Evolution

Evolution

Evolution

adaptation over a long period of time

- change in genetic composition of a population

- over populations and generations

Descent with modification

descent from a common ancestor with modification

Aristotle

saw species as fixed and unchanging

- life forms can be arranged on a ladder of increasing complexity

Ladder of Life Forms

more complex at the top, less complex at the bottom

- the're perfect no matter where they fall on the scale

Carolus Linnaeus

Classified organisms based on patterns of creation but thought they were perfect and unchanging

• the order that god created them

Erasmus Darwin - who

Charles Darwins grandfather

Erasmus Darwin

published first formal theories of evolution

- zoonomia

James Hutton

Father of modern geology

- studied earth and rocks and how they changed over time

- proposed gradualism

Gradualism

change occurs gradually

- earth underwent continuing transformation over long periods of time

• many small changes over a long period of time = large changes

Thomas Malthus

wrote an essay on the principle of population

Principle of Population

- populations cannot grow forever

- populations will always outgrow the food supply

- famine and disease will keep the population in check

Jean Baptiste Lamarck

First to propose a mechanism for how life changes over time

Lamarcks 2 principles

1. use and disuse

2. inheritance of acquired characteristics

Use & Disuse principle (Lamarck)

body parts that are used extensively become larger and stronger, while those that are not used deteriorate

Inheritance of Acquired Characteristics Principle (Lamarck)

an organism could pass these modifications to its offspring

- resurfaced in epigenetics

Epigenetics

modification of gene expression rather than alteration of the genetic code itself

MicroRNA

interferes with messenger RNA

Georges Cuvier

- really strongly influenced Charles Darwin

- largely developed paleontology

- believed in catastrophism

Fossils

- remains or traces of organisms from the past

- found in sedimentary rock

- new layers cover old ones and compress them into layers called strata

catastrophism

Major catastropphic events that wipe out populations

Charles Lyell

- Darwin read his book on his major voyage

- author of principles of geology

- proposed the principle of uniformitarianism

Uniformitarianism

- earths geologic features could be explained by gradual mechanisms

- geological events occur at the same rate now as they have always done

*the earth is going to continue to change and it will be different in the future

Charles Lyell - Nova Scotia

visited Joggins Fossil Cliffs and discovered (with his student) the earliest unquestionable reptile

Charles Darwin

very important in evolutionary thought

- recognized that species changed through time and described how the evolution occurred

- published the origin of species

Darwin - Voyage of HMS Beagle

invited to tour the north american cost line

- gone for 9 years

- visited the galapegos islands

Darwin - Galapagos Islands

- noticed similar species but with different traits on each island

- very similar to those animals in south america but they adapted to the diffrerent environments

*hypothesized that the islands were attached to south america but then broke apart and animals adapted to new conditions and food sources

Adaptive Radiation

might happen if one population is fragmented into several subpopulations isolated in different environments

- one species radiates into many species as the populations adapt over many generations to diffrerent sets of environmental factors

Natural Selection

individuals with inherited traits that are better suited to the local environment are more likely to survive and reproduce than less-well-suited individuals

- unequal reproduction success causes well-suited individuals to pass on their traits and not well siuted individuals die and do not pass on any traits

- increases biological fitness and decreases genetic variation

The Origin of Species - 2 main points

- contemporary species arose from a successsion of ancestors that differed from them "descent with modification"

- natural selection is the primary cause of descent with modification

Alfred Russell Wallace

Pushed Darwin to Publish his work and defended him after it was published

- many people did not support his ideas

Rosemary and Peter Grant

Observed Darwin's finches over 6 decades

Biological Fitness

the ability to survive to reproductive age, find a mate and produce offspring

- survival of the fittest

Three Modes of Natural Selection

1. Directional Selection

2. Disruptive Selection

3. Stabilizing Selection

Directional Selection

Favors one of the extreme variations of a trait

- brush fire turns the environment darker and extreme dark brown mice survive and light and medium ones die

Disruptive Selection

Favors individuals at both extremes of the phenotypic range

- environment with speckled rocks means the dark and light beetles survive but the in between dont survive

Stabilizing Selection

The center of the curve remains in its current position; occurs when individuals near the center of a distribution curve have higher fitness than individuals at either end

- something causes the dark and light mice to die and the in between to survive

Favored Traits

a trait that is favorable in one place or time may be useless or detrimental in another

Carolus Linnaeus

sought to classify life’s diversity “for the greater glory of god'“ organisms similar based on pattern of their creation

• god gave them their chraracteristics