Catalyst:Which of the choices below is an appropriate representation of commensalism?+/+c. -/-+/-d. +/0

How were the activities yesterday connected to evolution?

What is the difference between microevolution and macroevolution?

Evolution: A Darwinian View of Life

Overview: Darwin Introduces a Revolutionary Theory

A new era of biology began on November 24, 1859The day Charles Darwin published: On the Origin of Species by Means of Natural Selection

The Origin of SpeciesFocused biologists attention on the great diversity of organisms

Darwin made two major points in his book

He presented evidence that the many species of organisms presently inhabiting the Earth are descendants of ancestral speciesHe proposed a mechanism for the evolutionary process, natural selection

The Origin of Species

Shook the deepest roots of Western culture

Challenged a worldview that had been prevalent for centuries

Darwin: from childhood to publicationAs a boy and into adulthood, Charles DarwinHad a consuming interest in nature

Soon after Darwin received his B.A. degreeHe was accepted on board the HMS Beagle, which was about to embark on a voyage around the world

Darwins interest in the geographic distribution of species was kindled by the Beagles stop at the Galpagos Islands near the equator west of South America

As Darwin reassessed all that he had observed during the voyage of the Beagle

He began to perceive adaptation to the environment and the origin of new species as closely related processes

Darwin developed two main ideas:

1. Evolution explains lifes unity and diversity

2. Natural selection is a cause of adaptive evolution

The phrase descent with modification

Summarized Darwins perception of the unity of life

States that all organisms are related through descent from an ancestor that lived in the remote past

In the Darwinian view, the history of life is like a tree

With multiple branchings from a common trunk to the tips of the youngest twigs that represent the diversity of living organisms

Observation #1: For any species, population sizes would increase exponentially if all individuals that are born reproduced successfully

Observation #2: Nonetheless, populations tend to be stable in sizeExcept for seasonal fluctuations

Observation #3: Resources are limited

Inference #1: Production of more individuals than the environment can support leads to a struggle for existence among individuals of a population, with only a fraction of their offspring surviving

Observation #4: Members of a population vary extensively in their characteristicsNo two individuals are exactly alike

Observation #5: Much of this variation is inheritable

Inference #2: Survival depends in part on inherited traitsIndividuals whose inherited traits give them a high probability of surviving and reproducing are likely to leave more offspring than other individuals

Inference #3: This unequal ability of individuals to survive and reproduceWill lead to a gradual change in a population, with favorable characteristics accumulating over generations

Natural selection can produce an increase over time in the adaptation of organisms to their environment

Humans have modified other species over many generations by selecting and breeding individuals that possess desired traits, this is called artificial selection