B4 Summary

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B4 Summary
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Plant Cells
Vacuole Contains cell sap
Cell Membrane Allows substances in/out of cell
Cell Wall Provides support
Chloroplast Where photosynthesis takes place
Nucleus Controls the cells activities
Cytoplasm Where all cell reactions take place
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Leaf structure

• Cuticle
• Upper epidermis
• Palisade Chloroplasts
• layer Vacuole
• Cytoplasm
• Spongy Air spaces
• layer Phloem
• Xylem
• Lower epidermis Stomata Guard
  cells
• (cant see on my diagram)

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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.

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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)

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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

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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

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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)

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Transpiration

• Transpiration is the evaporation and diffusion of
  water from inside the leaves

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Leaf, Stem, Root
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Absorption by the Roots
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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

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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

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Plant Minerals
Mineral Nitrates Phosphates Potassium Magnesium
Used for To make amino acids and proteins for growth To make DNA cell membranes, respiration growth To help enzymes in respiration photosynthesis To make chlorophyll for photosynthesis
Symptoms if Deficient Poor growth and yellow leaves Poor root growth and discoloured leaves Poor flower fruit growth and discoloured leaves Yellow leaves
Diagram
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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

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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
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Energy Transfer

• Plants use a small percentage of the suns 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
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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
  80,000-10,000 70,000KJ

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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

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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

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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)

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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)

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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

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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

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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

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Organic Farming

• A farmer who does not use manufactured chemicals
  is called an organic farmer e.g.
• Artificial fertilisers
• Herbicides
• Pesticides

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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

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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

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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

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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)

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Food Preservation

• Preserving food stops it from decaying
• Adding sugar or salt
• Canning
• Cooking
• Freezing
• Drying
• Adding vinegar

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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

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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

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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

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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

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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

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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

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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

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Saprophytes