1. B4 Summary

2. Plant Cells Vacuole Cell Membrane Cell Wall Chloroplast Nucleus
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

3. Leaf structure Cuticle Upper epidermis Palisade Chloroplasts
layer Vacuole
Cytoplasm
Spongy Air spaces
layer Phloem
Xylem
Lower epidermis Stomata Guard cells
(can’t see on my diagram)

4. 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.

5. 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)

6. 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

7. 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

8. 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)

9. Transpiration
Transpiration is the evaporation and diffusion of water from inside the leaves

10. Leaf, Stem, Root

11. Absorption by the Roots

12. Xylem and Phloem Xylem (TRANSPIRATION) Phloem (TRANSLOCATION)
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

13. 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

14. 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

15. 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

16. 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

17. 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

18. Interpreting Data Rosebush  Greenfly  Ladybird  Bird
Can you work out the 2nd and 3rd trophic levels?
Interpreting Data
Rosebush  Greenfly  Ladybird  Bird
80,000KJ 10,000KJ KJ KJ
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

19. Can you work out the 2nd and 3rd trophic level efficiency?
Energy Efficiency
Rosebush  Greenfly  Ladybird  Bird
80,000KJ 10,000KJ KJ KJ
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

20. 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

21. 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)

22. 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)

23. 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

24. 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

25. 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

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

27. 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

28. 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

29. 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

30. 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)

31. Food Preservation Preserving food stops it from decaying:
Adding sugar or salt
Canning
Cooking
Freezing
Drying
Adding vinegar

32. 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

33. 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

34. 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

35. 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

36. 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

37. 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

38. 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

39. Saprophytes