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The Carbon Cycle

1. Carbon enters the atmosphere as carbon dioxide from respiration and combustion.

2. Carbon dioxide is absorbed by producers to make carbohydrates in photosynthesis.

3. Animals feed on the plant passing the carbon compounds along the food chain. The carbon the consume is exhaled as carbon dioxide formed during respiration. The animals and plants eventually die.

4. The dead organisms are eaten by decomposers and the carbon in their bodies is returned to the atmosphere as carbon dioxide. In some conditions decomposition can't occur. The plant and animal material may then be available as fossil fuel in the future for combustion.

In the sea, marine animals may convert some of the carbon in their diet to calcium carbonate which is used to make their shells. Over time the shells of dead organisms collect on the seabed and form limestone. Due to Earth movements this limestone may become exposed to the air and weathered, then the carbon is released back into the atmosphere as carbon dioxide.

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Asexual Reproduction

  • Needs only one parent = no fusion of gametes + no mixing of genetic information
  • No variation- a new disease could wipe out the whole population
  • Offspring are genetically identical to parent and each other. They are clones.
  • Cloning a plant has many important commercial implications. It allows a successful variety of a plant to be produced commercially and cheaply on a massive scale, in a short space of time.

Embryo Transplants: Developing embryo is removed from a pregnant animal at an early stage before cells are specialise. Cells are separated and grown in a lab, then transplanted into host mothers. Offspring are identical to each other but not to host mothers.

Fusion cell cloning involves replacing the nucleus of an unfertilised egg with a nucleus from a different cell. 1. Egg cell removed from ovary, and nucleus removed. 2. Nucleus from cell of donor animal inserted. 3. Fused egg develops normally. 4. Before cells are specialised, embryo is implanted into uterus of a foster mother. The result is an animal that is genetically identical to the donor.

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Asexual Reproduction 2

Examples: Potato plants, daffodils, spider plants, strawberries, sea anemones, starfish


1. Branch from parent plant is cut off. 2. Lower leaves are removed, stem is planted in damp compost. 3. Plant hormones are used to encourage new root development. 4. Covered in clear plastic bag to keep it moist + warm. 5. After a few weeks new roots develop + a new plant is produced.

Tissue Culture:

1. Small amounts of parent tissue is taken. 2. Plant material is put on plates of sterile nutrient agar jelly. 3. plant hormones are added, which stimulate cells to divide. 4. Cells grow rapidly to small masses of tissue. 5. More growth hormones are added. 6. Tiny plantlets are transferred to potting trays.

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