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Transcript
Living World Year 9
9B Botany
Year 9 Science 2013
1
The Plant Kingdom
All plants belong to the
same kingdom (Plantae).
Plants are called
autotrophs, which means
they make their own food
through the process of
photosynthesis which also
produces sufficient oxygen
to the atmosphere to allow
all living organisms to
respire. Plants have laid
down the fossil fuels that
provide humans with
energy.
Every other animal relies on
plants either directly or
indirectly for nutrition.
Year 9 Science 2013
Plants grow mainly on land but also can be found in
the oceans and fresh water. They have been on
Earth for millions of years. Plants species currently
number about 260,000.
The structure and functions of parts of the plant
The Shoot System
Above ground (usually)
Lifts the plant above the soil
Main functions include:
Leaves - photosynthesis
Flowers - reproduction
Fruit – seed dispersal
Stem - food and water transport
The Root System
Year 9 Science 2012
Underground (usually)
Anchor the plant in the soil
Main functions include:
Absorb water and nutrients
Transport water and nutrients
Food Storage
Plants take up water through root hairs
Water moves into the plant through root hairs. Water being drawn up the plants
xylem due to transpiration decreases the pressure inside the root hair cells and this
negative pressure pulls water in.
4
The xylem transports water and the phloem transports the products of
photosynthesis (extension)
Transport water around
the plant
Special features
>Cells join into long and
tube-like hollow vessels.
>Cells have no end walls,
so form a 'pipeline'
carrying water from
leaves to root.
>Spirals and rings of lignin
surrounding the cells
strengthen the walls, to
withstand pressure of
water.
Year 9 Science 2013
5
The xylem transports water and the phloem transports the products of
photosynthesis (extension)
The xylem is probably the longest part of the pathway that water takes on its way to the
leaves of a plant. It is also the path of least resistance, with about a billion times less
resistance than cell to cell transport of water.
Xylem cells are called tracheids
(cells with narrower diameters)
or vessels (cells with wider
diameters). Their cell walls
contain cellulose and lignin
making them extremely
rigid. Xylem cells contain no
membranes and are considered
dead. These cells overlap to
create a series of pathways that
water can take as it heads to
the leaves. There is no single
column of xylem cells carrying
water.
Year 9 Science 2013
6
Osmosis is the diffusion of water molecules through a partially
permeable membrane (extension)
Diffusion means
that the net
movement of
particles
(molecules) is
from an area of
high
concentration to
low
concentration.
Oxygen, Carbon
Dioxide and water
move across the
cell membrane by
diffusion.
Year 9 Science 2013
7
Osmosis is the diffusion of water molecules through a partially
permeable membrane (extension)
Osmosis is the diffusion of water only through a partially permeable
membrane from where water is in higher concentration to where it is in
lower concentration. (or where the solute is in higher concentration)
8
The effects of solutions of different concentrations on animal and plant
cells (extension)
Isotonic
Solution
type that cell Concentrations are the
same on both sides of
is in
the membrane and
water moves equally in
both directions
Animal cell
Plant cell
hypertonic
Concentration of
water is higher in the
cell and a net
movement of water
outside causing the
cell to shrink.
hypotonic
Concentration of
water is higher
outside the cell and a
net movement of
water inside the cell
causes swelling or
breakage
The effects of solutions of different concentrations on animal and plant
cells (extension)
Plants solve the water problem by having a rigid cell wall. The entering
water moves through the cell wall and the cell membrane. The water is
stored in a vacuole. The wall protects the cell against expansion, and the
resulting pressure makes the plant rigid or turgid. When the cell membrane
shrinks away from the cell wall this is called plasmolysis.
Year 9 Science 2013
10
The process of transpiration
Transpiration is the process where plants lose water from their leaves.
Water enters a plant through root hairs. When stomata, on the underside of leaves,
are open to allow CO2 to diffuse in and O2 to diffuse out, water vapour evaporates
and diffuses out.
Year 9 Science 2013
11
The process of transpiration
1. Water enters plant through root hairs by osmosis – high to low
concentration of water. 2. Attraction between water particles pulls water up
the plant through the xylem. 3. Water evaporates from the leaves through
transpiration.
Year 9 Science 2012
12
The process of transpiration (extension)
13
The role that stomata have in the process of transpiration (extension)
Stomata are normally found only
on the under or shaded sides of
leaves.
Their function is to capture CO2
from the atmosphere by
exchanging water for carbon
dioxide. The exchange is
accomplished by having water
directly open to air to facilitate
the capture.
