Transcript evolution
EVOLUTION The process by which species have changed over time Supporting Observations indicate certain organisms may have a common ancestor, not that one organism changed into another Supporting Observations • Fossils: the preserved remains of ancient organisms • Examples of Fossils – Imprints in sedimentary rocks – Organisms preserved in amber, ice, tar – Petrified shells or bones Fossil Sequence • It is assumed that the lower layers are older than upper layers • The fossils found in the lower layers are simpler while those in the upper layers are more complex, but resemble the more primitive forms Comparative Cytology • The cell is the unifying structure for al living things • Organelles are the same in structure and function in almost all organisms Comparative Biochemistry • Nucleic acids, proteins and enzymes are similar in all organisms • The closer the relationship, the greater the similarity in biochemistry Comparative Anatomy • Similarity in physical structures • Homologous Structuresparts that are similar in structure but have a different function • Ex: the forearm of a human, the wing of a bird and the flipper of a whale all have a similar arrangement and number of bones but they have a different function Comparative Embryology • Embryos of vertebrates resemble each other very closely Lizard Tortoise Pig Human Origins of Life • Spontaneous Generation- the belief that living things could be produced from non living things • EX- people believed that water in a pond produced frogs Redi’s Experiment helped to disprove spontaneous generation The Heterotroph Hypothesis • The theory of how primitive life forms developed on primitive earth Heterotroph Hypothesis • Conditions of the primitive earth – The atmosphere contained ammonia, methane, and hydrogen ( no oxygen) • The earth was described as being a hot body rich in inorganic substances and energy • The sources of energy included lightening, solar radiation, and radioactive materials • The oceans were gases and minerals mixed in a “ hot thin soup” • Energy caused the synthesis of organic compounds in the “hot thin soup” from inorganic compounds • Coacervates formed (organic compounds clustered together) • These coacervates absorbed new molecules (heterotrophic nutrition) • When the coacervates became too large, they split (reproduction). These are the first living things?!. • These organisms used anaerobic respiration for energy and released carbon dioxide. • Some organisms developed that could use carbon dioxide and the sun’s energy to synthesize organic compounds. These were the first autotrophs. They released oxygen. • Organisms developed that could use oxygen for respiration – aerobic organisms. • Anaerobic Heterotrophs Anaerobic Autotrophs Aerobic Organisms Theories of Evolution • Lamarck – Use and disuse – new organs arise according to the needs of the organism, unused organs are lost “Use It or Lose It” – Transmission of acquired characteristics- characteristic acquired by an individual are passed on to the offspring Ex –Man lifts weights and becomes muscular and his offspring will be born muscular? Ex- Woman learns piano – children will be good pianists? •This Theory is Wrong! • Weismann – cut the tails off mice to see if offspring would be born without tails – All offspring had tails – Disproved Lamarcks Theory! Darwin’s Theory of Evolution • Darwin was the naturalist on the ship the HMS Beagle(1831-1836) • He made many observations of fossils and animals that he saw in South America and the Galapagos Islands • Upon his return and after much research he come up with several related theories: 1. Evolution did occur 2. Evolutionary change is gradual, occurring over thousands to millions of years 3. The primary mechanism for evolution is a process called natural selection Darwin’s Theory of Evolution • Evolution occurs as a result of natural selection and variation Overproduction • In each generation, more offspring are produced than can survive • This leads to : Competition • Individuals struggle to survive by competing for food, water, shelter, mates etc Variation • Characteristics that are different among organisms of the same species • Ex- size, strength, color, disease resistance Adaptations • An inherited trait that increases an organism’s chance of survival Survival of the Fittest • The organisms that are best adapted to the environment will live long enough to reproduce Reproduction • Surviving individuals pass their traits on to their offspring Speciation • An accumulation of passed on variations will allow a new species to form • Darwin’s Theory does not explain a genetic basis for the variations that occur in organisms • DeVries stated that mutations were a source of new traits that permits evolution to occur Modern Theory of Evolution • Is a combination of Darwin’s Theory and DeVries Natural Selection • Traits that have a high survival value are retained and passed on • Traits with a low survival value diminish in frequency • Changes in the environment may change the survival value of a trait Examples • Peppered Moths • Microorganisms resistant to penicillin • Insects resistant to pesticides Peppered Moth Activity • http://www.techapp s.net/interactives/p eppermoths.htm Time Frame for Evolution • Gradualism – evolution is slow, gradual and continuous Time Frame for Evolution • Punctuated Equilibrium- species have long periods of stability interrupted by brief periods of change (mutations), during which new species may evolve Common Ancestors • Organisms that exhibit similar structures, biochemistry, etc. have common ancestors • More similarities Closer the evolutionary relationship • Illustrated by Phylogenetic Tree Phylogenetic Tree Phylogenetic Tree Extinction • When all members of a species disappear from the earth. • The mortality (death) rate exceeds the birth rate. • Extinction usually occurs because of changes in the environment • If there is variation within a species, it is more likely that some will survive.