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Evolution LectureHow Genotypes and Phenotypes Change Over Time (Part 1)
Textbook Reference: Chapter 21 in Biology How Life Works (2nd ed.)
Sections 21.1 – 21.3; pp.425 to 432
Adaptation, Unity and Diversity
• Three key observations about life:
1. Organisms suited to their environments
2. Shared characteristics (unity)
3. Rich diversity
Examples:
Grasshopper: In camouflage. Often a dramatic example of adaptation, one form
of evolution
Headstander beetle: able to get water in a very dry area(desert). Stands on head
and orients itself with its behind towards the fog in the morning – which is water
droplets. Can pick up water droplets from their structure (hair on body and legs).
Genetic Variation
• Since Darwin, we have appreciated that species do not conform to a type and
instead consist of a range of variants.
• What does natural selection depend on?
• Differential success, in terms of surviving and reproducing, of variants
• can be phenotypic (physical makeup) or genotypic (genetic makeup)
Comparison of genetic variation:
Page | 1
, Phenotypic variation Overall genetic variation
Humans High degree Low rank
More phenotypically similar 10 times more variable
Fruitflies
than humans than we are
2-3 times more genetically
Adelie penguins Low degree
variables than we are
Population genetics is the study of patterns of genetic variation in natural populations
• Important terminology:
– Species – a group of individuals that can exchange genetic material
through interbreeding, or share alleles through reproduction
– Gene pool – all the alleles present in all individuals in a species
– Populations – an interbreeding group of organisms of the same species
living in the same geographical area
Individuals represent different combinations of alleles from the species` gene
pool
What can cause genetic variation?
• Mutation - generates new variation
– Somatic
– Germ-line
– Deleterious
– Neutral
– Advantageous adaptations
• Recombination
shuffles mutations to create new
combinations of mutations – both of
which result in new alleles being formed
Measuring Genetic Variation
Page | 2
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