The whole thing is powered by photosynthesis. CO2 is removed from atmosphere by green plants and used to make carbohydrates, fats and proteins in plants.
Some CO2 goes back to atmosphere when plants respire.
Some carbon becomes compounds in animals when plants are eaten, carbon then moves through food chain.
Some CO2 returns to atmosphere when animals respire
When plants and animals die other animals called detritus feeders and micro-organisms eat them. When they respire CO2 returns to atmosphere.
Animals also produce waste which is broken down by detritus feeders and micro-organisms.
So carbon is constantly being cycled from air through food chains and eventually back to air!
Cells ( Animal)
Animals cells contain: Nucleus, Cytoplasm, cell membrane, Mitochondria and ribosomes.
Nucleus- controls cell
Cytoplasm- Where chemical reactions happen, contain enzymes which controll chemical reactions
Cell Membrane- Holds cell together and controls what goes in and out
Mitochondria- Where most reactions for respiration take place. Respirations releases energy which the cells need to work
Ribosomes- Where proteins are made in the cell.
Plant cells usually have all the bits of the animal cell plus a few extra things. (see animal cell card for list of parts)
Plant cells contain, Rigid cell wall, Permenant vacuole and Chloroplasts. (They also contain everything which is in animals cells)
Rigid cell wall- Made up of cellulose and supports the cells and strengthens it
Permanent vacuole- Contains cell sap, a weak solution of sugar and salts.
Chloroplasts- These are where photosynthesis occurs which makes food for the plant. They contain a green substance called chlorophyll.
Plant cell structure
The top layer of the leaf is called the waxy cuticle. This protects the leaf without blocking sunlight.
The next layer of the leaf is called the Upper Epidermis. This allows more light to the palisade cells.
The next layer of the lead is called Palisade Mesophyll. They absorb light.
The next layer of the leaf is called the Spongy Mesophyll. This has air spaces to allow carbon dioxide to diffuse through the leaf and to increase the surface area.
Below this is the Lower Epidermis. These do the same job as the upper epidermis.
Next to these are the guard cells with chloroplast.
Diffusion (Part one)
Diffusion is the passive movement of particles from an area of high concentration to an area of low concentration.
Diffusion happens in both liquids and gases because particles in them are free to move randomly.
The bigger the difference in concentration, the faster the diffusion rate.
Diffusion (Part 2)
Cell Membranes hold the cell together but they let stuff in and out as well. Substances can move in and out of the cell by diffusion and osmosis. Only very small molecules can diffuse through cell membranes though- things like glucose, amino acids, water and oxygen.
Big Molecules like starch and proteins can't fit through the membrane.
1)Particles flow through the cell membrane from a high concentration to a low concentration
2)The particles move randomly so they go through the membrane in both ways- but if there are a lot more particles on one side of the membrane, there is a net movement from that side.
3) The rate of diffusion depends on: Distance-diffuse more quickly when they don't have as far to move, Concentration difference-Diffuse quicker with bigger difference in concentration and Surface Area- The more surface available the faster they get from one side to the other.
Osmosis is the movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of low water concentration.
1)A partially permeable membrane has very small holes in it, so only tiny molecules (water) can pass through them and bigger molecules like (sucrose) cannot
2) The water molecule pass both ways during osmosis because water molecules move about randomly.
3)But because there are more water molecules on one side, there is a steady net flow of water into the region with fewer water molecules ie. into the stronger sugar solution
4)This means the strong sugar solution gets more dilute, the water acts like it is trying to "even up" the concentration either side of the membrane.
5) Osmosis is a type of diffusion-passive movement of water particles from high concentration to low.
Osmosis( Part two)
Water moves into and out of cells by osmosis
1)Tissue fluid surrounds cells in the body-basically water with oxygen,glucose and stuff dissolved in it. It's squeezed out of the blood capillaries to supply cells with everything they need.
2) Tissue fluid usually has a different concentration to a fluid inside the cell. Therefore water will move into the cell from the tissue fluid or out of the cell by osmosis.
3) If a cell is short of water, the solution inside becomes concentrated which usually means the solution outside is dilute and so water will move into the cell by osmosis
4) If a cell has lots of water the solution inside will be more dilute and water will be drawn out of the cells and into the fluid outside by osmosis
Experiment- Potatoes in sugar water and potatoes in pure water.
