Download a) Reproduction - iGCSE Science Courses

IGCSE BIOLOGY
SECTION 3 LESSON 1
Content
Section 3
Reproduction
and
Inheritance
a) Reproduction
- Flowering plants
- Humans
b) Inheritance
Content
Lesson 1
a) Reproduction –
flowering
plants
a) Reproduction
3.1 understand the differences between sexual and asexual
reproduction
3.2 understand that fertilisation involves the fusion of a
male and female gamete to produce a zygote that
undergoes cell division and develops into an embryo
Flowering plants
3.3 describe the structures of an insect-pollinated and a
wind-pollinated flower and explain how each is adapted for
pollination
3.4 understand that the growth of the pollen tube followed
by fertilisation leads to seed and fruit formation
3.5 understand the conditions needed for seed germination
3.6 understand how germinating seeds utilise food reserves
until the seedling can carry out photosynthesis
3.7 understand that plants can reproduce asexually by
natural methods (illustrated by runners) and by artificial
methods (illustrated by cuttings)
Reproduction
“Understand
the
differences
between sexual
and asexual
reproduction.”
Reproduction
Reproduction is the
production of new
organisms. It may be
sexual or asexual.
Reproduction
In either case,
reproduction involves
passing genetic
information from
parent to offspring
Reproduction
In either case,
reproduction involves
passing genetic
information from
parent to offspring
Reproduction
Sexual reproduction produces offspring that resemble their parents,
but they are not identical to them.
Reproduction
Sexual reproduction produces offspring that resemble their parents,
but they are not identical to them.
In asexual reproduction, the offspring, called clones, are genetically
identical to their parents
Reproduction
Sexual reproduction involves the fusion of gametes.
Reproduction
Gametes are the sex
cells. In animals, the
male sex cell is the
sperm, and the
female eggs or ova.
Reproduction
Gametes are the sex
cells. In plants, the
male sex cell is the
pollen, and the
female eggs.
Reproduction
Sexual reproduction involves the fusion of gametes.
SPERM
EGG
Reproduction
Sexual reproduction involves the fusion of gametes.
SPERM
ZYGOTE
EGG
Reproduction
Sexual reproduction involves the fusion of gametes.
SPERM
ZYGOTE
EGG
EMBRYO
Reproduction
Zygotes are formed
when the male
gamete fertilises the
female gamete.
Reproduction
Following
fertilisation, the
zygote divides into 2,
then 4, then 8, and
so on.
Reproduction
In animals, when the
zygote becomes
implanted in the
womb it is known as
the embryo.
Reproduction
In animals, after
about eight weeks of
development, the
embryo becomes
known as the foetus
Reproduction
3.1 understand the
differences between
sexual and asexual
reproduction
3.2 understand that
fertilisation involves the fusion
of a male and female gamete to
produce a zygote that
undergoes cell division and
develops into an embryo
Reproduction in flowering plants
Wind pollinated. The
pollen is carried by
the wind between
flowers
Insect pollinated. The
pollen is carried by
insects between
flowers
Insect pollination
Sepal – green, protects the flower whilst in
the bud.
Insect pollination
Petal – colourful, scented. Attracts insects to
the flower
Insect pollination
Anther – contains pollen sacs, in which are the
pollen grains (male gametes)
Insect pollination
Filament – holds the anther so that insects
will brush against it and collect pollen
Insect pollination
Together, the anther and the filament make
up the stamen, the male part of the flower
Insect pollination
Stigma – sticky, collects the pollen from
insects visiting the flower.
Insect pollination
Style – the pollen tube grows through this on
its way to the ovary
Insect pollination
Ovary – contains the ovules, the female parts
of the flower
Insect pollination
Ovule – this will develop into the seed when
the egg cell (female gamete) is fertilised
Insect pollination
Together, the stigma, style and ovary make up
the carpel, the female reproductive structure
in the flower
Insect pollination
Insects visit flowers to
collect nectar, a sugary
substance produced in
nectaries at the base
of the petals.
Insect pollination
Insects visit flowers to
collect nectar, a sugary
substance produced in
nectaries at the base
of the petals.
As the insect climbs
inside the flower in
search of nectar, so it
brushes against the
pollen on the outside of
the anthers.
Insect pollination
Insects visit flowers to
collect nectar, a sugary
substance produced in
nectaries at the base
of the petals.
As the insect climbs
inside the flower in
search of nectar, so it
brushes against the
pollen on the outside of
the anthers.
As the insect visits
other flowers, so it
transfers pollen to the
stigma.
Insect pollination
As the bee
enters the
flower, it
brushes against
the anther
As the bee
enters the next
flower, pollen
sticks to the
stigma
Wind pollination
In wind-pollinated
flowers the petals are
much reduced and are not
colourful.
