chapter 16 evolutionary theory. pre-class question 5/21/09 why were the beaks of the finches that...
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Chapter 16
Evolutionary Theory
Pre-class Question 5/21/09
Why were the beaks of the finches that Darwin observed on the Galapagos Islands different on different islands?
Homework (due Friday)
Active Reading “Developing a Theory”
Developing a Theory
Evolution is the process by which species change over time.
Charles Darwin was responsible for developing the modern theory of evolution
A broad explanation that has been scientifically tested and supported
3 Types of Selection
Artificial SelectionHumans can choose what traits are favorable in a species and breed plants and animals to have these traits
Natural SelectionThe process by which individuals that are better adapted to their environment survive and reproduce more successfully than those that are less adapted to do so.
3 Types of Selection Continued
Sexual Selection
An evolutionary process by which a mate is chosen on the basis of a particular trait
It’s Who You Know and What They KnowDarwin came up with the theory of evolution based on his observations and those of others:
LamarckObserved that each organism is usually well adapted to its environment.
MalthusIn 1798,Malthus observed that human food supply was increasing at a slower pace than the human population and hypothesized that many humans would die off due to disease, war and famine.
LyellGeologist that though that processes such as erosion and the formation of fossils was gradual and constant.
Evolution by Natural SelectionDarwin’s theory predicts that over time, the number of individuals that carry advantageous traits will increase in a population
Step1 OverproductionEvery population is capable of producing more offspring than can possibly survive.
Step 2 VariationVariation exists in every population in the form of inherited traits.
Step 3 SelectionBased on traits one individual is more likely to survive than another and reproduce.
Step 4 AdaptationOver time, those traits that improve the survival and reproduction will become more common.
Pre-class Question 5/27
Why do you think that giraffes evolved to have long necks?
What is the selective pressure that caused this change to occur?
Homework
Study for Chapter 16 Vocab Quiz (Friday, 5/29)
Hint: Selective pressure is any phenomena which alters the behavior and fitness of living organisms within a given environment.
Darwin – The Origen of Species by Natural Selection
Darwin presents evidence of evolution from multiple fields of science, where some species of animals have common characteristics
The Fossil Record The study of fossils or traces of living things from the past
Biogeography The study of the location of organisms around the world.
Developmental Biology The development of organisms from embryos
Anatomy The study of bodily structure of animals
Biochemistry The study of biomolecules such as amino acids and DNA
Evaluating Darwin’s Ideas – 3 major strengths
1. Evidence of evolution
2. A mechanism for evolution Natural Selection
3. The recognition that variation is importantPrior to Darwin’s theory, species were classified by
Common appearance, and ignored variation which
Was a starting point for evolution
Evaluating Darwin’s Ideas – Weaknesses
Inherited variation was important to Darwin’s theory, but he did not have a clear idea of how traits were inherited. He did not have an understanding of genetics.
There was roughly 100 years between when Darwin published his theory and the structure of DNA was discovered.
Pre-Class 5/28
Take out yesterday’s activity
Reading Selection: How Do Species Change Over Time?
Homework
Study for tomorrow’s chapter 16 vocab quiz
Studying Evolution at all Scales
tionMacroevoluSpeciationtionMicroevolu
The formation of new species as a result of
evolution
The appearance of new species
over time
Change in the genes of a population
Microevolution vs. Macroevolution
Processes of Microevolution (5)
Natural SelectionMigrationMate ChoiceCan be random or through sexual selectionMutationThe numbers and types of alleles can change from generation to generation although it is rare
Genetic Drift
Genetic drift affects genetic makeup of the population through an entirely random process..
Patterns of Macroevolution (6)
Covergent EvolutionWhen evolution is strongly directed by the environment, species living in a similar environment should evolve similar adaptations.
CoevolutionSpecies that share an environment can affect each others evolution. They develop adaptations to coexist
Patterns of Macroevolution Cont.
Adaptive RadiationSpecies splint into two or more lines of descent
Extinction
Gradualism
Many small changes occur gradually over time
Punctuated Equilibrium
New species suddenly appear after some environmental change.
Gradualism vs. Punctuated Equilibrium
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