Transcript The Six Main Points of Darwin`s Theory of Evolution

Happy Tuesday!
• Submit The Peppered Moth WS
• Title a new page in your notebook:
The Theory of Biological Evolution
• Finish Presentations (Per 4 and 6 only)
• Evidence Projects group scores @ end of class.
Can someone set an alarm for 3 minutes before the bell? Thank you!
Discuss!
A volcano erupted on an island. The ash released from
the volcano changed the acidity (pH) of the soil from
the level it had been for hundreds of years. This
significant change resulted in new environmental
pressures on species in the soil. Which of the following
is a likely outcome of these pressures?
a) Some species will disappear from the soil because they do not
have individuals with traits that allow them to survive in more
acidic soil.
b) Only some species will generate the needed mutations to adapt
to the change in pH; other species will become extinct.
c) Most species gain additional genetically-based traits, and this
increase in complexity allows them to live in the more acidic soil.
d) Individuals in each species will evolve the traits necessary to
survive under these new conditions.
A ship that had been used for many years in arctic exploration was
sold and moved to a harbor in the warm waters of the Caribbean.
Worms that had lived on the ship bottom crawled off in the warm
waters and attempted to attach to other ships in this tropical area
where there were no similar worms. Some of the worms were able to
survive and reproduce. What would you expect to happen to this
group of worms over many generations in this new environment?
a) The worms will mate and produce offspring just as they did in their
previous environment, and the group’s traits will likely remain unchanged
after many generations.
b) The worms will gain new, more complex traits through natural selection
that will help them better adapt to the warmer waters because natural
selection leads to more complex and better adapted organisms.
c) Worms possessing genetic variations that help them to survive and thrive
in the new environment will leave more offspring than others lacking those
traits. Over time, the proportion of the worm population with these adaptive
traits will likely increase.
d) The mutation rate will increase in this group of worms in order to promote
evolution.
The Theory of
Biological
Evolution
The Theory of Evolution, defined:
“All living species are descendants of
ancestral species and are different from
present day ones due to the cumulative
change in the genetic composition of a
population”
– In a nutshell: Populations of living things
came from other life – but look and behave
differently because of genetic change.
Charles Darwin (1809-1882)
• Father of the theory of Evolution
• Suggested that natural selection is the
mechanism by which species evolve over
geologic time.
• Proposed Descent with Modification:
– All organisms on Earth are related
through some unknown ancestral
type that lived long ago.
History of Evolution Theory
• As with any scientific theory, Evolution Theory
has been developed through many generations
of scientists interpreting new evidence to
refine and expand our understanding of
biological change across time.
– Darwin and Wallace (Evolution)
– Gregor Mendel (Genetics)
– Franklin, Watson & Crick (Genetics)
The Nuts and Bolts of Evolution
• Populations change, not
individuals.
• Evolution is like a tree. Many
branches emerged from a
common beginning, some
branches died off (extinction),
others branched multiple times
(diversity)
The Nuts and Bolts of Evolution
• Niche:
– A job or activity that is very suitable for someone.
“I have my dream job. I have found my niche in society”
– An environment that has all the things that a
particular form of life needs in order to live.
“The arctic fish have found their niche in cold waters
due to the adaptations in their cell membranes”
• The great diversity of life is the result of over
3.5 billion years of evolution, filling every
available niche with life forms.
Niche: An environment that has all the things that
a particular form of life needs in order to live.
• Discuss with a neighbor a
possible niche for a/an:
•
•
•
•
Elephant
Whale
Bacterium
Cactus
• Why are these life forms able to
fill these niches?
• How have these life forms filled
these niches?
The Origin of Species
Darwin developed two
main ideas:
– Evolution explains
life’s unity and
diversity
– Natural selection is
a cause of adaptive
evolution
Darwin’s
Tree of Life
Is there a connection to this?
Sirenia
Hyracoidea (Manatees
(Hyraxes) and relatives)
Elephas Loxodonta Loxodonta
maximus africana
cyclotis
(Africa)
(Asia)
(Africa)
Figure 22.7
Factors involved in Biological Evolution
interpreted through Observations and Inferences
from On the Origin of Species
Overproduction*
• Most species can (and do!) produce far more
offspring than are needed to maintain the
population.
• Populations remain more or less constant
(“stable”) because a small fraction of offspring
live long enough to reproduce.
Competition*
• Living space and food are limited, so offspring
from each generation must compete among
themselves in order to live.
(Genetic) Variation*
• Characteristics in individuals in any species are
not exactly alike.
• Example: Differences for Homo sapiens can be
exact size or shape of body, strength in running, or
resistance to disease.
Natural Selection*
• Nature (“environment”) selects for living organisms
with better suited inherited traits to survive and
reproduce in that particular environment.
• “Survival of the Fittest” – what does fitness mean?
• Fitness = likelihood of survival AND
reproduction. Both factors must be at play.
Polar Bear
Sun Bear
• For the sun bear (native to SE Asia), long fur is
harmful because the bear will overheat.
○ What does long fur do to a sun bear’s fitness?
• Polar bears use long fur to absorb heat in the cold
arctic environment.
○ What does long fur do to a polar bear’s fitness?
• Think about color…
○ What is the best color for absorbing heat?
○ What is the best color for reflecting heat?
• Traits balance out, resulting in the best fitness possible.
○ Why can’t polar bears be black, even though they would be warmer?
○ Why can’t a sun bear be white, to keep it more cool?
○ The ability to hunt is MORE valuable than color of fur for keeping the
bear alive.
Polar Bear
Sun Bear
Helpful mutations over many generations
=
“Adaptations”
This is why species appear to be adapted to
their environment.
Adaptation
• An adaptation is an inherited trait that
increases an organisms’ chance of survival and
reproduction in a given environment.
– Note: This is where the verbal shortcut of the term
“adapt” is used (painfully) incorrectly.
Speciation
• Over many generations, favorable adaptations
(for a particular environment) gradually
accumulate in a species and “bad” (unfavorable)
ones disappear.
• Eventually, accumulated changes become so
great, the result is a new species.
• Takes many generations. Does that mean it
takes a lot of time? Why or why not?
What’s next?
• Natural selection does not move in a predetermined direction! The changing earth
determines what will and can survive.
The four factors (*)
Biological evolution is a consequence of
4 factors working together. Without all
factors, species change will not occur.
1. Overproduction
2. Competition
3. Genetic Variation
4. Natural Selection
Pencils down for a
class quiz!
Which factors of evolution are
depicted in the following
pictures?
Diagram 1
Diagram 2
Diagram 3
Diagram 4
Key!
Competition
or
Overpopulation
Variation
Speciation
Adaptation
Your Task
• Begin the Lecture Review Questions. You
can work with a group or partner, but write
down your own answers (i.e., in your own
words). Use your notes to help you.
• Due on the day of test review. Don’t
procrastinate!
Modeling Natural Selection
through the
Evolution of
Lemurus
hypotheticus
The Evolution of Lemurus hypotheticus
• Population: The species, Lemurus hypotheticus.
• Environment: Floornchair Rainforest
• Resources: Food = Landing on a Chair
• Variation: The slight differences between
individuals brought to you by mutation and genetic
recombination (aka sexual reproduction)
Simulation:
The Evolution of Lemurus hypotheticus
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
No variation
Monopeds
Opti-nots
Audio-nots
Vertically challenged
Bad SOD
Tunnel Vision
Manual Nots
PITN
Lotsamass