14
The role that stomata have in the process of transpiration (extension)
Leaves are the main site of
photosynthesis. They make food from
carbon dioxide and water in the
presence of light. As stomata open in
the presence of light, carbon dioxide
will diffuse into the leaf and at the
same time, water vapour will exit the
leaf through the stomata to the
surrounding atmosphere through the
process of transpiration.
Plants will lose water vapour while
taking up carbon dioxide through their
stomata. If this water loss is
uncontrolled, plants can deplete their
water reserve.
Stomata prevent water loss from the
stoma by closing once the leaf has
sufficient carbon dioxide.
Year 9 Science 2013
15
The leaf structure and types of cell inside a leaf (extension)
Cuticle: Waxy layer water proofing upper leaves.
Upper epidermis: Upper layer of cells. No
chloroplasts. Protection.
Vascular Bundle: Bundle of many vessels (xylem and
phloem) for transport. Xylem: Living vascular system
carrying water & minerals throughout plant.
Phloem: Living vascular system carrying dissolved
sugars and organic compounds throughout plant.
Palisade Mesophyll: Tightly packed upper layer of
chloroplast containing cells.
Spongy Mesophyll: Lower layer of cells.
Air space: Area for gases to disperse
Lower Epidermis: Lower external layer of cells in leaf.
Stomata: Opening between guard cells for gas &
water exchange.
Guard Cells: 2 cells surrounding stomata that control
rate of gas & water exchange.
Year 9 Science 2013
16
The significance of photosynthesis in making food
Most living organisms
depend on plants to
survive. Plants convert
energy from sunlight
into food stored as
carbohydrates through
photosynthesis. Because
animals cannot make
their own food they
must eat plants to gain
nutrition. Plants produce
oxygen, which is
released during
photosynthesis, which
all organisms need for
respiration.
Year 9 Science 2012
17
Photosynthesis transfers energy from sunlight into energy in chemicals
such as glucose and starch.
Light enters the leaf and is
trapped by chlorophyll contained
within the chloroplasts in the
cells.
Water is transported via xylem to
the cell and the carbon dioxide
enters through the stomata and
diffuses to the cell.
These substances react
chemically within the
chloroplasts, powered by the
light and glucose (a sugar) is
produced along with oxygen
which diffuses out. The sugar
leaves the leaf via the phloem.
Carbon dioxide + Water +light → Glucose + Oxygen
The adaptations of leaves for photosynthesis
The flat surface of the leaf called
the blade helps capture maximum
sunlight for photosynthesis.
The leaf is attached by a stem-like
petiole to the plant which branch
out into veins. Inside these are
xylem tubes to transport water to
the leaf cells, which they require
for photosynthesis and to keep the
leaf cells turgid or rigid. The veins
also contain phloem tubes which
are able to transport the sugars
(and starch which they are
converted into), produced during
photosynthesis, away to other
parts of the plant for use and
storage.
Year 9 Science 2013
19
The adaptations of leaves for photosynthesis
A waxy cuticle on the
outside of the leaf
provides a waterproof
covering while remaining
transparent to allow light
into the leaf cells for
photosynthesis.
Openings (usually on the
underside of the leaf)
called stomata allow
carbon dioxide to enter
and diffuse into cells as
well as allowing oxygen
to move in and out.
Two guard cells on
either side of the stomata
open and close the
openings.
Year 9 Science 2013
20
How the structure of a leaf enables photosynthesis to occur effectively
The cells at the top of the leaf are filled with chlorophyll, which gives leaves the
green colour. The chlorophyll allows the leaf to absorb light energy which is
required for photosynthesis. The spaces between cells in the spongy mesophyll
allow carbon dioxide to diffuse around through the cells.
Starch test
When a plant
undergoes
photosynthesis it
produces glucose
which is converted
into starch for
storage. If we want
to investigate what
factors are required
for photosynthesis
we use the starch
test to enable us to
reach a conclusion.
22
The parts of the flower and the role of the flower in pollination, seed
production and dispersal
Plants that
produce
flowers are
known as
angiosperms.
The flowers
are the
reproductive
structures
where
fertilisation
occurs and
seeds are
produced.
Year 9 Science 2012
23
The reproductive parts of an insect-pollinated flower and their
functioning
Insect-pollinated flowers
have visible, often colourful
petals that surround the
flower's sexual
reproduction parts. The
petals can "advertise" for
specific pollinators through
their shape, size, colour and
sometimes smell. The
flowers are surrounded by
sepals, which are small and
usually green structures
that protect the flower as
its developing.
