variation and inheritance
- 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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