Evolution Biology Biology

What is evolution? Process by which organisms pass on traits from generation to generation Process by which organisms pass on traits from generation to generation Over large stretches of time Over large stretches of time Explains the origin of new species and diversity Explains the origin of new species and diversity The living species of today are related to each other through common traits The living species of today are related to each other through common traits

Charles Darwin Theory of Natural Selection Theory of Natural Selection –Species that are better adapted to their environment will live longer and reproduce creating more offspring like them –“Survival of the fittest”

How did Darwin form his theory? 1831: naturalist on the H.M.S. Beagle for a 5 year voyage around the world 1831: naturalist on the H.M.S. Beagle for a 5 year voyage around the world Galapagos Islands Galapagos Islands –Finches  13 species of finches  Beak size and shape varied, most likely due to their island locations and available food  Finches had adapted to best obtain food in their environment

Darwin’s Finches

Microevolution Any evolutionary change below the level of species Any evolutionary change below the level of species Small changes in within alleles of a population or species Small changes in within alleles of a population or species Effects the phenotype of organisms that make up that population or species. Effects the phenotype of organisms that make up that population or species. Leads to natural selection Leads to natural selection –Peppered moths –Antibiotic resistance

Macroevolution Change at or above the level of species Change at or above the level of species Speciation: Speciation: –the splitting of a species into two –the change of a species over time into another History of life using all available evidence: geology, fossils, and morphology of living organisms. History of life using all available evidence: geology, fossils, and morphology of living organisms.

Micro vs. Macro

MUTATIONS CAUSE VARIATION! MUTATIONS CAUSE VARIATION!

Natural selection happens because of: Mutations Mutations Variation Variation Environmental influence Environmental influence Let’s look at an example Let’s look at an example

Example: In the U.S., where people use shampoos with particular chemicals in order to kill lice, we have a lot of lice that are resistant to the chemicals in those shampoos. Resistant means unaffected

Hypothesis A: Exposure to lice shampoo actually caused mutations for resistance to the shampoo.

Hypothesis B: Resistant strains of lice were always there—and are just more frequent now because all the non-resistant lice died a sudsy death.

Which of these hypotheses is correct? Hypothesis B Hypothesis BWhy? Variation is there already Shampoo killed the “weaker” lice Other lice live and reproduce to make more resistant lice

MUTATION ARE NOT CAUSED! Lamarck was an evolutionist who believed in hypothesis A. Lamarck was an evolutionist who believed in hypothesis A. He was proven wrong. He was proven wrong. He called his theory “Acquired Characteristics”. He called his theory “Acquired Characteristics”.

DARWIN Hypothesis B is what Darwin discovered. Hypothesis B is what Darwin discovered. He called these mutations or changes ADAPTATIONS He called these mutations or changes ADAPTATIONS

Acquired Acquired characteristics passed down to offspring Essentially Essentially saying that because something was to be beneficial in a given environment, then an organism could “pass that trait” to its offspring Variation, Variation, natural selection & heredity Random Random mutations brought about changes in traits If If that change was better suited to an environment, that organism had a better chance of survival

What EVOLUTION is NOT!!