Download Evolution, Biological Communities, and Biodiversity

Evolution, Biological Communities, and
Biodiversity
Evolution Produces Species Diversity
• What are species?
• How do species evolve?
• Why do some species live in one place and not another?
Natural selection
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Survival of more advantageous traits
Don't confuse “more advantageous” with “better”
Better for survival at that time and in that place
Not universally better.
Genetic Change:
Mutation
• Exposure to
radiation
• 'Typos' or errors in
DNA replication
Evolution is not a "Red in Tooth-and-Nail"
Process
• Competition is only one factor in evolution
• Competition is not always violent
• Its often about getting to a resource faster, etc
• Cooperation can be an effective technique for
adaptation and survival
Selection pressures
• Physiological stress (moisture, light, temp, pH,
etc)
• Competition among species
• Predation
• Luck
Physiological Stress: Tolerance limits
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Range within which species can survive
Many factors, each with corresponding ranges
Example: salt level, moisture, temperature, etc
Alpine Tree Line
(Banff Nat Park - Canada)
Critical Factor
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Many organisms have a limited geographical
distribution because of a single factor
 Saguaro
cactus range is strictly limited by
temperature
Penguin movie as an example of agedefined tolerance limits

Penguins live all over the place but give birth in
specific places because babies couldn't survive
in other adult habitats
Species as indicators
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Reflect certain
conditions of the
environment and
ecosystem dynamics
Trout
Bull thistle
Defenseless
creatures
Scars of Evolution
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We get the impression of
perfect adaptation to
habitat
Many characteristics are
“left over” from previous
survival strategies
In humans: toes,
goosebumps
Speciation – the source of
Biological Diversity
• Eventual split of a single species into more than
one
• Directional selection (ex: adaptation to toxins)
• Stabilizing selection (narrow the range of a trait)
• Disruptive selection (ex: Darwin's finches)
“If Evolution Is
True, Why Isn't It
Still Going on
Today?”
Evolution as Ongoing
• It's gradual, imperceptible except with rapidly
reproducing species
• We can see evolution happen in
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Fruit flies
Anti-bacteria-resistant bacteria
Pesticide-resistant insects
drug-resistant microbes
• Useful for bioremediation
Critical View of Species Taxonomy
• This system is for:
• ease of communication
between scientists
• display in museums
• not the only possible
categorization scheme
Species Interactions Shape Biological
Communities
• How do species interact?
• How do these interactions shape ecosystems?
Survival Strategies
Survival Strategies - Generalist vs
specialist
• Generalist (like a rat or cockroach) has a large
niche, but with lots of competitors
• Specialist (like Panda) has a small niche with
few competitors
• Strategy affects reproductive characteristics,
food habits, population size, and vulnerability
to change
Reducing Competition
• Interspecific competition
• Developing better strategies for resource use
• Specialization
• Intraspecific competition
• Young dispersal
• Territoriality
• Intergenerational partitioning
Competitive Exclusion
• The idea that competitive species can't coexist
for long
• The less-skilled/adapted species must find a
different niche or die out
• Resource partitioning “makes room”
Strategies
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Producers
Consumers
 Predators
(herbivores, carnivores, etc)
 Non-predators (scavengers, decomposers, etc)

Predator-mediated competition
 Predators
keeping successful populations in check
Predatormediated
competition
Predator-prey relationship influences
speciation
Predator-prey relationship influences
speciation
Conceptualizing the environment
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Environmental systems: a network of
interactions
In terms of scale: Large scale (global
environment) or small scale (fish bowl)
As flows and storage: processes that change
over time.
As a closed or steady state: Mapping these
flows from a distance creates the illusion of
“balance” which leads to the idea of
“environmental health.”
Ecosystem Resilience
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Constancy (lack of fluctuation in composition or
function)
Inertia (resistance to external influences or
“wobble”)
Renewal (ability to repair after 'damage')
Complexity
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Refers to the number of species in each trophic
level and the number of trophic levels
(trophic level: step in the flow of energy through
an ecosystem – something like a step in the
food chain)
Tropical rainforests
Ecological Structure

