Evolution

Evolution processes earliest forms diversityThe processes that have transformed life on earth from it’s earliest forms to the vast diversity that characterizes it today. The first life on Earth was most likely simple single cell organisms that appeared about 3 to 3.5 billion years ago.

Evidence of Evolution 1. Fossil Record: Fossils and the order in which they appear in layers of sedimentary rock. 2. DNA Studying the DNA of different organisms allows scientists to compare those organisms relationship to each other. The more similar DNA organisms contain the more closely related they are.

Fossil Record Going down the fossils get older. Oldest on the bottom, youngest on the top. Can be dated with radioisotopes.

Because many species become extinct, the only way to see the evolution of a species is through the fossil record. The evolution of the horse can be seen through leg and tooth fossils. 60 mya 40 mya 25 mya 7 mya 3 mya

Old Theories of Evolution Jean Baptiste LamarckJean Baptiste Lamarck (early 1800’s) proposed: “The inheritance of acquired characteristics” develop characteristicspasses offspringHe proposed that by using or not using its body parts, an individual tends to develop certain characteristics, which it passes on to its offspring.

“The Inheritance of Acquired Characteristics” Example:Example: A giraffe acquired its long neck because its ancestor stretched higher and higher into the trees to reach leaves, and that the animal’s increasingly lengthened neck was passed on to its offspring.

Charles Darwin Influenced by Charles Lyell “Principles of Geology”.Influenced by Charles Lyell who published “Principles of Geology”. DarwinThis publication led Darwin to realize that natural forces gradually change Earth’s surface and that the forces of the past are still operating in modern times.

Charles Darwin H.M.S. Beagle (mainly South America and the Galapagos Islands)Darwin set sail on the H.M.S. Beagle ( ) to survey the south seas (mainly South America and the Galapagos Islands) to collect plants and animals. Galapagos Islands,On the Galapagos Islands, Darwin observed species that lived no where else in the world. These observations led Darwin to write a book.

Charles Darwin Wrote in 1859“On the Origin of Species by Means of Natural Selection”Wrote in 1859: “On the Origin of Species by Means of Natural Selection” Three main points:Three main points: 1.Complex organisms develop from simple organisms over a long period of time. 2.Present day species develop from earlier species. 3.Some species die out (become extinct) when environmental changes occur. 3. Some species die out (become extinct) when environmental changes occur.

Natural Selection Individualsfavorabletraits environment.Individuals with favorable traits are more likely to leave more offspring better suited for their environment. –“Survival of the Fittest” Variation (genetic difference) occurs among individuals in a population.Variation (genetic difference) occurs among individuals in a population. –Due to meiosis and fertilization More individuals are produced than will survive.More individuals are produced than will survive. –Some organisms produce thousands of offspring

There must be competition between organisms for natural resources (food, water, space) These are needed for survival. Competition keeps the population under control and is a driving force of evolution. Competition

Highest Rate of Natural Selection In a changing environment, organisms that exhibit genetic differences due to mutation and genetic recombination show the highest rate of natural selection.

Lowest Rate of Natural Selection In a stable environment, organisms tend to exhibit less genetic differences due to mutation and genetic recombination because there is little reason to evolve.

Artificial Selection selective breedingThe selective breeding of domesticated plants and animals by man.

Evidence of Evolution 1. Taxonomy: Classification of life forms. 2. Homologous structures: Structures that are similar because of common ancestry (comparative anatomy)

Evidence of Evolution 3. Comparative embryology: Study of structures that appear during embryonic development. 4. Molecular biology: DNA and proteins (amino acids)

Population Genetics sciencegenetic changeThe science of genetic change in population.

Population individuals same speciesA localized group of individuals belonging to the same species.

Species populationsindividuals interbreed viableA group of populations whose individuals have the potential to interbreed and produce viable offspring.

Gene Pool collection of genesThe total collection of genes in a population at any one time.

Macroevolution higher than the species levelThe origin of taxonomic groups higher than the species level.

Microevolution population’s gene poolA change in a population’s gene pool over a secession of generations. Evolutionary changes geological timeEvolutionary changes in species over relatively brief periods of geological time. –Insects in reaction to pesticides –Bacteria in reaction to antibiotics

Mechanisms of Microevolution Gene Flow: Tgain or loss of genes movement The gain or loss of genes from a population by the movement of individuals or gametes. Immigration or emigrationImmigration or emigration.

Mutation: Change in an organism’s DNA. Change in sex cells are passed down to next generation. Change in body cells are not passed down. - random chance - mutating agent, ie., chemicals or radiation Non-random mating: The selection of mates other than by chance. - mating behaviors