B4 Biology OCR higher

Biology revision. B4. 

  • Created by: rebee
  • Created on: 03-06-11 17:22

Leaf Structure: Questions


1. Why are leaves broad and thin? 

2. What is the mesophyll layer, and how has it been adapted?

3. What is chlorophyll and where is it commenly found? 

4. What is the upper epidermis?

5. Whats special about a palisade cell?

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Leaf Structure: Answers


1. Broad: large surface area for sunlight. Thin: shorter distance for gases to travel.

2. Has air spaces: allows gases to move easily: large surface area for gas exchange.

3. Chlorophyll is found in chloroplasts it is a pigment which absorbs sunlight for photosynthesis.

4. The upper epidermis is transparent allowing light to travel to the palisade layer beneath.

5. Packed with chloroplast for photosynthesis, tall -> large for surface area for absorption of carbon dioxide

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Diffusion in leaves: Questions

1. Define Diffusion

2. What happens to a plant at night? 

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Diffusion in Leaves: Answers

1. The passive movement of particles from an area of higher concentration to an area of lower concentration.

2. There's no photosynthesis happening as there is no sun. Lots of Carbon dioxide is made by respiration and lots of oxygen is used up. 

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Osmosis: questions

1. Define Osmosis

2. What is Turgor Pressure?

3. What is the opposite to a turgid plant cell? 

4. what kind of cells have an inelastic cell wall? 

5. What happens to an animal cell when water gets in it?

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Osmosis: Answers

1. Osmosis is the movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration. 

2. Turgor Pressure supports plants. -> water is taken into the cell by osmosis.

3. Flaccid; then plasmolysed.

4. Plant cells. 

5.     -When it bursts (lysis)

        -Loses too much (crenation)

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Waterflow through plants part 1: Questions

1. How do root hairs take in water?

2.What is transpiration, and how is it caused? 

3. What are the 4 benefits of transpiration? 

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waterflow through plants part 1: answers

1. Osmosis of course?! Root hairs gives plant a big surface area usually a higher concentration of water is in the soil, so water is drawn in my osmosis.

2. Loss of water from plants caused by evaporation and diffusion from within the leaves. 

3.        -It helps to keep the plant cool.

           -It supplies plant with constant supply of water for photosynthesis.

           -The water creates turgor pressure which helps support the plant and stops it wilting.

   -minerals needed are found in the water.. 

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Waterflow through plants part 2: Questions

1. What four things is transpiration rate affected by?

2. How have plants adapted to reduce water loss?

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Waterflow through plants part 2: Answers

1.  -Light intensity - stomata closed when dark

-Temperature - Particles have more energy

-Air movement - lots of movement means faster transpiration

-Air humidity - dry air means faster transpiration. 

2. Plants have:

waxy cuticles

stomata at the bottom of the leaf - cooler/darker slows diffusion.

more or less stomata on plants that are in different climates.

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Transport systems in plants: Questions

1. What do phloem tubes do?

2. What is their structure?

3. What is the movement of food substances called?

4. What do xylem tubes do?

5. What is their structure?

6. What is another function of xylem tubes? 

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Transport systems in plants: Answers

1. Transport Food.

2. Made of living cells with perforated end-plates to allow stuff to flow through.


4. Take water up plant.

5. Made of dead cells joined end to end with no end walls between them and a hole down the middle.

6. Gives plants support as they are strong and stiff.

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Minerals needed for healthy growth: Questions

1. Why does a plant need Nitrates?

2.Why does a plant need Phosphates?

3. Why does a plant need Potassium?

4. Why does a plant need Magnesium? (in small amounts)

5. What is active transport? 

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Minerals for healthy growth: Anwers

1. To make amino acids and proteins needed for cell growth. without it; stunted growth occurs and the plant gets YELLOW leaves. 

2. For making DNA and cell membranes needed for respiration and growth without it: poor root growth and PURPLE older leaves.

3. To help the enzymes needed for photosynthesis and respiration. Without it plant has poor flowering/fruit production, and discoloured leaves.

4. For making chlorophyll. without magnesium plant gets YELLOW leaves.

5. Uses energy from respiration to get minerals it needs. Goes against osmosis principles. 

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Biomass and intensive farming: Questions

1. What are the uses of Biomass?

2. What's significant about fast growing trees for bio-fuels? 

3. What's a fermenting bio-fuel?

4. What are the benefits of Bio-fuels?

5. How can intensive farming destroy the environment? 

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Biomass and intensive farming: Answers

1. Ways of releasing energy stored in Biomass: Eating it, Feeding it to livestock, growing seeds and use as a fuel.

2. No overall CO2 contributions as the trees have been replaced which takes in the carbon. 

3. Fermenting bacteria or yeast anaerobically, you can use micro-organisms to make bio-gas using a digester.

4. It is renewable, reduces air pollution, no acid rain, energy is self reliant. 

5. Destroys national habitats by soil erosion. 

Eutrophication caused by NPK feritlisers.

Pesticides disturb food chains

Animal Cruelty 

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Pesticides and Biological control: Questions

1. Why is it bad to use pesticides?

2. What is an alternative to using pesticides?

3. What are the advantages of this method?

4.What are the disadvantages? 

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Pesticides and Biological control: Answers.

1. DDT cannot be excreted by animals, so it accumulates along food chains, gets higher

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thanks very helpful.x




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