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Spatial distribution of individuals and
populations within a community
Three basic configurations
 Random
 Uniform
(territorial bird species)
 Clumped
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(schools of fish or stands of trees)
Ultimately bound by nutrient/water/energy
availability
Random Distribution
Uniform Distribution
Clumped Distribution
Two Models for Understanding
Ecological Communities
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Equilibrium model
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Non-equilibrium model
Equilibrium Model of Ecosystem
Communities
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Ecosystems tend toward a stable climax
community
A series of stages, each more complex,
develops from a starting point, following
disturbance
Disturbance under
the equilibrium model
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Any event or process that disrupts established
patterns
Both human-induced and 'natural'
Pioneer species
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Capable of colonizing harsh environments
quickly
Build up soil
Annuals and biennials often don't need a lot of
soil
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Seeds disperse easily
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Generalists
Second-stage succession
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Perennials (grasses, herbs, shrubs, trees)
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Specialists
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Theoretically, stability and complexity develop
over time
Non-Equilibrium Ecosystem Model
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Because conditions of evolution are constantly
changing, ecosystems are unpredictable
The stability of any particular configuration is an
illusion resulting from a narrow frame of
reference
Any ecological configuration is dependent on a
unique historical set of events
Over the long term, perceived patterns like
equilibrium become meaningless
Disturbance under
the non-equilibrium model