Wind pollination
Stamens have anthers
that hang outside of the
flower, so they are
exposed to the wind.
Wind pollination
The stigmas are feathery
and exposed, so that they
can catch pollen grains
blown by the wind
Comparison of insect and
wind pollinated flowers
Comparison of insect and
wind pollinated flowers
Wind pollinated flowers
Insect pollinated flowers
Flowers are small and do not have
brightly coloured petals (if at all)
Flowers are large and have brightly
coloured petals
Comparison of insect and
wind pollinated flowers
Wind pollinated flowers
Insect pollinated flowers
Flowers are small and do not have
brightly coloured petals (if at all)
Flowers are large and have brightly
coloured petals
Large amounts of small, very light
pollen grains produced.
Sticky pollen is produced in small
amounts.
Comparison of insect and
wind pollinated flowers
Wind pollinated flowers
Insect pollinated flowers
Flowers are small and do not have
brightly coloured petals (if at all)
Flowers are large and have brightly
coloured petals
Large amounts of small, very light
pollen grains produced.
Sticky pollen is produced in small
amounts.
Stigmas are long and feathery and
held outside of the flower
Stigmas are positioned inside the flower
so insects brush against them
Comparison of insect and
wind pollinated flowers
Wind pollinated flowers
Insect pollinated flowers
Flowers are small and do not have
brightly coloured petals (if at all)
Flowers are large and have brightly
coloured petals
Large amounts of small, very light
pollen grains produced.
Sticky pollen is produced in small
amounts.
Stigmas are long and feathery and
held outside of the flower
Stigmas are positioned inside the flower
so insects brush against them
Anthers are held outside of the
flower by long filaments
Anthers are positioned inside the flower
so that insects will brush against them.
Comparison of insect and
wind pollinated flowers
Wind pollinated flowers
Insect pollinated flowers
Flowers are small and do not have
brightly coloured petals (if at all)
Flowers are large and have brightly
coloured petals
Large amounts of small, very light
pollen grains produced.
Sticky pollen is produced in small
amounts.
Stigmas are long and feathery and
held outside of the flower
Stigmas are positioned inside the flower
so insects brush against them
Anthers are held outside of the
flower by long filaments
Anthers are positioned inside the flower
so that insects will brush against them.
Wind pollinated flowers do not
produce nectar
Insect pollinated flowers produce
nectar in nectaries.
Comparison of insect and
wind pollinated flowers
Wind pollinated flowers
Insect pollinated flowers
Flowers are small and do not have
brightly coloured petals (if at all)
Flowers are large and have brightly
coloured petals
Large amounts of small, very light
pollen grains produced.
Sticky pollen is produced in small
amounts.
Stigmas are long and feathery and
held outside of the flower
Stigmas are positioned inside the flower
so insects brush against them
Anthers are held outside of the
flower by long filaments
Anthers are positioned inside the flower
so that insects will brush against them.
Wind pollinated flowers do not
produce nectar
Insect pollinated flowers produce
nectar in nectaries.
Eg. the grasses, cereals
Eg. orchids, foxgloves
Fertilisation
STIGMA
Understand that the
growth of the pollen
tube followed by
fertilisation leads to
seed and fruit
formation
STYLE
OVARY
Fertilisation
The pollen grain lands
on the sticky stigma,
and produces a pollen
tube.
STIGMA
STYLE
OVARY
Fertilisation
STIGMA
The pollen tube,
containing the male
nuclei, grows down
through the style
STYLE
OVARY
Fertilisation
STIGMA
STYLE
The pollen tube
continues until it
reaches the embryo
sac of the ovule in the
ovary
OVARY
Fertilisation
STIGMA
STYLE
The male nucleus in
the pollen tube fuses
with the egg nucleus
in the embryo sac.
OVARY
EMBRYO SAC
EGG NUCLEUS
Fertilisation
The fertilized egg
then divides by
mitosis and grows into
a seed which will
become a new plant.
The male nucleus in
the pollen tube fuses
with the egg nucleus
in the embryo sac.
STIGMA
STYLE
OVARY
EMBRYO SAC
EGG NUCLEUS
Fertilisation
The fertilized egg
then divides by
mitosis and grows into
a seed which will
become a new plant.
The layers around the
ovule harden and
become the seed coat.
The male nucleus in
the pollen tube fuses
with the egg nucleus
in the embryo sac.
STIGMA
STYLE
OVARY
EMBRYO SAC
EGG NUCLEUS
Fertilisation
The fertilized egg
then divides by
mitosis and grows into
a seed which will
become a new plant.
The layers around the
ovule harden and
become the seed coat.
The male nucleus in
the pollen tube fuses
with the egg nucleus
in the embryo sac.
In some plants the ovary grows into a
fruit to help with seed dispersal.
