Evolution and Natural Selection HistoryCausesEvidence

Remember… Evolution is a scientific theory Evolution is a scientific theory Evolution is a major theme in biology Evolution is a major theme in biology You must learn about it, but where you fit in the spectrum is up to you You must learn about it, but where you fit in the spectrum is up to you

What is evolution? By definition, a change in a population over time. By definition, a change in a population over time. –Considered the process by which modern organisms have descended from ancient organisms –Helps to explain biodiversity

History James Hutton (1700’s) and Charles Lyell (1800’s) – both focused on how geologic processes change Earth over long periods of time James Hutton (1700’s) and Charles Lyell (1800’s) – both focused on how geologic processes change Earth over long periods of time –Proposed Earth to be millions of years old –Previously believed to be a few thousand –Lyell’s book, Principles of Geology, was read by Charles Darwin

History Thomas Malthus (1700’s) – proposed human populations outgrow resources, creating a struggle for existence Thomas Malthus (1700’s) – proposed human populations outgrow resources, creating a struggle for existence Jean-Baptiste Lamarck (1800’s) – hypothesized that organisms can adapt during their lifetime and pass on those acquired traits Jean-Baptiste Lamarck (1800’s) – hypothesized that organisms can adapt during their lifetime and pass on those acquired traits –Proposed organisms could alter the size and shape of organs by using them in new ways – law of use and disuse –He was WRONG!!!

Charles Darwin Born in 1809; father was a doctor Born in 1809; father was a doctor Initially studied medicine in college and then decided to become a clergyman Initially studied medicine in college and then decided to become a clergyman Was recommended by a professor to a captain who was preparing a survey ship for a voyage around the world Was recommended by a professor to a captain who was preparing a survey ship for a voyage around the world –HMS Beagle –5-year trip; began in 1831

Voyage of the Beagle

Darwin’s Voyage Made numerous observations about organisms and their environments, reproduction, traits, and locations Made numerous observations about organisms and their environments, reproduction, traits, and locations Collected many plant and animal species and fossils Collected many plant and animal species and fossils –Studied and compared them on the ship Observations led him to the idea that species slowly change over time Observations led him to the idea that species slowly change over time

The Galapagos Islands Small group of islands off the coast of South America Small group of islands off the coast of South America Most influential to Darwin’s ideas Most influential to Darwin’s ideas Although close, the islands had different climates and terrains Although close, the islands had different climates and terrains –Similar, yet different species on each island –Species seemed suited to their particular habitat

Finches & Tortoises Finches & Tortoises

Variation and Artificial Selection Darwin noticed that members of the same species vary from one another Darwin noticed that members of the same species vary from one another Farmers and animal breeders took advantage of this by selective breeding Farmers and animal breeders took advantage of this by selective breeding –Darwin termed this artificial selection Darwin believed this happened in nature as well Darwin believed this happened in nature as well

Natural Selection Darwin proposed the idea of natural selection as a mechanism for evolution Darwin proposed the idea of natural selection as a mechanism for evolution –Also called “survival of the fittest” –Results in ADAPTATIONS – inherited traits that increase survival Can be anatomical, structural, physiological, or behavioral Can be anatomical, structural, physiological, or behavioral Fitness - a measure of one’s ability to survive and reproduce (pass on traits) Fitness - a measure of one’s ability to survive and reproduce (pass on traits) –Organisms most fit are “selected” by the environment

According to Darwin, natural selection will occur if…. Variation exists among the population Variation exists among the population More individuals are produced than will survive More individuals are produced than will survive Members of a population compete for food, space, mates, etc (struggle for existence) Members of a population compete for food, space, mates, etc (struggle for existence) Individuals that are better adapted have a better chance of survival Individuals that are better adapted have a better chance of survival

Descent with Modification Darwin proposed that over long periods, natural selection produces organisms that have different structures, establish different niches, or occupy different habitats Darwin proposed that over long periods, natural selection produces organisms that have different structures, establish different niches, or occupy different habitats –Species today may look different from their ancestors –Each living species has descended, with changes, from other species over time

On the Origin of Species Title of Darwin’s book published in 1859, over 20 years after his return to England Title of Darwin’s book published in 1859, over 20 years after his return to England He published after reading an essay by Alfred Russell Wallace, who proposed similar ideas He published after reading an essay by Alfred Russell Wallace, who proposed similar ideas

Evolution and Natural Selection Evolution is a change in a species over time Evolution is a change in a species over time Natural selection is the process that leads to that change Natural selection is the process that leads to that change –Organisms that are most fit pass on their traits –Others die or leave fewer offspring

Evidence for Evolution Fossils Fossils –Shows a change in living things over millions of yrs –Different layers of rock represent different times Relative dating – age based on layers Relative dating – age based on layers –Radioactive dating is used to determine the age of rocks and fossils Based on half-life of radioactive elements Based on half-life of radioactive elements

Geographic Distribution Geographic Distribution –Similar species on different continents/regions descended from common ancestors –Similar organisms are found in similar environments, although separated Derived from idea of Pangaea and continental drift Derived from idea of Pangaea and continental drift More Evidence

Even More Evidence Anatomy Anatomy –Homologous structures Similar due to ancestry or relatedness Similar due to ancestry or relatedness –Arms, wings, legs, and flippers (vertebrates) –All have same basic bones, but vary in form and function –Analogous structures Similar due to function Similar due to function –Bird wing and bat wing; fins –Vestigial structures Remains of a structure that is no longer functional Remains of a structure that is no longer functional –Humans have a tail bone, but no tail; wisdom teeth

Anatomical Evidence Homologous structures Analogous structures

Evidence Embryology Embryology –Vertebrate embryos are very similar in early stages of development –Embryonic cells develop in the same order and in similar patterns to produce tissues and organs

Evidence Biochemical (DNA!!) Biochemical (DNA!!) –Almost all living things use the same basic biochemical molecules DNA, ATP, enzymes, other proteins, etc. DNA, ATP, enzymes, other proteins, etc. –Common ancestry may be explained by similar amino acid sequences, DNA codes, genes, etc. –Remember, the genetic code is universal to all life!