertilization –
fusion of
gametes

14. SEQUENTIAL HERMAPHRODITISM (SEXUAL REVERSAL)
• Individuals can change
their sex in response to
social or environmental
pressures.
• Bluehead-wrasse coral fish
✔Protogyny – from female
to male
✔Protandry – from male to
female

15. • Hamlet bass is a
hermaphrodite capable of
producing egg and sperm
cell.
• During mating, one fish
can switch from producing
egg cells to produce
sperm cells.

16. • Whiptail Lizards take
turns in acting the male
role.
• When estrogen is high, a
whiptail lizard acts as a
female during mating
and before laying eggs.
When her progesterone
low, she acts as male,
which is usually after
laying eggs.

17. • Animals produce
their gametes (sex
cells) through the
gonads (reproductive
organs).
✔Testes – sperm
✔Ovaries – egg
• The primary goal is
the fertilization of an
egg.

18. TYPES OF
FERTILIZATION
Informal Fertilization
✔sexual reproduction occurs
outside the body
✔most fish or amphibians, female
lay eggs somewhere, usually on
the seabed or riverbed.
✔then female comes along and
spray the eggs with sperm cells
and fertilization takes place
(external fertilization).
• Examples: frogs, crabs,
corals, most fish
✔oviparous organisms – animals
that practice external
fertilization.

19. External
Fertilization in
Fish
a. Female fish release
unfertilized eggs and
the male fish release
sperms.
b. The sperm fertilizes the
egg and soon develops
into zygote.
c. The egg hatches to
release a new
individual.

20. Most vertebrates (birds, fish, amphibians and reptiles) lay eggs.
The egg is surrounded and protected by a tough membrane or shell.
Eggs are often incubated by the mother or father until it hatch and released as fully-developed
young.
Most mammals give birth to a live and fully-developed young.
Marsupials and placental animals (mammals) possess a yolk sac membrane
Platypus and the spiny anteater (egg-laying mammals) have placenta which temporarily
nourishes the young with nutrients.
Viviparous – placental mammals which means the young develops inside the mother’s body
until they are mature enough to be born and live independently.

21. • the young develops inside the
mother’s body until they are
mature enough to be born and
live independently.
• they give birth to live offspring
instead of eggs.
• Examples: Kangaroo
Viviparous (Placental Mammals)
• lay eggs that develop and hatch
outside the parent’s body
• Examples: snake
Oviparous

22. TYPES OF FERTILIZATION
Internal Fertilization
✔it takes place inside the body of the
female
✔the male places its semen (a fluid
containing sperm) directly into the
female’s body, increasing the chance of
fertilization.
✔copulation (physical sexual union) – aids
in the delivery of the sperm to the
female
✔Terrestrial vertebrates – males possess a
penis that facilitates the transfer of
sperm cells into the female’s vagina
✔Birds – lack a vagina and penis have
cloaca (a special chamber that receives
products from the urinary, digestive, and
reproductive tracts.

23. • Zygote – the union of
the haploid sperm and
haploid egg that result
in a single diploid,
which later develops
into an embryo. The
zygote divides and
differentiate into an
embryo. The embryo
grows and develops
until the time of birth
or hatching.

24. Cross-fertilization –
involves two
separate individuals
of the same species
(male and female) in
reproduction
Examples: earthworms

25. •Self-fertilization
– union of
sperm and egg
is not possible
✔Examples:
tapeworms in
the intestines