Natural Selection & Evidence for Evolution

Notes 15.1

Evolution – change in a populations genetic makeup that takes place over many generations

Species – group of organism that can interbreed and produce fertile offspring

Members of species may share similar characteristics but variations exist among members (meiosis is a source of variation

Charles Darwin

1809-1882Born in EnglandEducated at Cambridge; degree in

theologyNaturalist on HMS Beagle at age 21Voyage lasted five years (1831-1836)

Observations

Collected biological specimensOn Galapagos Islands, Darwin observed

species with similarities but unique differences from those elsewhere

Figure 15–1 Darwin’s Voyage

Pinta IslandIntermediate shell

Pinta

Isabela IslandDome-shaped shell

Hood IslandSaddle-backed shellHoodFloreana

Santa Fe

Santa Cruz

James

Marchena

Fernandina

Isabela

Tower

Giant Tortoises of the Galápagos Islands

Hypothesis

Species change over timeHow does it occur?

Jean Baptiste Lamarck – first person to claim that species changed over time and could go extinct

first idea – use and disuse – claimed that body parts used regularly by organisms grow stronger and larger. Ie giraffes’ neck

second idea – acquired characteristics can be passed down from parent to offspring

Figure 15–7 Lamarck’s Theory of Evolution

Experiment/Gather evidence

Collecting & studying more specimensReading & studyingMalthus (economist) - populations

increase faster than food supplyOrganisms must compete for food &

space in order to surviveConducting experiments: pigeon

breeding

Conclusions

Darwin developed the Theory of Evolution by Natural Selection

Theory of natural selection:Organisms best suited to their environment

as a result of favorable characteristics survive and reproduce

Publish

1858 - Alfred Russel Wallace formed similar conclusions

1858 - Wallace & Darwin jointly presented conclusions to scientific community

1859 - Darwin published On the Origin of Species by Natural Selection

Theory

Further evidence led to acceptance of theory by the scientific community.

Evidence of Evolution

Adaptations - inherited variations that improve an organism’s chance of survivalStructural

Mimicry: one species resembles anotherCamouflage: species blends with surroundings

Physiological - changes in metabolic processes

Bacterial, insect, or weed resistance

Evidence of Evolution

Fossil recordRecord of early life, although incomplete

BiochemistryDNA & RNA comparisons establish

relationships between species

Evidence of Evolution

AnatomyStructural or functional similarities

With common origin (homologous structures)Without common origin - common adaptations to

similar circumstances (analogous structures)Structure that no longer has a function

(vestigial structures)

Concept Map

includes

Evidence of Evolution

Physical remains of organisms

Common ancestral species

Similar genes Similar genes

which is composed of which indicates which implies which implies

The fossil recordGeographic

distribution of living species

Homologous body structures

Similaritiesin early

development

Beaver

NORTH AMERICA

Muskrat

Capybara SOUTH AMERICA

Coypu

Figure 15–14Geographic Distribution of Living Species

Beaver

Muskrat

Beaver andMuskrat

Coypu

Capybara

Coypu andCapybara

Turtle Alligator Bird Mammal

Ancient lobe-finned fish

Figure 15–15 Homologous Body Structures