• Category:Key Stage 3 Biology Revision Notes

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Life processes

Living things have certain life processes in common. There are seven things that they need to do to count as being alive. The phrase MRS GREN is a way to remember them:


R-Respiration Getting energy from food

S-Sensitivity Detecting changes in the surroundings


R-Reproduction Making more living things of the same type

E-Excretion Getting rid of waste

N-Nutrition Taking in and using food

Animal cells and Plant cells

The basic building block of animals and plants is the cell. Cells are very small and we need a microscope to see them. The photographs show animal cells and plant cells, as seen through a microscope.

Animal cells and plant cells both contain: -Cell membrane -Cytoplasm -Nucleus

Plant cells only also contain: -Chloroplasts -Vacuole -Cell wall

Cell Function

Cell membrane -Controls what substances can get into and out of the cell.

Cytoplasm Jelly-like substance, where chemical reactions happen. In plant cells there's a thin lining, whereas in animal cells most of the cell is cytoplasm.

Nucleus Controls what happens inside the cell - it is not a 'brain'.

Chloroplast Where photosynthesis happens – chloroplasts contain a green substance called chlorophyll.

Vacuole Contains a liquid called cell sap, which keeps the cell firm.

Cell wall Made of a tough substance called cellulose, which supports the cell.

Type of animal cell

Red blood cells To carry oxygen Large surface area, for oxygen to pass through Contains haemoglobin, which joins with oxygen

Nerve cell To carry nerve impulses to different parts of the body Long Connections at each end Can carry electrical signals

Female reproductive cell (egg cell) To join with male cell, and then to provide food for the new cell that's been formed Large Contains lots of cytoplasm

Male reproductive cell (sperm cell) To reach female cell, and join with it Long tail for swimming Head for getting into the female cell

Type of Plant Cell

Root hair cell To absorb water and minerals Large surface area

Leaf cell To absorb sunlight for photosynthesis Large surface area Lots of chloroplasts

Cells, tissues, organs and organ systems

Tissues Animal cells and plant cells can form tissues. A living tissue is made from a group of cells with a similar structure and function, which all work together to do a particular job. Here are some examples of tissues: Muscle, The lining of the intestine, The lining of the lungs, Phloem (tubes that carry dissolved sugar around a plant) and Root hair tissue (for plants to take up water and minerals from the soil)

Organs An organ is made from a group of different tissues, which all work together to do a particular job. Here are some examples of organs: Heart, Lung, Stomach, Brain, Leaf and Root

Organ systems An organ system is made from a group of different organs, which all work together to do a particular job. Here are some examples of organ systems: Circulatory system, Respiratory system , Digestive system, Nervous system , Reproductive system and Leaf canopy

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