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Evolution and
Biodiversity
Overview Questions
 How
do scientists account for the
development of life on earth?
 What is biological evolution by natural
selection, and how can it account for the
current diversity of organisms on the earth?
 How can geologic processes, climate change
and catastrophes affect biological evolution?
 What is an ecological niche, and how does it
help a population adapt to changing the
environmental conditions?
Overview Questions (cont’d)
 How
do extinction of species and formation of
new species affect biodiversity?
 What is the future of evolution, and what role
should humans play in this future?
 How did we become such a powerful species
in a short time?
Rest assured, you are not alone!
Core Case Study
Earth: The Just-Right, Adaptable
Planet
 During
the 3.7 billion
years since life
arose, the average
surface temperature
of the earth has
remained within the
range of 10-20oC.
Figure 4-1
In the Beginning…according to Science

Chemical Evolution- (hypothesis) the first
organic (life forming) molecules formed from
inorganic molecules and energy; formed
protocells

Lightening; Heat (geothermal); Radiation (UV-sun)
Produced by Stanley Miller and Harold Urey

Biological Evolution-the change in a
populations’ genetic make-up through
successive generations (takes time; not on an
individual basis)

Evidence from fossils (comparative anatomy) and
DNA
ORIGINS OF LIFE
1
billion years of chemical change to form the
first cells, followed by about 3.7 billion years
of biological change.
Figure 4-2
Biological
Evolution
 This
has led to
the variety of
species we
find on the
earth today.
Figure 4-2
Modern humans (Homo
sapiens sapiens) appear
about 2 seconds before
midnight
Age of
mammals
Age of
reptiles
Insects and
amphibians
invade the
land
Recorded human history
begins about 1/4 second
before midnight
Origin of life
(3.6-3.8 billion
years ago)
First fossil
record of
animals
Plants
begin
invading
land
Evolution and
expansion of life
Fig. 4-3, p. 84
How Do We Know Which Organisms
Lived in the Past?
 Our
knowledge
about past life
comes from fossils,
chemical analysis,
cores drilled out of
buried ice, and DNA
analysis.
Figure 4-4
EVOLUTION, NATURAL
SELECTION, AND ADAPTATION
 Biological
evolution by natural selection
involves the change in a population’s genetic
makeup through successive generations.


genetic variability
Mutations: random changes in the structure or
number of DNA molecules in a cell that can be
inherited by offspring.
The Theory Evolution
Evolution Theory- the idea that all species
descended from earlier, ancestral species


Gene Pool- a populations’ genetic make-up (all
the genes found in the individuals in a population)



Explains HOW life has changed and why life is so diverse
Microevolution- small genetic changes that
occur in a population
Macroevolution- long-term, large scale
changes; cause 2 outcomes:
1)
2)
New species are formed from ancestral species
Other species are lost through extinction
How Evolution Occurs
 Mutation-
a random change in the structure (alleles)
or number of DNA molecules in a cell; 99% fatal;
Mutagens-radiation (gama, x-ray, UV) or natural or manmade chemicals
2. Abnormalities- mistakes made during the copy process
when cells divide or during reproduction
1.
 Natural
Selection- the process through which some
individuals exhibit traits that increase their chances of
survival and ability to produce offspring; 3 required
conditions
Variability of trait in species
2. Must be heritable, able to be passed from one generation
to another
3. Differential Reproduction- increase the number of
offspring or survivability of offspring of an individual
1.
Adaptation

Natural Selections Causes (1) alleles or sets of alleles
that are beneficial to become more common in
successive generations and (2) other less beneficial
alleles to become less common

Adaptation- the improved ability of an
organism to survive and reproduce; a specific
trait that increases these chances is called and
adaptive trait; often caused by the
environment and do one of the following:
1.
2.
3.
Species adapt through natural selection
Migrate to another area
Become extinct
Natural Selection and Adaptation:
Leaving More Offspring With
Beneficial Traits
 Three
conditions are necessary for biological
evolution:

Genetic variability, traits must be heritable, trait
must lead to differential reproduction.
 An
adaptive trait is any heritable trait that
enables an organism to survive through
natural selection and reproduce better under
prevailing environmental conditions.
Snail coloration
best adapted
to conditions
Average
New average
Natural
selection
Previous
average
Number of individuals
Number of individuals
Directional Natural Selection
Average shifts
Coloration of snails
Coloration of snails
Proportion of light-colored
snails in population increases
Directional Selection
Light snails
eliminated
Dark snails
eliminated
Natural
selection
Number of individuals
Number of individuals
Stabilizing Natural Selection
Snails with
extreme
coloration are
eliminated
Coloration of snails
Coloration of snails
Average remains the same,
but the number of individuals with
intermediate coloration increases
Stabilizing Selection
Intermediate-colored snails
are selected against
Light
coloration
is favored
Dark
coloration
is favored
Natural
selection
Number of individuals
Number of individuals
Diversifying Natural Selection
Snails with light and dark
colors dominate
Coloration of snails
Coloration of snails
Number of individuals
with light and dark coloration
increases, and the number with
intermediate coloration decreases
Disruptive Selection
Natural Selection

