EvolutionMr. Ardito’s Living Environment Classes

Overview

• No change, no evolution

• If individuals and species stayed exactly the same OR

• If the environment stayed exactly the same

• THERE WOULD BE NO EVOLUTION

Sources of Change

• Overproduction

• Genetic variation

• Struggle for existence (competition)

• Differential survival and reproduction

Overproduction

• Organisms tend to produce more offspring than are necessary

• This allows a greater likelihood of any of the offspring to survive to adulthood and reproduce

Genetic Variation

• No two individuals in a species are exactly alike

• This is normal and desirable

Struggle for existence

• Also called competition

• There are limited resources (food, climate, etc.) available to a species at any one time

• Individuals within the species must compete for these limited resources (someone must be most fit)

Differential Survival ...

• Those individuals that are the most well adapted to their environment will survive and reproduce

• When they reproduce, they pass their traits to their offspring, who are then more likely to survive

Evidence for Evolution• Fossil record

• Physical/anatomical similarities

• Geographic differences

• Genetic differences and similarities

Fossil Record• The collection of fossils tell a story of the

development of species over time

Physical similarities, part 1

• Homologous structures

• Analogous structures

Physical similarities, part 2• Vestigial structures

• Embryonic development

Geographic Separation• Species start out the same, but are

subject to geographic isolation (they are separated in space)

• Adaptations and evolution occur to better fit the species to their new habitats (see the pollenpeepers)

• Can also result from migration of species in or out of an area

Genetic Differences

• We can examine the DNA of organisms and species to see how related they are on a molecular level

• We can look at cellular DNA or mitochondrial DNA

• This tool lets us go beyond what Darwin was able to see

Theories of Evolution

• Spontaneous Generation

• Lamarck - Inheritance of Acquired Traits

• Darwin - Natural Selection

• Heterotroph Hypothesis

Spontaneous Generation

• Living things come from dead things

• Examples: flies develop from dead garbage; maggots from dead bodies; mice from straw

Jean Baptiste Lamarck• Lamarck developed laws to account for

changes in species

• Law of use and disuse (use it or lose it)

• Law of inheritance of acquired traits (acquired traits are passed from parent to offspring)

Lamarck, continued

• Lamarck believed that species moved from simplicity to complexity in the direction of progress and perfection

Charles Darwin• Darwin developed theory of natural

selection (also called “survival of the fittest”)

Natural Selection

• Natural selection is the biological theory that explains why living creatures seem to match their environmental niches so well – the process by which individual organisms with favorable traits are more likely to survive and reproduce than those with unfavorable traits.

(citation from Wikipedia/Natural Selection)

Heterotroph Hypothesis• Evolution tends to move from the simple

to the complex

• Heterotrophs developed first and then autotrophs

• Mitochondria and chloroplasts originally separate organisms that developed with and inside of heterotrophs creating autotrophs

Types of Evolution

• Gradualism

• Punctuated Equilibrium

Gradualism

• Gradualism is the slow, steady trend of a species towards evolution

Punctuated Equilibrium

• Long periods of stability are followed by rapid changes to a species

Humans and Evolution

• Harmful impacts on evolution

• Beneficial impacts on evolution

Harmful impacts• Human activity, pollution, fashion, etc.

leading to extinct species

Beneficial Impacts• Conservation

• Agriculture/animal husbandry/domestication of animals

What is co-evolution?• Species develop together and the

relationship between them increases their chances of survival and reproduction

• Example -- man and corn

Evolution in our lifetimes

• Pesticide resistant insects

• Drug resistant bacteria