Biology aqa additional

just a few notes :) 


Specalised cells:

Cells may be specailised to carry out a particular function.

Examples of sepcailised cells are, fat cells, cone cells, root hair cells and sperm cells.

Getting in and out?

Dissolved substances move in and out of a cell by diffusion, osmosis and active transport.

Diffusion is the net movement of particles from on area where they are at high concentraion to and area of low concentraion. 

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Limiting factors for photosynthesis. 

there are three main factors that limit the rate of photosynthesis- light- temperature and carbon dioxide levels. 

we can artifically change the environment in which we grow plants. we can use this to observe the effect of different factors on the rate of photosynthesis. we can also use it to control their rate of photosynthesis. 

How plants use glucose: 

plant cless use some of the glucose they make during photosynthesis for respiration. 

some of the soluble glucose produced during photosynthesis is converted into insoluble starch for storage. 

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why do plants need minerals?

plant roots absorb mineral salts including nitrate needed for healthy growth.

Nitrates and magnesium are two important mineral ions. they need magnesium to make chlorophyll.

pyramids of biomass:

radiation from the sun is the main source of energy for all living things. The suns energy is captured and used by plants during photosynthesis. 

the mass of living material at each stage of a food chain is less than... (carried onto the next card :) ) 

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at the stage before. The biomass at each stage can be drawn to scale and shown as a pyramid of biomass. 

Energy losses:

the amount of biomass and engery get less at each successive stage in a food chain.

this is because some materail is always lost in water, abd some is used for respiration to supply energy for movement and for maintaining the body temperature.

Energy in food productions: 

Biomass and engery are lost at each stage of a food chain. the effciency (carried onto the next page)

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of food production can be improved by reducing the number of stages in our food chains. It would be most efficient if we all just ate plants. 

If you stop animals moving about and keep them warm, they lose a lot less energy. This makes food production much more efficient. 


living organisims remove materials from the environment as they grow. They return them when they die through the action of decomposers. 

Dead materials decay because they are broken down (digested) by microorgaisms.

Decomposers work more quickly in warm moist conditions. Many also need a good supply of oxygen.( next card) 

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The decay porcess releases substances which plants need to grow.

In a stable community the process that remove materials (particulary plats growth) are balanced by the processes which return materials. 

The carbon cycle 

the constant cycling of carbon in nature is known as the carbon cycle.

Carbon dioxide is removede from the atmosphere. it  is returned to the atmosphere through respiration and combustion. 

The energy originally captured by green plants is eventually transferred into consumers, into decomposers or as heat into the environment. 

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Aman Habib



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