Animals need to eat food to get their energy. But green plants and algae do not. Instead they make
their own food in a process called photosynthesis. Almost all life on Earth depends upon this process.
Photosynthesis is also important in maintaining the levels of oxygen and carbon dioxide in the
atmosphere.
These are the things that plants need for photosynthesis: carbon dioxide, water, light (a source of
energy)
These are the things that plants make by
photosynthesis: glucose oxygen
Disease & Immunity
When you are infected by a microbe, it takes time for your body to start fighting the infection. It does
this by making enough white blood cells with the correct antibody. During this time, you continue to
feel unwell.
After a second infection by the same microbe, your body makes the correct antibodies much faster,
because of the white blood cells that remain from when you had the first infection. The microbe
doesn't get a chance to make you ill this time, and we say that you are immune to the microbe and
the disease it causes.
You begin to recover when enough antibodies have been produced. After the microbes have been
killed, the amount of antibodies goes down again. But some of the white blood cells that produce the
correct antibody remain in your blood.
Immunisation is a process that doctors use to make people immune from certain illnesses, even
before they have been infected. It involves you receiving an injection containing a vaccine.
Vaccines contain a dead or weak form of the disease-causing microbe, or some of its antigens. In
response to the vaccine your immune system produces white blood cells with the correct antibody to
kill the microbe, so you become immune without falling ill.
You are likely to have been immunised against several microbes, viruses and bacteria, including the
ones that cause diphtheria, whooping cough, polio, tetanus, meningitis, measles, mumps and
tuberculosis. Girls are also immunised against rubella.