EVOLUTION

What is evolution?

• Genetically based change in phenotype Genetically based change in phenotype over generationsover generations

• Process in which species undergo Process in which species undergo modifications over generations. In some modifications over generations. In some cases these changes can result in the cases these changes can result in the formation of a new species.formation of a new species.

Why does evolution occur?

Evolution is not survival of the strongest, or failure of the weakest. Evolution is not fair; it's not predictable; it's not kind. Nor is it cruel, or chaotic, or unfair, for that matter. It's what happens when environmental pressures change.

Michael Jon Jensen

This essay was originally presented as the Keynote Speech at the Illinois Association of College and Research Libraries (IACRL) Biannual Meeting, Bloomington/Normal, IL, March 30, 2006.

• What changes do we see over time & why?

• From dog sized in rainforests to large animals on the plains

• Its multi-toed feet, adapted for walking across the forest floor, evolved into single-toed hooves more suited for running over open country

Darwin’s Voyage

DARWIN’S PRINCIPLES

• Descent with modification

• Natural selection

What is natural selection?

• Process

• Differential adaptations of organisms with beneficial traits

• The environment selects for those traits that will be passed on with greater frequency

What is meant by variation?

What is meant by adaptation?

• Any variation that increases an organisms chance for survival

• When does variation become an adaptation?

• What does adaptation depend on?

The environment

Who said characteristics or traits (variations) that are acquired in ones

lifetime and are passed on (inherited)?

An extension of Lamarck's ideas of inheritance that has stood the test of time, however, is the idea that evolutionary change takes place gradually and constantly

Lamarck

Example from Lamarck

• This weight lifter has built up arm muscles from working hard

• According to Lamarck the offspring should have strong muscles

DARWIN’S THEORY: KEY POINTS• Variations exist• Variations can be inherited• Populations tend to overproduce• There is a struggle for survival due to

limited resources• Animals that are best fit, survive and

reproduce (fitness is relative to a specific time and location)

• There is an evolution of the population with the traits of the fittest becoming most frequent.

Classic example, the Peppered Moth

• As a result, species must change through time in order to survive.

• Organism that change most successfully, they survive and reproduce are the fittest.

Antibiotic

Resistance

Endnagered species, why?

Types of Adaptations

For each of the following slides list at least one of example of each type of adaptation

MorphologicalPhysiologicalBehavioral

WHAT ARE DIFFERENT TYPES OF EVIDENCE TO SUPPORT THE THEORY

OF EVOLUTION?

• EMBRYOLOGY

• FOSSILS

• MORPHOLOGY

• BIOCHEMICAL (DNA)

EMBRYOLOGY

FOSSILS

HOMOLOGOUS STRUCTURES (MORPHOLOGY)

DNA EVIDENCE

Organisms are classified in the same species if they are potentially capable of interbreeding and producing fertile offspring. In general, they must be in the same geographical location.

Organisms may appear to be alike and be different species. For example, Western meadowlarks and Eastern meadowlarks look almost identical to one another, yet do not interbreed with each other—thus, they are separate species according to this definition. The Western meadowlark (left) and the Eastern meadowlark (right) appear to be identical, and their ranges overlap, but their distinct songs prevent interbreeding.

Organisms may look different and yet be the same species.

For example, look at these ants. You might think that they are distantly related species.

In fact, they are sisters—two ants of the species Pheidole barbata, fulfilling different roles in the same colony.

How does a new species

form?

•During allopatric speciation, a population splits into two geographically isolated allopatric populations.

•New speciation starts because populations are prevented from interbreeding.

•Scientists think that geographic isolation is a common way for the process of speciation to begin: rivers change course, mountains rise, continents drift, islands break away from the main lands, habitats fragment and become unfavorable, organisms migrate, and what was once a continuous population is divided into two or more smaller populations

• Macroevolution is the process by which new species are produced from earlier species (speciation). It also involves processes leading to the extinction of species.

• Microevolution is evolutionary change at the level of the population, and is defined by changes in allele frequency within the population over time. Such changes take place over relatively short time periods.

• Accumulated gradual changes in two populations that preclude their interbreeding may lead to the formation of a new species.

Microevolution: Speciation

Genetic Drift

Bottleneck Effect

3 Modes of Natural Selection

Common Example of Stablizing Selection

Organisms may look different and yet be the same species.

For example, look at these ants. You might think that they are distantly related species.

In fact, they are sisters—two ants of the species Pheidole barbata, fulfilling different roles in the same colony.

Directional Selection Rough to Smooth

Disruptive Selection

Can’t have Hardy Weinberg Equilibria if these are occuring

Non Random Mating; Artificial Selection