Changes Over Time
SOL: BIO 8 a-e
• Standard BIO 8 a-e
The student will
investigate and understand how populations
change through time. Key concepts include:
• a) evidence found in fossil records;
• b) how genetic variation, reproductive
strategies, and environmental pressures
impact the survival of populations;
• c) how natural selection leads to
adaptations;
• d) emergence of new species; and
• e) scientific explanations for biological
evolution.
Charles Darwin
The Father of Evolution
History
•
•
•
Darwin’s World (1809 - 1875)
Height of the British colonial period.
Beginning of the Industrial
Revolution.
• New Ideas:
– Taxonomy of Carolus Linnaeus
– Lyell’s “Principles of Geology”
Binomial
System of
Nomenclature
Carolus Linnaeus
(1707 – 1778)
Believed in the
“Fixity of Species”
Charles Lyell
• Father of Geology
Charles Lyell’s view of the process of formation of
sedimentary rock
• Suggests that sedimentary rock is
very old – therefore the species that
are represented in this rock must
also be old.
• Most fossils are found in sedimentary
rock.
• Older fossils will be found below
younger fossils.
Charles Darwin
At the age of 22,
he joined a 5 year
expedition aboard
the HMS Beagle to
map the coast of
South America
The voyage of the Beagle
Charles Darwin’s Theory
of Evolution:
1. Members of a
population have
heritable
variations.
(Inheritance of
traits)
2. In a population, more individuals are
produced than the environment can
support. They compete for food and
shelter. (overpopulation- struggle for
survival).
3. Some individuals have adaptive
characteristics that enable them to
survive and reproduce better than other
individuals (survival of the fittest).
4. An increasing number of
individuals in succeeding generations
have these adaptive characteristics
(natural selection)
Darwin described his theory in the form
of a long essay which he called
“On the Origin of Species”.
Concerned about the public’s response
to his ideas
(remember what happened to Galileo)
Arranged to publish his work …
AFTER HIS DEATH !!
Publication of “On The Origin of Species”
in 1859
Charles Darwin
At age 50 (1859)
At age 65 (1874)
Charles Darwin
Before publication
After publication
• Through his observations made in the
Galapagos Islands, Charles Darwin
formulated a theory of how species
change over time, called natural
selection.
• Natural selection is governed by the
principles of genetics.
• The change in the frequency of a
gene in a given population leads to a
change in a population and may result
in the emergence of a new species.
• Natural selection operates on
populations over many generations.
Evolution
• A change in successive generations of
organisms, due to random mutation
and changes in the organisms’
surroundings
• Evolution takes place
through a set of
processes that
include:
–
–
–
–
mutation,
adaptation,
natural selection,
extinction.
Mutation
• Genetic mutations and variety
produced by sexual reproduction allow
for diversity within a given population.
• Many factors can cause a change in a
gene over time.
Mutation
• Mutations are
important in how
populations
change over time
because they
result in genetic
changes to the
gene pool.
• Mutations are inheritable changes
because a mutation is a change in the
DNA code
Mutation- a change in the DNA
A mutation may
result in a:
1. favorable change or
adaptation in genetic
information that
improves a species’
ability to exist in its
environment
Mutation- a change in the DNA
2. an unfavorable
change that does
not improve a
species’ ability to
exist in its
environment.
Mutation- a change in the DNA
3. in a change in the
genetic information
that neither harms
nor helps the
species.
Adaptation
• Adaptations are structures,
functions, or behaviors that enable a
species to survive.
Adaptation
• Depending on the rate of
adaptation, the rate of
reproduction, and the
environmental factors
present, structural
adaptations may take
millions of years to
develop.
Natural Selection
• the survival and reproduction of the
individuals in a population that exhibit
the traits that best enable them to
survive in their environment.
• The Survival of the Fittest
Natural Selection
• Populations produce more offspring
than the environment can support.
Natural Selection
• The unequal ability
of individuals to
survive and
reproduce leads to
the gradual change
in a population,
generation after
generation over
many generations.
Natural Selection
• Organisms with
certain genetic
variations will be
favored to
survive and pass
their variations
on to the next
generation.
• These five canine species evolved from a
common ancestor through natural selection
Jackal
African wild
dog
Fox
Thousands to
millions of years
of natural selection
Ancestral
canine
Wolf
Coyote
When humans choose organisms with
specific characteristics as breeding
stock, they are performing the role of
the environment
• This is called “artificial selection”
Example of artificial
selection in plants: five
vegetables derived from
wild mustard
Artificial Selection in Animals: Dog Breeding
German
shepherd
Yorkshire terrier
English springer
spaniel
Hundreds to
thousands of years
of breeding
(artificial selection)
Ancestral dog
Mini-dachshund
Golden retriever
The evolution of insecticide resistance is an
example of natural selection in action
Chromosome with gene
conferring resistance
to insecticide
Additional
applications of the
same insecticide will
be less effective, and
the frequency of
resistant insects in
the population
will grow
Insecticide
application
Survivor
Extinction
• no longer in existence; "the extinction
of a species"
• If a species does not include traits
that enable it to survive in its
environment or to survive changes in
the environment, then the species
may become extinct.
Individuals die, a
species becomes
extinct.
• Individuals of a
population exhibit a
range of variations
in a trait as a result
of the variations in
their genetic codes.
No gene
Variation in
these
generations
Human
genetic
variation
• The evidence for evolution is drawn
from a variety of sources of data,
including:
–
–
–
–
–
the fossil record,
radiometric dating,
genetic information,
the distribution of organisms,
anatomical and developmental
similarities across species.
Fossil Record
• Although there is not a complete
record of ancient life for the past
3.5 billion years, a great deal of
modern knowledge about the history
of life comes from the fossil record.
• The study of fossils provides strong
evidence for evolution.
Hominid skulls
Petrified Trees
Ammonite casts
Fossilized organic
matter in a leaf
Scorpion in amber
“Ice Man”
Distribution of species
• Most marsupials
live in Australia
• This supports
the theory of
continental drift.
Distribution of species
Geographic isolation can lead to speciation
Species
• Organisms that
can breed and
produce FERTILE
offspring.
Adaptive Radiation
• where species all
deriving from a
common ancestor
have over time
successfully
adapted to their
environment via
natural selection
Homologous Structures
• Body parts in different organisms
that have similar bones and similar
arrangements of muscles, blood
vessels, and nerves and undergo
similar embryological development,
but do not necessarily serve the same
function; e.g., the flipper of a whale
and the forelimb of a horse.
Homologous Structures
Human
Cat
Whale
Bat
Vestigial Structures
• Features that apparently serve no
function in an organism and are
allegedly holdovers from an
evolutionary past. Such features,
though no longer useful, are presumed
to have been useful in ancestral
species.
EX.: Wings in
flightless birds
EX.: appendix
in humans,
whale pelvis,
tiny snake
pelvic and limb
bones, and the
eyes in cavedwelling
salamanders
and fish that
are completely
blind.
Developmental Similarities
• Many species have very similar
embryonic development.
• The embryo of a chicken, a pig, and a
fish are almost identical at certain
points in their development.
• Stephen Jay Gould’s idea
of punctuated equilibrium
proposes that organisms
may undergo rapid (in
geologic time) bursts of
speciation followed by long
periods of time unchanged.
• This view is in contrast to
the traditional
evolutionary view of
gradual and continuous
change