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Ch 5 ( = Ch 3 in 4th ed)
Evolution, Biodiversity, and
Population Ecology
Part 1: Foundations of
Environmental Science
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Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Study Guide
• Natural selection
• How evolution influences
biodiversity
• Reasons for species
extinction
• Ecological organization
• Population characteristics
• Population ecology
Monte Verde Cloud Forest
Costa Rica (~10oN)
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Striking gold in Costa Rica
• Golden toads were
discovered in 1964, in
Monteverde
• The mountainous cloud
forest has a perfect
climate for amphibians
• Unfortunately, they
became extinct within 25
years
- Due to global
warming’s drying
effect on the forest
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Golden Toads at Monte Verde
Evolution:
→ Earth’s biodiversity
A gradual process in which something changes/develops into different form
Biological evolution:
Development of more complicated form of life from earlier & simpler form
through genetic changes in populations of organisms across generations
by natural or artificial selection
A process in which groups of organisms (Species), change and develops through natural
(& artificial) process so that descendants differ morphologically and physiologically,
producing new species (Speciation).
Natural Selection: the process by which traits that enhance
survival and reproduction are passed on more frequently to
future generations than those that do not
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Understanding Evolution is vital:
Basis of Evolution
Individual offspring differs in their genetic characteristics.
Some individuals are better suited to adapt to changing
environment than others, reproducing more; those can’t
adapt to a new environment perish.
It is not the strongest that can survive and dominates.
• It alters the genetic makeup of a population
• It is important for understanding antibiotic and pesticide
resistance, agricultural issues, production, medicines, etc.
• Organisms adapt to their environment and change over
time
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2009, Feb. 12th: 200th Anniversary of C. Darwin
(1809.2.12-1882.4.19)
Feb. 11-16, Annual Conference of AAAS, Chicago.
Theme: “Our Planet and Its Life” Celebrating of Darwinism
Nov. 24th: 150th Anniversary of ”Origins of Species” (1859)
Significance/ Impact:
→ replaced the concept of a Supreme Being & Creation
with a Dynamic Natural Process of Evolution - God derailed.
→ made Science and Christian Religion incompatible.
Strong Influences to
• K. Marx(1818-1883) : Atheistic Materialism - Communism
(“Das Kapital” to Darwin, “Communist Menifesto”)
• H. Spencer(1820-1903): Biologist/Philosopher
Introduced to Sociology & Ethics, “Survival of the Fittest”
• T. Huxley(1825-1895): Botanists, Advocate, Darwin’s Bulldog
• F. Nitzsche(1859-1900): Father of Atheistic Existentialism
• A. Bergsong(1859-1941): Creative Evolution
• J. Dewey(1859-1952): Pragmatism, Evolutionary Naturalist
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Video Assignment: (Media Section in the Library)
“Evolution” WGBH(Boston) Video, 2001, Seven Parts Series
1.
2.
3.
4.
5.
6.
7.
Darwin’s Dangerous Idea
Great Transformation : Assignment
Extinction: Assignment
The Evolutionary Arms Race
Why Sex?
The Mind’s Big Bang
What about God?
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Why some people do not believe Evolution?
How rational are human beings? Blind Belief & Emotions?
Human Life Span (100 yrs) : ~5,000 wks
Human History :
~5,000 yrs
Earth History :
~5,000 M yrs (5 G yrs)
Why many educated people does not believe in the Evolution?
Their scope of the world is extremely limited, without understanding
how old and how vast the universe are → leads to ignorance on the
entire World /Cosmos & its vast Scope.
Time: Earth History - 4,500 M yrs vs. 0.005 M yrs (a millionth, a
negligible fraction)
Space: Earth vs Milky Way (10,000km vs. 100,000 ly, 1017)
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Natural selection shapes organisms
•
In 1858, Darwin and Wallace both proposed natural
selection as the mechanism of evolution
- Organisms face a constant struggle to survive and
reproduce
- Organisms tend to produce more offspring than
can survive
- Individuals of a species vary in their
characteristics due to genes and the environment
- Some individuals are better suited to their
environment and will survive and pass their genes
on in their offspring → Survival of the Fittest
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Natural selection acts on genetic variation
• Directional selection =
drives a feature in one
direction
• Stabilizing selection =
produces intermediate traits,
preserving the status quo
• Disruptive selection =
traits diverge in two or
more directions
If the environment changes, a trait may no longer be adaptive
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Evidence of natural selection is everywhere:
eg., Galapagos Finches
Hawaiian Honeycreepers
• It is evident in
every adaptation of
every organism
• Evident in bacteria
and fruit flies in
laboratories
• Selective breeding
of animals
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Artificial selection
• The process of selection conducted under human direction
- led to the great variety of dog breeds (15,000BP)
- Rice with larger/more grains, Corn with larger kernals.
