Nothing in biology makes sense except in the light of evolution. – Theodosius Dobzhansky Evolution Charles Darwin in later years

Words to Know Descent: to come from (think down in time) Heritable: can be passed on from parent to offspring Gene: section of DNA that codes for a specific protein (trait) Population: group of the same organism living in the same area

Words to Know Variation: differences between individuals Adaptation: An inherited biological or behavioral trait that increases a population’s chances for survival in a specific environment.

What is Evolution? The kind we ’ re talking about is sometimes called organic evolution to distinguish it from non-biological changes over time. Working definition: Evolution is the progressive change in an organism’s DNA over time (over many generations).

Evolution Holds a Unique Place in Biology Other disciplines ask how? Evolutionary biology asks why?

Evolution ’ s Core Principles Natural selection.

Evolution ’ s Core Principles Common descent with modification.

Darwin ’ s Voyage of Discovery A reconstruction of the HMS Beagle sailing off Patagonia.

The Voyage of the Beagle

Darwin ’ s Ideas Did Not Develop in a Vacuum Contributor ’ s to Darwin ’ s thinking included: Charles Lyell – uniformatarianism Georges Cuvier – species extinction

Darwin ’ s Ideas Did Not Develop in a Vacuum Contributor ’ s to Darwin ’ s thinking included: Thomas Malthus – struggle for existence Jean Baptiste de Lamarck – evolution by acquired characteristics

Alfred Russel Wallace Independently Drew the Same Conclusions as Darwin Papers from Wallace and Darwin were jointly presented (with little impact) to the Linnaean Society in 1858.

Darwin ’ s Observations and Inferences Observation 1: Left unchecked, the number of organisms of each species will increase exponentially, generation to generation. Observation 2: In nature, populations tend to remain stable in size. Inference 1: Production of more individuals than can be supported by the environment leads to a struggle for existence among individuals, with only a fraction of offspring surviving in each generation. Observation 3: Environmental resources are limited.

Darwin ’ s Observations and Inferences Observation 4: Individuals of a population vary extensively in their characteristics with no two individuals being exactly alike. Observation 5: Much of this variation between individuals is heritable.

Inference 2: Survival in the struggle for existence is not random, but depends in part on the heritable characteristics of individuals. Individuals who inherit characteristics most fit for their environment are likely to leave more offspring than less fit individuals. We call those characteristics that make individuals more fit adaptations. Darwin ’ s Observations and Inferences

Inference 3: The unequal ability of individuals to survive and reproduce leads to a gradual change in a population, with favorable characteristics accumulating over generations (natural selection). Taken together, these three inferences are a statement of Darwin ’ s Theory of Evolution. Darwin ’ s Observations and Inferences

STOP HERE for DAY 1 (3/19/12

The Weak Link of Genetics and the Modern Synthesis A major problem in Darwin ’ s theory was the lack of a mechanism to explain natural selection. How could favorable variations be transmitted to later generations? With the rediscovery of Mendel ’ s work and its vast extension in the first half of the 20th century, the missing link in evolutionary theory was forged. Darwinian theory supported by genetics is known as the modern synthesis. Darwin in his early years.

Discomfort With Evolution An early disparaging view of evolutionary theory and its creator. The upheaval surrounding evolution began with publication of On the Origin of Species and continues nearly 150 years later. 1925

November, 2005 Discomfort With Evolution

December, 2005 Discomfort With Evolution

Two of many arguments made against evolution are: Evolution is only a theory. No one ’ s ever seen evolution. Discomfort With Evolution The first point is true, but misses the meaning of scientific theory, and the second point is easily countered.

Evidence for Evolution – The Fossil Record

Evidence for Evolution - Comparative Morphology Why use the same skeletal plan for these very different appendages?

Evidence for Evolution - Comparative Embryology Why do embryos of different animals pass through a similar developmental stage? Recent discoveries of the conservation of molecular mechanisms of development are even more compelling.

Evidence of Evolution – Conservation and Diversification at the Molecular Level Why should different organism possess related genes? Why does the degree of relationship of genes match their degree of relationship established by other methods?

Evidence for Evolution – Evolution Observed Evolution of pesticide resistance in response to selection.

Evidence for Evolution – Evolution Observed Evolution of drug-resistance in HIV

Evolutionary Time Scales Macroevolution: Long time scale events that create and eliminate species.

Evolutionary Time Scales Microevolution: Short time scale events (generation-to-generation) that change the genotypes and phenotypes of populations. We ’ ll begin our more intensive look at evolution with microevolution.