3- Natural History and Evolution

1. natural selection

2. genetic drift

primary mechanisms that drive evolution [2]

New species

physical and ecological process interact with selection and drift to produce:

observation and appreciation of nature, rather than understanding through experimentation

Natural history is mainly about [2]

Voyage of the Beagle

example of long voyage to describe natural environment in 1831-1836

in ten generations

Ecologically significant evolutionary change can occur how often?

speciation

result of natural selection and genetic drift

Evolution

change in gene frequencies within a population over time

Natural Selection

Differential reproduction and survival of individuals in a population due to environmental influences on the population

Genetic drift

Change in gene frequencies in a population due to chance or random events

Galapagos islands

the voyage of the beagle was inspired by what?

1. observations of the natural world

2. simple experiments

how did Darwin come to develop theory? [2]

1. more offspring are produced each generation than can be supported by the environment

2. some heritable variation in physical, physiological, and behavioural traits in a population

3. some traits give some individuals an advantage over other members of the population, have a higher chance of survival

4. Traits that result in increased fitness will become more common within a population over subsequent generations

KEY elements of Natural Selection theory (4)

Fitness

Number of offspring contributed by an individual relative to the number of offspring produced by other members of the population

Adaptation

an evolutionary process that changes anatomy, physiology or behaviour that results in an increased ability of a population to live in a particular environment

stabilizing selection

Selection where extreme phenotypes in a population have lower rates of reproduction and survival. Extreme phenotypes are more rate, average phenotype remains most common.

Directional selection

Selection where most phenotypes have lower reproduction and survival compared to exceptional phenotypes. Population average changes in a particular direction over time.

Disruptive selection

selection where average phenotypes have lower reproduction and survival compared to extremes in the population. Average phenotype becomes less common and population becomes phenotypically diverse.

crossbills.

example of disruptive selection:

Species

Groups of actually or potentially interbreeding populations which are reproductively isolated from other groups.

1. allopatric

2. sympatric

3. parapatric

Three forms of speciation

speciation

Where physical and ecological processes interact with selection and drift to produce new species

Allopatric speciation

Speciation that occurs when isolating mechanisms evolve among geographically separated populations

sympatric speciation

Speciation that occurs when isolation mechanisms evolve among populations with overlapping geographic ranges

Parapatric speciation

Speciation that occurs when a population expands into a new habitat-type within a pre-existing range of the parent species.