AQA GCSE BIOLOGY Unit 1b

• If animals and plants were not adapted to survive in the areas they live in, they would die.

• Animals in cold environments, eg polar bears, have thick fur and fat under the skin to stay warm. They also have white fur for camouflage, but underneath that they have black skin to trap heat energy from the sun. Their feet are large to allow them to walk on the snow, and a small surface area (small ears) to minimise heat loss.
• Animals in hot environments, eg elephants, have larger surface areas, ie large ears. These large areas of skin allow the animals to lose heat efficiently.

• Plants must be adapted to live in hot climates, eg the desert, and to avoid being eaten by other animals. Their adaptations include long roots (to absorb lots of water), small leaves and spikes (eg a cactus) to discourage animals from eating them.

Animals and plants compete with each other for many things. The most successful ones survive and pass their genes on to the next generation.

• Animals compete for water, food, space, mates and breeding sites

Eg; Cheetahs have adapted to run very fast to catch the best prey, and therefore the fastest ones survive. Some animals, eg caterpillars may be poisonous, and have warning colours so that other animals will not eat them!

• Plants compete for water, nutrients, light and space

Eg; snowdrops in a woodland have learned to flower early in the year while there are fewer leaves on the trees, so that they get enough light. Other plants spread their seeds over a large area so they do not compete with themselves.

Information from parents is passed to the offspring in the genes. These genes are part of the chromosomes, which make up the nucleus of the cell.

The male and female sex cells (gametes; also called egg and sperm) contain the genes so the genetic information is passed on to the offspring.

Genes control the development of the characteristics of the offspring.

There are 2 types of reproduction, sexual (animals) and asexual (plants and bacteria)

• Sexual reproduction involves the fusion of gametes (sex cells) from 2 parents. There is a mixing of genetic information, so the offspring show variation.
• Asexual reproduction only uses one parent, so all the offspring are genetically identical to the parent and to each other - they are called clones.

Individuals identical to their parents are known as clones. It is easy to clone plants, but very hard to clone animals.

• In plants, we can clone either by taking a cutting, or by taking groups of cells and growing them in a lab under special conditions (tissue culture).

Scientists can clone animals using fusion cell (embryo) cloning and adult cell cloning. This is a very expensive and quite new process, and we don't know how well it works in the long term!

• In embryo transplants, fertilised embryos are split into smaller groups of cells, which are each allowed to develop into a new animal.

• In adult cell cloning (eg Dolly the Sheep), the nucleus of the the animal you want is placed in an empty egg cell. This cell is then grown in a different animal.

Genetic engineering is used to ensure that organisms have 'desired characteristics', ie cows with good milk yields.

New or alternative genes are added to the chromosomes. It is a controversial idea.

Basically, if you place a gene in a new organism, the new organism will have the characteristic that the gene is responsible for. Eg; Potatoes which are resistant to 'blight', a disease which kills them!

Genes are cut out of the chromosome using an enzyme, and the gene is then placed into the chromosome of a different organism; eg firefly genes into tobacco plants, which made the tobacco plants glow in the dark!

Bacteria have been genetically engineered to have the insulin production gene. Insulin is a hormone that people with diabetes need to inject. Bacteria can make insulin very quickly, to help people with diabetes.

The Earth is about 4500 million years old, and life appeared about 3500 million years ago. Fossils have helped us to find out when life began, but it is really hard to find good evidence, as most of the fossils are buried really deep in rocks under the Earth's crust.

Evolution is the process by which the first animals evolved into the animals we have on Earth today.

There are 2 main theories, those of Darwin and Lamarck.

Darwin - All organisms vary, and therefore some will survive better than others. (Natural Selection). Those that have the best adaptations will breed and pass on their characteristics.

Lamarck - If an organism uses a feature, eg rabbits using their ears a lot to hear predators, this feature will be passed on to their offspring.

It took a long time for people to realise that Darwin was right, because he had no evidence then, and people wanted to believe it was God who made animals the way they are.

Organisms of a species all vary from one another. Some organisms are more likely to survive and breed as they have 'better' characteristics. This is known as 'natural selection'.

Weaker members of the species may die from disease, lack of food, predators. The survival of organisms with the 'best characteristics' is known as 'survival of the fittest'. This was Darwin's idea, and explains evolution.

Extinction is where all of a species has become wiped out, eg the dinosaurs. It is triggered by a change in circumstances, ie a new disease, climate change, new predator or destruction of its habitat (where it lives).

Many species on Earth today are at risk of extinction, eg giant panda, white rhino etc.

The human population is increasing rapidly. This means we use up more resources and produce more waste and pollution.

We are using up raw materials eg fossil fuels (coal, oil and gas), and using more and more land, (building, quarrying, farming and waste dumping) which means animals lose their habitat, eg cutting down the rainforests.

Pollution;

Water - With sewage, fertiliser and toxic chemicals

Air - Greenhouse gases eg suphur dioxide, carbon dioxide and methane

Land - Pesticides and Herbicides (weed and pest killers) which can wash into the water supply.

Acid rain is caused by Sulphur Dioxide gas, which dissolve in water to make acid. This makes rainwater acidic. This kills organisms, and can damage buildings. (The statues on the front of Exeter Cathedral are being eroded by acid rain)

Global warming is caused by 2 gases, carbon dioxide and methane.

Carbon dioxide comes from burning fossils fuels, and methane comes from rice production and cows farting!

As the population increases, we are burning more fossil fuels for cars, homes etc, and more rice and beef is needed to feed everyone.

These gases form a 'blanket' around the Earth, so it retains more heat from the sun, which makes the Earth warmer. This could cause ice caps to melt, sea levels to rise and low-lying countries (like us!) to be flooded!

Deforestation adds to global warming, as trees take in carbon dioxide and turn it into oxygen through photosynthesis. With fewer trees, less carbon dioxide can be absorbed.

If we continue to use up the Earth's resources, they will run out, IN OUR LIFETIME!

Sustainable development means finding ways of reducing our need for non renewable resources, eg coal, oil and gas.

This includes new fuel sources, eg wind and solar power, recycling and reclaiming land to avoid expanding the cities.

The world population is increasing, and needs housing. It is important not to build on green areas of the countryside, but use areas which have already been built on. This helps a lot in sustainable development.

Pollution indicators; (Common exam question in section 2!!)

Lichen (moss!) indicates the level of air pollution; the more species of lichen, the cleaner the air is.

Freshwater invertebrates (tiny creatures) indicate the level of pollution in rivers and streams; the more species there are, the cleaner the water is.