STIGMA
STYLE
OVARY
EMBRYO SAC
EGG NUCLEUS
Content
Lesson 1
a) Reproduction –
flowering
plants
a) Reproduction
3.1 understand the differences between sexual and asexual
reproduction
3.2 understand that fertilisation involves the fusion of a
male and female gamete to produce a zygote that
undergoes cell division and develops into an embryo
Flowering plants
3.3 describe the structures of an insect-pollinated and a
wind-pollinated flower and explain how each is adapted for
pollination
3.4 understand that the growth of the pollen tube followed
by fertilisation leads to seed and fruit formation
3.5 understand the conditions needed for seed germination
3.6 understand how germinating seeds utilise food reserves
until the seedling can carry out photosynthesis
3.7 understand that plants can reproduce asexually by
natural methods (illustrated by runners) and by artificial
methods (illustrated by cuttings)
Germination
What’s needed?
Germination
What’s needed?
Water
- to hydrate
the
protoplasm, to
mobilise
enzymes, to
hydrolyse
stored food
(starch)
Germination
What’s needed?
Water
- to hydrate
the
protoplasm, to
mobilise
enzymes, to
hydrolyse
stored food
(starch)
Warmth – to enable
enzymes to work
Germination
What’s needed?
Water
- to hydrate
the
protoplasm, to
mobilise
enzymes, to
hydrolyse
stored food
(starch)
Oxygen
- For aerobic
respiration to
supply energy
for growth
Warmth – to enable
enzymes to work
Germination
What’s needed?
Water
- to hydrate
the
protoplasm, to
mobilise
enzymes, to
hydrolyse
stored food
(starch)
Oxygen
- For aerobic
respiration to
supply energy
for growth
Warmth – to enable
enzymes to work
Germination
A: No
water
B: No
oxygen
Seeds
D: Water,
oxygen,
warmth
C: No
warmth
Wet
cotton
wool
Dry
cotton
wool
NaOH
All tubes
except C put in
a warm place
NaOH and pyrogallol to
absorb oxygen
Put in
refrigerator
Germination
A: No
water
B: No
oxygen
C: No
warmth
Result:
only
Wet
Seeds
seeds cotton
in
tube D
wool
germinate! So
Dry
cotton
seeds need
wool
water, oxygen
and
warmth
All tubes
except C put in
a warm place
NaOH and pyrogallol to
absorb oxygen
D: Water,
oxygen,
warmth
Put in
refrigerator
NaOH
Seed germination
1
1. The seed germinates and the first growth is
seen. The stored food is utilised.
Seed germination
1
2
2. The first roots and shoot begin to grow.
Food stores in the seed are still being used.
Seed germination
3
1
2
3. The first leaves begin to uncurl and
photosynthesise. The food store in the seed is
used up.
Seed germination
4
3
1
2
4. The leaves are now fully photosynthesising
and providing all the nourishment that the plant
needs.
Understand that plants can
reproduce asexually by
natural methods (illustrated
by runners) and by artificial
methods (illustrated by
cuttings)
Asexual reproduction
All the offspring from
one asexually-reproducing
parent are known as a
clone, and are all
genetically identical.
Asexual reproduction
Natural method – eg. strawberry runner
Strawberry runners
are more correctly
called “stolons”.
They are horizontal
stems that run above
the ground and
produce new clone
plants at “nodes”
spaced at varying
intervals
Asexual reproduction
Natural method – eg. strawberry runner
Under favourable conditions (warm,
sufficient water), most strawberry plants
produce lots of runners. It is not uncommon
for a single plant to produce between 30 and
50 runners.
Strawberry runners
are more correctly
called “stolons”.
They are horizontal
stems that run above
the ground and
produce new clone
plants at “nodes”
spaced at varying
intervals
Asexual reproduction
Artificial method – eg. cuttings
When a cutting
is taken, a
short length of
a young stem is
cut just below
a node.
Asexual reproduction
Artificial method – eg. cuttings
The cut end is then dipped
in rooting powder. – this
contains plant hormones
that encourage the growth
of roots. The cutting will
then be planted in aerated
damp soil. Some leaves may
be removed to lessen
transpiration
Reproduction in flowering plants
3.3 describe the structures of an insect-pollinated and
a wind-pollinated flower and explain how each is
adapted for pollination
3.4 understand that the growth of the pollen tube
followed by fertilisation leads to seed and fruit
formation
3.5 understand the conditions needed for seed
germination
3.6 understand how germinating seeds utilise food
reserves until the seedling can carry out
photosynthesis
3.7 understand that plants can reproduce asexually by
natural methods (illustrated by runners) and by
artificial methods (illustrated by cuttings)
End of Section 3 Lesson 1
In this lesson we have covered:
Sexual and asexual reproduction
Fertilisation
Reproduction in flowering plants
Germination