• Belyaev, Russia, 1950~ : Silver Fox → Domestic Elite Fox (Docile)
~ 35 generations in over 50 yrs ,
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700 (1996), sell them as pet
Evolution generates biodiversity
• Biological Diversity: Variety of life across all levels of
biological organizations
diversity of
species, their genes, their populations, their communities
• Species: a population or group of populations whose
members share characteristics and can freely breed with
one another and produce fertile offspring
~ 1.8 million species reported (can be higher).
• Population: a group of individuals of a species that live in
the same area
• Is mule or liger species ?
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Speciation produces new types of organisms
• The process of generating new
species
- A single species can generate
multiple species
• Allopatric Speciation: species
formation due to physical
separation of populations
- Can be separated by glaciers,
rivers, mountains
- The main mode of species
creation
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Allopatric Speciation
•
1. Single interbreeding
population
•
2. Population divided by a
barrier; subpopulations isolated
Figure 5.2
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Allopatric Speciation (cnt’d)
•
3. The two populations evolve
independently, diverge in their
traits.
•
4. Populations reunited when
barrier removed, but are now
different enough that they don’t
interbreed.
Figure 5.2
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Causes of Allopatric Speciation
• Many geological and climatic events can serve as barriers separating populations
and causing speciation.
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Sympatric speciation
•
3. Fish specialize on different
habitats and foods, and come
to breed separately.
•
4. Mutually exclusive
breeding leads to independent
evolution of traits and
speciation.
Figure 5.3
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Speciation results in diverse life forms
Speciation generates complex patterns of diversity
• Phylogenetic trees (Cladograms) represents the history of
species divergence, showing relationships between species
• Scientists can trace when certain traits evolved
Mya
500, Jawless Fish (Sil.)
350, Amphibians (Dev.)
220, Mammals
(Tri.)
200, Birds
(Jur.)
Branch: Speciation
10~50 My
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Extinction
• Species generally evolve from
simple to complex and small to big,
but the opposite can occur, and
some even disappear
• Extinction : the disappearance of a
species from Earth
- Occurs when a species cannot
adapt quickly enough to a
changing environment
- Speciation and extinction affect
species numbers
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Cambrian Periods: ~530mya
Based on fossils from the
Burgess Shale in Canadian
Rocky
Extinction is a natural process
N. America 12kya before human arrival
• Extinction is irreversible: once a species is lost, it is
lost forever
• Humans profoundly affect rates of extinction
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Some species are more vulnerable to extinction
• Extinction occurs when the environment changes too rapidly for
natural selection to keep up
• Endemic species = a species only exists in a certain, specialized
area
- Very susceptible to extinction
- These species usually have small populations
• Many other factors also cause extinction
- Severe weather
- New species
- Specialized species
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Earth has had several mass extinctions
• Background extinction rate: extinction usually
occurs one species at a time
• Mass extinction events: five events in Earth’s history
that killed off massive numbers of species at once
- 50-95% of all species went extinct at one time
• Humans are causing the sixth mass extinction event
- Resource depletion
- Population growth
- Development
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Species’ ranges can be severely restricted
About 40 U.S. salamander species live on peaks of single mountains
Otter salamander on only a few peaksnin Blue Ridge Mountains
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Ecology: Science of relationship between organisms & environments
.
studied at several levels
• Ecology and evolution are
tightly intertwined
• Biosphere: the total living
things on Earth & the areas
they inhabit
• Ecosystem: communities &
the nonliving material and
forces they interact with
• Community: interacting
species that live in the same
area
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Levels of ecological organization
• Population ecology: investigates the quantitative
dynamics of how individuals within a species interact
• Community ecology: focuses on interactions among
species
• Ecosystem ecology: studies living and nonliving
components of systems to reveal patterns
- Nutrient and energy flows
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Organismal ecology: habitat
• Habitat = the environment in which an organism lives
- Includes living and nonliving elements
- Scale-dependent: from square meters to miles
• Habitat use = each organism thrives in certain
habitats, but not in others
• Habitat selection = the process by which organisms
actively select habitats in which to live
- Availability and quality of habitat are crucial to an
organism’s well-being
- Human developments conflict with this process
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Organismal ecology: niche
• Niche = an organism’s use of resources and its
functional role in a community
- Habitat use, food selection, role in energy and
nutrient flow
- Interactions with other individuals
• Specialists = species with narrow niches and very
specific requirements
- Extremely good at what they do, but vulnerable to
change
• Generalists = species with broad niches that can use a
wide array of habitats and resources
- Able to live in many different places
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Population characteristics
• All populations show
characteristics that help
scientists predict their
future dynamics
• Population size : the
number of individual
organisms present at a
given time
- Numbers can increase,
decrease, cycle or
remain the same
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(end 9/17/08)
Population characteristics
• Population density = the number of individuals within a
population per unit area
- High densities make it easier to find mates, but
increase competition, and vulnerability to predation
- Low densities make it harder to find mates, but
individuals enjoy plentiful resources and space
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(start 9/23/08)
Population characteristics: Age Structure Diagram
• Sex ratio = proportion of males to females
- In monogamous species, a 50/50 sex ratio maximizes
population growth
• Age Structure = the relative numbers of organisms of each
