Biology unit 1

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Inherited variation

Variation due to genetic causes is inherited variation. A person or an animal receives half of their features from each parent. This means that a person will look a little like the father and a little like the mother. E.g

  • Eye colour
  • Hair colour
  • Skin colour
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Environmental variation

Charateristics of animal and plant species can be affected by factors such as:

  • Climate
  • Diet
  • Culture
  • Lifestyle
  • Language
  • Religion
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Continuous variation

This is shown in a line graph and are normally to do with population, height and weight seeing as there is a trend

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Discontinuous variation

This is shown in a bar graph and is normally to do with hair and eye colour because there are categories.

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These are a change in the amount or type of DNA and can happen at random. However  sometimes they can be harmful.

  • Can cause Down's Syndrome
  • Cystic Fibrosis can be caused by a recessive gene
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Cystic Fibrosis

Gene therapy can be used for people with Cystic Fibrosis, this is where copies of a normal allele are inserted into the chromosome of an indiviual who carries the faulty allele. These alleles are inhaled into the lungs.

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Sexual reproduction

This produces offspring that resembles the parents but are not identical.

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Asexual reproduction

Produces offspring which are genetically identical to the parent (clone)

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Gregor Mendel

Did the pea plant experiments and discovered that there were things called factors that controlled the way we are, called genes.

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This theory is supported by evidence from fossils and by rapid changes that can be seen to occur in microogranisms such as antibiotic resistant bacteria.

The theory states that different species have developed over time from simple life forms.

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