Chapters 12 & 13

History of Life on EarthThe Theory of Evolution

Chapter 12 - History of Life on Earth

• Section 1: How Did Life Begin?• Section2: The Evolution of Cellular

Life• Section 3: Life Invaded the Land

The Age of Earth• The Earth formed about

4.5 billion years ago• Scientist have

measured the age of the rocks found on Earth using radiometric dating (radioactive isotopes)

• Half-life - time it takes for half of the radioactive isotope to decay. (K-40)

• Water vapor in atmosphere condensed to form the oceans

Theories……

• The Primordial Soup Model - basic chemicals of life could have formed spontaneously

• The Bubble Model- suggests that the key processes that formed chemical of life took place within bubbles on the ocean’s surface

Precursors of the First Cells

• Scientist have not been able to produce DNA and proteins in water, but have been able to form short chains of RNA.

• Scientists think that RNA and RNA enzymes catalyzed the earliest proteins and DNA

• The concept of how life might have originated naturally or spontaneously remains a subject of intense interest, research, and discussion.

Evolution of Cellular Life • Scientist have found

fossils of earliest prokaryotes that are 2.5 billion years old

• Cyanobacteria - oldest marine, photosynthetic made oxygen

• 2 groups of prokaryotes (Eubacteria, and Archaebacteria)

Evolution of Eukaryotes• Eubacteria- contain

chemical (peptidoglycan) in their cell walls - cause disease and decay

• Archaebacteria- lack pepti. In cell wall, but has unique lipids in cell membrane - 1st Eukaryotic cells came from Archaebacteria

• 1.5 billion years ago the first eukaryotes appeared.

• Eukaryotes have complex system of internal membranes.

• (nucleus, mitochondria, chloroplast)

• Mitochondria and chloroplast have own DNA

Life Invaded the Land

• Sun provides life-giving light and dangerous UV radiation

• Ozone formed from oxygen in atmosphere and protects against UV radiation from the sun

Life on Land• 1st - plants and fungi living together

(mutualism) mycorrhizae, lichens• Arthropods- hard outer skeleton (insects)• Fish- vertebrates, (live in water, ancestors)• Amphibians-vertebrates (reproduce in H20)• Reptiles- vertebrates (reproduce on land)• Mammals and Birds - vertebrates• Continental Drift and extinctions led to

evolution

Chapter 13- Theory of Evolution

• Section 1: Theory of Evolution by Natural Selection

• Section2: Evidence of Evolution

• Section3: Examples of Evolution

Charles Darwin

• 1831 Darwin was naturalist aboard the HMS Beagle • Darwin found evidence that species gradually changed over

time• He found fossils of extinct armadillos that were different than

present day armadillos.• Galapagos Islands-examined finches and compared them with

S. American finches. They were slightly different

Evolution by Natural Selection• Individuals that have

physical or behavioral traits that better suit their environment are more likely to survive and will reproduce more successfully than those that do not have such traits

• Adaptation- species have changed in response to particular environment

Darwin’s Theory• 1) Variation exists within the genes of every

population or species (result of mutation or translation errors)

• 2) In a particular environment, some individuals are better suited to survive and reproduce (natural selection)

• 3) Over time, the traits that make certain individuals able to survive and reproduce are spread in that population.

• 4) There is overwhelming evidence from fossils that living species evolved from organisms that are extinct.

Darwin’s Ideas Updated• Reproductive

isolation condition in which 2 populations are separated by geography and can’t reproduce

• Punctuated Equilibrium rapid change in a species followed by extended periods of no change

Evidence of Evolution• Most scientists

agree on the following 3 major points:– Earth is 4.5 billion

years old– Organisms inhabited

Earth for most of its history

– All organisms living today share common ancestry with earlier life forms

Anatomy and Development / Biological

Molecules• Vestigial structures:

body structures that are evidence of organisms past (examples: hind limb of whales)

• Homologous structures: structures that share common ancestry (arm on humans, bats, alligators) page 286 - examples

• Biological molecules- genes should have changed over time by mutation and selection

• Humans and gorillas have only 1 difference in amino acids in hemoglobin

• Page 287

Factors of Natural Selection

• 1) All populations have genetic variation• 2) The environment presents challenges

to successful reproduction• 3) Individuals tend to produce more

offspring than the environment can support

• 4) Individuals that are better able to cope with the challenges presented tend to leave more offspring than those that can not cope.

Evolution of Antibiotic Resistance

• Mutant bacteria able to survive the antibiotic and cause a resistance

• Deadly in some cases (tuberculosis)

• Antibacterial craze that hit the world a few years ago….. People still got sick

Evolution of Darwin’s Finches

• Darwin collected 31 specimens of finches from 3 of the Galapagos Islands. (9 different species)

• He found the shape of the beaks to vary based on what the finch ate (big beak more favorable during dry years)

Formation of New Species

• Divergence: accumulation of differences between groups (leads to new species)

• Speciation: process by which new species form (subspecies)