Download Evolution

1. What does the word “theory”
mean in everyday language?
2. What does the word “theory” mean
in science?
3. What is evolution?
Evolution
• Evolution is JUST a theory?
• Theories are the single highest level of
scientific achievement and nothing is just a
theory.
Evolution
• Evolution: A Change Over Time
• Essential Questions:
• How can there be so many similarities among
organisms yet so many different kinds of
plants, animals, and microorganisms?
• How does biodiversity affect humans?
Evolution
Theory in Science
• In science, theories are statements or models
that have been tested and confirmed many times.
• Theories have some important properties:
They explain a wide variety of data and observations.
They can be used to make predictions.
 They are not absolute.
They serve as a model of understanding the world
and can be changed as the world view changes.
Evolution
• Some questions that can be answered by
evolution.
• Why do so many different animals have the
same structures?
– The arm bones in a human are the same bones as
a flipper in a whale.
Evolution
Some questions that can be answered by
evolution.
• Why do organisms have structures they no
longer use, like the appendix or tailbone in a
human ?
Evolution
Some questions that can be answered by
evolution.
• Why are there bones and fossil
evidence of creatures that no
longer exist? What happened to
these
creatures?
Evolution
Some questions that can be answered by
evolution.
• Why is the sequence of DNA very similar in
some groups of organisms but not in others.
Evolution
Some questions that can
be answered by
evolution.
• Why do the embryos of
animals look very
similar at an early
stage?
Evolution
• The Theory of Evolution is considered a
Unifying Theory of Biology, because it
answers many of these questions and
offers an explanation for the data.
Evolution
• Evolution begins with variation.
• NO VARIATION = NO EVOLUTION
Evolution
What is variation? What causes variation?
• Mutation
• Sex
• Migration
Evolution
• 1. Mutations may:
•
•
•
•
A.
B.
C.
D.
Have positive effects
Have negative effects
Have no effect
All of the above
Evolution
2. Whether a mutation is positive or
negative depends on the location of the
mutation in the genome:
A. True
B. False
Evolution
• 3.
Whether a mutation is positive or negative
depends on the environment that the
organism lives in.
A. True
B. False
Evolution
•
•
•
•
Which of the following statements is false:
A. Mutations occur all the time.
B. Everyone has mutations.
C. Mutations always lead to a decrease in
success of the organism.
• D. Mutations can be caused by a variety of
factors.
Evolution
• Meiosis and fertilization allow for great diversity
in sexual species compared to asexual species.
• In evolutionary terms, sex is more important than
life itself. Sex fuels evolutionary change by
adding variation to the gene pool. The powerful
urge to pass our genes on to the next generation
has likely changed the face of human culture in
ways we're only beginning to understand.
Evolution
• Traits can be positive, negative or neutral in a
given environment.
• The alleles coding for negative traits are likely
to be reduced in the presence of alleles for
more favorable ones.
Evolution
• Biologically speaking, what is “success?”
• Success is passing on your genes to offspring.
Evolution
• Essential requirements for Evolution
• 2 Variation: All life forms vary genetically within a
population. It is this genetic variation upon which
selection works.
• 2 Inheritance: Genetic traits are inherited from
parents and are passed on to offspring.
• 2 Selection: Organisms with traits that are favorable to
their survival get to live and pass on their genes to the
next generation.
• 2 Time: Evolution takes time. Evolution can happen in
a few generations, but major change, such as
speciation, often takes long periods of time.
Evolution
• When you think of Evolution what person
comes to mind?
CHARLES DARWIN
Evolution
CHARLES DARWIN – 1809-1882
• English naturalist and geologist
• He established that all species of life have descended
over time from common ancestors
• Published his theory of evolution with compelling
evidence in his 1859 book: “On the Origin of Species,
overcoming scientific rejection of earlier concepts of
transmutation of species.”
• His five-year voyage on HMS Beagle established him as
an eminent geologist and publication of his journal of the
voyage made him famous as a popular author.
Evolution
Voyage of the HMS Beagle
Stopped in Galapagos Islands 500 miles off coast
of Ecuador.
Evolution
• What’s so important about the Galapagos
Islands?
• First, because they are extremely isolated, the
Galapagos Islands are home for dozens of
species of both plants and animals found
nowhere else in the world.
Evolution
The Galapagos
Tortoise is the
largest reptile
found anywhere
on the planet,
and it lives
longer than any
animal known to
man.
Evolution
• Second, Darwin’s visit to
the Galapagos for five
weeks in 1835 provided
the starting point for
the development of his
theory of natural
selection.
Evolution
• Darwin found many
unique species
• Many of Darwin’s
observations made him
wonder... Why?
• Darwin asked:
• Why were these
creatures found only
on the Galapagos
Islands?
Evolution
• Darwin found clues in the fossils
– He found evidence that organisms have
changed over time.
