variation and inheritance

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  • Created by: mary
  • Created on: 22-01-13 16:41
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  • Variation & inheritance
    • evolution-1)variation in a population. 2)over production to guarantee adulthood survival. 3)struggle for existance/ competition. 4)those with advantageous characteristics will survive easier. 5)better adapted organisms are more likely to reproduce/ pass on good characteristics. 6)over time most will be better adapted.
    • variation is due to: genetic causes (inherritance) and environmental causes (personal adaptations)
    • speciation is the process of evolution by which new species form.
    • continuous variation-doesnt fit into groups
    • discontinuous variation fits into a small number of clearly defined groups. e.g eye colour
    • the infertile offspring from two animals of different species is called a hybrid e.g-whale+dolphin= infertile wholphin
    • in the nucleus of a normal human body cell there are two sets of chromosomes.-one from the mother/one from father.
    • each human body cell has 23 pairs/46 chromosomes.
    • chromosomes are divided into sections called genes (all made by a chemical called DNA)
    • a gene is a part of a chromosome that controls a characteristic. for each gene there is a 2 different versions that code for a characteristic, these are called alleles.
    • a dominant allele is an allele that controls the characteristic even when its only present in one of the chromosomes in a pair.
    • a recessive allele only controls the characteristic if it is present in both chromosomes.


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