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SBI3U – Evolution
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7.1 – Biological Change over Time
The sources of genetic variation are mutations which are changes in genetic information.
Read pg. 282-283 and fill in the Chat below:
Mutations: The Source of Genetic Variation
Mutations
Description
don't result in any selective advantage or
disadvantage;
Neutral
produce no visible change in an individual
Harmful
Beneficial
Example(s)
Human’s eye colour
reduce the reproductive success of an
individual and is therefore selected
against;
Disease-causing viruses such as flu viruses
make an organism less able to resist
disease or avoid predators, or less
efficient at obtaining food; tend to
disappear with time
Bacteria that have developed resistance to
antibiotics
Resistance of insect to various pesticides
increase the reproductive success of an
organism;
Mutations that lead to genetic disorders such
as cystic fibrosis or Huntington’s disease
Sickle-cell allele gives its carriers a high degree
of resistance to malaria
favoured by natural selection and
accumulate over time
Colourful flowers in some plants allow them
to attract more pollinators
Limitations of Artificial Selection: Influence of Mutations (pg. 286)
-
Beneficial or neutral mutations have a good chance of being passed on to future generations
because they are either favoured or go unnoticed.
-
Harmful or undesirable mutations have little influence on the potential success of artificial
selection efforts since breeders do not choose such individuals for breeding.
-
An undesirable mutation may accompany a beneficial one. E.g. developing strawberry plants
that are tolerant to cold weather leads to producing odd-coloured berries.