Goal 3 - Evolution of Species
Natural Selection acts on variations
Speciation
- Variations increase or decrease organism’s chances of survival in an environment.
- Variations can be inherited and are controlled by alleles (genes). Thus frequencies in a population’s gene pool will change over generations due to the natural selection of variations.
Speciation
- Remember a species is a group of organisms that look alike and can interbreed to produce fertile offspring in nature.
- The evolution of a species is called speciation = evolution of a new species that occurs when numbers of similar populations no longer interbreed to produce fertile offspring. Speciation is also the evolution of one or more species from a common ancestor.
Ways a species can originate…
There are several ways a new species can originate (don’t forget the variations!)
Divergent Evolution – species come from a common ancestor but evolve independently due to…
Convergent Evolution
Convergent Evolution – When natural selection produces similar adaptations in species from different ancestors. Convergent evolution occurs when different unrelated species occupy similar environments. (Ex. Organ pipe cactus and Euphorbia – two different species, similar environment, similar adaptation fleshy body type and no leaves)
Co-Evolution
POPULATIONS EVOLVE NOT INDIVIDUALS!!! Natural Selection acts on the difference on the phenotypes on a population.
Co-Evolution = two species evolve together. (Ex. Plants: insects like symbiotic relationships)
Modern Day Examples 1) peppered moths in England – industrial revolution (pollution and tree color) moths are light and dark 2) bacteria: antibiotics over time bacteria becoming resistant to antibiotics (TB, MRSA)
Co-Evolution = two species evolve together. (Ex. Plants: insects like symbiotic relationships)
Modern Day Examples 1) peppered moths in England – industrial revolution (pollution and tree color) moths are light and dark 2) bacteria: antibiotics over time bacteria becoming resistant to antibiotics (TB, MRSA)
Evolutionary Rates
Gradualism - Slow and Steady with small, adaptive changes over time in a population. See gradual changes in the fossil record. Punctuated Equilibrium – speciation occurs quickly, in rapid bursts with long periods of genetic equilibrium in between. Also supported in the fossil record. |