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DARWIN’S THEORY OF EVOLUTION
I.
THE PUZZLE OF LIFE’S DIVERSITY
i. BIOLOGICAL DIVERSITY –
1. How did all these different organisms arise?
2. How are they related?
3. What scientific explanation can account for the diversity of life?
a.
ii. EVOLUTION –
iii. THEORY –
•
BRAIN TEASER
a. VOYAGE OF THE BEAGLE a. Darwin would collect plant and animal specimens at each port
b. Study and record information
b. DARWIN’S OBSERVATIONS
a. In 1 day in the Brazilian forest Darwin collected 68 different beetle species
b. Patterns of diversity
i. Plants and animals seemed remarkably well suited to whatever environment they
inhabited
1. WHY WERE NO RABBITS IN AUSTRALIA DESPITE THE PRESENCE OF
HABITATS THAT SEEMED PERFECT FOR THEM?
2. WHY WERE THERE NO KANGAROOS IN ENGLAND?
c. Living organisms and fossils
i. Fossils –
1. WHY HAD SO MANY OF THESE SPECIES DISAPPEARED?
2. HOW WERE THEY RELATED TO LIVING SPECIES?
d. Galapagos Island
i. Different islands, close together, very different climates
1. Hot dry barren
a. WHAT TRAITS DO YOU THINK AN ANIMAL MIGHT NEED TO
SURVIVE ON A HOT DRY ROCKY ISLAND?
i.
2. Sparse vegetation
3. Rainfall, different assortment of plants and animals
4. Rich vegetation for tortoise to reach
a. WHAT TRAITS DO YOU THINK AN ANIMAL MIGHT NEED TO
SURVIVE ON A RICH VEGETATED ISLAND?
i.
5. Tortoises varied from island to island
a. Picture pg. 371
e. The journey home
i. After returning Darwin began to wonder if animals living on different islands had
once been members of the same species?
1.
4. What is a fossil?
a.
5. Darwin found fossils of many organisms that were different from any living species. How would this
finding have affected his estimates of biological diversity?
a.
Continued………Part II
II.
IDEAS THAT SHAPED DARWIN’S THINKING
• People believed all forms of life and earth had been created only a
few thousand years ago
• Since creation nothing hand changed, example a robin today looks
and sounds like a robin from the beginning of time
• Fossils found????????? WHAT DID SUCH FOSSIL EVIDENCE
INDICATE ABOUT LIFE IN THE PAST??
1.
b. AN ANCIET CHANGING EARTH
i. JAMES HUTTON AND CHARLES LYELL
1. Together, Hutton and Lyell helped scientists recognize the earth is millions of years
old, the process that changed earth in the past are the same processes that operate in
the present.
ii. Hutton’s Theory of Geological change, 1795
1. Layers of rock are moved by forces beneath earths surface
a. Pushed up from seafloor to make mountains
b. Rocks shaped by natural forces, rain, heat and cold temperature, this weathers
rock extremely slow
c. Proposed earth to be much more then a few thousand years old
iii. Lyell’s
1. Scientists must explain past events in terms of processes that they can actually observe,
since process that shaped the earth millions of years ago continue in the present
2. Darwin witnessed a volcanic eruption
3. Darwin wrote about an earthquake
a. ? If we saw these things what can we explain about geology?
b. ? If the earth could change overtime, might life change as well?
c. Thought: Lyell realized that it would have taken many, many years for life to
change in the way he suggested, this would have been possible only if the
Earth were extremely old.
c. Lamarcks Theory of Evolution
1. Among the first scientists to recognize that living things change over time, and that
all species were descended from other species
2.
3. Lamarck proposed that by selective use or disuse of organs, organisms acquired certain
traits during their lifetime. These traits could then be passed on to one’s offspring’s.
Overtime this process led to change in a species.
a. Figure 15.7 and explanation!!!
ii. Tendency towards perfection
1. All organisms trying to be perfect
a. Example –
iii. Use and Disuse
1. Organisms could altar shape or size of particular organs by using their bodies in new
ways.
a. Example –
iv. Inheritance of acquired traits
1. Example –
a. ? If you became a body builder would your children have muscles when they
are born???
v. Evaluating Lamarck’s theory
1. Incorrect, an animals behavior and activity have no effect on it’s inheritable
characteristics adapted to environment
a. BUILDING SCIENCE SKILLS
• Challenge students to design an experiment to test lamarck’s theory
of the inheritance of acquired traits. Students’ experimental designs
should include a hypothesis, procedure, and possible outcomes. Ask:
WHAT SPECIES WOULD YOU USE, AND WHAT VARIABLE
WOULD YOU TEST?
1.
2.
vi. Population Growth
1. 1798, Thomas Malthus observed that babies were being born faster than people dying
2. Malthus reasoned that if the human population continued to grow unchecked, sooner
or later there would be insufficient living space and food for everyone
3. ? WHAT WORKS AGAINST GROWTH?
a.
4. Darwin noticed this worked more strongly with plants and animals than humans.
a. ? WHY DO HUMANS PRODUCE FEWER OFFSPRING?
