Transcript Academic Biology Chapter 14-15

I. How Did Life Begin?
Prior to the 17th century:
1. Spontaneous Generation:
The belief that living things could
come from non-living things.
Francesco Redi (1668) Italian scientist
Attempted to
discredit
Spontaneous
Generation.
Experimented to
prove that maggots
came from flies
Redi’s Exeriment
1668 – Experiment showing how
maggots come from flies
Lazzaro
Spallanzani (1700)
Italian scientist
Experimented with spontaneous
generation of microorganisms.
1. Created meat broth
2. Boiled broth to kill
microorganisms
3. Capped some flasks and left
others open.
Spallazani’s Experiment
Opponents of his
study claimed that he
overheated the
samples…
Destroying the VITAL
FORCE
Louis Pasteur
(1800’s) French scientist
*The conclusions of Pasteur, brought about the theory of
BIOGENESIS – Living things come
from other living things
B. Formation Of The Earth
About 5 billion
years ago, the
solar system
was a mass of
swirling gas and
dust.
Possible result
of a
SUPERNOVA
As millions of years passed, a large
amount of material collapsed to the
center and created the sun.
Around 4.6 billion years
ago, the earth and
some of the other
planets were formed.
As earth cooled, water vapor
in the air condensed to form
water and the first oceans.
3.8 to 3.9 billion years ago.
C. Measuring Earth’s Age
Radiometric dating:
Estimate the age of an object by
measuring its content of radioactive
isotopes.
Radioactive isotopes:
Unstable and “decay” over time.
Half-life:
The time that it takes for a radioactive
isotope to decay by one half
D. Life On The Earth
The oldest evidence of life on the
earth is found in rock estimated
to be 3.5 billion years old.
The evidence shows in the form
of FOSSILS.
The first fossils were referred to
as MICROFOSSILS, ancient
prokaryotic cells.
1. Formation of Simple Organic
Compounds
A. Primordial Soup
Model
Alexander Oparin (1923)
• Soviet scientist
• Gases of the primitive
atmosphere came
together and created
simple organic
compounds
When the atmosphere cooled
and the rain fell, so did the
compounds
Over time the compounds
entered chemical reactions and
proteins and other organic
compounds resulted
* DID NOT run any
experiments to
support theory
-In 1953, Americans, Stanley
Miller and Harold Urey, set up an
experiment that was based on
Oparin’s theory.
B. The Bubble Model
Ammonia and Methane were
released from volcanoes into
bubbles
Bubbles rise to the surface and
burst
2. Formation of Complex Organic
Compounds
Formation of protein occurred
either by amino acids
spontaneously combining…
Or they were heated in the
absence of oxygen
-Similar mechanisms may have led
to the formation of
carbohydrates, lipids, and nucleic
acids
3. Concentration and
Enclosure
Proteins clump together
to form microscopic
droplets…
A. Coacervates droplets of different
types of irregularly
shaped molecules .
Includes Amino Acids and sugars
B. MicrospheresRound, usually from one type of
molecule.
Separated from the environment by
a membrane
Chemical reactions occur here
more easily than in water
Can bud off
4. Evolution of Growth, Metabolism,
and Reproduction
Coacervates and microspheres
lack the complexity of living
cells …
-They can grow
-They can bud
• They lack the ability to respond
to natural selection.
5. The Role of RNA
RIBOZYME:
A special type of RNA was
discovered to be able to act like
an enzyme
They can replicate themselves
Research indicates life may have
started with RNA
II. Evolution of Cellular Life
A. The First Prokaryotes
Scientists hypothesize that
the first cells were:
• Anaerobic
• Heterotrophic
• Prokaryotic
B. The First Eukaryotes
Some early Eukaryotes may have
gone through a relationship known
as SYMBIOSIS.
Endosymbiosis Theory:
Prokaryotic intracellular parasites
evolved into various cell organelles
Evidence in the mitochondria and
chloroplasts
ENDOSYMBIOSIS THEORY
Life Invaded Land
Cyanobacteria: photosynthesizing
organisms gave off oxygen as a
waste product. (At about 2.8 billion years ago)
Oxygen had two effects on the
environment:
1) Those organism that could bond
oxygen to other compounds survived
- beginning of aerobic respiration.
