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Biodiversity refers to the variety of organisms
and their genetic diversity on our planet
Today over 1.5 million living and 300,000 extinct
species have been named and described
With this tremendous amount of diversity the
question becomes “Why or how are there so
many forms of life on our planet?”
The answer to this question is evolution
Today biologists use the process of evolution to
explain the diversity and relationships of life on
our planet
Biological evolution explains the diversity of life
The fossil record gives evidence for natural
selection and its evolutionary consequences
Organisms can be classified based on
evolutionary relationships
The similarity of DNA (genetic) sequences gives
evidence of relationships between organisms
The extinction of species can be a natural
Biological evolution explains the
diversity of life
Evolution or descent with modification explains how
the gene pools of species or populations change over
time leading to the development of new species and
therefore diversity of life
These are members of different species - These are members of different species –
eastern (left) and western (right) meadowlark.
Biologists have described several
mechanisms that lead to changes
They include:
 Mutations
 Gene recombination
 Gene flow
 Genetic drift
 Natural Selection
Nature produces variations within
members of the same species or
population which can result in
uneven advantages in their ability
to survive
Over time this can result in the
change in the gene pool of a
This process can lead to enough
change that over time a new
species appears
New species means increased
Darwin’s theory was based on four
1. Variations exist among individuals
within the same species.
2. All organisms produce more
offspring that are able to survive.
3. Competition for space, food, other
survival needs leads to the elimination
of some organisms of each population.
4. The organisms that have variations
which enable them to survive within
their environment and through
competition, are the ones most likely
to survive and reproduce, thereby
passing their characteristics on to their
offspring (survival of the fittest, or
natural selection)
1. Natural selection can best be defined as the
a. survival of the biggest and strongest organisms in a population
b. elimination of the smallest organisms by the biggest organisms
c. survival and reproduction of the organisms that occupy the largest area
d. survival and reproduction of the organisms that are genetically best adapted
2. The major unifying concept in biology that provides for an explanation for the vast diversity of life on
our planet is
a. the theory of evolution.
b. the cell theory.
c. the classification theorem.
d. gene-chromosome theorem.
3. In the illustration to the right, which answer best explains the difference
in the length of the animals’ necks?
a. The theory of use and disuse.
b. The change in gene pool due to mutation.
c. The theory of natural selection.
d. The desire for organisms to change and adapt.
4. Genetic variations are the raw material for evolution. These variations cannot be acted upon by natural
selection unless
a. they are expressed in the phenotype of the organism.
b. they produce only unfavorable characteristics.
c. they produce only favorable characteristics.
d. they are expressed in non-sex cells.
The study of fossils is called paleontology
The study of rocks and land formations is called
Fossils are the remains of once living organisms
The most common types of fossils form when
shells, bones, or other parts of organisms are
rapidly covered with layers of sediment
Fossils are found in sedimentary rocks
Sedimentary rock forms in layers
Different types of fossils are found in different aged layers
of rock
Therefore, the fossil record supports evolutionary theory by
providing evidence that organisms that have lived in the
past did change over time
This is evidence that the kinds of plants and animals, and
other organisms have changed over time and is called the
Law of Fossil Succession
1. Why is a mammoth more likely to fossilize than a caterpillar?
a. hard parts such as bones and teeth fossilize easier than soft
b. mammoths lived a long time ago and caterpillars live today.
c. large organisms tend to fossilize easier than small organisms.
d. caterpillars have too short of a life span for fossilization to
2. Some organisms never become fossils because
a. they live in water environments where no fossils form.
b. they are destroyed after death so nothing remains to be
c. a hard shells prevent fossilization from occurring.
d. there are no minerals in the soil where the organism dies.
4. Which of the following is one reason that fossils from all organisms
where ever alive will NEVER be found?
a. organisms moved from one place to another, so the location of some
fossils will never be found.
b. some parts of the world have never had sedimentary rock, and
therefore fossils could not form
c. some animals consume fossils and therefore, there are none left to be
d. many organisms that have lived had no hard solid structures that
survived long enough to be fossilized.
5. Several fossils were uncovered in different layers of rock in a desert
area. The following diagram indicates the fossils found and the layers
they were found in.
