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Chapter 5

NATS 1840 Chapter 5: 5.2- Evolution and Adaption


Department
Natural Science
Course Code
NATS 1840
Professor
Carl Wolfe
Chapter
5

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Evolution: The change in a population's genetic makeup over time, through successive
generations.
Theory of Evolution: described by Charles Darwin, all species descended from earlier,
ancestral species. “Life comes from life”
Microevolution: small genetic changes that occur in a population
- Genes mutate, individuals are selected, populations evolve
Macroevolution: long-term,large scale evolutionary changes through which new species form
and other species are lost.
Gene Pool: collection of genes or genetic resources potentially available to members.
- Genes have two or more particular forms called alleles and when sexual reproduction
occurs random shuffling and recombination of alleles take place. Each individual in a
population except identical twins have a different combination of alleles.
Mutations: random changes in the structure or number of DNA molecules in a cell that can be
inherited by offspring. How do they occur?
-Mutagents: radioactivity, X-rays, chemicals
- Random mistakes that occur in coded DNA instructions when a cell divides.
- Only mutations that occur in reproductive cells are passed onto offspring
- some mutation are lethal, some are harmless, some are beneficial
Natural Selection
- 3 types: directional, stabilizing, diversifying natural selection
- When some individuals of a population have genetically based traits that increase their
chances of survival and their ability to produce offspring with the same traits.
- There must be genetic variability, the trait must be heritable, the trait must lead to
differential reproduction (must enable individuals with trait to reproduce more offspring
than other members.
Adaptive Trait: any heritable trait that enables organisms to better survive and reproduce.
- Natural selection causes an allele that results in an adaptive trait to be more common
and any alleles without the trait become less common
When faced with a critical change in the environment species can:
1) Adapt to new conditions through natural selection
2) Migrate to to an area with more favourable conditions
3) Become extinct
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