2) Ozone (O3) was created
Lamarck’s Explanation
French scientist (1744-1829)
Similar species descended from common
ancestors
ACQUIRED TRAITS: explanation for species
change.
• Changes arise from experiences and
behavior over a lifetime
• Not determined by genes.
EXAMPLES: web feet, giraffe neck, tails
“USE and DISUSE”
Charles Darwin
Went to medical school
Study become a
minister
Interested wildlife and
the environment
Took a voyage on a
ship, the BEAGLE, as
the boats naturalist
Darwin proposed a mechanism for
evolution
Natural Selection: occurs because
of ADAPTATIONS
Published a book: “On the Origin
of Species” 1859, 1 year after
Alfred Wallace (same basic ideas)
Evolution by Natural Selection
“Human
populations are able to
increase faster than the food
supply can” – Thomas Malthus 1798
Only a limited number of
offspring survive to reproduce
Individuals with traits that best
suit their environment are most
likely to survive and reproduce
Darwin’s Theories
1. Descent with
modification:
Newer life forms appearing
in the fossil record are
modified versions of the
old species
2. Modification by Natural
Selection:
Mechanism for how
evolution can occur.
Why some organisms survive
when others do not:
The environment affects individuals
differently
Some traits provide an advantage
Populations ADAPT as the proportion
of favorable genes increases
FITNESS: Single organisms genetic
contribution to the next generation.
Favorable traits provide an ADAPTIVE
ADVANTAGE
Adaptations:
Inherited traits that have become
popular due to a selective
advantage
Darwin’s Theory:
Based on 4 major points….
1. Inherited variation exists within
the genes of every population
2. Some individuals are better
suited for their environments
3. Traits that provide an
advantage are spread as
individuals survive and have
offspring
4. Fossils provide evidence that
living species evolved from
extinct species
The Scopes Trial
PBS VIDEO ON EVOLUTION
Darwin and Evolution
Evidence of Evolution
The Fossil Record:
Fossils:
Preserved or mineralized
remains or imprints of an
organism that lived long ago
Concerns with using fossils for
source of evidence
The fossil record is NOT
COMPLETE
Many times genetic information
is not available from the fossils
Not all organisms are equally
likely to be fossilized
Types of Fossils
Imprints
A film of carbon remains after other
elements of an organism have
decayed
Mold
created by the impression of a
shape/track
Cast
sediment fills in a cavity left by a fossil
Fossil Video
FOSSIL DATING
Ways of
determining fossil
age:
1. Position within
sedimentary rock
• Look at different
strata:
•
Deeper is older
2) Carbon dating
 Dating is done by
comparing ratio of carbon 12
and carbon 14
 Used to date things up to
50,000 yrs. old
•Isotopes
•Parent
•Daughter
•Half Life
(yrs)
•Dating Range (yrs)
•Materials
•Carbon-14
•Nitrogen-14
•5730±30
•0100-70,000
•Anything with C
•Muscovite
Biotite
Hornblende
Whole volcanic rock
•Potassium-40
•Argon-40
Calcium-40
•1.3 billion
•50,000-4.6 billion
•Uranium-238
•Uranium-235
Uranium-232
•Lead-206
•Lead-207
Lead-208
•4.5 billion
•710 million
14 billion
•10 million-4.6
billion
•
•Rubidium-87
•Strontium87
•47 billion
•10 million-4.6
billion
•Zircon,U
containing
•Muscovite
Biotite
Potassium Feldspar
Whole
metamorphic
or Igneous rock
Evidence From Living
Organisms
1) Evidence of Common Ancestry
-Organisms that are similar in
structure had a common ancestor
2. Homologous Structures vs.
Analogous Structures
A. Homologous:
Structures that are
embryologically similar
and functionally different
B. Analogous:
Structures that are
embyologically different
but function the same
Homologous Structures
3. Vestigial Organs:
Organs that are
seemingly
functionless
4. Biochemical
Comparisons:
-Examine
biochemical
compounds
within organisms
5. Embryological
Development:
Compare organisms at
various stages of
development
Embryonic
Similarities
Indicate
Common ancestor