How plants use glucose
1) For respiration-plants make glucose in their leaves. They then use some glucose to respire.This releases energy which enables them to convert the rest of the glucose into other useful substances which they can use to build new cells and grow. To produce some of these substances they also need to gather minerals from soil.
2) Making Fruits- Glucose, along with another sugar called fructose is turned into sucrose for storing in fruits. Fruits deliberatly taste nice so animals will eat them and spread seeds everywhere through their turd.
3)Making Cell Walls-Glucose is converted into cellulose for making cell walls especially in a rapidly growing plant
4)Making Proteins- Glucose is combined with nitrates (from soil) to make amino acids which are made into proteins.
5)Stored In Seeds-Glucose is turned into lipids (fats and oils) for storing in seeds. Sunflower seeds, for example contains lots of oil, we get cooking oil and margarine from them
6) Stored As Starch- Glucose is turned into starch and stored in roots, stems and leaves ready for when photosynthesis isn't happening- winter. Starch is insoluble which makes it better for storing because it doesn't bloat storage cells by osmosis like glucose would. Potato and carrot plants store starch underground over winter so a new plant can grow from it the following spring. We eat the swollen storage organs.
Rate Of Photosynthesis
The rate of photosynthesis is affected by the amount of light, the amount of CO2 and the temperature.
The limiting factors are:light (at night time), temperature (winter) and when it is both warm and bright the amount of CO2 is usually a limiting factor.
If the temperature goes above about 45 degrees the enzymes will be destroyed.
You can artificially create the ideal conditions for farming by growing plants in a greenhouse. They help to trap the suns heat and stop the temperature from being limiting, also in winter they may use a heater and in summer may use shade.
Artificial light is used after the sun goes down to give the plants more time to photosynthesise, you can also control carbon dioxide level by pumping it into the greenhouses. The most common way to do this is by using a paraffin heater.
Keeping plants inside greenhouses makes it easier to keep them free from pests or diseases. Farmers can add fertilizers to the soil to provide minerals needed for healthy growth. All of these conditions help the plant to grow faster.
Minerals for Healthy Growth
Plants get their minerals from the soil by absorbing them through their roots.
The main 2 minerals are:
Nitrates- Are needed for making amino acids which are then used to make proteins
Magnesium- Is needed to make chlorophyll which in turn is needed for photosynthesis
Other minerals needed by plants include: Potassium and Phosphates which are used for things like making DNA and cell membranes and helping the enzymes involved in photosynthesis and respiration to work properly.
Lack of Nutrients...
Lack of nutrients causes deficiency symptoms
Sometimes plants can't get all of the mineral ions they need to be healthy, eventually it will start to show symptoms of deficiency .
1) Lack of Nitrates- If the soil is deficient in nitrates, the plant starts to show stunted growth and won't reach it's usual size. This is because proteins are needed for new growth and they can't be made without nitrates.
2) Lack of Magnesium- If the soil is deficient in magnesium, the leaves of the plant start to turn yellow. This is because magnesium is needed to make chlorophyll, and it gives the leaves its green colour.
If the plant is left short of the minerals it needs for too long it might die.
Deficiencies can be caused by monoculture
1) Monoculture is where one type of crop is grown in the same field year after year.
2)All the plants are the same crop so they need the same minerals. This means the soil become deficient in the minerals which the crop uses lots of.
3)Deficiency of just one mineral is enough to cause poor growth and give a reduced yield.
4) This soon resorts in poor crops unless fertilizer is added to replenish the depleted minerals.
Managing Food Production
Reduce the number of stages in the food chain
1)More food can be produced by growing crops in an area of land than grazing animals in that same area of land.
2) However people need to eat a varied diet. There is still much demand for meat product. Also some land is unsuitable for growing crops. Animals and sheep might be the best way to get food from the land in these places.
Restrict the energy loss by farm animals
1)Pigs and chickens are often intensively farmed ( kept close together indoors) so they are warm and cannot move around.
2)This saves energy being wasted on heat and movement. This will be more efficent because the energy from food is going towards making the animals grow.
3) This makes things cheaper for us and the farmer.
There are ethical issues with intensive farming.