Bellringer
1. How did the Earth form?
2. What is evolution?
3. What is natural selection?
Origin and History of Life
Evolution
Abiogenesis
• AKA: Spontaneous generation
the idea that life comes from nonliving
things.
NO.
Biogenesis
The idea that life can only come from preexisting life
Proven by several experiments.
Redi’s Experiment
• 1st attempt to disprove abiogenesis (to
prove biogenesis)
• Proved maggots come from flies.
Pasteur’s Experiment
Used an S-shaped flask to prove that the
microorganisms only came from other
microorganisms
Clearly proved biogenesis and disproved
abiogenesis (spontaneous generation)
Early Earth
• Earth formed over 4 billion years ago
• Oldest rocks on Earth are 3.9 byo
• Conditions on early Earth were HARSH with
no oxygen in the atmosphere (and very
HOT)
The first forms of life had the following
characteristics:
Unicellular
Heterotrophic
Prokaryotic
Anaerobic
Oparin’s hypothesis
• Hypothesized that energy from the sun,
lightning, and Earth’s heat triggered
chemical reactions that formed small
organic compounds using molecules from
the atmosphere.
Miller & Urey
• Performed an experiment supporting
Oparin’s hypothesis
• The sample created contained amino acids
Endosymbiosis
Theory describing
how eukaryotic cells
evolved from
prokaryotic cells.
What is EVOLUTION?
Process by which the frequency of different alleles
in a GROUP or POPULATION of organisms changes
over time
Remember – alleles are different versions of a gene
When one allele becomes more common in a
population, its corresponding phenotype also
becomes more common
This is EVOLUTION
Takes place of many generation!
Theories…
Lamarck’s Theory
• Organisms develop traits by use or disease
• Organisms acquire characteristics/traits as
they need it and pass it on to their offspring
– EX: a guy goes through surgery to lengthen his legs and
gains two inches. All of his future sons will be taller because
of the surgery.
• DISPROVED by experiments
Darwin’s Theory
• Based on observations and evidence
collected on a 5 year voyage around the
world (and multiple experiments in labs)
• 4 main ideas:
– Overproduction  each species produces more
organisms than can survive and reproduce
Why? Because most offspring do not survive!
– Competition  organisms compete for the same
resources for survival
– Variations  differences among traits that
occur among members of the same species
• Variations occur by…
–Mutation
–Crossing over in meiosis
–Sexual reproduction
If there are no variations then evolution CANNOT occur!
– Survival of the fittest  organisms with alleles that
give them phenotypes that make them well adapted
to their environment have a better chance of
surviving & reproducing.
Fit means the one best suited for the environment,
NOT the strongest!!
This leads to NATURAL SELECTION
• If this environment stayed the same,
then over time the number of darker
colored moths in the population
would increase because they have a
better chance at surviving to
reproduce.
This is EVOLUTION by natural selection.
 When nature selects the traits that are best for the
environment.
Which column of
giraffe evolution
represents
Lamarck’s theory
and which
represents
Darwin’s theory?
Adaptation
trait/phenotype that makes an organism
more fit/gives it an advantage at surviving
in its environment
Ex: a polar bear’s black skin and clear fur
Camouflage
An adaptation that allows an organism to
bend with its environment
Mimicry
 An adaptation in which one organism
mimics another more deadly/toxic organism
EVOLUTION by natural selection in
the news…
1. PESTICIDE RESISTANCE
 when pesticide does NOT kill its target
(pesticides can be for insects, plants, for fungi)
Use of pesticides is
changing the
environment in which
insects live
Some insects have
alleles that make them
more fit for the new
environment
 Those insects that are more fit survive and
reproduce (pass on their alleles)
Future populations of that insect are now
resistant to the pesticide and the pesticide does
not work anymore.
EVOLUTION has occurred.
Overuse of pesticides has helped insects and
weeds become pesticide resistant.
Antibiotic Resistance
 When an antibiotic does NOT kill the
bacteria
 Due to incorrect and overuse of antibiotics
Evolution by chance?
Called EVOLUTION by genetic drift
When a chance event allows a specific
phenotype (determined by a set of alleles) to
become more of less common in a population.
 Occurs in small populations