Lecture 1: Introduction to Evolution

evolution

change in heritable characteristics of biological populations over successive generations

hypothesis

potential explanation based on existing data/models

bacterial mutant that are resistant to antiobiotics occur in ____ frequency in most natural populations of bacteria

low

the use of _____ intensely selects for these restraint mutants

antibiotics

the increased usage and diversity of antibiotics is selecting for more and more _____ bacteria

multiple drug-resistant

the evolution of antibiotic resistance in bacteria is extremely _____

rapid

high S =

high selective pressure

Charles Darwin published __________ in 1859

The Origin of Species

essentialism

the philosophical belief that entities have a fixed essence or set of characteristics that define their fundamental nature and identity; caused variation to be ignored by biologists

Plato and Aristotle believed in ..

essentialism

“The Great Chain of Being” or Scala naturae

• gradation from the inanimate, to lower life forms, to plants and invertebrates, and up to the higher forms of life

• nature follows an ordered plan

• a creator made all species with perfect form; no changes were expected in species over time

Carolus Linnaeus

• life goal: catalogue nature and make manifest the “plan of creation”

• established the framework of modern classification in the book Systema Naturae

• classified species into genera, families, classes: all intended to relate life in its closeness to “the Creator”

Principle of Uniformitarianism

• ancient geological formations can be explained by mechanisms that we still observe today

• processes cause small, gradual changes can result in massive change over long time periods

Lamarckian evolution

• inheritance of acquired characteristics: species vary because each has different needs and strongly exercised organs attract more nervous fluids

• wrong but first to propose a mechanism to explain adaptation in nature

Charles Darwin

• naturalist

• 5 year worldwide voyage on the HMS Beagle

• received a manuscript from Alfred Russel Wallace that described a similar theory of natural selection

John Gould

• observed mockingbirds from neighboring islands are different enough to be species

• triggered idea that different species evolved from common ancestors

Thomas Malthus

• wrote Essay on the principle of population

• human growth is faster than food production, famine will be the result

• led to idea of the “struggle for existence”

• there are usually more individuals born than can survive

descent with modification

all organisms have descended, with modification, from common ancestral forms of life

natural selection

individuals with superior features survive and reproduce more successfully than individuals with inferior features

evolution by natural selection

if these differences are inherited, then the average character of a species can be altered over time

Darwin’s Evolutionary Theory had 5 big ideas:

1. evolution: characteristics of the lineages of organisms change over time

2. common descent: all life, living or extinct, has descended without interruption from one or a few original forms

3. gradualism: even radical differences between organisms have evolved from incremental changes over time

4. populational changes: evolution occurs by changes in the proportions of individuals with particular traits in populations

5. natural selection: changes in the proportions of individuals in a population are caused by heritable differences in their ability to survive and reproduce

mutationists

believed that all change over time is caused by major mutations that could form entirely new species in a single generation

blending inheritance

• inherited material from 2 parents “blends together”

• leads to loss of variation

particulate inhertance

• the idea that parents pass on discrete heritable units (genes)

• Gregor Mendel documented this model in experiments with garden peas