Introduction to the Theory of Evolution Why Theory
- Slides: 46
Introduction to the Theory of Evolution
Why Theory?
What is a Scientific Law? • A scientific law is a well-substantiated statement based on repeated experimental observations that describes some aspects of the universe. • Laws are generally expressed as either a single sentence, or as a mathematical relationship
What is a Scientific Law? some examples of scientific laws include: The Law of Conservation of Matter cannot be created or destroyed, it can only change forms. Snell’s Law
What is a Scientific Theory?
What is a Scientific Theory? • A scientific theory is a well-substantiated explanation of some aspect of the natural world that is acquired through the scientific method and repeatedly tested and confirmed through observation and experimentation.
What is a Scientific Theory? • A named scientific theory is generally a central set of ideas in a field of science. some examples of scientific theories include Chemistry Atomic Theory Valence Bond Theory Physics Theory of General Relativity Quantum Theory String Theory Biology Cell Theory Germ Theory of Disease Theory of Evolution by Natural Selection
What Does Theory Of Evolution Explain? • It provides an explanation of how species change over time. • It suggests that modern species came to be as a result of changes to the heritable information passed on from one generation to another • It explains that all life on Earth shares a common ancestor
Central to Biology “Nothing in Biology Makes Sense Except in the Light of Evolution” - Theodosius Dobzhansky (1973) … from an essay originally published in the journal The American Biology Teacher
The Theory of Evolution By Natural Selection • Originally published in 1859 by Charles Darwin in his book, On the Origin of Species
Eu ka ry ot es Modern Understanding of Species Relatedness ok a Pr a e ch r A ry F ot es ll Ce irst
Main Lines of Evidence Supporting Evolution Today Theory of Evolution is consistent with and supported by evidence across all related fields of science. Of particular importance is the evidence gathered in the following areas: • Taxonomy • Anatomy / Physiology • Fossil Record • Genetics
What Does It Mean to Evolve? To evolve simply means to CHANGE
What Does It Mean to Evolve? To evolve simply means to CHANGE
What Does It Mean to Evolve? To evolve simply means to CHANGE
What Does It Mean to Evolve? To evolve simply means to CHANGE
Change ≠ Better
Change Over Time • Each image you see below represents an artists rendition of an extinct animal based on evidence derived from whole skeletons or partial skeletons that have been discovered and studied.
Selection Pressure • A factor affecting mortality or fertility that tends to make a population change genetically. example: Predation
Ingredients for Evolution 1. Variation 2. Selection pressure (not all individuals will have the same ability to survive or reproduce)
Where does variation come from?
Where does variation come from?
Where does variation come from?
How Often Do Mutations Happen?
Where does variation come from? (2 n) … or during this (n) Meiosis x 4 Heritable mutation must occur here Only gametes become the next generation
Where does variation come from? • DNA contains the instructions needed to build, assemble and maintain cells • Each time cells divide, their copying mechanism makes “mistakes” called mutations. • These changes to the genetic code can be inherited by the next generation if the organism is asexual and unicellular, or if the mutation occurs in gametes.
How Often Do Mutations Happen? • Your copying machinery incorrectly copies about 3 letters out of the 3 billion letters of your genetic code every time your cells divide. • This means that your DNA today is slightly different from the day you were born with and is not identical in all your cells. • Some of these mutations are heritable
How Can Random Mutations Lead to New Traits? • Most mutations have a negative impact on survival and reproduction – Harmful mutations are less likely to persist in future generations.
How Can Random Mutations Lead to New Traits? • Many mutations either result in no change, or a change of no consequence or benefit. – If heritable, neutral mutations will be present in future generations
How Can Random Mutations Lead to New Traits? • Rarely, a mutation will result in a change that increases the reproductive success of an organism. – If heritable, beneficial mutations will be more widely represented in the next generation
What About Selection Pressure?
Artificial Selection • Directed breeding by humans where we select which individuals in a population will breed by selecting particular desired traits
Natural Selection • the differential survival and reproduction of individuals due to differences in their traits.
Other Examples of Evolution in our Lives
Other Examples of Evolution in our Lives
Variation + Selection = Evolution
- Pictures
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