Based on the fossils found, this area was most likely once a
a. forest that was replaced by a lake
b. lake that was replaced by a forest
c. an ocean that was replaced by a forest
d. a lake that was replaced by a desert.
Similarity of DNA sequences gives
evidence of relationships
The building blocks, called nucleotides, that make up the DNA
in all organisms are the same: A, T, G, and C
It is the sequence of these nucleotides, and ultimately the number,
type, and sequence of genes that makes one organism different
from another
DNA of many organisms and the similarity between DNA
samples is used to determine relationships between organisms
Organisms can be classified based
on evolutionary relationships
Because biological evolution involves genetic changes (mutations) over
time, the evolutionary relationship of organisms can be determined by
comparing DNA
Different species with very similar DNA more recently descended from
a common ancestor than did species with very different DNA
Because DNA codes for the production of proteins, comparison of
proteins between species also provides evolutionary relationships
between organisms
Organisms can be classified into groups based
on morphological, behavioral, and evolutionary
Classifying organisms is important to scientists
as it provides a framework and a common
“language” which enables scientists everywhere
to study and understand more about life on
Taxonomy is the science of classification
Scientists currently recognize 3
The Linnean system of classification
Domain, Kingdom, Phylum, Class,
Order, Family, Genus, Species
Category Domestic cat
Domain Eucarya
Kingdom Animalia (animals)
Phylum/Division Chordata (chordates)
Class Mammalia (mammals)
Order Carnivoria (carnivores)
Family Felidae (cats)
Genus Felis
Species silvestris
1. A horse and a donkey may interbreed with each
other and produce offspring. The offspring are
generally sterile, however, because the horse and
the donkey are of different
a. orders
b. kingdoms
c. species
d. phyla
2. The following illustration represents a
phylogenetic tree which includes several different
organisms. Based upon this diagram, which of the
following groups of organisms have the closest
evolutionary relationship?
a. mammals and lizards
b. mammals and frogs
c. lungfish and frogs
d. lizards and snakes
3. Which of the following would provide the best data for
determining the phylogeny (evolutionary history) of three very
closely related species?
a. fossil records
b. comparison of anatomical structures
c. comparisons of their scientific names
d. comparison of DNA sequences
4. Which of the following characteristics did Linnaeus use to
classify organisms?
a. DNA similarities
b. Environments in which the organisms lived
c. The color of the fur, skin, or feathers
d. Shape, size and structure
The extinction of species can be a
natural process
Extinctions occur “often” in evolutionary
Scientists estimate that more than 90% of the
species that have lived on earth are probably
Most extinctions occur due to selective nature
of the species
The fossil record provides evidence that
background extinctions regularly occur
throughout time
Scientific studies show another type of
extinction in which massive numbers of species
become extinct in a short period of time
These are called mass extinctions
There are 5 recognizable periods of mass
extinction in the earth’s history
There are several theories as to the cause of the
mass extinctions, most of which hypothesize
that major climatic and environmental changes
occurred globally
A graph of invertebrate extinctions over the last 600 million years.
The mass extinctions appear as periodic peaks rising above the background extinction levels. This
data is from the work of D. M. Raup and J. J. Sepkoski.
The extinction of a species can occur through
the process of evolution
Extinction by natural causes may be due either
to actual death of a species or due to evolution
of the species into one or more different species
Evidence from the fossil records substantiates
that many species have become extinct and new
species have developed over time
Many scientists believe that Earth may be in a
6th mass extinction phase, as many species are
going extinct every day
1. Which of the following has NOT been implicated as contributing to mass
a. volcano eruptions
b. changes in ocean water level
c. major hurricanes
d. asteroid impact
2. What percent of species that have ever lived on earth are probably extinct?
a. 28%
b. 52%
c. 77%
d. 90%
3. Which of the following does NOT likely contribute to background
a. evolution through natural selection
b. destruction of a habitat due to natural or human cause
c. interbreeding between species
d. changes in local environmental conditions
4. The following diagram illustrates numbers of extinctions that
have occurred over time. What is the highest rate of background
extinction indicated in this diagram?
a. 10 families per million years
b. 7 families per million years
c. 17 families per million years
d. 5 families per million years