5. Malthus formed his theory by studying factors that control the population growth of humans. How might factors
operating on organisms in nature differ from those of Malthus theory?
Continued Part III…..
III.
Darwin Presents his case
i. Darwin returned 1836 with lots of specimens
ii. His mocking birds resulted in 3 separate species found no where else in the world
iii. Birds he thought were wrens, warbles, and blackbirds were all finches and found no where else
iv. Tortoises, marine iguanas
b. Publication of “On the origin of Species”
i. He wrote in notebooks his findings, but did not publish
1. Discussion: Darwin’s reluctance to publish his work is a good example of how science
is influenced by its social context.
a. Question: what current areas of scientific research are controversial, much as
evolution was controversial in Darwin’s time?
•
ii. 1858, Darwin received an essay from Alfred Russell Wallace, it summarized thoughts on
evolutionary change that Darwin had been mulling over for 25 years, Darwin published 18
months later, “On the origin of Species”
c. Natural Variation and Artificial Selection
i. Natural Variation –
1.
Example –
2. some cows give more milk, some plants bear larger fruits these traits can be inherited
3. farmers would use selective breeding to determine which natural variation that they
found,
a. example
ii. Artificial Selection –
1.
How is this used today?
d. Evolution by Natural Selection
i. The struggle for existence
1. Darwin was convinced that a process like artificial selection worked in nature
a. Struggle for existence
•
•
Prey that are faster, better camouflaged or better protected can
avoid being caught
Predators that are faster or outsmart the prey can catch more prey
ii. Survival of the fittest
1. how well suited an organism is to its environment
2. fitness –
3. adaptation –
4. figure 15 – 12 statement and over head
5. survival of the fittest –
6. Natural Selection –
a. Overtime, natural selection causes a change in the inherited characteristics of a
population. It directs these changes in ways that increase a species fitness in its
environment
b. ?What did Darwin mean when he described certain organisms as “more fit”
than others?
•
iii. Descent with modification
1. Each living species has descended with changes from other species over time
a. All living organisms are related to one another
• Back in time ancestors were shared by tigers, panthers, and cheetahs
2. Common descent –
a. Tree of life –
iv. Evidence of evolution
1. Darwin argued that living things have been evolving on earth for millions of years.
Evidence for this process could be found in the fossil record, the geographical
distribution of living species, homologous structures of living organisms, and
similarities in early development.
a. Fossil record
•
Different layers of rock had bee formed at different times in earths
history
1. figure 15.13 overhead
a. ? what are the major changes that occurred as these
cephalopods evolved
i.
b. Geographic distribution of living species
• ? why can two species that look very different from each other be
more closely related than two other species that look similar to each
other?
1.
c. Homologous body structures
• Similarities among body parts of animals with backbones
1. the limbs differ greatly in form and function, yet they are all
constructed from the same basic bones.
a. Over head forelimbs of vertebrates
b. ?what similarities in the limbs suggest that they
developed from the same basic structure?
i. The number and placement of the bones
c. ?what are some major changes in bone structure that
occurred as these vertebrates evolved along different
paths?
d. ?what is the scientific explanation for these similarities?
i. Each of these limbs has adapted in ways that
enable organisms to survive and reproduce in
different ways in different environments.
• Homologous structures –
•
Vestigial organs –
1.
?How might vestigial organs provide clues to an animal’s
evolutionary history?
a.
2. ? How can biologists use the idea of homologous structures to
determine whether particular species are closely related?
a.
d. Similarities in Early Development
• Overhead comparing vertebrate embryo development
1. ?why might you expect the embryos of fishes to be more
similar to the embryos of sharks than to the embryos of
humans?
a.
v. Summary of Darwin’s theory
1. Individual organisms in nature differ from one another. Some of this variation is
inherited
a. Example – Due to where the animals live they will have to adapt to their area,
leave or will die
2. Organisms in nature produce more offspring than can survive, and many of those that
survive do not reproduce
a. Example – Arthropoda, Animals that are on the bottom of the food chain.
3. More organisms are produced than can survive. Members of each species must
compete for limited resources
a. Example – To many bunney rabbits, only the strong, fastests, and smartests
will be able to get the food that is available, the others will die!!
4. Because each organism is unique, each has different advantages and disadvantages in
the struggle for existence
a. Example – Hummingbirds have long beaks which allow them to get nectar
from certain flowers, hawks have strong beaks which allow them to rip flesh.
5. Individuals best suited to their environment survive and reproduce most successfully.
The characteristics that make them best suited to their environment are passed on to
offspring. Individuals whose characteristics are not as well suited to their environment
die or leave fewer offspring.
a. Example – Survival of the fittests
6. Species change over time. Over long periods, natural selection causes changes in the
characteristics of species, such as in size and form. New species form, and other species
disappear.
a. Example – mutations!! If a mutation is beneficial it will allow that animal to
reproduce, sometimes reproduce often with many mates which allows for
many offspring – some with the mutation.
7. Species alive today have descended with modifications from species that lived in the
past.
a. Example – fossil records
8. All organisms on Earth are united into a single tree of life.
a. Example – We all have DNA, we make protein the same way. When sperm
and egg are first brought together the first cells all make the same parts of the
body.