EVOLUTION and NATURAL SELECTION

Evolution

gradual change in species over long periods of time

What are evolution driven by

genetic variation and natural selection

What do evolution explain

how life diversified from common ancestors

Where was Charles Darwin and the Theory of Natural Selection proposed

in his book “On the Origin of Species” (1859)

The theory of natural selection found that:

organisms better adapted to their environment survive and reproduce more

Natural selection key steps

variation exists in all species, competition for limited resources, survival of the fittest, reproduction, over time more favorable traits become more common

Mutation

random change in DNA sequence

Meiosis

shuffles genes during gamete formation

Adaptation

a trait that increases survival chances

Adaptation can be:

structural, behavioral, physiological

Fossil record

shows gradual changes over time

DNA similarities

humans share ~98% DNA with chimpanzees

Comparative anatomy

homologous structures (arm bones, wings)

Embryology

similar embryos suggest common ancestors

Observed evolution

bacteria evolving resistance to antibiotics

Artificial selection

Humans choose which traits to breed

Artificial selection use

farming, pet breeding

Artificial selection pros and cons

faster than natural selection but limits genetic diversity

Evolution of antibiotic resistance

bacteria reproduce rapidly, random mutation may give one bacterium resistance, antibiotics kill non-resistant bacteria, resistant bacteria survive, reproduce-resistance spreads

Speciation

New species form when groups of organisms are isolated and evolve differently

Types of isolation in speciation

geographic, behavioral, temporal