Coevolution- the
hypothesis that the
population of two
interacting species
(over a long-term) can
cause changes in the
gene pool that affect
changes in the gene
pool of the other
species
Fig. 5-5 p. 101
Coevolution: A Biological Arms Race
 Interacting
species can engage in a back and
forth genetic contest in which each gains a
temporary genetic advantage over the other.

This often happens between predators and prey
species.
Hybridization and Gene Swapping:
other Ways to Exchange Genes
 New

species can arise through hybridization.
Occurs when individuals to two distinct species
crossbreed to produce an fertile offspring.
 Some
species (mostly microorganisms) can
exchange genes without sexual reproduction.

Horizontal gene transfer
Limits on Adaptation through
Natural Selection
A
population’s ability to adapt to new
environmental conditions through natural
selection is limited by its gene pool and how
fast it can reproduce.

Humans have a relatively slow generation time
(decades) and output (# of young) versus some
other species.
Common Myths about Evolution
through Natural Selection
 Evolution
through natural selection is about
the most descendants.


Organisms do not develop certain traits because
they need them.
There is no such thing as genetic perfection.
GEOLOGIC PROCESSES, CLIMATE
CHANGE, CATASTROPHES, AND
EVOLUTION
 The
movement of solid (tectonic) plates
making up the earth’s surface, volcanic
eruptions, and earthquakes can wipe out
existing species and help form new ones.


The locations of continents and oceanic basins
influence climate.
The movement of continents have allowed
species to move.
225 million years ago
65 million years ago
135 million years ago
Present
Fig. 4-5, p. 88
Climate Change and Natural
Selection
 Changes
in climate throughout the earth’s
history have shifted where plants and
animals can live.
Figure 4-6
Catastrophes and Natural Selection
 Asteroids
and meteorites hitting the earth and
upheavals of the earth from geologic
processes have wiped out large numbers of
species and created evolutionary
opportunities by natural selection of new
species.
ECOLOGICAL NICHES AND
ADAPTATION
 Each
species in an ecosystem has a specific
role or way of life.


Fundamental niche: the full potential range of
physical, chemical, and biological conditions and
resources a species could theoretically use.
Realized niche: to survive and avoid
competition, a species usually occupies only part
of its fundamental niche.
Generalist and Specialist Species:
Broad and Narrow Niches
 Generalist
species tolerate
a wide range of
conditions.
 Specialist
species can
only tolerate a
narrow range of
conditions.
Figure 4-7
SPOTLIGHT
Cockroaches: Nature’s Ultimate
Survivors
 350
million years old
 3,500 different species
 Ultimate generalist



Can eat almost anything.
Can live and breed almost
anywhere.
Can withstand massive
radiation.
Figure 4-A
Specialized Feeding Niches
 Resource
partitioning reduces competition
and allows sharing of limited resources.
Figure 4-8
Avocet sweeps bill through
mud and surface water in
search of small crustaceans,
insects, and seeds
Ruddy
turnstone
Herring gull is a
searches
tireless scavenger
under shells
and pebbles
Dowitcher probes deeply
for small
into mud in search of
invertebrates
snails, marine worms,
and small crustaceans
Brown pelican
dives for fish,
which it locates
from the air
Black skimmer
seizes small fish
at water surface
Louisiana heron wades into
water to seize small fish
Flamingo
feeds on
minute
organisms
in mud
Scaup and other
diving ducks feed
on mollusks,
crustaceans,and
aquatic vegetation
(Birds not drawn to scale)
Oystercatcher feeds on
clams, mussels, and
other shellfish into which
it pries its narrow beak
Piping plover feeds
on insects and tiny
crustaceans on
sandy beaches
Knot (a sandpiper)
picks up worms and
small crustaceans left
by receding tide
Fig. 4-8, pp. 90-91
Evolutionary Divergence
 Each
species has a
beak specialized to
take advantage of
certain types of
food resource.
Figure 4-9
SPECIATION, EXTINCTION, AND
BIODIVERSITY
 Speciation:
A new species can arise when
member of a population become isolated for
a long period of time.

