Biological Change
over Time
Ms. Cowman
SBI3U
Mutations: The Source of Genetic Variation
• All species exhibit genetic variation
• Mutations create new genes that provide a
continual supply of new genetic information
• Mutations may be:
NEUTRAL- provide no benefit or harm to the
individual
HARMFUL- reduce the reproductive success of an
organism, do no accumulate over time
BENEFICIAL- produce a change in the individuals
phenotype that gives the individual an
advantage, accumulate over time
Mutations can have significant
consequences
Bacteria have developed resistance to antibiotics
are becoming more widespread as less-resistant
strains are killed off.
Viruses can mutate to become more virulent
(harmful), which can increase its ability to spread.
Selective Breeding: Artificial Selection of
Traits
• Domestication of Animals and Plants
Provide humans with the majority of our food
supply
Formed the basis for the development of modern
civilization
• Domestication is the changing of members of a
species to suit human needs through controlled
captive breeding (Artificial Selection)
Examples of Artificial Selection
First species to be domesticated: Canis lupus, the wolf
Wild Sea Cabbage (1000’s of years) 7 vegetables
How does artificial selection work?
• The breeder picks seeds from the plants that
have the best flavour or largest fruit and sows
them
• The plants cross-pollinate each other
producing more fruit with the desired trait
Genetic Engineering
• Transfer beneficial genes from an individual of
one species to an individual of another species
• If successful, genetically modified individual is
mass produced
Power of Artificial Selection
• Production of individuals that exhibit traits that
are far beyond the natural variability present in
the original population
• Can reduce genetic diversity within a population
 Breeder favours only certain traits in a
population, then many alleles linked to other
versions of a particular characteristic are reduced
or eliminated
Implications for Natural Populations
What do we know about genetics?
- All species exhibit genetic variation
- Mutations produce heritable changes in
individuals, and these changes may be
beneficial, harmful, or neutral
- Some species, such as bacteria and insects, can
change over relatively short periods of time
- Some domesticated species have changed
dramatically under the influence of artificial
selection