Biology 11 : Evolution

Evolution Test Hardy Weinberg Equilibrium (Non-evolving population)

No migration or gene flow is involved within a non-changing population thereby mathematically, the interchanges between population changes are probablistic.

Random sampling involves the process whereby individuals within a certain population mate together without any exceptional conditions.

No natural selection

No mutation

Large population

Microevolution Gene drift, gene flow, mutation, nonrandom meeting, natural selection

By elimination

If a single allele has any slight advantage, an augmented chance will be attributed to that allele thereby a higher frequency is exhibited within a specified population overtime.

Stablization selections

D

Overtime, the distribution of extremities is shortened and the median or the common population will be the dominant one overtime.

In directional selection, one side of extremities are favoured over others thereby a directional change of preference will greatly be reflected in a population overtime.

In disruptive selection, the extremities of either side are favoured over the intermediate.

Speciation

- No genetic drift

- Reproductive Isolation

- Pre-existing or existing species

- Prezygotic (fertilized egg/ before!)

- Behavioral limitations

- Temporal mating limitations

- Ecological/habitat differences

- Fertilization doesn't occur due to mechanical isolation/genetic isolaton - gentalia/enzyme of egg, prevention (gametic)

- Infertility

- Post-zygotic Limitations - infertility due to zygotic/hybrid differences-limited mortality(first-generation cross/might be viable however second generation ends up infertile when hybrid ab v ab

Egg and sperm work together but the embryo as its developping but it ceases to develop (sheet + goat)

Sympatic Speciation - When populations in the same geographical region diverge and become reproductively isolated. Factors such as chromosomal changes (in plants) and non-random mating (in animals) alter gene flow. This occurs more frequently in plants than animals (polyploidy)

Allopatric Speciation - (geographical speciation) a population is split into two or more isolated groups by a geographical barrier. Eventually the two groups become so distinct that they can no longer interbreed. Eg. glacier and lava flow isolate populations, fluctuations in ocean levels can change into a penisula into an island - colonizers leading to eventual diverging populations from the mainland populations.

Ex. Darwin Finches - over time ancestral species divided into different populations, some evoling into to new species (in-genetic problems)

Divergent and Convergent Evolution

Divergent evolution occurs - populations change as they adapt to different environmental conditions (less, less alike and become two different species)

Convergent evolution- two distinctly different species share similar traits (birds/insects), these similar traits arise because each species adapt to similar environmental conditions (ie:mobility)

Gradualism - evolutionary change is slow and steady after divergence and big changes occur as a result of an accumulation of many intermediate changes (fossil records rarely show gradual change)

Punctuated equilibrum - evolutionary history consists of long periods of stasis or equilibrum that are punctuated or interrupted by periods of divergence