Genetic makeup changes, preventing them from
producing fertile offspring with the original
population if reunited.
Speciation, Extinction, and Biodiversity
 Speciation
 Geographic isolation
 Reproductive isolation
Geographic Isolation
 …can
lead to reproductive isolation,
divergence of gene pools and speciation.
Figure 4-10
Extinction: Lights Out
 Extinction
occurs
when the
population
cannot adapt to
changing
environmental
conditions.
The
golden toad of Costa Rica’s
Monteverde cloud forest has
become extinct because of
changes in climate.
Figure 4-11
Extinction
 Background extinction- due to
environmental changes; occurs slowly
 Mass extinction- catastrophic and or
widespread;
 Adaptive radiation- occurs just after a
mass extinction when many niches are
available in the changed environment
Cenozoic
Era
Period
Millions of
years ago
Quaternary
Today
Tertiary
65
Mesozoic
Cretaceous
Jurassic
180
Triassic
Species and families
experiencing
mass extinction
Extinction Current extinction crisis caused
by human activities. Many species
are expected to become extinct
Extinction within the next 50–100 years.
Cretaceous: up to 80% of ruling
reptiles (dinosaurs); many marine
species including many
foraminiferans and mollusks.
Extinction
Triassic: 35% of animal families,
including many reptiles and marine
mollusks.
Bar width represents relative
number of living species
250
Extinction
345
Extinction
Permian
Paleozoic
Carboniferous
Devonian
Permian: 90% of animal families,
including over 95% of marine
species; many trees, amphibians,
most bryozoans and brachiopods,
all trilobites.
Devonian: 30% of animal
families, including agnathan and
placoderm fishes and many
trilobites.
Silurian
Ordovician
Cambrian
500
Extinction
Ordovician: 50% of animal
families, including many
trilobites.
Fig. 4-12, p. 93
Effects of Humans on Biodiversity
 The
scientific consensus is that human
activities are decreasing the earth’s
biodiversity.
Figure 4-13
GENETIC ENGINEERING AND THE
FUTURE OF EVOLUTION
 We
have used artificial selection to change
the genetic characteristics of populations with
similar genes through selective breeding.
 We
have used
genetic engineering
to transfer genes
from one species to
another.
Figure 4-15
Genetic Engineering:
Genetically Modified Organisms (GMO)
 GMOs
use
recombinant
DNA

genes or portions
of genes from
different
organisms.
Figure 4-14
Phase 1
Make Modified Gene
E. coli
Cell
Extract DNA
Gene of
interest
DNA
Identify and
Identify and
remove portion
extract gene
of DNA with
with desired trait
desired trait
Extract
Plasmid
Genetically
modified
plasmid
Insert modified
plasmid into E. coli
Plasmid
Remove
Insert extracted
plasmid
(step 2) into plasmid
from DNA of
(step 3)
E. coli
Grow in tissue
culture to
make copies
Fig. 4-14, p. 95
Phase 2
Make Transgenic Cell
E. Coli A. tumefaciens
(agrobacterium)
Foreign DNA
Plant cell
Host DNA
Nucleus
Transfer plasmid
copies to a carrier
agrobacterium
Transfer plasmid to
surface of microscopic
metal particle
Agrobacterium inserts
foreign DNA into plant cell
to yield transgenic cell
Use gene gun to inject
DNA into plant cell
Fig. 4-14, p. 95
Phase 3
Grow Genetically Engineered Plant
Transgenic cell
from Phase 2
Cell division of
transgenic cells
Culture cells
to form plantlets
Transfer
to soil
Transgenic plants
with new traits
Fig. 4-14, p. 95
Phase 3
Grow Genetically
Engineered Plant
Transgenic cell
from Phase 2
Cell division of
transgenic cells
Culture cells
to form plantlets
Transfer to soil
Transgenic plants
with new traits
Stepped Art
Fig. 4-14, p. 95
How Would You Vote?
 Should
we legalize the production of human
clones if a reasonably safe technology for
doing so becomes available?


a. No. Human cloning will lead to widespread
human rights abuses and further overpopulation.
b. Yes. People would benefit with longer and
healthier lives.
THE FUTURE OF EVOLUTION
 Biologists
are learning to rebuild organisms
from their cell components and to clone
organisms.

Cloning has lead to high miscarriage rates, rapid
aging, organ defects.
 Genetic
engineering can help improve human
condition, but results are not always
predictable.

Do not know where the new gene will be located
in the DNA molecule’s structure and how that will
affect the organism.
Controversy Over
Genetic Engineering
 There
are a number of privacy, ethical, legal
and environmental issues.
 Should genetic engineering and development
be regulated?
 What are the long-term environmental
consequences?
Case Study:
How Did We Become Such a Powerful
Species so Quickly?
 We



lack:
strength, speed, agility.
weapons (claws, fangs), protection (shell).
poor hearing and vision.
 We
have thrived as a species because of
our:

opposable thumbs, ability to walk upright,
complex brains (problem solving).