Transcript B4 - ME School of Excellence

B4 Summary
Plant Cells
Vacuole
Cell Membrane
Contains cell sap
Allows substances
in/out of cell
Cell Wall
Provides
support
Chloroplast
Where
photosynthesis
takes place
Nucleus
Cytoplasm
Controls the cells
activities
Where all cell
reactions take place
Leaf structure
Palisade
layer
Spongy
layer
Stomata
(can’t see on my diagram)
Cuticle
Upper epidermis
Chloroplasts
Vacuole
Cytoplasm
Air spaces
Phloem
Xylem
Lower epidermis
Guard cells
Keywords - Definitions
• Cuticle
– waxy layer on the top of a leaf. This helps to stop water from
evaporating. A cactus has a thick cuticle.
• Palisade layer
– Closely packed together, elongated and contains lots of chloroplasts
for photosynthesis.
• Xylem
– The vessel that carries water
• Phloem
– The vessel that carries dissolved food substances
• Guard cell
– Surround the stomata and cause it to open or close.
• Stomata (or stoma)
– Holes underneath the leaf. Needed for gas exchange for
photosynthesis. HOWEBER water can evaporate from these holes.
This is called TRANSPIRATION.
Leaf Adaptations
• Broad so large surface area
• Thin so short distance for gases to
travel
• Contain chlorophyll to absorb light
• Have a network of veins for support and
transport
• Stomata for gas exchange (by diffusion)
Osmosis
• Osmosis is the movement of water
across a partially permeable membrane
from an area of high water
concentration (a dilute solution) to an
area of low water concentration (a
concentrated solution)
• Osmosis is a type of diffusion
Osmosis Extras……
• How does water move through a plant?
– Absorption from the soil through root hairs
– Transport through the stem to the leaves
– Evaporation from the leaves (transpiration)
• What is the role of the root hairs?
– They increase the surface area to increase
uptake of water
• How is the leaf adapted to reduce water
loss?
– Waxy cuticle
– Small number of stomata on the upper surface
Key Terms
• Flaccid – when water leaves the plant cells
and the cell becomes soft and floppy
• Plasmolysed – when water leaves a cell and
the contents shrink and there is less water
pressure against the cell wall
• Turgid – when water enters a cell and it
swells up. The cell becomes hard and rigid.
(turgor pressure against cell wall)
Transpiration
• Transpiration is the evaporation and diffusion
of water from inside the leaves
Leaf, Stem, Root
Absorption by the Roots
Xylem and Phloem
• Xylem (TRANSPIRATION)
– Movement of water and minerals from the roots
to the shoot and leaves
• Phloem (TRANSLOCATION)
– Movement of food substances (sugars) up and
down stems to growing and storage tissues
Affects on Transpiration
• Light Intensity increases – stomata open, more
water escapes
• Temperature increases – random movement of
water molecules increases, more water escapes
• Wind – more water molecules near stomata to be
removed, increases evaporation and diffusion of
water
• Dry Conditions – low concentration of water
outside leaf, more diffusion of water from inside
to outside
Plant Minerals
Mineral
Used for:
Symptoms
if Deficient
Diagram
Nitrates
Phosphates
Potassium
Magnesium
To make
To make
DNA & cell
amino acids
membranes,
and proteins
respiration
for growth
& growth
To help
enzymes in
respiration
&
To make
chlorophyll
for
Poor growth
and yellow
leaves
Poor root
growth and
discoloured
leaves
photosynthesis
Poor flower
& fruit
growth and
discoloured
leaves
photosynthesis
Yellow
leaves
Active Transport
• Minerals exist in the soil in quite low
concentrations
• Plants need to use energy (from respiration)
to take them into the roots
• They move against the concentration gradient
Biomass Pyramids
• Biomass – the mass of living material
• This goes down as you move along the
food chain
• Can draw as a pyramid – always look
right way up!
Grade C
Energy Transfer
• Plants use a small percentage of the sun’s
energy to make food during photosynthesis
• This energy then moves through the food
chain through feeding
• Energy is lost at each stage – through heat
and waste (egestion)
• So much energy is lost at each stage there
is not enough to support more organisms
after 4-5 stages
Grade C
Interpreting Data
Can you work out
the 2nd and 3rd
trophic levels?
Rosebush  Greenfly  Ladybird  Bird
80,000KJ 10,000KJ 900KJ
40KJ
• The numbers show the amount of energy
available to the next level e.g. 80,000KJ is
the energy available to the greenfly
• You can work out how much energy is lost at
each trophic level
• e.g. energy lost at 1st trophic level is 80,00010,000 = 70,000KJ
Energy Efficiency
Can you work out the
2nd and 3rd trophic
level efficiency?
