What is Evolution?

• In biology, evolution is the change in the inherited traits (a.k.a. genes/alleles, genotypes/phenotypes) of species (or populations of a species) over time.

• Throughout this unit, you will see that three main processes determine the rate of evolution:– 1) variation within a species (i.e. the fact that no one is an

identical clone to another person)– 2) reproduction: the method of reproduction and the rate at

which a species reproduces will affect how fast it evolves.– 3) selection: whether natural selection or sexual selection,

you will see that those best suited to their particular environment will pass on their genes more frequently.

Evolution by Natural Selection• The most famous

explanation of evolution was made by Charles Darwin, who stated that those organisms best suited to their environment will be more successful at passing on their traits to the next generation.

• This he called Evolution by Natural Selection.

Darwin’s Influences

• Charles Darwin did not foresee himself getting into the field of evolutionary biology.

• He wanted to be a doctor like his father, but he could not stand the sight of blood and the savagery of surgery.

• He then wanted to be a minister, but he did not want to study. He preferred riding and shooting to studying.

• He eventually became interested in biology through his fascination with such exciting animals as barnacles, beetles and pigeons.

Darwin’s Influences• He changed his path at college and took more biology

courses as he developed a great love of taxonomy (yes, the classification stuff we did in the first unit) and studied intensely under the tutelage of botany professor John Stevens Henslow.

• Henslow recommended Darwin for work as an unpaid naturalist on a voyage around the world upon the HMS Beagle, under captain Robert Fitzroy.

• As you will see, this journey not only changed Darwin’s life, but also the face of biology forever…

Adaptation and Variation• Organisms face constant environmental challenges that

limit their ability to survive– Weather– Famine– Competition (food, space and mating)

• Organisms must survive long enough to pass along to offspring the genetic information that helped them survive

• If not, species will eventually become extinct

• Species do not “choose” to adapt, They either adapt or die!

Adaptation and Survival

• Adaptation is a structure, behavior, or physiological process that helps an organism survive and reproduce in an environment

• Camouflage• hibernation

Camouflage

Mimicry

Mimicry: A type of Structural Adaptation • A harmless species resembles a

harmful species in coloration or structure

• Viceroy mimics Monarch. Monarch is toxic, Viceroy is not, birds avoid both

Development of Adaptations

• Result of gradual accumulative changes that help an organism survive and reproduce

• Random heritable mutations in DNA

• Variations are structural, functional differences between individuals of the same species

• Not all variations become adaptations

Peppered Moth: Variation to Adaptation

Pre Industrial Revolution After Industrial Revolution

The English Peppered Moth

http://www.youtube.com/watch?v=LyRA807djLc

In Class Work

• Pg 299, Q 1-6

Variation Within Species

• Why is there so much variationAmongst members of human species?

Genetic variation in a population results from the variety of genetic information in all individuals of the population

Mutations lead to genetic variation

• Mutations are a permanent change in the genetic material

• Provide new alleles in a species and source of new genetic variation when inherited

• Can occur spontaneously or through mutagens (UV, cigarettes, X-rays)

• Most mutations are benign or harmful

Mutations in gamete cells

• If a mutation occurs in a somatic cell, it disappears from the population when the organism dies.

• If mutation is in gametes, can be passed to future generations as a new allele

Mutations can provide a selective advantage

• If a mutation is beneficial it becomes a selective advantage; improves an organisms chance of survival

• Individuals living in malaria-plagued regions have a selective advantage of what genotype?__________

Rapid reproduction and selective advantage

• Some bacteria can double their population in under 10 minutes!

• Rapid reproduction means that an allele that was insignificant in the population may provide a selective advantage when the environment changes

• http://www.youtube.com/watch?v=UxHacm6gA0c

Antibiotic Resistance

• Activity 7.2, pg 302

• Thoughtlab pg 312 (Due Wed May 2) all the questions up to extend further