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Science B1,2,3

Biology 1: Genes
Unit 1.1: What your genes do (Pg. 4)

Genes carry instructions that control how you develop and function ­ They are long molecules of a chemical
called DNA.

Genotype: A person's genetic makeup. (Dimples)
Phenotype: Observable physical features ­ Can be affected by the environment.…

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males.

Unit 1.4: Gene disorders, carriers and genetic testing. (Pg. 7)

Some disorders are caused by faulty or defective alleles.

Huntington's disease is a dominant disorder, the presence of just one dominant allele can cause the disease. It
occurs in middle age.
Symptoms include:
Uncontrollable shaking
Memory loss
Inability to…

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Clones:
Advantages: Disadvantages:
Successful No genetic variation, if
characteristics shown living conditions change,
the population could be
wiped out.
Useful when organism
lives in isolation
Embryonic stem cells can change into any cell doing a different job.
Adult stem cells stay the same.

Because embryonic stem cells can develop into…

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The body's external defences include skin, saliva and tears, and acid in the stomach.
The body's internal defence is our immune system.

The immune system uses white blood cells to defend the body. White blood cells:
are made in the bone marrow
are found as several types: some engulf and…

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Links the veins and arteries
One cell thick transfers substances to and from cells
Veins:
Collects blood and returns it to the heart
Thin, elastic and muscular
Transfers blood under low pressure

The coronary arteries can become blocked by fatty deposits, this prevents the heart from receiving the blood
it…

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The kidneys help to balance levels of water, urea, salts and other chemicals in the blood.
The kidneys respond to changes in the blood plasma by changing the concentration of urine that is excreted
from the body.

Alcohol causes the kidneys to produce a large volume of dilute urine and…

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Carbon is key element of the chemicals that make up all living things, it is continuously recycled through the
carbon cycle.


Nitrogen is an essential component of living things. It is recycled through the nitrogen cycle.



Environmental change can be measured using:
Nonliving indicators, e.g. carbon dioxide levels, temperature and…

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To ensure sustainability, we need to maintain biodiversity. The loss of a single species removes a food
supply and can have a big impact on the whole ecosystem.

Intensive monoculture crop production maximises crop yields but it not sustainable reduces biodiversity.

We can improve sustainability in product manufacture, for example…

Comments

naf

Hello Hajrah!

Thanks for these resources, they're really good! I don't suppose you have B456, C456 and P456?

Thanks again, Isa.

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