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Transcript
James Hutton (1785)- proposed that earth was shaped by geological forces that took place over extremely long periods of time. He estimates the Earth to be millions of years old. Lyell agreed with him and stated that volcanoes and earthquakes have and continue to change the earth. Thomas Malthus (1798) – predicted the human population would grow faster than the space and food supplies needed to sustain them. Example: War, famine, disease Jean-Baptiste Lamark (1809) – proposed that organisms changed over time due to use and disuse of certain organs/parts. The traits that were “used” in an organism’s lifetime could be passed on to their offspring. His theory was flawed! › Tendency towards perfection- continually changing to be successful. Ex: birds acquired urge to fly › Use and Disuse- by using organ eventually change Ex: birds in order to fly develop wings › Inheritance of Acquired Traits Ex: Lift weights build muscles and offspring will inherit big muscles All of the previous peoples ideas influenced Darwin’s thinking… Charles Darwin (1831) – Set sail on the Darwin’s “Theory of Evolution” would turn the scientific world upside down!!! H.M.S. Beagle. This voyage provided him with much of the data and evidence that lead to his theory of evolution James Hutton Charles Darwin Jean-Baptiste Lamark Thomas Malthus Lamarck vs. Darwin http://www.angelfire.com/bug/darwinvs lamarck/ Extreme diversity existed among plant and animal species around the world. The organisms found within a certain area were well suited to survive in that environment. Living organisms he observed greatly resembled fossils that he found on his voyage. The Galapagos Islands This tiny group of islands influenced Darwin the most! › Although the islands were close together, the climates and environments differed greatly. › Similar organism found on different islands had varying characteristics, like appearance and behavior, this is variation. › Examples: Giant Galapagos Tortoises with varying shell shape. Darwin’s Finches – beak shape differed among the birds. A trait/characteristic that an organism is born with All organisms have adaptations that help them survive and thrive › Structural adaptations are physical features of an organism like the bill on a bird or the fur on a bear. › Behavioral adaptations are the things organisms do to survive. For example, bird calls and migration are behavioral adaptations. › Physiological adaptations are chemical responses to stimuli to maintain homeostasis Occurs in all populations Sexual reproduction increases the chance of natural variation because of the gene shuffling of meiosis Occurs far less frequently in asexual reproduction 1859 – Darwin published his work: On the Origin of Species Two main points: 1. Species were not created in their present form, but evolved from ancestral species. 2. Proposed a mechanism for evolution: NATURAL SELECTION Humans had been employing “artificial selection” for many years! The selective breeding of domesticated plants and animals by man. Question: What’s the ancestor of the domesticated dog? Answer: WOLF Struggle for Existence Survival of the “Fittest” – Fitness results from adaptations that give an organism advantages for survival. The most “fit” organisms will survive and reproduce; passing along the advantageous characteristics to their offspring. These changes can only be seen after many generations! Examples of adaptations that make organisms “fit”… Descent with Modification – As organisms change over time; they become different, resulting in many varied species. This illustrates “common descent.” All living things have a common ancestor. Fossil Record Older fossils are in lower rock layers Geographic Distribution of Living Species › Species evolve differently based on where they live. › Due to different climate changes adaptations resulted in differences. › Similar areas tended to have similar adaptations Anatomy-body parts Homologous Structures › Wing bat resembles forelimb of mammal, not bird › Bird wing resembles reptile forelimb Analogous Structures similar looking but evolutionary unrelatred Vestigial organsno function now but did have a function in ancestors. Ex: appendix, tailbone Similarities in Early Development › Embryos of related ancestors are similar in early stages Biochemical Evidence › Common DNA and RNA sequences; genes Definition: forming a new species What is a species? › Group of similar organisms that can breed and produce fertile offspring. Isolating Mechanism › features of behavior , morphology, or genetics which serve to prevent breeding between species. Reproductive Isolation › mechanisms that prevent two or more populations from exchanging genes Isolating Mechanism = Reproductive Isolation= Formation of a new species Behavioral Isolation – Two separate species are capable of interbreeding, but they do not because of behavioral differences. › Example Meadowlarks, different songs to attract mates; courtship Geographic Isolation – When one species becomes separated by some barrier (river, mountain, etc.) they may develop into two distinct species over time. › Example Squirrel population split by Colorado River 10,000 years ago