Topic 1
Variation
Adaption
Cold Climate
The polar bear
Polar bears are well adapted for survival in the artic.
They have:
A white appearance as a camouflage
A thick layer of blubber for insulation
A small surface area to volume ratio to minimise heat loss
A greasy coat which sheds water after swimming
Extreme Environments
The Pompeii worm
The Pompeii worm is adapted to high temperatures
They use:
A thick layer of bacteria to protect it from heat
By hiding inside a papery tube they are protected from predators
Variation
Continuous variation
Example is human height, weight or foot length
Discontinuous variation
Example is human blood group, gender or eye colour
Causes of variation
Inherited (genetic)
Example: eye colour, hair colour or skin colour
Environmental
Example: language or religion
Topic 2
Telescopes
How a lens works
Converging lens
A converging lens is curved on both sides. This means the light rays coming out of it come together at a point.
Focal point = the point at which light rays meet
Focal length = the distance between the centre of the lens and the image
Focal length is found by focusing a distant object on a piece of paper through the lens.
How telescopes work
Optical Telescopes
Optical telescopes observe visible light from space but they can only be used at night and bad weather makes it difficult to see.
Radio Telescopes
Radio telescopes detect radio waves from space.
Refracting Telescopes
Refracting telescopes bends light through the lens so that it forms an image
Reflecting Telescopes
An image from a reflecting telescope is formed by reflection from a curved mirror it is then magnified by a secondary mirror
Topic 3
Diabetes
Diabetes is a disorder in the blood glucose levels remain too high
It can be treated by injecting insulin into the body
Type 1
Type 2
Cause
Lack of insulin
Resistance to insulin
Control
Monitoring the diet
Injecting insulin
Monitoring the diet
Regular exercise
Topic 4
Plant Hormones
Tropism is a growth towards a stimulus like light or water
Auxin = a plant hormone produced in the stems tip and roots which controls the direction of growth
There are different types of tropisms:
Positive tropism – towards the stimulus
Negative tropism – away from the stimulus
Phototropism – growth in response to the direction of light
Geotropism – growth in response to the direction of gravity
Plant hormones are used in weedkillers, rooting powder, controlling fruit ripen
