The Theory of Evolution 10/11/11

MA Frameworks  3.3 Explain how mutations in the DNA sequence of a gene may or may not result in phenotypic change in an organism. Explain how mutations in gametes may result in phenotypic changes in offspring.

MA Frameworks 5. Evolution and Biodiversity  Central Concepts: Evolution is the result of genetic changes that occur in constantly changing environments. Over many generations, changes in the genetic make-up of populations may affect biodiversity through speciation and extinction.  5.1 Explain how evolution is demonstrated by evidence from the fossil record, comparative anatomy, genetics, molecular biology, and examples of natural selection.

MA Frameworks 5. Evolution and Biodiversity  5.2 Describe species as reproductively distinct groups of organisms. Recognize that species are further classified into a hierarchical taxonomic system (kingdom, phylum, class, order, family, genus, species) based on morphological, behavioral, and molecular similarities. Describe the role that geographic isolation can play in speciation.  5.3 Explain how evolution through natural selection can result in changes in biodiversity through the increase or decrease of genetic diversity within a population.

What is Evolution?  Change over time  The process by which modern organisms descended from ancient organisms  Theory: A well supported testable explanation of phenomena that have occurred in the natural world

Charles Darwin  Born in England (Same day as Abe Lincoln)  Traveled around world on ship – Beagle  Collected evidence and made observations that he used to develop ideas that became today’s Theory of Evolution

Key Questions  Where did the huge amount of biodiversity on the Earth come from?  Why are organisms so well suited to the environment that they inhabit?

Darwin & the Galapagos Islands  Group of small islands located off South America  Have very different climates, but close together  Observed that characteristics of plants and animals varied among different islands  Began to wonder – could these different animals have come from a common ancestor? Could they have once been members of the same species?

Darwin & the Galapagos Islands

Darwin’s Influences  Around the same time, scientists gained greater understanding of Earth’s changes over time, population growth, and developed primitive Evolution ideas

Darwin’s Influences  James Hutton: Showed that the Earth was far older than a few thousand years  Charles Lyell: Explained the geologic features of Earth shaped over very long time.  J.B. Lamarck: Observed that organisms adapted to environment.  Incorrectly proposed that use and disuse of body part will influence whether passed down to next generation

Darwin’s Influences: Pop. Growth  Thomas Malthus: Suggested that if human population continued to grow rapidly, sooner or later there would not be enough living space or food for everyone  Darwin applied this idea to other organisms

The Origin of Species, 1859  The book that contained Darwin’s ideas about Evolution  Proposed a mechanism for evolution that he called Natural Selection Provided evidence that Evolution has been happening for millions of years

Early Evolution Controversy  Responding to the Bishop of Oxford, Samuel Wilberforce's question whether he traced his descent from an ape on his mother's or his father's side, Thomas Huxley said:  If then, said I, the question is put to me would I rather have a miserable ape for a grandfather or a man highly endowed by nature and possessing great means and influence and yet who employs those faculties for the mere purpose of introducing ridicule into a grave scientific discussion—I unhesitatingly affirm my preference for the ape.

Natural Selection  Premise that organisms stuck in struggle for existence- food, shelter, resources, etc.  Success depends on ability of an organism to survive and reproduce in its environment – known as Fitness  Fitness results from adaptations – inherited characteristic that increases organisms chance of survival

Natural Selection  Is survival of the fittest when the traits being selected for (whether a trait is good or not) is being determined by fitness in an environment  Results in changes in characteristics of population.  Increases a species fitness over time

Descent with Modification  Idea of Darwin’s suggesting that every living species as descended, with changes, from other species over time.  Principle of Common Descent : All species, living and extinct, were derived from common ancestors.

Evidence for Evolution  Fossil Record: See change in organism structures over time  Similar organisms living in similar environments in places very far apart  Homologous body structures: Structures that changed over time to suit the needs of different species, but that originated as one type of structure (fish fin)

Homologous Structures

Vestigial organs  Structures in organisms that may have served purpose in ancestral species, but no longer have function in current organism  Ex. Human Tailbone

More Evidence: Embryology  The very early stages of development for a wide variety of organisms look the same  Similar cells grow and divide in very similar ways in many species