Ch. 22 Descent with Modification, A Darwinian View of Life

Charles Darwin (1859)

Theologist that noted that current species are descendants of ancestral species + published The Origin of Species

Evolution

“descent with modification”

both a pattern and process

Different Views (Aristotle + Bible)

Aristotle: viewed species as fixed and arranged them on scala naturae

Bible: species were designed by God

Carolus Linnaeus

Interpreted organismal adaptations as evidence that each species was designed for a specific purpose

• Co-found taxonomy (classifies organisms) + naming species

Fossils

remains or traces of organisms from the past, usually found in sedimentary rock with appears in layers called strata

• document important transitions

Paleontology

the study of fossils, developed by Georges Cuvier

Georges Cuvier

speculated that the boundaries between strata represent catastrophic events

James Hutton & Charles Lyell

thought that changes in Earth’s surface resulted from slow, steady actions still operating today at the same rate

• influenced Darwin

Jean-Baptiste de Lamarck

hypothesized that species evolve through use and disuse of body parts and the inheritance of acquired characteristics

• based on their environment

Darwin on Beagle (3)

1. collected specimens of South American plants and animals

2. fossils resembled living species from the same region

3. influenced by Lyell’s Principles of Geology (earth > 6000 yrs)

All lead to idea of adaptation

Natural Selection

a process in which individuals with favorable inherited traits are more likely to survive and reproduce = new species (not new traits)

• 1844: Darwin’s theory

• 1858: competed with Wallace for publication

Ideas from The Origin of Species (3)

1.The unity of life (everyone is related somehow)

2. The diversity of life

3. The ways organisms are suited to life in their environments

Descent with modifcation

refers to the view that all organisms are related through descent from an ancestor that lived in the remote past

• branching process used to explain past extinction events

Artificial Selection

humans have modified other species by selecting and breeding individuals with desired traits

Thomas Malthus

noted the potential for the human population to increase faster than food supplies and other resources

• heritable traits = more offspring = higher frequency

What supports evolution? (4)

1. Direct observations

2. Homology

3. The fossil record

4. Biogeography

Evolution of Drug-Resistant Bacteria

• Direct Observation

1945: resistance to penicilin evolved in S. aureus

1961: Resistance to methicillin evolved in S. aureus

Methicilin

inhibits an enzyme used by bacteria to produce cell walls

• MRSA strains survive + reproduce when exposed = resistant

What actually evolves?

Populations (through mutations + changes in DNA sequence)

Homologous Structures

anatomical resemblances that represent variations on a structural theme present in a common ancestor

Vestigial structures

remnants of features that served a function in the organism’s ancestors

• EX: appendix

Evolutionary Trees

diagrams that reflect hypotheses about the relationships among different groups (made using didd data: anatomical or DNA sequence)

• homologies form nested patterns

Converent Evolution

“The function”

the evolution of similar, or analogous, features in distantly related groups from when groups independently adapt to similar environments in similar ways

• does NOT provide ancestry info

Biogeography

the scientific study of the geographic distribution of species, provides evidence of evolution

• Earth originally together but separated by continental drift: Pangaea

Endemic species

species that are not found anywhere else in the world

• related to nearest mainland or island species due to colonization