Chapters 12

1
Chapters 12 13

• History of Life on Earth
• The Theory of Evolution

2
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

3
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

4
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 oceans surface

5
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.

6
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)

7
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

8
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

9
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

10
Chapter 13- Theory of Evolution

• Section 1 Theory of Evolution by Natural
  Selection
• Section2 Evidence of Evolution
• Section3 Examples of Evolution

11
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

12
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

13
Darwins 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.

14
Darwins Ideas Updated

• Reproductive isolation condition in which 2
  populations are separated by geography and cant
  reproduce
• Punctuated Equilibrium rapid change in a species
  followed by extended periods of no change

15
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

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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

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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.

18
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

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Evolution of Darwins 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)

20
Formation of New Species

• Divergence accumulation of differences between
  groups (leads to new species)
• Speciation process by which new species form
  (subspecies)