Rosebush  Greenfly  Ladybird  Bird
80,000KJ 10,000KJ
900KJ
40KJ
• You can also calculate the efficiency of
energy transfer:
Efficiency = energy available to the next level
x 100
energy that was available to previous level
E.G. 1st trophic level efficiency =
10,000/80,000 x 100 = 12.5% efficient
Biomass and Biofuels
• The mass of plants and animals is called
biomass
• Biomass can be eaten, fed to livestock,
used as a source of seeds, used as a
biofuel
• Wood, alcohol (fermenting) and biogas
are all examples of biofuels
Intensive Farming
• This means trying to produce as much food as
possible from the land, plants and animals
available
• Pesticides can be used to kill pests e.g.
insecticides to kill insects and fungicides to kill
fungi
• Herbicides can be used to kill plants (weeds)
Pesticide Build-Up
• Pesticides may enter and accumulate in food
chains
• Pesticides may harm organisms which are not
pests e.g. bees
• Concentration of DDT in parts per million (ppm) in a food chain:
Lake  Microscopic life  Fish  Grebes (birds)
(0.02)
(5)
(2000) (get a lethal dose)
Food Production
• The efficiency of food production can also be
improved by:
– Restricting energy loss from food animals by
• limiting their movement
• Controlling the temperature of their surroundings
– Using hormones to regulate the ripening of food on
the plant and during transport to consumers
Intensive Farming
• It is very efficient
• More energy is usefully transferred because:
– There are fewer weeds in crops
– There are fewer pests to attack and eat crops or
cause disease in livestock
– Less heat is lost from animals kept in sheds and
their movement is restricted
Hydroponics
• Can be used to grow lettuces or tomatoes
• Allows plant growth in areas of barren soil
• Does not use soil so less chance of disease or
pests
• Roots are specially treated in water that
contains required amounts of fertiliser and
oxygen
Organic Farming
• A farmer who does not use manufactured
chemicals is called an organic farmer e.g.
– Artificial fertilisers
– Herbicides
– Pesticides
Organic Farming
• Biological control e.g. introducing pests like
ladybirds or wasps
• Use of animal manure and compost
• Crop rotation
• Use of nitrogen fixing crops e.g. peas and
beans
• Weeding
• Varying seed planting times
Advantages and Disadvantages
• Expensive chemicals do not have to be bought
• There is no chemical pollution or build up in
food chains
• Biological control methods are often slow and
do not kill all the pests
• Crop yields are reduced and the cost of
production is higher
• Some people think the products taste better
Decay
• Earthworms, maggots and woodlice all feed
on dead and decaying matter – they are called
detritivores (they produce a large SA for
saprophytes)
• Bacteria and fungi are saprophytes – they
release enzymes to break down the dead
matter
Conditions for Decay
• Microorganisms, temperature (warmth),
oxygen (good aeration e.g. regular mixing of
contents) and moisture are all needed for
decay
• Microorganisms are used to:
– Break down human waste (sewage)
– Break down plant waste (compost)
Food Preservation
• Preserving food stops it from decaying:
– Adding sugar or salt
– Canning
– Cooking
– Freezing
– Drying
– Adding vinegar
The Carbon Cycle
• Carbon dioxide is removed from the environment
by green plants for photosynthesis
• The carbon is used to make carbohydrates,
proteins and fats which make up the body of
plants
• Some carbon is returned to the atmosphere when
plants respire
The Carbon Cycle - 2
• Green plants are eaten by animals and so on – the
carbon becomes part of their bodies
• Animals respire and return some carbon to the
atmosphere
• When plants and animals die, micro-organisms feed on
their bodies
• Carbon is released to the atmosphere when they respire
Carbon Cycle at Sea
• Marine organisms make shells made of
carbonates
• Shells become limestone
• Carbon returns to the air as carbon dioxide
during volcanic eruption or weathering
The Nitrogen Cycle – B4
• 78% of the air is Nitrogen – it is very abundant
• BUT it is too un-reactive to be used directly by
animals and plants
• Nitrogen is an important element that is used to
make proteins.
• It is constantly recycled in the Nitrogen Cycle
The Nitrogen Cycle (Grade C) – B4
• Plants take in nitrates from the soil to
make protein for growth
• Feeding passes nitrogen compounds
along a food chain or web
• Nitrogen compounds in dead plants and
animals are broken down by
decomposers into nitrates and returned
to the soil
The Nitrogen Cycle (Grade A) – B4
• Soil bacteria and fungi, acting as decomposers,
convert proteins and urea into ammonia
• This ammonia is converted to nitrates by
nitrifying bacteria
• Nitrates are converted to nitrogen gas by
denitrifying bacteria
• Nitrogen gas is fixed by nitrogen-fixing bacteria
living in root nodules or the soil or by the action
of lightening
Nitrogen Cycle - B6
Nitrogen recycling depends on different types of bacteria:
• Saprophytic soil bacteria start to decompose the dead
animals and plants forming ammonia
• Nitrifying bacteria, such as Nitrosomonas and
Nitrobacter, use the process of nitrification to convert
ammonia into soluble nitrates that plants can absorb
• Nitrogen-fixing bacteria such as Azotobacter,
Clostridium in the soil and Rhizobium in the root nodules
of leguminous plants, convert nitrogen from the air and
use it to make their own proteins
Saprophytes