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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 Modelsuggests 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 moleculesgenes 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)