OCR GCSE Biology- B3

What is a species?

A group of similar organisms that are capable of breeding to produce fertile offspring.

How does a species survive in its environment?

Adaption to the environment, which makes it better at survival and reproduction.

How is a fish adapted to water?

It has gills, to take oxygen from water and allow respiration; it has a streamlined shape and fins, which allow fast and easy movement in the water; it has an air-filled sac known as a swim bladder, to help it maintain a position in the water.

What causes extinction?

Organisms share their habitats with other species, which leads to competition for food and resources. This, disease and predators can wipe out an entire species.

What is a food chain?

It shows the feeding relationships between particular organisms, and the dependence some have on others (predators need the prey, so they can have food and survive).

What is a food web?

A diagram, which shows how all food chains in a habitat are interrelated. This joins up many food chains and can end up complicated, due to animals having varied diets. It also shows the interdependence of all living organisms in a habitat. The make-up of a food web is affected by the environment, and changes in this will alter the food web.

What is energy transfer?

The movement of the sun's energy along a food chain- plants absorb the sun's energy in photosynthesis, which is transferred to animals when they are eaten, to predators when the animals are eaten, and to decay organisms when they die and decompose. Along the way energy is lost in heat, respiration and excretion.

What is an ecosystem?

An area containing a self-sustained community of organisms and their physical surroundings.

What is an autotroph?

A self-feeder, an organism which makes its own food, e.g. plants. They are also called producers.

What is a heterotroph?

An organism which is unable to make its own food, so gets energy by consuming other animals, e.g. animals and decay organisms.

What is a herbivore?

Heterotrophs that eat plants (primary consumers).

What is a carnivore?

Heterotrophs that eat other animals (secondary/tertiary consumers).

What is a detritivore?

An organism that feeds off dead organisms, and decomposes them.

How do you calculate energy efficiency?

Input energy/Output energy X 100

What is the nitrogen cycle?

Nitrates in soil are broken down into nitrogen by bacteria in denitrification, which is taken in from soil by plant roots and removed from soil nitrates by denitrifying bacteria. Plants get more from the nitrogen-fixing bacteria in soils and plant roots, which remove the nitrogen from the air, and from nitrate fertilisers. The plants are eaten by animals, and nitrogen is transferred to them. When plants die and animals excrete and die, the nitrogen is transferred further. It is taken back into the air by denitrifying bacteria, and into the soil by nitrifying bacteria and during storms.

What is the carbon cycle?

Carbon dioxide is taken from the air by plants in photosynthesis, and it goes into their cells. Animals eat the plants, and use the carbon in their cells. Other animals eat these, and the process continues. Carbon dioxide is sent back into the air as a waste product of respiration. Further carbon dioxide comes into the atmosphere from combustion of fossil fuels and forest fires, and decomposers break down waste or dead material, releasing more.

What is an indicator?

A living organism that is used to measure changes in environment, e.g. mayfly larvae in rivers, lichens in air, and phytoplankton in plankton.

How long has life been on Earth?

Around 3500 million years- the first living things developed from simple molecules that could asexually reproduce (replicate themselves), in the harsh conditions of the Earth at this time.

What do fossil records and DNA evidence show?

All organisms that currently exist could come from a common ancestor.

How do fossil records show this?

Fossils are formed of parts of dead animals that haven't decayed, and fossils have gradually changed- younger ones are different to older ones.

How does DNA evidence show this?

DNA from living organisms and fossils shows many similarities- more the further back you go. Comparisons of gene sequences show that some organisms are much more similar to others than it seems- humans share 98.8% of their DNA with chimpanzees, who share 85% with mice.

What is evolution?

The continual change of a species over many generations, which results in new species, adapted to their environment.

What is Darwin's theory of evolution by natural selection?

All individuals are different to other individuals of the same species, due to genetics- variation. In each ecosystem there is competition for both food and mates, and population sizes are kept down by predators and diseases. Those that can survive are better adapted to the environment, and will continue to reproduce. When survivors pass on their genes, the traits that make them better for survival are also passed on, essentially improving the organism for future generations.

What is selective breeding?

Animals are chosen by humans to mate, due to having certain desirable traits or characteristics. They then produce offspring with those traits (e.g. cows that produce more milk).

What is the effect of human activity on other species?

The rate of extinction is increasing, due to human activity. This is because of deforestation, industrial activity and the human introduction of predators. Species becoming extinct reduces the biodiversity and sustainability of an ecosystem.

How has man directly caused extinction?

The Great Auk was a bird of the North Atlantic Ocean, before its extinction in the 19th Century. It was already vulnerable, because pairs would only produce a single offspring a year, but it was regularly hunted for food and feathers.

How has man indirectly caused extinction?

The Rodrigues pigeon inhabited Rodrigues Island in the Indian Ocean, before men started visiting the island on ships. They accidentally took rats with them on the ships, which killed the birds and made the pigeon extinct.

What is biodiversity?

The variety of life on Earth. The more species, the more the variety and biodiversity on Earth. When a species is lost by extinction, its genetic code and the information that carries is also lost, which could potentially be useful (for medicine etc.).

How is biodiversity sustainable?

Conservation of species- looking after them so they survive- manages the needs of current generations and doesn't damage the need of future generations.

How is life classified?

All living things are put into kingdoms and species, and are given Latin names for both. For example, humans are in the kingdom Animalia (animals) and are called Homo sapiens.

What happens to packaging on goods and food?

Most packaging ends up in landfill sites, where it gets left and remains for many years. Anything in landfill won't get broken down very quickly, due to the lack of oxygen restricting decomposer organisms. The sites are running out of space, so we need to find alternatives.

What can be done to reduce the packaging in landfill?

Recycling waste (household/community schemes); reduce the amount of packaging being used, which will also save energy and reduce pollution from transporting the goods; using biodegradable options, such as cardboard as a polystyrene alternative, or cellulose carrier bags.