Natural selection & Artificial selection

Theory of evolution by Natural selection

The process by which organisms better adapted to the environment survive and reproduce fertile offspring.

The process of natural selection (4)

1) Variation

2) Competition

3) Adaptation

4) Selection

1) Variation

Refers to the genetic variation within a population which can be inherited

• mutations

• sexual reproduction

• gene migration/ gene flow

2) Competition

Overproduction of offspring leads to competition for survival

• produce more offspring than environment can sustain

• → intense competition for limited resources

  • food

  • territory

  • mates

  • water

3) Adaptations

Individuals with beneficial adaptations are more likely to survive and pass on genes

• survival of fittest

• surviving individuals reproduce

  • pass favourable alleles to subsequent generations

4) Selection

• environmental pressures or selective agents

  • biotic (predators, competitors, disease)

  • abiotic (temperature, rainfall)

• frequency of adaptive alleles increase in gene pool

• over many generations

• this drives evolutionary adaptation

Fitness

Refers to an organisms ability to survive and reproduce in a specific environment and any changes which may occur.

3 ways genetic variation occurs for variation

1) random mutations

2) gene migration (gene flow)

3) sexual reproduction

Examples of natural selection in modern world

• antibiotic resistence in bacteria

• insecticide resistence in pests

• animal camouflage

Artificial selection

Selection in which humans actively choose which traits should be passed onto offspring.

Process of artificial selection (domesticated)

1) Humans decide on the trait or characteristic of interest

2) Breed the choices together

3) Choose offspring with ideal characteristics to breed/mate (cross breed)

4) Repeat for many generations

5) The appearance of the characteristic increases

What was Corns wild ancestor called

• Teosinte

  • tiny hard ears

  • stone like shells protecting each kernal

  • not edible

Which type of ears did farmers choose in the evolution of Teosinte into Corn?

Farmers picked the larger, softer ears which had kernals that attatched to the cob and didn’t shatter when breeding.

• cause genetic shift

• mutations

• 4 or 5 genotipical differences

Type of selection process (NvsA)

• N: natural selection process

• A: Man-made selection process

How does selection occur? (NvsA)

• N:Organisms better adapted to their environment tend to survive and produce more offspring

• A:Choosen by the breeder to produce desirable and inheritable characteristics in the successive generations

Affect on diversity (NvsA)

• N:Produces huge biological diversity (increases)

• A:Produces organisms with selected traits (decreases)

What type of population (NvsA)

• N:natural populations

• A:mainly in domestic populations

What is inherited over in the successive generation? (NvsA)

• N:Only allows favourable characteristics

• A:Only allows selected traits

How fast is the process(NvsA)

• N:slow (100’s of 1000’s years)

• A:rapid process

Does it allow evolution and how? (NvsA)

• N:Allows evolution through generating biological diversity

• A:Doesn’t facilitate evolution

What theory did Charles Darwin formulate?

• Theory of evolution by natural selection

• co-published with Alfred Russel Wallace (1858)

• Expanded through On the Origin of Species (1859)

What beliefs did it change regarding fixity of species?

• Replaced longheld view

• species were divinely created, unchanging

• immmutable

What beliefs did it challenge regarding Lamarckism?

• disprove idea that physiological traits developed during individuals lifetime are → to offspring

How did Theory of NS establish common descent?

• Established all living organisms

• share common ancestors

  • have diversified through descent

  • with modification