Chapter 26-The Evolution of Life

BIG IDEA: Evolution- inherited changes over time- has produced all the different kinds of living things on Earth

26.1 The Origin of Life

According to the fossil record life on Earth began about 3.5 billion years ago

(According to scientists) ancient Earth was filled w/ volcanic eruptions, rain storms, and lightning storms.

Miller and Urey built a model of ancient Earth in a flask containing the same compounds present in ancient Earth. -Organic molecules formed, including amino acids (the building blocks of life)

Other scientists think that organic molecules were brought by meteorites, or by deep-sea thermal vents.

26.2 How Living Things Change over Time

Fossils suggest that life on Earth has changed over time.

French scientist Lemarck suggested that modern species were descendants of ancestors that had evolved.

His theory was not correct, but set the stage for Darwin

Acquired traits cannot be passed genetically.

Evolution is inherited changes in organisms over time, and was caused by natural selections

Traits that best suit environment help organism survive, those traits are passed to offspring.

Advantageous traits become more popular in population

26.3 Natural Selection & How it Works

1.Variation- Traits that vary from individual to individual

2. Heritability- Traits that can be passed from parents to offspring. (Ex: hair color is, hairstyle is NOT)

3. Natural selection- Organisms w/ advantageous traits survive longer, and pass those traits to offspring.

4.Adaptation- Population evolves to become better suited to environment

26.4 Adaptation

Adaptation is a trait that makes an organisms good at surviving and reproducing in an environment

Survival requires the ability to obtain food, attract mates, and to avoid predators.

ThermoregulationThermoregulation is the body’s ability to keep temperatures stable. Surface area and volume are important for thermoregulation

Heat lost heat produced

Hot and cold climate animals have diff. sizes and shapes.

26.5 Genetics and Evolution

Allele frequency- how common diff. alleles are in a population.

Natural selection on phenotype, not genotype- Ex: AA and Aa look the same to a predator, and will still get eaten if visible

Genetic Drift- random chance. Ex: natural disasters

Heterozygous advantage- Situation in which heterozygotes do better than both types of homozygotes

Variation- More variation= more likely that there are alleles in population ideal for survival in new conditions

26.6 How New Species Form

Species is a group of organisms that can breed and produce viable offspring.

Speciation=formation of new species

When species can no longer breed and produce viable offspring they are no longer the same species.

Geographic barriers may cause speciation

26.7 Evidence of Evolution

1.Observations of natural selection in action2. Artificial selection- when humans breed

organisms w/ desired traits3.Vestigial organs- nonfunctional organs4. Similarities in body structure

Evidence cntd

5. Similarities in DNA structure in related species

6. Related species develop in similar ways

7. Fossils show how organisms have evolved over time.

8. Biogeography- where species are found on Earth

26.8 How Humans Evolved

Humans are primates. Does NOT mean we descended from any existing species of monkey or ape. Just more closely related to them than other living things

Humans are the only species of hominids.

Earliest fossils of modern humans are from Ethiopia, 195,000 years ago.