Temporal Isolation – This mechanism occurs when species reproduce at different times (different mating times). › Example Orchids in the rainforest, only release pollen 1 day! Reproductive Isolation- Can’t interbreed and have separate gene pools Example Lion and a Tiger make a Liger which is sterile. Darwin had a disadvantage when he developed his theory of evolution…he did not understand the mechanisms of heredity. Today, we understand how genes, heredity, and evolution all tie together. Gene Pool = the combined genetic info of all the members of a specific population. Genetic Variation is Critical to Evolution › Mutations › Gene shuffling as a result of sexual reproduction Single-Gene Traits vs. Polygenic Traits Both lead to evolution, but polygenic traits (wide variety of phenotypes possible) lead to a more complex process of natural selection. Genetic Equilibrium: when allele frequency remains constant in a population. Hardy-Weinberg Principle: allele frequency remains constant in a population (no evolution)of these factors are present in the population. Random mating Population size very large No movement in or out No mutation No natural selection Three Major Types of “Natural Selection” Directional Selection Stabilizing Selection Disruptive Selection Form of natural selection by which the entire curve moves. Occurs when individuals at one end of the distribution curve have higher fitness than individuals in the middle or at the other end of the curve. Key Directional Selection Low mortality, high fitness High mortality, Food becomes scarce. low fitness Form of natural selection by which the center of the curve remains in its current position. Occurs when individuals near the center of distribution curve have higher fitness than individuals at either end. Stabilizing Selection Key Low mortality, high fitness High mortality, low fitness Birth Weight Selection against both extremes keep curve narrow and in same place. Form of natural selection in which a single curve splits into two. Occurs when individuals at the upper and lower ends of a distribution curve have higher fitness than individuals near the middle. Disruptive Selection Low mortality, high fitness High mortality, low fitness Population splits into two subgroups specializing in different seeds. Number of Birds in Population Key Beak Size Number of Birds in Population Largest and smallest seeds become more common. Beak Size Random change in allele frequency, based on the laws of probability. Example Founder Effect › Founder Effect: change in allele frequencies as a result of the migration of a small subgroup of population. Fossil Evidence Fossils provide proof of changes to life on earth Relative dating – estimate fossil’s age compared to other fossils Radioactive dating – age of fossil based on amount of remaining radioactive isotopes it contains Geological Time Early History Early atmosphere contained carbon dioxide, carbon monoxide, nitrogen, water vapor Miller and Urey’s experiment show how a mixture of early atmospheric compounds could produce simple organic compounds found in living things Rise of oxygen drove some life forms to extinction but many evolved and used oxygen for respiration and prospered Endosymbiotic theory – eukaryotic cells arose from prokaryotic cells Geological Time Table Paleozoic – Marine life Devonian – animals invade land Mesozoic – Dinosaurs and flowering plants Cenozoic - Mammals Patterns of Evolution Mass extinction Adaptive Radiation: Single species evolves into many species quickly Ex. Dinosaurs and mammals Convergent evolution – unrelated organisms resemble each other Ex dolphin and shark Coevolution – 2 species evolve in response to changes in each other Ex flowers and insects Punctuated Equilibrium – long stable periods interrupted by brief periods of rapid change Changes in developmental genes- new research shows “hox” genes are master control genes and can control how evolution occurred. The Miller-Urey Experiment Miller and Urey created a simulation of the predicted early atmosphere of the Earth. When they combined the atmospheric components with electricity, they produced organic compounds including amino acids. The Evolution of Life Some scientists believe that RNA was the first genetic information The first life forms are thought to be single-celled prokaryotes (found from microfossils in rock) similar to bacteria. Later, photosynthetic bacteria produced oxygen. › This oxygen combined with iron in the water, forming rust, which dropped to the ocean floor and left the ocean blue-green Most organisms evolved new metabolic pathways that would allow them to live in the new oxygen-rich environment. The Evolution of Life Eukaryotic Cells evolved from prokaryotes that began evolving internal cell membranes. Some small prokaryote then entered a larger prokaryote to form a mutualistic relationship. › These smaller prokaryotes were able to use oxygen (aerobic respiration) and evolved into what is now our mitochondria…recall that mitochondria have different DNA than the rest of the cell. This is called the Endosymbiotic Theory. The evolution of Sexual Reproduction allowed much more genetic variation among eukaryotes. The Endosymbiotic Theory A descriptive Diagram: