Evolution
What is evolution? Evolution is the process of biological change by which species of organisms change over time. Evolution is a central theme in all fields of biology today.
Evolution is when organisms change over time Evolution is when organisms change over time. So, modern organisms descended from ancient ones.
Evolution is a Theory – Just like Gravity! Evolution is a well supported explanation of phenomena that have occurred in the natural world A theory in science is a well tested hypothesis, not just a guess
Evolutionary Scientists Charles Bonnet mid-1700s First to use term evolution Studied fossils James Hutton 1795 Theory of Geological change Jean-Baptiste Lamarck 1809 Charles Lyell Geographical features can be built up or torn down Charles Darwin Thomas Malthus Russell Wallace Gave Darwin the drive to publish his findings
Malthus Reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone
Jean-Baptiste Lamarck He proposed the idea of inheritance of acquired characteristics: changes in an environment caused an organism’s behavior to change this would lead to greater use or disuse of a structure or organ. the structure would become larger or smaller and would then be passed down to offspring For example: giraffes’ long necks Idea was WRONG!!
Charles Darwin Natural selection was the theory he proposed to explain evolution. He attempted to provide reasons for the biological diversity on Earth. Developed his theory from personal observations and research of other scientists.
Charles Darwin (1809-1882) Sailed around the world 1831-1836 on the British ship H.M.S. Beagle.
What did Darwin’s Travels Reveal? The diversity of living species was far greater than anyone had previously known!! These observations led him to develop the theory of evolution!! He observed the land and its inhabitants. Finches and Tortoises
What did Darwin do? He noticed the physical differences among island species. Species on one island looked different from those on another island. Island species looked different from those found on the mainland. This is known as variation. Genetic variations arise from mutations He noticed that the physical differences among the species were appropriate for their environment and diet.
Darwin finally published his ideas in 1859. Other naturalists were developing the same theory that Darwin did. Even though he was afraid of the Church’s reaction to his book he wanted to get credit for his work.
Natural Selection The traits that help an organism survive in a particular environment are “selected” in natural selection
Evidence of Evolution Fossil Record Homologous Body structures Similarities in Embryology Biochemical Evidence
Evidence of Evolution: The Fossil Record Fossil record provides evidence that living things have evolved Fossils show the history of life on earth and how different groups of organisms have changed over time
Relative vs. Absolute Dating
Relative Dating Can determine a fossil’s relative age Performed by estimating fossil age compared with that of other fossils Drawbacks – provides no info about age in years
Absolute Dating Can determine the absolute age in numbers Is performed by radioactive dating – based on the amount of remaining radioactive isotopes remain Drawbacks - part of the fossil is destroyed during the test
Radiometric dating uses decay of unstable isotopes. Isotopes are atoms of an element that differ in their number of neutrons. A half-life is the amount of time it takes for half of the isotope to decay.
Primate Fossils Australopithecus Homo erectus Homo sapien
Primate Bone Structure
Evidence of Evolution: Homologous Body Structures Turtle Structures that have different mature forms but develop from the same embryonic tissues Ex: Wing of bat, human arm, leg of turtle Alligator Bird
Evidence of Evolution: Homologous Structures Features that are similar in structure but appear in different organisms and have different functions. Strong evidence for common ancestor. Ex: forelimbs of humans, bats and moles. Human hand Bat wing Mole foot
Analogous Structures Structures that perform a similar function. Not evidence of common ancestry.
Vestigial Structures Remnants of organs or structures that had a function in an early ancestor. Ex: Ostrich wings, used for balance but not flight Ex: Humans’ appendix
Evidence of Evolution: Similarities in Embryology In their early stages of development, chickens, turtles and rats look similar, providing evidence that they shared a common ancestry.
Embryological Development
Evidence of Evolution: Biochemical Similarities Scientists study nucleotide sequences in DNA and proteins in different organisms to determine ancestry. If the organisms are closely related they will have similar sequences of nucleotides in their DNA and arrangement of amino acids in proteins.
Evidence of Evolution: Biochemical Similarities Organism Amino Acid Differences Human beta chain Mouse 27 Gorilla 1 Kangaroo 38 Rhesus monkey 8 Chicken 45 Dog 15 Frog 67 Cow 25 Soy bean 124 The more similar the
Patterns, Processes, and Rates of Evolution
Adaptation Darwin’ observations led him to realize that species must somehow be able to adapt to their surroundings. Adaptations allow species to better survive in their surroundings. Adaptations can lead to genetic change in a population over time.
Variation Among Species… Organisms in the same species have different traits… Known as variation Variations may result from mutations or from how genetic material is rearranged during sexual reproduction Variations within a species can have two results: Speciation Extinction
VariationSpeciation Individuals with beneficial trait are well suited for the environment They reproduce and pass the beneficial trait to their offspring Individuals without the beneficial trait are less likely to survive and reproduce Their traits are not passed. Beneficial traits are passed while other traits disappear These changes can eventually cause speciation
Speciation Evolution of a new species from an existing species Occurs if the environment changes Individuals with beneficial traits will survive and pass their traits on to offspring Ex: Colder weather-animal with thicker fur Ex: Type of food-animal equipped to eat new type Ex: New predator-animal able to escape Speciation Creates Biodiversity Variety of organisms, their genetic information, and their habitats.
Mechanisms of Evolution Genetic variation that leads to evolution can be a result of several things: Mutations Changes in DNA Only mutations in gametes affect evolution Gene flow Introduction of genes from one population to another Low gene flow=evolution of different species Gene pool Combination of genetic material from all members of a population Affected by mobility-more mobility=higher rate of gene flow
Rates of Evolution Catastrophism-Georges Cuvier He believed that a natural disaster would occur, cause landforms to change and cause species to become extinct Once that species went extinct another would come in and take its place Did not believe species changed over time
Rates of Evolution Gradualism-James Hutton Punctuated Equilibrium Two main views: Gradualism-James Hutton Evolution occurs slowly and constantly over a long period of time Darwin Punctuated Equilibrium Evolution occurs in spurts Period of rapid speciation then long period of little to no change Caused by random mutations or sudden changes in environment Cambrian explosion
Rates of Evolution Uniformitarianism-Charles Lyell Expansion of gradualism Favored theory of geologic change Proposed that changes occur slowly at a constant rate continuously
VariationExtinction Permanent loss of a species. Two causes: Populations fail to adapt Sudden, drastic changes in the environment Humans attempt to prevent extinction of species through captive breeding, restricting hunting, and creating sanctuaries.
Mass Extinction Extinction of huge numbers of species in a short period of time Earth has experienced several mass extinctions 250 million yrs. ago-ocean invertebrates 65 million yrs. ago-dinosaurs