Download NATURAL SELECTION OBSERVED TODAY

NATURAL SELECTION
OBSERVED TODAY
• Peppered
Moths
• Microorganism
s resistant to
penicillin
• Insects
resistant to
pesticides
Examples
Modern Examples of Evolution:
1. Peppered Moths
• England, 1848
• Moths rest on Lichencovered tree barks.
• There are more white
moths in the population.
Evolution In Action!
• Why is Sexual reproduction better for a
species than Asexual reproduction?
The Peppered Moth: England 1848
INDUSTRIAL REVOLUTION
Evolution
Evolution
2. Antibiotic-Resistant
Bacteria
2. Antibiotic-Resistant
Bacteria
Antibiotic-Resistant Bacteria
–What was the
selective pressure?
–Who applied it?
Antibiotic-Resistant
Bacteria
Antibiotic-Resistant
Bacteria
Did the antibiotic mutate the
bacteria’s DNA?
Did bacteria become resistant
because they needed to?
Did the bacteria get “used to” the
antibiotic?
WHY did one survive?
Antibiotic-Resistant
Bacteria
Evolution
Original Population
New Population
Would this have happened without antibiotics?
Why does penecillin not work on bacteria anymore?
1.
The bacteria that survived exposure to penicillin learned to
avoid it.
2.
During each generation, the bacteria modified their own DNA
to increase their ability to resist penicillin and passed this ability
on to their descendants.
3.
Members of the original population of bacteria that were
penicillin resistant survived and reproduced, creating a more
resistant population.
4.
The bacteria that caused the new outbreaks were from
populations that had never been exposed to penicillin.
Do NOT take antibiotics unless
absolutely necessary!
Antibiotics do NOT kill viruses.
3. DDT-Resistant Insects
• DDT is an insecticide (bug-killer) that
has been used to kill pests on crops.
At first, DDT killed most of the
pests.
• But soon, the majority of the pest
population had a DDT-resistance
gene.
• Explain (in at least 3 steps) the
events that led to this evolution of
pests.
DDT also killed Falcons, Eagles, and
Osprey by making the egg shells
thinner.
A large population of house flies was
sprayed with a newly developed,
fast-acting insecticide. The
appearance of some house flies that
are resistant to this insecticide
supports the concept that:
1. species traits tend to remain
constant
2. pesticides cause mutations
3. variation exists within a species
4. the environment does not change
Evolution part 5
• Rates of evolution
• Be able to explain gradualism vs
punctuated equillibrium and why 2 beliefs
exist.
How fast does evolution occur?
SLOW Evolution:
Horseshoe Crab
150
millionyear old
fossil
Rate of Evolution
How Fast Will a Species Change?
Evolution will occur more quickly if:
– Lots of VARIETY
– High selective pressure
(The environment changes.)
– Lots of competition to survive and reproduce.
How fast is evolution when…
• The Environment stays
stable?
– SLOW
• Selective pressure is
applied?
– FAST
• Conditions are harsh?
– FAST
• Lots of competition?
– FAST
Time Frame for Evolution
• Gradualism –
evolution is slow,
gradual and
continuous
Time Frame for Evolution
• Punctuated
Equilibrium- species
have long periods of
stability interrupted by
brief periods of
change (mutations),
during which new
species may evolve
Extinction:
Failure of a
species to adapt
to a changing
environment.
Fun Facts
• Possibly 10 billion species have ever
existed.
• Of all species that ever inhabited the Earth
over 99% of them are now extinct.
• The primary reason for these extinctions is
environmental change or competition.
• They did not have the mutation that would
have enabled them to survive.