• Darwin asked:
• Why should extinct armadillos & modern
armadillos be found on same continent?
Evolution
• Two important and unexpected patterns:
1. Traits exhibited by species
– Galapagos finches had different beaks than
finches on the mainland.
Evolution
2. Similarity between the fossils of extinct
species and the living species in that same
area.
Evolution
• The Book that Would “Rock the World”
q In 1842, Darwin finally hammered out a first draft
of his ideas.
q In a letter to a close friend, he wrote “At last
gleams of light have come, and I am almost
convinced (quite contrary to the opinion I started
with) that species are not immutable.”
q The book spent 14 years in a drawer.
q A letter from another scientist, Alfred Wallace,
prompted Darwin to finally publish the book.
Ideas About Evolution
Before Darwin’s book:
1. Organisms were all placed on Earth at the same
time by a Creator.
2. Organisms are fixed– no
additions or subtractions.
3. Earth is about 6,000 years old.
4. Earth is mostly unchanging.
Ideas about Evolution
• After publication of Darwin’s book:
1.
2.
3.
4.
Organisms change over time.
Some organisms have gone extinct.
Earth is over 6,000 years old.
The geology of earth is not
constant – it is always
changing.
Earlier Ideas About Evolution
• LaMarck: Earlier ideas on
Evolution
• – evolution by acquired traits
– creatures developed traits during their lifetime give those traits to their offspring
– example: in reaching higher
leaves, giraffes stretch their necks & give the
acquired longer neck to offspring
Evolution
LaMarck: Earlier ideas on Evolution
– Evolution by acquired traits
• creatures developed traits during
their lifetime - give those traits to
their offspring
– example: in reaching higher
leaves, giraffes stretch their necks &
give the acquired longer neck to
offspring
This idea has been refuted!!
Evolution
• Darwin’s view of Evolution
– giraffes that already have long necks survive
better
– leave more offspring who inherit their long necks
• variation
• selection & survival
• reproduction &
inheritance of
more fit traits
Evolution
They, in turn, pass their favorable traits to
their offspring.
 The offspring are then more likely to survive.
As the process of natural selection goes on
over many generations, species change.
Evolution
•Evolution is a change in
allele frequencies within
a population.
Evolution
Individuals do NOT evolve.
Populations evolve
 Allele frequencies
change
Evolution
Agents of Evolutionary Change
1. Mutation
2. Natural selection and sexual selection
3. Migration
• Evolution is genetic change in a population.
Agents of Evolutionary change
MUTATION
Mutation is the
ultimate source of
genetic variation in
a population.
Agents of Evolutionary Change
2. NATURAL SELECTION
A process where
organisms with traits well
suited to an environment
are more likely to survive
and produce more
offspring than organisms
without these favorable
traits.
Evolution
• When three simple conditions are satisfied,
evolution by natural selection occurs.
1. There must be variation for the particular trait
within a population.
2. That variation must be inheritable.
3. Individuals with one version of the trait must
produce more offspring than those with a different
version of the trait.
Variation
SEXUAL SELECTION
• A special type of natural
selection that acts on an
organism’s ability to
obtain or successfully
copulate with a mate.
• This process may produce
traits that seem to
decrease an organism’s
chance of survival, while
increasing its chances of
mating.
What drives Natural Selection?
1.
2.
3.
4.
Overproduction
Competition
Variations
Survival of the fit
What Drives Natural Selection?
1. Overproduction
 Organisms produce
more offspring than
the environment
can support.
There is not enough
food or living space
for all the offspring.
What drives Natural Selection?
2. Competition
 Overproduction leads to a
struggle.
 All the organisms
compete for food, water,
and the other necessities
of life.
 Only those organisms that
are well suited to their
surroundings survive and
reproduce.
 The rest die.
What drives Natural Selection?
3. Variations
Organisms of the same
species are very similar.
But they do have
individual differences
among traits, or
variations.
These differences are
important in the “struggle
for survival.”
What drives Natural Selection?
For example, extra speed
can mean the difference
between life and death. A
fast wildebeest may
escape an attacking lion. A
slower neighbor may
become the lion’s next
meal.
What Drives Natural Selection?
4. Survival of the Fit
 Organisms with traits
that make them well
adapted, or suited to the
environment, survive
and reproduce.
 Darwin used the term
natural selection to
describe the survival of
organisms with favorable
traits.
Fitness
 Definition: how good a
particular genotype is at
leaving offspring in the
next generation relative
to how good other
genotypes are at it.
 Depends on the
environment in which
the organism lives.
Fitness
Who has a
higher fitness?
Discussion Questions:
1. What does the word fitness mean?
2. Is calling good or bad for a cricket's
fitness?
3. Give some examples of selection
at work in this cricket story.
4. How does selection favor calling?
How does selection favor not calling?