Classification is organising living organisms into groups.
Natural classification is based on the evolutionary relationships and genetic similarities between organisms.
Artificial classification is based on appearance rather than genes.There used to identify organisms.
Living things are divided into kingdoms.
The kingdoms are then divided into smaller groups.
It goes Kingdom,Phylum,Class,Order,Family,Genus,Species.
You can remember this by remembering King Philip Came Over For Great Sausages.
Newly discovered species might not really fit into any of the categories.
DNA sequencing allows us to see genetic differences between different groups.
Evolutionary relationships can be shown with evolutionary trees.
A species is an organism that can breed to produce fertile offspring.
Asexual Reproduction is where an organism reproduces by making a copy of itself.There is no interbreeding with another organism so they don't fit the definition of a species.

If you interbreed a male from one species with a female from a different species you'll get a hybrid.Hybrids are infertile.
Organisms change and evolve over time,so the way they've been classified might also have to change.Sometimes a group of organisms will change so much it will form a new species.
In the binomial system,each species is given a two-part Latin name.The first part refers to the genus that the organism belongs to and the second part refers to the species.
Each bar on a pyramid of biomass shows the mass of living material at that stage of the food chain.
Biomass pyramids are almost always pyramid shaped because biomass is lost at each stage in the food chain.

Pyramids of numbers are similar to pyramids of biomass,but each bar on a pyramid of numbers shows the number of organisms at that stage of a food chain.
Pyramid of numbers can be other shapes apart from a pyramid shape.
Energy from the sun is the source of energy for all life on earth.
Plants use a small percentage of the light energy from the sun to make food during photosynthesis.
The energy lost at each stage is used for staying alive.
Most of the energy is eventually lost to the surroundings as heat.
Material and energy are also lost from the food chain as waste products.
Waste products and uneaten parts can become starting points for other food chains.
There can be no more than five tropic levels because by the last one there is not enough energy to sustain another population.
There are two types of competition between organisms.organisms. Inter specific competition and intra specific competition.

Interspecific competition is where organisms compete for resources against individuals of another species.
Intraspecific competition is where organisms copete for resources against individuals of the same species.
The population of a species is usually limited by the amount of food available.If the population of the prey increases,then so will the population of the predators.
However as the population of predators increases,the number of prey will decrease.
Parasites live off the host.They take what they need to survive,without giving anything back.This often harms the host.
Mutualism is a relationship where both organisms benefit.
Adaptations are the features that organisms have that make them better suited to their enviroment.
Organisms that are adapted to the enviroment are better able to compete for resources.This means that they're more likely to survive,reproduce and pass on their adaptatios to their offspring.
Specialists are organisms whih are highly adapted to survive in a specific habitat.

Generalists are organisms that are adapted to survive in a range of diffrent habitats.
Some features that help animals survive in cold conditions are:
Having a thick coat or layer of blubber to insulate the body and trap heat in.
Having a large size and compact body shape to give a small surface ares to volume ratio.
This reduces heat loss as less body heat can be lost through the surface of the skin.
Having counter-current heat exchange systems:
Animals like penguins have to stand on cold ice all day.
Blood vessels going to and from the feet carry blood that flows in opposite directions.
The vessels pass close to each other,allowing heat to transfer between them.
Warm blood flowing in arterie to the feet heats cold blood returning to the heart in the veins.
This means that the feet stay cold,but it stops cold blood from cooling down the rest of the body.
Some organisms have adapted to live in hot enviroments.
Animals that live in very hot climates often spend the day in the shade or underground to minimise the amount of heat their bodies gain from their surroundings.
Animals can also reduce their heat gain by being active at night,when it is much cooler.
Animals can increase heat loss by bathing in water.As the water eveaporates it transfers heat from the skin to the surroundings,cooling the animal down.

Animals that are adapted to survive in hot enviroments are often small.This gives them a large surface area to volume ratio which allows them to lose more body heat to their surroundings.
Other adaptations,like having large ears,can also increase an animals surface area to volume ratio and help them to lose heat.Large thin ears allow more blood to flow near the surface of the skin.
Some animals,like camels,store fat in just one part of the body.This stops the rest of the body from being too well insulated and allows heat to be lost more easily.
Some desert plants:
Have a rounded shape,giving them a small surface area to volume ratio to minimise water loss from the surface.
Have a thick waxy layer ans spines instead of leaves to further reduce water loss.
Store water in the stems to allow them to survive in times of extreme drought.

Have shallow,but very extensive roots to ensure water is absorbed quickly over a large area.

	Created by angel915 over 10 years ago

GCSE Science (science exam) Note on Science unit 2 exam, created by angel915 on 29/05/2014.

Science unit 2 exam