Year 9 Science 2013
24
The reproductive parts of an insect-pollinated flower and their
functioning
The female part of
the flower is called
the pistil. The
pollen from a male
part of a flower is
brought to the
stigma by a
pollinator. This
process is called
pollination.
The pollen travels
down the style
into the ovary to
join with an egg
cell inside the
ovules in a process
called fertilisation.
Year 9 Science 2013
The male part of a
flower is called the
stamen. The pollen
is produced in the
anther which is
held up by the
filament. The
pollen is collected
by a pollinator. The
pollen contains
male gametes
which will later
fuse with the
female gametes in
the ovule during
fertilisation.
25
The reproductive parts of an insect-pollinated flower and their
functioning
Year 9 Science 2013
26
Insect-pollinated Flowers
often contain nectar, a
sweet sugar produced by
the plant, to attract an
insect. As the insect
reaches into the flower
for the nectar it may be
brushed with pollen from
the anther. If the insect
moves to another flower
it may brush the pollen
against the stigma and
therefore pollinate the
flower.
Flowers ripen their male
and female parts of the
flower at different times
to prevent self
pollination.
The differences in structure between insect-and wind-pollinated flowers
Insect pollinated flowers are easily
seen and often contain scent and
nectar to attract the insects. The
male parts are adapted so they make
contact with the insect as it feeds
from the flower.
Wind pollinated flowers are often small
and green with no scent. Male anthers
protrude out from the flower to allow
the wind to pick up the pollen and
disperse it away from the plant. Male
and female parts develop at different
times.
Year 9 Science 2013
27
Examples of insect-pollinated flowers
Year 9 Science 2012
28
Examples of wind-pollinated flowers
Year 9 Science 2012
29
Summary of pollination in plants
1. The male parts of the flower are the anther and filament
2. The female parts of the flower are the stigma, style and ovary
3. Male gametes are found in Pollen Produced in the Anther
4. Pollen needs to be moved to the female part called the Stigma of the
same species of plant to reproduce
5. This process is called Pollination
6. Pollination can be helped by Wind Or Animal
7. An example of wind pollination is grass plants
8. A wind pollinated flower is most likely to look like - small, green, unscented
9. An example of animal pollination is a rose plant pollinated by insects
10. An animal pollinated flower is most likely to look like – colourful, with large
petals, perhaps with a scent
Year 9 Science 2013
30
Fertilisation in flowering plants (extension)
1. Pollen from either the same
plant (self-pollination) or
another plant (crosspollination) needs to arrive
on the flowers stigma
2. The pollen sends a tube
down the style to reach the
ovule, and the male
gametes (there are two in
every pollen grain) enter
the ovule to fertilise the
egg (female gamete)
Year 9 Science 2013
31
3. One male gamete joins with
one female gamete to form
a zygote and the plant is
fertilised. (The fertilised
ovule develops into a seed)
The differences between pollination and fertilisation in flowering plants
Pollination just refers
to pollen landing on
the female stigma of
the plant. This can
either be with a
pollinator or wind.
Fertilisation refers to
the sperm cell (that
was in the pollen grain)
joining with the egg
cell to form a single cell
(zygote).
Pollination does not
always lead to
fertilisation
The formation of seed and fruit from ovule and ovary
Once the flower has been
fertilised by pollen the
ovary grows to form the
fruit.
The ovules become the
seeds.
The outer part of the ovule
grows into the seed coat.
The zygote grows into the
young plant – or embryo
A fruit may have one or
more seeds.
The petals, sepals and
other parts of the flower
start to die and fall off.
Year 9 Science 2013
Seed dispersal
How are seeds dispersed?
By animals
By the wind
34
Year 9 Science 2013
Self dispersal
The conditions needed for germination of seeds
Seeds will remain dormant until they receive
water
warmth
light
oxygen
Then they will germinate.
Other types of seeds may also require
>fire to burn seed coat
>soaking in water
>scratched seed coat
>being digested by animals
Before they germinate
Year 9 Science 2013
35
The structure of a seed
The seed consists of the
seed coat or the testa
which surrounds the
cotyledons or the food
storage area. The
embryo consists of the
radicle which is the
embryonic root and the
hypocotyl which forms
the first shoots and
leaves of the plant. A
small pore in the seed
may be seen called the
micropyle. This is where
the pollen originally
entered the ovule.
Year 9 Science 2013
36