Download Science 9 Topic 3 Passing It On

Passing It On
Topic 3
Biological Diversity
Passing It On
Heritable:
a genetic characteristic that can be
passed on from parent to offspring.
Reproductive Strategies:
the method an organism uses to
reproduce and pass on genetic
information to offspring
Reproductive Strategies
Asexual Reproduction:
– When only one parent supplies
genetic information to offspring
– Seen in bacteria and fungi
Sexual Reproduction:
– When two parents supply genetic
material to offspring
Asexual Reproduction
Offspring are genetically
identically to parent.
Benefits:
– There is no need to find a mate
– It can occur quite rapidly
Types of Asexual
Reproduction
Binary Fission
– Happens only in single-celled
organisms
– Cell Duplicates its contents,
including nucleus and other
organelles.
– Cell Divides, each new cell has a
copy of genetic material and half
the cytoplasm.
– Offspring are genetically identical.
Types of Asexual
Reproduction
Asexual Spores
– Organism produces many single-celled
reproductive structures called spores.
– Asexual spores contain genetic material
from only one parent.
– Many spores produced to ensure survival.
– Zoospores are spores which move using a
tail-like flagella.
– Some organisms that produce asexual
spores also reproduce sexually.
Types of Asexual
Reproduction
Asexual Reproduction in Plants
– At the tips of roots and stem plants have areas
of rapidly reproducing cells called meristem.
– Meristematic cells are able to make repairs
when activated.
– Asexual reproduction can occur in plants by
activating merstematic cells in different plant
structures.
– You can then take cuttings from the plants and
plant it.
– Offspring are clones (exact copies) of parents.
Types of Asexual
Reproduction
Budding
– A cell (usually near the
base of the organism)
produces a new group of
cells called a bud.
– When developed the bud
detaches itself and
becomes independent.
The Best of Both Worlds
Many organisms are able to
reproduce both asexually and
sexually.
Zygospores contain genetic
material from two different sources,
therefore is a form of sexual
reproduction.
Sexual Reproduction
Offspring not identical to either
parent, but will be a combination of
characteristics from both parents.
Benefit:
sexual reproduction leads to a
greater genetic diversity.
Types of Sexual
Reproduction
Bacterial Conjugation
– A transfer of genetic material directly
from one cell to another.
– Primitive form of sexual reproduction
because 2 parent cells involved.
– Benefit because a new combination of
inherited characteristics.
– Bacterial conjugation is a genetic
recombination but not a reproduction
because there is no increase in number
of cells.
Sexual Reproduction in
Plants and Animals
Sexual Reproduction occurs
when an egg (female gamete) and
a sperm cell (male gamete) join
together to form a new cell called a
zygote.
12
Types of Sexual
Reproduction
Plant Sexual Reproduction:
– Angiosperms and Gymnosperms
reproduce sexually by forming seeds.
– Angiosperms are flowering plants.
– Gymnosperms do not produce
flowers.
Angiosperms
14
Gymnosperms
15
Sexual Reproduction in
Plants
Sexual Reproduction in
Plants
Pistil:
female reproductive organ. Made up
of the ovary, style and stigma.
Stamen:
male reproductive organ. Made up of
the filament and anther
Sexual Reproduction in
Plants
Pollination
– Pollen grains are produced in the stamen.
– Pollination occurs when the pollen grain
reaches the pistil of the flower.
– The pollen grain grows a pollen tube which
when it reached the ovule, the sperm
nucleus fertilizes the egg.
– When fertilization happens a zygote forms.
18
Sexual Reproduction in
Plants
Sexual Reproduction in
Plants
Plants can:
Self-pollinate
• When the sperm and egg come from the
same plant.
Cross-pollinate
• When due to wind, water, insects, birds
or other animals carry pollen from one
plant to another. This means that the
sperm and egg come from two different
plants.
20
Sexual Reproduction in
Plants
The zygote formed during fertilization
undergoes many cell divisions to form a
multicellular embryo.
The embryo contains a miniature leaf,
root and stem.
Food is supplied to the embryo by one or
two cotyledons (seed leaves).
The seeds will only germinate when the
growing conditions are good.
21
Sexual Reproduction in
Plants
Sexual Reproduction in
Plants
In angiosperms the seeds are
surrounded by a fruit. The fruit
usually develops from the wall of
the ovary.
23
Sexual Reproduction in
Animals
For Sexual Reproduction to be
successful some conditions must
be met:
– the male and female gametes need to
arrive at the same place, at the same time
for fertilization to occur.
– after fertilization the zygote needs to have
enough nutrition, moisture and in some
cases warmth and protection.
24
Sexual Reproduction in
Animals
Gametes are delicate and so timing is
important.
Fertilization can take place:
– outside the body of the female
• e.g. sponges, worms, some fish, some
amphibians
– inside the body of the female
• e.g. insects, reptiles, mammals, birds, some
25
fish, some amphibians
Sexual Reproduction in
Animals
Mammals have a high rates of successful fertilization
(reproductive success) due to internal fertilization.
In internal fertilization eggs are protected inside the body
of the female.
Sperm is deposited and when a mature egg is present
fertilization may occur.
When the egg and sperm join a zygote is formed.
The zygote divides to form an embryo.
The embryos are protected by being close to or in the
female’s body.
26