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