gcse b1

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  • Created by: lizzie
  • Created on: 15-05-10 16:17

what is evolution?

the development of simple life forms (bacteria) into more complex ones (humans)

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Lamark's Theory

Theory of acquired characteristics from your parents. all living organisms descended from worms. one organism passes its acquired characteristics onto its offspring.

it wasn't accepted because people didn't like the idea of coming from worms and organisms didn't have characteristics that their parents had developed

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Darwin's Theory

Suggests evolution occurs via natural selection. only gradually accepted because people were very religious and it contradicted their religious beliefs.

A random mutation occurs, usually causes faulty characteristics to develop which leads to death, sometimes gives organisms an advantage to their environment, they are more likely to breed, offspring are at an advantage. new characteristics only useful if they make the organism more suited to their environment.

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Causes of extinction

extreme climate change, new/improved competitor, new virus/pathogen, massive natural disaster.

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Sexual and Asexual reproduction

Sexual: fusion of two parent cells, mixing of genetic info, genetic variety in offspring, offspring are genetically different to parents.

Asexual: one parent cell, no mixing of genetic information, no genetic variety in offspring (clones), illegal in humans

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Embryo transplants

fertility hormones are given to a top quality female cow forcing her to produce lots of mature eggs. they are given a few weeks to develop into embryos before being implanted into the host mothers womb who is injected with fertility drugs to make her act as if she is pregnant. clone calfs are bore possessing genes of top quality cow. clones of eachoter but differ from parents.

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Fusion cell cloning

Nucleus is removed from a cell of adult a. Egg cell removed from ovaries of adult b. the nucleus is removed from the egg cell and the nucleus from adult a is placed into egg cell. the fusion cell is then implanted in adult c who gives birth to a clone of adult a.

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Cloning plants

take stem and root cutting from older plant and use hormone rooting powders to encourage growth.

Positives: cheap and easy

Negatives: takes time, mass production not possible

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Cloning tissue

Take plant tissue, use the right mixture of hormones to produce a small mixture of cells from the plant you want to produce a big mass of, mix in the right mixture of chemicals, use a mixture of hormones and conditions to stimulate new plants to form.

positives: guaranteed same characteristics, makes 1000s, quick

negatives:expensive, involves a lab, technicians and chemicals

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