age within a population
- Age structure diagrams (pyramids) = show the age
structure of populations
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Four factors of population change
• Natality = births within the population
• Mortality = deaths within the population
• Immigration = arrival of individuals from outside the
population
• Emigration = departure of individuals from the
population
• Growth rate formula =
(Crude birth rate + immigration rate) - (Crude death rate
+ emigration rate) = Growth rate
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Exponential population growth
• Steady growth rates cause
exponential population
growth
- Something increases by a
fixed percent
- Graphed as a J-shaped
curve
• Exponential growth cannot be
sustained indefinitely
- It occurs in nature with a
small population and ideal
conditions
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Limiting factors restrain growth
• Limiting factors = physical, chemical and
biological characteristics that restrain
population growth
- Water, space, food, predators, and disease
• Environmental resistance = All limiting
factors taken together
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Carrying capacity
• Carrying capacity = the
maximum population size
of a species that its
environment can sustain
- An S-shaped logistic
growth curve
- Limiting factors slow
and stop exponential
growth
• Carrying capacity changes
Humans have raised their carrying capacity by decreasing the
carrying capacity for other species
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The “J “ curve
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The “ S “ curve
Perfect logistic curves aren’t often found
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Computer simulations predict the future
• Simulations project trends in
population, food, pollution, and
resource availability
• If the world does not change,
population and production will
suddenly decrease
• In a sustainable world,
population levels off,
production and resources
stabilize, and pollution declines
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Oct 31st, 2011
7 Billion
Jan, 2012
7 Billion
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Biotic potential and reproductive strategies
vary
• Biotic potential = the ability of an organism to produce
offspring
• K-selected species = animals with long gestation periods
and few offspring
- Have a low biotic potential
- Stabilize at or near carrying capacity
- Good competitors
• r-selected species = animals which reproduce quickly
- Have a high biotic potential
- Little parental care
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K-selected vs. r-selected species
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Population changes affect communities
• As population in one species declines, other species may
appear
• Human development now displaces other species and
threatens biodiversity
- As Monteverde dried out, species from lower, drier
habitats appeared
- But, species from the cloud-forest habitats disappeared
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Preserving biodiversity
• Natural parks and protected areas help preserve
biodiversity
- Often, they are underfunded
- Ecotourism brings jobs and money to developing
areas: Madagascar, some part of Indonesia,
Amazon, etc.
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QUESTION: Review
Which of the following is NOT a part of the process of
natural selection?
a) Organisms struggle to survive
b) Organisms limit the number of young they produce
c) Individuals vary in their genetic characteristics
d) Some individuals are better suited to their
environment than others
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QUESTION: Review
Disruptive selection would result in which of the following?
a) Dogs with black coats evolving whiter coats in
colder areas
b) Red and white flowers interbreeding, producing pink
flowers
c) Fish evolving bigger eyes as the water gets muddier
d) A population of birds, some with thicker beaks that
eat seeds and others with thinner beaks that eat
insects
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QUESTION: Review
Biological diversity includes all of the following, except:
a) Species diversity
b) Genetic diversity
c) Population diversity
d) Community diversity
e) All of these are included in the concept of
biodiversity
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QUESTION: Review
Sympatric speciation would occur in ....
a) One population that mates in May, and another
that mates in June
b) Two populations separated by the Mississippi
River
c) Two populations separated by a glacier
d) Two populations separated by the Rocky
Mountains
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QUESTION: Review
Which of these species is least vulnerable to extinction?
a) A species with a population size of 50 individuals
b) A species distributed throughout the United States
c) A species that eats only river snails
d) A species that lives on mountaintops
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QUESTION: Review
An ecosystem is defined as:
a) The total living things on Earth
b) Members of the same population that can interbreed
c) Interacting species in an area
d) Species and the nonliving material they interact
with
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QUESTION: Viewpoints
Should we care whether a species goes extinct?
a) Yes, because all life is important and valuable
b) Yes, because we are causing this wave of
extinction, so we should fix it
c) We should not, because it’s natural
d) I don’t care; it really does not affect me
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QUESTION: Viewpoints
Do you think humans are subject to limiting factors and,
ultimately, a fixed carrying capacity?
a) Yes, although we have raised the carrying capacity,
there are limits to the number of humans the Earth
can support
b) Yes, but technology will keep raising the carrying
capacity, so it’s not much of a problem
c) No, humans are no longer constrained by
environmental limits, due to our technology and
ability to manipulate the environment
d) I don’t care; it really does not affect me
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QUESTION: Interpreting Graphs and Data
Which of the following graphs shows a population that will
have fewer individuals in the future?
(a)
(b)
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(c)
(d)
QUESTION: Interpreting Graphs and Data
Which type of distribution is a
result of individuals guarding
their territory?
a) Random
b) Uniform
c) Clumped
d) None of these
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QUESTION: Interpreting Graphs and Data
What does this graph show?
a) The effects of
carrying capacity
on population
growth
b) A population that
keeps growing
c) The effects of
exponential growth
d) The effects of
increasing carrying
capacity
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