IB Bio HL - A 4.1 Evolution

Evolution

The gradual change of inherited traits of a species over a period of time

Lamarkian Evolution

• Change in the environment led to the use of certain organs and disuse of others among organisms.

• Organs that were used more would increase in size over the lifetime of the organisms. Similarly, organs that were not used over the lifetime of the organism would shrink.

• These changes acquired over the lifetime of an individual would be passed on to the offspring.

Darwinian Evolution

• In nature, tendency to produce more offspring than can be supported by the environment

  • ‘overproduction’ eventually —> competition for natural resources

  • As a result, the population size remains fairly constant.

• Individuals within a population ≠ identical & exhibit variations

• Individuals w/ variations that help them adapt better are more likeley to survive, reproduce & pass on the variations to their offspring

  • Individuals w/ less favourable variations are less likely to survive.

  • This ‘selection’ by nature = natural selection

• Over many generations, natural selection —> populations adapted for specific environments

• Reproductive isolation —> formation of a new species

Molecular Phylogeny

Comparative analysis of the nucleotide sequences of DNA and RNA and the amino acid sequences of proteins

Selective Breeding

humans select individuals from a species to breed together based on desirable characteristics

Homologous structures

Structures that the same basic structural plan & share a common ancestor, but perform different functions in different species; indicate divergent evolution

Divergent Evolution

when organisms arising from the same ancestral species adapt to different environmental conditions according to the pressures of natural selection.

Analogous Structures

body parts that have the same or similar function in different groups of organisms but have different structures; indicate Convergent Evolution

Speciation

The formation of new species by the splitting of one pre-existing species into two or more new species

Reproductive isolation

barriers that prevent populations of the same species from interbreeding and/or producing fertile offspring; ex - Bonobos & Chimpanzees

Biodiversity

variety of life on Earth, or in a specific area; 3 levels = genetic diversity, species diversity, ecosystem diversity

Species Biodiversity

number and types of organisms that existed during a specific amount of time. 

Ecosystem diversity

Variety in ecosystems in a given area.

Anthropogenic Extinction

extinction relating to humans;

caused by:

• overexploitation due to overhunting or overharvesting

• habitat loss due to human activity

• introduction of invasive or alien species outcompeting native species

• habitat degradation due to pollution

• climate change

Richness

Number of different species in a sample

Evenness

whether each species has the same number of individuals

Convergent Evolution

distantly related groups of organisms face similar environmental conditions and adapt in similar ways.