Chapters 12 & 13 History of Life on Earth The 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 H 2 0) 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 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)