Objectives Summarize Darwin’s theory of natural

selection Describe the evidence for evolution

SCS: B-5

Charles Darwin 1809-1882 HMS Beagle Traveled for 5 years

Gathered specimens Made observations Galapagos Islands

Darwin’s finches

He came up with a few ideas: Species produce a lot of offspring

Struggle for survival

animals/plants are selected by nature based on their best traits to survive in that particular environment.

Evolution is decent with modification Includes small scale changes

Changes in the gene frequency from 1 generation to the next

Includes large scale changes Descent of different species from a

common ancestor over many generations Unifying concept in biology

All life shares a common ancestor Explains diversity Responsible for the remarkable

similarities

The central ideas of evolution include that life has a history (changed over time) and Different species share common ancestors

The process of evolution produces a pattern of relationships between species Lineages evolve and split and modifications are

inherited We can study these relationships and

reconstruct the evolutionary history of an organism phylogeny

Life began about 3.8 billion years ago Insects diversified 290 mya Humans and chimps diverged 5 mya

What methods do scientists use? Radiometric dating Stratigraphy

Sequence of events Molecular clocks

Uses genetic divergence between organisms to extrapolate backwards

Mutation Can be beneficial, neutral, or harmful

Random mistakes in copying, environmental Change in the genetic makeup that is

passed on

Migration (gene flow) Movement into and out of population affect

the gene pool

Sex introduces to variations in populations

Genetic drift Chance changes that are passed on

Natural selection When organisms with adaptations survive

and pass on these traits to the next generation

Natural selection at work Peppered moths in England

Artificial selection When man selection desirable traits and

breeds these organisms

Misconceptions about natural selection It’s not all powerful; does not produce

perfection; if it allows you to survive to pass on your genes

natural selection as a process rather than as a guiding hand.

result of variation, differential reproduction, and heredity—it is mindless and mechanistic

no goals; it’s not striving to produce “progress” or a balanced ecosystem.

Fossil EvidenceExamples: whale evolution

Horse evolution

homologies Evolutionary theory predicts that related

organisms will share similarities that are derived from common ancestors.

Similar characteristics due to relatedness are known as homologies.

cellular similarities and differences, studying embryological development, and vestigial structures within individual organisms.

Homologous structures Similar in arrangement and function

Analogous structures Body parts of organisms that do not have an

evolutionary origin but are similar in function Vestigial structures

A body structure that has no function in present day organism but was useful in an ancestor

Cellular level similarities

Molecular level DNA, proteins, etc.

embryology

Distribution in time and space Chronology

Geography

Examples of evolution today Viruses Bacteria Artificial selection agriculture

Medical research Diseases and their victims evolve

Flu, TB, HIV, and other diseases Antibiotic resistance

Agriculture and economics Need for diversity Bigger, better, tastier, healthier, disease

and pest resistant conservation

Misconception: “Evolution is a theory about the origin of life.”

Evolutionary theory deals mainly with how life changed after its origin.

Misconception: “Evolution is like a climb up a ladder of progress; organisms are always getting better.”

It is true that natural selection weeds out individuals that are unfit in a particular situation, but for evolution, “good enough” is good enough. No organism has to be perfect.

Misconception: “Evolution means that life changed ‘by chance.’ ”

Chance is certainly a factor in evolution, but there are also non-random evolutionary mechanisms. For example, some aquatic animals are

more likely to survive and reproduce if they can move quickly through water. Speed helps them to capture prey and escape danger. Their offspring also had these traits

Misconception: “Natural selection involves organisms ‘trying’ to adapt.”

Organisms cannot will themselves to change

Misconception: “Natural selection gives organisms what they ‘need.’ ”

Mutations are random. Sometimes organisms cannot adapt fast enough to their changing environments

Misconception: “Evolution is ‘just’ a theory.”

Misconception: “Gaps in the fossil record disprove evolution.”

Not all organisms can make fossils. Fossils are often destroyed by geologic processes. Transitional fossils have been found.

Misconception: “Evolution leads to immoral behavior. If children are taught that they are animals, they will behave like animals.”

Because we are animals does not mean will behave like wild animals

Misconception: “Evolution and religion are incompatible.”

Religion and science (evolution) are very different things. In science, only natural causes are used to explain natural phenomena, while religion deals with beliefs that are beyond the natural world.

Biographyhttp://evolution.berkeley.edu/evosite/evohome.html