Download Evolution - HHS Biology-Blattman

Change over time
1. Jean Baptiste Lamarck
Lamarck wrote about evolution before
Darwin but his explanations for it were
incorrect.
His ideas were:
a. organisms are born with a desire to change.
(the ancestors to birds wanted to fly)
b. Organisms could change their shape by using
their body differently
(flapping your arms would lead to your arms
becoming wings)
c. acquired traits are inherited
(giraffe example)
Giraffes got long necks by stretching
them to reach food
Over time their necks got longer.
That trait was then passed on to
their offspring.
2. Thomas Malthus
 He studied populations.
 He predicted the end of the world
based on when the number of
people would be greater than the
resources
 Darwin thought this applied to plants and animals
more than humans. Other species produce more
offspring than humans. Most of those will die.
3. James Hutton-geologist
Published an idea about the forces that have
shaped the earth. These processes take a long
time so the earth must be millions of years old.
4. Charles Lyell-geologist
 Said the processes acting on the earth are still
happening. These processes include earthquakes,
volcanoes, erosion, etc.
 Darwin reasoned that this would apply to
organisms as well as the earth.
5. Charles Darwin-(1809-1882)
 Well educated
 Interested in natural history
 graduated from college and took a job as a naturalist
on a ship.
 The ship was called the Beagle and would be gone for 5
years sailing around the world.
 On this journey Darwin made observations and
collected evidence that led him to the theory of
evolution.
Voyage of the Beagle
Several years after his voyage he wrote his book called
“On the Origin of Species”
His ideas included:
a. Organisms have variations and these are
inherited.
b. Artificial selection occurs
when the best organisms
are selected to mate
c. Natural selection occurs
when nature selects the
best to survive
d. Organisms struggle for existence or compete for
resources.
e. The ability to survive and reproduce is the
organism’s fitness. Organisms with the best traits
suited for their environment will survive, those not
best suited will die. This is called survival of the
fittest.
f. Descent with modificationsover time a species will change
and not longer look like its
ancestor.
g. Common descent-all species both living and
extinct came from a common ancestor.
Evidence that supports evolution:
1. Fossils-are the remains of ancient life. Different
layers of rock were formed at different times in
earth’s history. Examining fossils will show how a
species changed over time.
2. Geographic distribution unrelated organisms on different continents will
evolve to be similar if their environments are
similar
 Related organisms will evolve to be different if
their environments are different.
3. Homologous structures-similar structures on
different organisms that have different purposes.
Example: arm bones of bat, human, horse and frog.
4. Vestigial organs-structures that have lost their
purpose.
Examples: tailbone, appendix, ear muscles
5. Embryos-the embryo is
the early stage of development
in the organism. Many embryos
look similar which shows
they have similar DNA.
Examples of natural selection
1. Camouflage-blending in with the environment
 Example: peppered moths
In early 19th century England oak trees had light
bark, moths that were light in color were
camouflaged and not eaten, dark ones were easily
seen and eaten by birds.
 In London after the industrial revolution the trees
were covered with soot from coal and turned dark.
 Now the moths that were selected to survive were
the dark ones.
2. Mimicry-looking like something else to avoid being
eaten.
a. Some try to look like something harmful
example: Monarchs and viceroy butterflies
b. Some harmful organisms look alike to increase the
message that they are bad
example: ants, bees, wasps with yellow and black stripes.
Monarch and Viceroy
good tasting one copies the bad tasting one
Another example of a harmless copying a
harmful
Making the message to avoid “stronger”
3. Isolation-a species becomes reproductively isolated
so that they cannot mate with each other.
There are 3 types:
a. Behavioral-courtship rituals or displays of one
species are not recognized by other species.
b. Geographic-two populations are created by a
physical barrier
Example-Grand Canyon squirrels. They were
originally the same species. They were isolated
from each other when the canyon grew deeper and
now they cannot mate with each other.
c. Temporal- two species reproduce in the same
area but at different times of the year.
Frog on the left mates
January to February
Frog on the right mates
March to May
Evolution and genetics
 A population is a group of the same type of
organisms in the same area.
 Gene pool is all the genes found in the
population.
 Frequency is the number of times that a gene occurs in
the population.
Sources of variation:
1. Mutations-a change in the DNA sequence.
Mutations can effect an organism’s ability to
survive
 2. Gene shuffling-independent assortment and
crossing over, which occurs during the formation
of egg and sperm cells.
 Natural selection works on phenotypes not genes.
Phenotypes will often fit a bell curve when
graphed.
Stabilizing-graph shifts inward
Directional-shifts toward one extreme
Disruptive-shifts to both extremes
Genetic drift-random changes in gene frequency,
occurs just by chance.
example-a small group leaves a large population and
moves to a new area to colonize. Their genes may not
represent the whole population they came from so they
evolve differently.
Gene flow-migration into or out of a population brings in
new traits or may eliminate others.
How fossils form:
1. an organism dies
2. it is covered by layers of sedimentary rock
3. it’s tissues are slowly replaced by minerals
4. it is uncovered.
 Relative dating-determining the age of a fossil by
comparing its depth with that of other fossils in the
area.
 Radioactive dating-Some elements in rocks are
radioactive. These will decay at a predictable rate.
Measuring the rate of decay can determine the age of
fossils in the rock.
 Geologic time represents evolutionary time.
 It is based on rock layers and fossils.
 The Eras are Paleozoic, Mesozoic and Cenozoic.
 Periods divide the Eras
into smaller time units
 Extinction-death of species, they occur naturally all
the time.
 99% of everything that has lived on the earth has
gone extinct.
 Mass extinction-huge numbers disappear at the
same time
Adaptive radiation:
 A single species evolves into several forms.
Convergent evolution:
unrelated organisms evolve to look like each other
Co-evolution:
two organisms evolve to depend on each other closely.
 Examples:
wasp and orchid
cuckoo and warbler
How quickly does evolution takes place?
 Gradualism-changes are slow and steady through
long periods of time.
 Punctuated equilibrium-long periods of time with
no evolution and then big changes occur.