Chapter 6
Evolution
6.1 Fossils
 Fossils provide evidence of earlier life
 The information provided by fossils and
their location in rocks is called the fossil
record.
 The fossil record lets scientists identify
periods during which different species
existed.
6.1 Organisms
 More complex organisms
developed over time
 The first living things
were simple prokaryotes
 As Earth has changed over
time so has the organisms
that live on Earth
6.1 Early Forms of Life
 According to our book Earth was formed
about 4.5 billion years ago.
 The first organisms on earth were
prokaryotes called cyanobacteria.
 Overtime the Earth’s atmosphere changed,
Oxygen increased and other toxic gases
such as methane and ammonia decreased to
allow other organisms to grow.
Cyanobacteria
6.1 Extinctions
 Organism developed on land and in the
ocean.
 Just as organisms can develop and multiply
they can also go extinct.
 Extinction is the loss of all members of a
species.
6.1
 During Earth’s history there have been several
periods when huge numbers of species have
become extinct.
 Mass extinctions are where a large number of
species become extinct in a short period of time.
 The fossil record shows at least 5 mass
extinctions during Earth’s History.
 Of these 5 the Permian and Cretaceous
extinctions are the best studied.
6.1 Permian Extinction
 During the Cambrian period there was a
explosion of new species.
 By the Permian period (286-248 million
years ago), Earth was teeming with species
in the oceans such as corals, jawless fish,
and squid like animals.
6.1 Permian Extinction
 By the end of the Permian period, however,
roughly 95% of the species on Earth had become
extinct.
 The Permian extinction was the largest mass
extinction in Earth’s history.
 Theories on What happened- rise in CO2 levels
and a change in temperature, Volcanic activityash would block the sun, lowering temps
6.1 Cretaceous Extinction
 The start of the Cretaceous period was
about 145 million years ago.
 Earth had recovered from the last mass
extinction.
 Many plants had evolved and animals had
become widespread including the dinosaurs.
6.1 Cretaceous Extinction
 Yet, by the end of this period the dinosaurs were
extinct.
 More than ½ of all other species also vanished.
 Theories on what caused this
Scientists believe a very large object collided with
the Earth and the after effects caused the
extinction (dust clouds- no sun etc)
Impact created a 200 km crater off the coast of
Mexico
Microevolution
 Microevolution is the change in allele
frequencies that occur over time within a
population.
 Changes happens in the current population
due to selection and other pressures.
Macroevolution
 Macroevolution is evolution on a scale of
separated gene pools.
 Macroevolution is the somewhat more
controversial, that requires the introduction
of new genetic information.
6.1 Question: ____provide
evidence of earlier life.




A. DNA
B. Fossils
C. Dreams
D. Plates
6.1 Question: Life on Earth
started out simple (prokaryotes)
 A. True
 B. False
6.1 Question: What is extinction?

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A. Where many species die.
B. Where one squirrel dies.
C. Where 100 squirrels die.
D. Where all gray squirrels die.
6.1 Question: What caused the
Permian extinction?
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A. Large object colliding with Earth
B. Animals committing suicide
C. Volcanic Eruptions
Flooding
6.1 Question: What caused the
Cretaceous extinction?




