Lecture-3 - Evolution – Major Unifying Concept of Biology...

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Unformatted text preview: Evolution – Major Unifying Concept of Biology Generation 1 Some evolutionary process e.g., natural selection Generation 10 Population – group of individuals from same species that live in same area & regularly interbreed A change in the traits of a population over time EVOLUTION Hypothesis : early stages of an idea or a model Theory : hypothesis widely accepted by the scientific community via rigorous experimentation and re-testing (replication) with same results. Hypothesis in Science “ WHY is my flashlight is not working!” • hypotheses is: • specific to the question • based on knowledge • testable and falsifiable You will learn more about hypotheses during lab. Theory – Everyday Use vs Science IT IS JUST A THEORY! Implies“untested speculation”. (e.g. In theory, she should do fine in the course) THEORY – in science • Broad explanation based on many lines of evidence. • Aids in the generation of many new hypotheses. • Has withstood rigorous scientific testing. (e.g. Natural selection is a method of evolution.) Two major unifying concepts of Biology 1. Theory of Evolution by Natural Selection • Characteristics of a population change over time. (pattern) • Individuals with certain heritable traits produce more offspring than those without those traits. (mechanism) 2. Cell Theory • All organisms are made up of cells. (pattern) • All cells come from pre-existing cells. (mechanism) All spp are related by descent from a common ancestor. & All spp come from (descend) from other pre-existing spp. All single-cell organisms in a population related to a common ancestor. & All cells in a multicellular organism descend from an ancestral cell. Life as an Inevitable Consequence • Evolution of life on our planet may have been an inevitable outcome of initial physical and chemical conditions established by Earth’s origin – Reducing atmosphere – Size that generates moderate gravitational forces – Distance from the Sun that results in average surface temperatures between freezing and boiling points of water Stromatolites - Earliest evidence of life • Stromatolites: Layered rock formed when microorganisms bind particles of sediment together, forming thin sheets • Dated to 2.3 billion years ago represent earliest fossil evidence of life Humans Mammals Origin of Earth (4.6 bya) Bacteria 4 bya Present Vascular plants Shelly invertebrates 1 bya 20% O 2 O 2 Algal diversity 2 bya 3 bya Origin of Eukaryotes Earth is slowly oxygenated Origin of cyanobacteria Anoxygenic phototrophic bacteria Anoxic Earth (N 2 , CO 2 , CH 4 atmosphere) Ozone shield Anoxygenic Photosynthesis- NOT producing oxygen. Oxygenic Photosynthetic bacteria appears - Oxygen produced Two major unifying concepts of Biology 1. Theory of Evolution by Natural Selection • Characteristics of a population change over time. (pattern) • Individuals with certain heritable traits produce more offspring than those without those traits. (mechanism) 2. Cell Theory 2....
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This note was uploaded on 01/04/2012 for the course BIOLOGY 1000 taught by Professor Rebeccajubis during the Fall '11 term at York University.

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Lecture-3 - Evolution – Major Unifying Concept of Biology...

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