Transcript Activity 9 Plant Life Cycle and flower structure

Plant reproduction
Sexual reproduction
Learning Intentions

I can describe methods of sexual
reproduction in plants

I can describe the process of pollination,
fertilisation , seed formation and dispersal
Success Criteria
Success Criteria








I can state plants use flowers as a method of sexual
reproduction
I can put the stages of a plants life cycle in order
I can define pollination and fertilisation
I can describe how pollination and fertilisation occurs in
plants
I can explain how seeds are formed
I can describe methods of seed dispersal
I can explain the advantages of seed dispersal
I am able to label diagrams correctly
Plant Life Cycle

A plants life cycle shows all the
stages in a flowers life


Tomato plant
From seed to flower
And back to seeds

This is plant reproduction

It allows plants to reproduce so
new flowers will form again and
again
This flower has been
pollinated. Now the
fruit, containing
seeds, is developing.
Flower
Tomato plant life cycle
Germination
Fruit and seed
development and
dispersal
Pollination
and
fertilisation
Plant growth
Flower formation
Parts of a flower


Petals – bright to attract
insects
Stamen contains the
anther which splits down
the middle to release the
pollen
Stigma

The stigma is the
region to which pollen
grains become
attached

Nectary – makes
sugary nectar which
insects eat

Sepals - protects
unopened flower

Ovary – female part of
the flower that
contains the ovules
Arrangement of ovules as seen
in cross section of ovary
Pollination
•The pistil is part of the stigma.
•Pollination is the transfer of pollen from the anther to the
stigma
Insect pollination
e.g.
Passion
flower
Wind Pollination
e.g. Sedge
Methods of Pollination
Insect pollination
Wind pollination
Have a scent
No scent
Sticky, spiky pollen
Sticky stigma inside
flower
Stamens surrounded
by petals
Produce nectar
Large amounts of light
pollen
Feathery stigmas hang
outside the flower
Large stamens hang
outside flower
Don’t produce nectar
Petals large & bright
Petals small & dull
Fertilisation

Once the pollen grain lands on the stigma, it
grows a pollen tube down to the ovule.

Fertilisation is when the nucleus of the pollen
grain fuses with the nucleus of the ovule

The fertilised ovule develops into a seed

The ovary wall develops into the fruit.
Seed dispersal

Following pollination and
fertilisation seed formation
and dispersal takes place

Seed Dispersal – this is
where seeds are scattered
away from the parent

Seeds are scattered to
avoid competition for
water, light and nutrients
Animal (external)



Seeds can be
dispersed by animals.
The seed has hooks
which catch onto
animals’ fur and are
transported by the
animal until they fall off
and hopefully
germinate elsewhere.
E.g. Burdock
Animal (internal)



Seeds can also be
eaten by animals along
with the fruit.
The seeds pass
through the animal and
are deposited in the
droppings elsewhere
E.g. bramble
Wind Dispersal


Plants can also use the
wind to scatter their
seeds and they use
different mechanisms to
achieve this.
E.g. the poppy uses the
“pepper pot” method
Wind Dispersal


Ragwort, dandelions,
cotton, etc. use the
“parachute” method.
Each seed has a
number of small
feather-like structures
to help it float in the
wind.
Wind Dispersal


Some seeds have
wings to help them fly
in the wind.
E.g. sycamore, ash,
etc..
Explosive


Some plants such as
peas and gorse use
pods which “explode”
to fire the seeds away
from the parent.
As a pod dries,
tensions are set up in
the wall of the pod
eventually causing it
to split along two lines
of weakness.
Advantages of seed dispersal

It reduces competition for resources eg. light,
water and mineral nutrients

It reduces the spread of disease

It allow plants to grow in a wider area so
more likely to survive in event of a flood or
fire.
Seed germination




With water, oxygen and the right
temperature the seed swells and begins
to make a new plant
Germination occurs
Stems grow up towards the light, leaves
unfold to take more sunlight and roots
anchor the plant
Growth