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3.3 Unit 1: Biology 1
B1.1 Keeping healthy
A combination of a balanced diet and regular exercise is needed to help keep the body healthy. Our
bodies
provide an excellent environment for many microbes which can make us ill once they are inside us. Our
bodies
need to stop most…

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being vaccinated against a particular disease.
a) Microorganisms that cause infectious disease
are called pathogens.
b) Bacteria and viruses may reproduce rapidly inside
the body and may produce poisons (toxins) that
make us feel ill. Viruses damage the cells in which
they reproduce.
c) The body has different ways of…

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inappropriate use of antibiotics has increased
the rate of antibiotic resistant strains of bacteria.
i) Many strains of bacteria, including MRSA, have
developed resistance to antibiotics as a result of
natural selection. To prevent further resistance
arising it is important to avoid overuse of antibiotics.
j) Mutations of pathogens produce…

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conditions inside our bodies. Hormones are used in some forms of contraception and in fertility
treatments. Plants
also produce hormones and respond to external stimuli.
Candidates should use their skills, knowledge
and understanding to:
evaluate the benefits of, and the problems that may
arise from, the use of hormones to…

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responds by contracting and a gland responds
by releasing (secreting) chemical substances.

B1.2.2 Control in the human body
a) Internal conditions that are controlled include:
the water content of the body ­ water leaves
the body via the lungs when we breathe out and
via the skin when we sweat…

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fertilised by sperm from the father. The fertilised
eggs develop into embryos. At the stage when
they are tiny balls of cells, one or two embryos
are inserted into the mother's uterus (womb).
Additional guida

B1.2.3 Control in plants
a) Plants are sensitive to light, moisture and gravity:
their shoots…

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used. Drugs are tested in a series of stages to find
out if they are safe and effective.
New drugs are extensively tested for toxicity,
efficacy and dose:
in the laboratory, using cells, tissues and
live animals
in clinical trials involving healthy volunteers
and patients. Very low doses of the…

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Awareness of the benefits of medical drugs, the impact
of non-medical drugs such as alcohol and the possible
misuse of legal drugs should be considered.
Additional guidance:

B1.4 Interdependence and adaptation
Organisms are well adapted to survive in their normal environment. Population size depends on a
variety of factors
including…

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thickness of insulating coat
amount of body fat
camouflage.
Plants may be adapted to survive in dry environments
by means of:
changes to surface area, particularly of the leaves
water-storage tissues
extensive root systems.
g) Animals and plants may be adapted to cope with specific
features of their environment, eg…

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a) Radiation from the Sun is the source of energy for
most communities of living organisms. Green plants
and algae absorb a small amount of the light that
reaches them. The transfer from light energy to
chemical energy occurs during photosynthesis.
This energy is stored in the substances that make…

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