B4 Biology extra GCSE revision must knows

community - populations of different species in a habitat make up a community

population - all the organisms of one species in a habitat

ecosystem - all the organisms living in a particular area , as well as all the abiotic conditions e.g. temperature, salinity and soil quantity

zonation - the gradual change in the distribution of species across a habitat

biodiversity - a measure of the variety of life in an area

three limiting factors of photosynthesis:

1) not enough LIGHT, slows down the rate of photosynthesis because light provides the energy needed for photosynthesis

2) too little CARBON DIOXIDE slows down the rate of phhotosynthesis because CO2 is one of the raw materials needed for photosynthesis

3) the TEMPERATURE has to be just right because photosynthesis works best when it's warm but not too hot

diffusion - the net movement of particals from an area of higher concentration to an area of lower concentration

Plants exchange gases via diffusion

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Main three minerals plants need for healthy growth:

1) nitrates - contain nitrogen for making amino acids and protei. these are needed for cell growth; if a plant doesnt have enough, it's growth will be poor and it will have yellow older leaves

2) phosphates - needed for respiration and growth. Contain phosphorus for making DNA and cell membranes. Plants without enough phosphate have poor root growth and discoloured older leaves.

3) potassium - to help the enzymes needed for photosynthesis and respiration. If there's not enough potassium in the soil, plants have poor flower and fruit growth and discoloured leaves.

four problems assosiated with intensive farming:

1) removal of hedges to make huge great fields destroys the natural habitat of wild creatures. It can also lead to serious soil erosion.

2) careless use of fertilisers can pollute rivers and lakes (eutrophication)

3) pesticides disturb food chains

4) lots of people think that intensive farming is cruel because they have very little space or freedom to move around

osmosis - the net movement of water molecules across a partially permeable membrane from a region of higher water concentration (i.e. a dilute solution) to a region of lower water concentration (i.e. a concentrated solution)

hydroponics - when the plant grows without soil. The plants are grown in nutrient solutions (water and fertilisers) instead of soil. Often used to grow glasshouse tomatoes on a commercial scal, as well as to grow plants in areas with barren soil.