natural selection

macroevolution

Evolutionary change occurring at or above the species level over long periods of time.

natural selection

The process by which the environment favours individuals best adapted to its conditions, enabling them to survive and produce the most offspring.

artificial selection

The process of selecting and breeding organisms with desirable characteristics to produce offspring with traits that benefit humans.

what is stasis/equilibrium in a tree of life

A period in which little or no evolutionary change occurs in a lineage.

what is cladogenesis

An evolutionary splitting of a parent lineage into two or more distinct species (speciation or lineage-splitting).

what is adaptive radiation

A burst of divergence from a single ancestral lineage to produce many new species adapted to diverse ecological niches.

name 2 theories pertaining to the rate of evolution

Punctuated equilibrium and gradualism.

what is punctuated equilibrium

A theory proposed by Stephen Jay Gould stating that species experience long periods of stability (equilibrium) punctuated by short periods of rapid evolutionary change.

what is gradualism

A theory proposed by Charles Darwin stating that species evolve gradually through small, continuous changes over long periods of time.

process of natural selection (8)

1. Organisms produce large numbers of offspring. 2. Great variation exists among offspring. 3. Environmental change or competition causes a struggle for survival. 4. Some individuals have favourable traits. 5. Some individuals have unfavourable traits. 6. Those with favourable traits survive and reproduce. 7. The desirable traits are inherited by an increasing proportion of the population. 8. Over time, new species may arise.

5 differences between artificial and natural selection

1. Process: occurs artificially vs naturally. 2. Driven by: humans vs environmental selective agents. 3. Rate of change: fast vs slow. 4. Variation: produces less variation vs preserves more variation. 5. Consequence: traits beneficial to humans vs adaptations to the environment.

species

A group of organisms that closely resemble each other and are able to interbreed freely to produce viable, fertile offspring.

mutation

Any sudden alteration in the genetic makeup of an organism.

genotypic variation in populations

The variation in genotypes between individuals of the same species, often resulting from genetic mutations.

inbreeding

The mating of individuals that are genetically closely related.

homozygosity

The state of possessing two identical alleles of a particular gene, one inherited from each parent.

haemophilia

A genetic condition where blood clots much more slowly than normal, resulting in extensive bleeding from even minor injuries.

outbreeding

The mating of individuals that are genetically unrelated.

heterozygosity

The state of having two different alleles for a specific gene.

founder effect

The loss of genetic variation that occurs when a very small number of individuals from a large population establish a new colony.

convergent evolution

The process whereby organisms that are not closely related independently evolve similar traits to adapt to similar environments or ecological niches.

analogous structures

Structures in different species that evolved independently to perform similar functions without sharing a common evolutionary origin.

divergent evolution

The process in which a trait or lineage from a common ancestor evolves and accumulates differences over time.

homologous structures

Body structures in different species that share a common evolutionary origin, even if they have evolved different functions.

speciation

The evolutionary formation of new species that are genetically distinct from the ancestral species.

allopatric speciation

The formation of a new species resulting from a population becoming geographically isolated from the ancestral species.

sympatric speciation

The formation of a new species occurring within the same geographical area as the ancestral species without physical isolation.

reproductive isolation

Biological mechanisms that prevent different species from exchanging genes and producing viable, fertile offspring even when not geographically separated.

hybrid

An organism produced by crossing two different varieties, breeds, or species to obtain desirable characteristics from both parents.

4 ways that proves genetics to be random

• meiosis:

  • rearrangement of genetic material

  • random arrangement of homologous chromosomes on the equator

  • crossing over

• sexual reproduction: random fusing

what effect does inbreeding have + example

inbreeding → homozygosity → decreases genetic variation → inhibits natural selection → decreases chance of survival

example: hemophilia in royal family

what effect does outbreeding have + example

outbreeding → increased heterozygosity → different traits → different species

example: mustard plant species → cabbage, broccoli etc

explain the founder effect + example

few individuals contribute to the genes of founder population → reduced genetic diversity → new species → cannot interbreed with original population

cheetahs went through severe bottleneck → many cheetahs except small founder population died → low genetic variation → vulnerable to extinction

explain allopatric speciation

• population of single species become isolated → split into two
  population

• no gene flow between them

• each population exposed to different environmental conditions
  → natural selection occurs independently in each

• each population becomes very different from each other (phenotypically and genotypically)

• cannot interbreed anymore

3 types of reproductive isolation

• breeding at different times of year

• species-species courtship behavior

• adaptation by plants to different pollinators