A. Large object colliding with Earth
B. Animals committing suicide
C. Volcanic Eruptions
Flooding
6.2 Species Change Over Time
 Phones have changed over time.
 Evolution refers to the process through
which species change over time.
6.2 Change
 Scientists began to see that species changed
over time by looking at the fossil record, but
no one was sure how it happened.
 Lamarck was one of the first scientists to take
a guess, he thought animals changed to fit their
environment, for an example giraffes had long
necks because they had to stretch to reach
trees.
 Lamarcks ideas were rejected.
6.2 Darwin
 Charles Darwin served as a naturalist aboard a
British navel ship called the Beagle.
 He traveled for 5 years making observations and
theories on how evolution worked.
 He made many of his discoveries at the Galapagos
Islands.
 He compared plants and animals from different
places.
6.2 Darwin’s Observations
 Darwin observed tortoises on the islands:
He observed that short necked turtles lived
in wet areas and long necked turtles lived in
dry areas.
 Darwin also observed finches on the islands
and noticed they were very similar except
for beak size and shape.
6.2 Darwin
 After the voyage Darwin returned home to
England in 1836 and spent several years
analyzing his observations.
 He published a book about his theories on
evolution.
 Darwin believed that Natural Selection
explains how new species can evolve.
6.2 Natural Selection
 Natural selection is the process through
which members of a species that are best
suited to the environment survive and
reproduce at a higher rate the other
members of the species.
 Darwin based natural selection on 4 key
principles: overproduction, variation,
adaptation, and selection.
6.2 Keys of Natural Selection
Overproduction
 A population is a group of individuals of the
same species.
 In nature, organisms usually produce more
offspring than is needed.
 Example: Salmon produce thousands of eggs but
only a few will hatch- many die from disease or
predators
 Only the best of the best will reproduce
6.2 Keys of Natural Selection
Variation
 In all organisms there are slight variations
(not all squirrels, humans etc are the same.
 We all have genetic variation- differences
in our DNA.
 Genetic variation comes from us getting a
blending of traits from both parents.
6.2 Keys of Natural Selection
Adaptation
 Different traits can offer an advantage in
different environments
 In a fast moving river a slight difference in tail
shape or size can make a big difference. (help
the salmon swim better etc.)
 An inherited trait that gives an organism an
advantage in its environment is called an
adaptation.
6.2 Keys of Natural Selection
Selection
 Environmental factors are conditions that
affect survival.
 They include things like food supply, habitat,
predators, and disease.
 Adaptations help an animal survive and
reproduce getting its genes on to the next
generation. Animals without this benefit are
more likely to die and not reproduce
Choosing of Mates, Getting
Resources
6.2 New Species
 Darwin proposed that new species develop
from earlier species.
 The evolution of a new species from an
existing species is called speciation.
 Today scientists believe that isolation is a
big factor is the development of a new
species.
6.2 Artificial Selection
 Artificial selection is where humans select
animals to breed to get certain traits:
Examples Dogs and pigeons.
6.2 Question: Who is the scientist
who studied evolution?
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A. James Watson
B. Robert Hooke
C. Gregor Mendel
D. Charles Darwin
6.2 Question: Natural selection
is___.
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A. Survival of the Fittest
B. Weak animals living longer
C. Only good animals will live
D. Animals Dying
6.2 Question: What is speciation?
 A. Death of all animals
 B. Evolution of a new species from an
existing species
 C. One species evolves into 3 species
 D. Species compete for food
6.2 Question: What is genetic
variation?
 A. All squirrels have the same DNA
 B. All genes are the same
 C. Differences in DNA among the same
species
 D. All squrriels look alike
6.2 Question: An inherted trait
that gives an organism an
adavantage.
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A. Good genotype
B. Adaptation
C. Awesome thing
D. Environmental factor
6.3 Environmental Changes
 Can a population of beetles just keep
growing??
 Population size is limited by environmental
conditions.
 Darwin noticed that populations have the
ability to grow rapidly over time, and that
populations of organisms tend to remain
about the same size.
6.3 Populations
 Populations need certain resources to
survive (food, water, shelter, etc).
 Populations increase in size through births
and immigration.
 Immigration is the movement of
individuals into a population.
 2 buffalo join the herd or a family from
Canada move to the U.S.
6.3 Factors Limit Population Size
 Death and emigration decrease a
population’s size.
 Emigration is the movement of individuals
out of a population.
 2 penguins move away or 10 U.S. families
move to France.
6.3 Limiting Factors
 Environmental factors that limit population
size are called limiting factors.
 These factors include food, water, space,
shelter, air, other organisms, sudden
changes such as a storm or fire.
6.3 Other Factors
 Competition- How many organisms are
competing for the resources. (# of squirrels
looking for shelter, nuts to eat)
 Predators- animals that prey on other animals
(sharks, hawks, mountain lions etc) They eat other
animals therefore lowering a populations size
6.3 Other Factors
 Disease- Animals and
plants also suffer from
disease. Trees can get
infected by fungus and
die.
 Catastrophic EventsWildfires, hurricanes,
floods, and droughts
can all effect
population size.
6.3 Survival
 The survival of a species depends on its
ability to adapt to change.
 The survival of the fittest – is where the best
animals and plants survive to reproduce.
6.3 Question: What is
immigration?
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A. Animals making new friends
B. Animal death
C. Animals moving into a population
D. Animals moving out of a population
6.3 Question: What is
emmigration?
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A. Animals making new friends
B. Animal death
C. Animals moving into a population
D. Animals moving out of a population
6.3 Question:Environmental
factors (ex disease) that limit a
population szie are called____?
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A. Animal Killers
B. Limting Factors
C. Plague
D. Disease
6.3 Question: Which choices are
examples of limiting factors?
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A. Predators and Competion
B. Disease and catastrophic events
C. Both A and B
D Cars, humans, and houses
6.4 Evidence for Evolution
 Darwin was unsure of his theories at first, it took
him many years to form his conclusions
 Darwin did not publish his book until 20 years
after the voyage on the Beagle.
 A theory is an explanation of natural phenomena
based on a wide range of scientific evidence.
 A theory is widely accepted.
6.4 Evidence
 Evolution doesn’t have
To always mean that we
Came from monkeys,
It can also mean that
Change happens over time
 There are 3 types of evidence that supports
evolution: Fossil, biological, and genetic
evidence.
6.4 Fossil Evidence
 Fossils of extinct animals can resemble
animals that are alive today- elephant and
mammoth
 An ancestor is an early form of an
organism from which a later form descends.
(armadillo and a glypotodon).
 Common ancestors are a key to the theory
of natural selection.
6.4 Biological Evidence
 Two Types of biological evidence existsimilarities in structure and similarities in
development
 Structure- vestigial organs are structures that
were fully developed in ancestral organisms
but are reduced an unused in later species.
 Examples: Whales and snakes have leg-like
bones.
 This suggests a common ancestor
6.4 Biological Evidence cont.
 Development- stages of development of a
chicken, rabbit, and a salamander are very
similar in form.
Genetic Evidence
 Scientists can analyze different organisms
DNA.
 They have found that organisms have
similar DNA and that it functions in much
of the same way.
6.4 Question: ____are structures
that were fully developed in our
ancestors but are reduced or
unused in later species.
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A. Bones
B. Digestive Organs
C. Heart and Lungs
D. Vestigial Organs
6.4 Question: ___shows
similarities in animals function
and structure of body parts. (ex.
Vestigial organ)
 A. Fossil Evidence
 B. Biological Evidence
 C. Genetic Evidence
6.4 Question: ___provides
evidence of evolution by giving
us physical objects to look at and
study. (ex. Bones of a T-rex)
 A. Fossil Evidence
 B. Biological Evidence
 C. Genetic Evidence
6.4 Question: The study of DNA
helps provie____ for evolution.
 A. Fossil Evidence
 B. Biological Evidence
 C. Genetic Evidence