What counts as disturbance changes depending
on the scale of analysis
 Both

in terms of time and space
Disturbance is an inherent part of ecosystem
functioning
 Helps
lesser competitors by having a greater effect
on supercompetitors
Forms of Disturbance
'Natural' Disturbance
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Landslide
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Earthquake
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Fire
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Stampede
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Tree fall
Human induced disturbance
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Logging
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Farming
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Forestry practices
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Urban growth and other land conversion
Fire prevention in the US
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Informed by
equilibrium model and
organismal view
Also by economic
desire (for timber)
Creates highly
flammable landscapes
Controlled burns now a
common practice
Fire as Disturbance
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Many species take
advantage of fire
(e.g. Manzanita)
Depend on frequent
fires for survival
 To
clear competitors
 Prepare
 Enrich
seeds
soil
Introduced Species as Disturbance
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Most often, introduced species fail to survive or
are incorporated harmlessly
Occasionally an outside species is able to
outcompete all other organisms in a niche
Wide-ranging effects of invasive species
 Extinctions
 Changes
of other organisms
in landscape
 Overpopulation
and damage to crops
Complicating the idea of Introduced
Species
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Scale is again an important factor
Succession is often a case of new species
coming in to outcompete others
What might really be going on
 our
desire for a particular ecological configuration
 The
(temporal/spatial) scale at which we understand
'ecosystem' defines what is invasive
Deer – Invasive or Not?
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Cause damage similar to many “foreign” species
 Landscape
 Over
population
 Extinction
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change
of other organisms
Deer aren't foreign – deer problem is a result of
eradication of predators and land conversion
to agriculture and "sprawl" by humans
Disturbance at Ecosystem
Boundaries
Edges and Boundaries
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Ecosystem boundaries are called ecotones
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Energy often flows across boundaries
 Some
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birds are a good example of this
The greater the flow of energy (crossing of
organisms) the more “open” the ecosystem
This flow of energy can disrupt ecosystem
functions
This disruption is called edge effect
Habitat Fragmentation
Habitat fragmentation threatens ecosystems by
creating too much edge
Biomes
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Biomes – broad general categories characterized
by their general climatic characteristics and the
kinds of organisms that thrive there
Biomes have changed and moved many times
during the history of life on Earth. More recently,
human activities have drastically altered these
communities.
By understanding different biomes, we can
understand the impacts of human activity on them
Tropical Forest Biome
Tropical Seasonal
Forest Biome
Savanna and Tropical Grasslands
Desert Biome
Sahara
Desert
Sonoran Desert
Temperate Grasslands
Temperate and Boreal Forests
Tundra
Freshwater Ecosystems
Wetlands
Oceans
Coasts
Coral Reefs
Deltas and Estuaries
Biodiversity
Genetic Diversity
Ecological Diversity
Species Diversity
Biodiversity of Species
What We Know:
1.5 Million known species
At least 1.5 million have not been
identified –
Maybe as Many as 50 Million
Why the discrepancy?
Hot Spots:
Places of high biodiversity
High numbers of endemic species
Seriously threatened
Hot Spots:
1.4% of the Earth's Land Surface
but
About Half of All Known Plant and
Animal Species
Hot Spots:
Contain 3/4 of the world's most
threatened mammals, amphibians,
and birds
Hot Spots:
Hotspots don't cover much land, but
have a lot of species, including most
of those that are in danger of
extinction
Limits of Hot Spot Conservation:
• ignores intact/non-threatened
areas, which also contain
threatened, endemic species
• doesn't address cultural survival,
which is often linked with
biodiversity
Why does Biodiversity Matter?
Food
Medicine
Recovery from disturbance
Ecological Services
Aesthetics
1. Food
Small groups of people derive most
of their food from biodiverse sites
Important for diversification of diet
globally
2. Medicine
50% of all medicine is derived from
wild species
Highly effective in treating childhood
leukemia
3. Recovery from Disturbance
Ecosystem Resilience
Constancy
Inertia
Renewal
Constancy:
(lack of fluctuation in composition or
function)
Inertia:
(resistance to external influences or
“wobble”)
Renewal:
(ability to restore functioning after
disturbance)
Greater Biodiversity
means
More Resilient Ecosystems
4. Ecological Services
Maintenance of soil
Purification of air and water
Pollination of crops
•Colony Collapse Disorder
1/3 of global food output depends on animal
pollination
Between 80% and 90% of pollination is done by
domesticated bees
5. Aesthetics
For some people, it's just nice to
know “it's there”
6. E.O. Wilson and Hotspots
Survival of hotspots enables ecological
recovery after global trauma
Some believe that the sixth Great
Extinction is being cause by human
beings
Why is biodiversity being lost?
Extinction
=
Loss of biodiversity
Anthropogenic (human-induced)
causes of extinction
Habitat Destruction
Invasive Species
Pollution
Population
Overharvesting
Habitat Destruction
Invasive Species
Pollution
Population
Overharvesting
Habitat Destruction
Fragmentation
Reefs destroyed by cyanide, traps, and
dynamite.
Overharvesting
Passenger Pigeon
(Extinct Sept 1, 1914)
Hunting "keystone" species
Bycatch
Everything surrounding a Mexican trawlerman's hands will
go to waste; he will sell only the shrimp.
Species-based solutions to
Biodiversity Loss
Hunting and Fishing Laws
Endangered Species Act
Convention on International Trade in
Endangered Species (CITES)
Captive Breeding Programs
Restriction of hunting and fishing in late
1800s
Mainly to preserve species for game
Endangered Species Act (US)(1973)
Regulates 'taking', import/export,
commerce, and transport
Protects Critical Habitat (essential for
a species' survival), public or private
Fraught with Controversy
• What is protected and why?
• List of new species of slow
• Lack of funding (leading to the 'warranted but
precluded' designation)
• Conservation on private lands
What gets protected?
"Charismatic" species are overrepresented
Privileges mammals over other
forms of life
Special Categories
• Keystone species
• Indicator species
• Umbrella species (require large areas of land to
survive. Protecting them means protecting others)
• Flagship species (attract support and motivate the
public)
Should we spend money to save ugly
creatures, bacteria and parasites?
How many can we save? What
determines the answer?
How many should we try to save?
Is this the best way to go about
things?
Another Political Challenge:
Conservation on Private Lands
Critical Habitat designation
supersedes ownership
Rural property owners are often demeaned
as a 'backwards' or anti-environmental
But land is part of people's livelihood, and
owners might not be compensated for lost
economic potential
Controversy over removal from the list
Pro: removal from list highlights
success
Con: exposes species to threats
Difficulty of Preserving Biodiversity in
"Third World"
Third World Debt
• 1970s energy crisis
• Oil shortage
• High energy prices required
world nations to
borrow from World Bank/IMF at high interest
rd
3
• Debt is difficult or impossible to pay off
• Often partially forgiven in exchange for
privatization and opening markets (esp in the
case of socialist states)
Preserving Nature
in the Third World:
Debt-for-nature swaps
• Conservation groups buy a country's debt in the
form of reduced bonds
• Debt is 'forgiven' in exchange for a commitment
to preserve forests, etc
Debt-for-nature problems
• Doesn't overcome the underlying insecurity of
Third World Nations
• Accounts for a tiny portion of debt (book
example: $650,000 paid off. $1 trillion is owed)