Chapter 4
Ecosystems and Living Organisms
Case Study:
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Where did all the aspen trees go?
How did the park rangers/biologists work
to find an answer to this question?
What happens when a top predator is
removed from an ecosystem?
How do you feel about “the solution” to
Yellowstone’s problem? Did it improve the
environment?
Re-introduction of Wolves to
Yellowstone
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Discussion of National Geographic article
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Put your desks in a circle please!
Overview of Chapter 4
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Evolution
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Biological Communities
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Primary & Secondary Succession
Symbiosis
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Natural Selection
Domains and Kingdoms
Mutualism, Commensalism, Parasitism
Predation & Competition
Resource Partitioning
Keystone Species
Species Richness & Community Stability
Evolution
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The cumulative genetic changes that occur
in a population of organisms over time
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Current theories were proposed by Charles
Darwin, a 19th century naturalist
Evolution occurs through natural selection
Natural Selection
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Individuals with more favorable genetic traits
are more likely to survive and reproduce
Frequency of favorable traits increase in
subsequent generations
Natural Selection
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Based on four observations about the
natural world
1.
Overproduction
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2.
Variation
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3.
Individuals in a population exhibit variation
Limits on Population Growth
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4.
Each species produces more offspring than will
survive to maturity
Resource limitations will keep population in check
Differential Reproductive Success
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Individuals with most favorable traits are more
likely to reproduce
Natural
Selection
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Darwin’s finches
exemplified the
variation
associated with
natural selection
Domains and Kingdoms of Life
Biological Communities
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Communities vary greatly in size and lack
precise boundaries
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They are often nestled within each other
Succession
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The process where a community develops
slowly through a series of species
Earlier species alter the environment in
some way to make it more habitable by
other species
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As more species arrive, the earlier species are
outcompeted and replaced
Two types of succession
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Primary succession
Secondary succession
Primary Succession
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Succession that begins in a previously
uninhabited environment
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No soil is present!
Ex: bare rocks, cooled lava fields, etc.
General Succession Pattern
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Lichen secrete acids that crumble the rock
(soil begins to form)
Lichen
mosses
grasses
shrubs
forests
1
3
2
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Primary Succession
1.
2.
3.
Bare rock with lichen
Grasses and shrubs
Forest community
Secondary Succession
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Succession that begins in an environment
following destruction of all or part of the
earlier community
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Does NOT follow primary succession!
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Ex: abandoned farmland, open area after fire
Even though name may imply this
Generally occurs more rapidly than primary
succession
Secondary Succession
of an abandoned farm
field in North Carolina
How do organisms interact?
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Activity with partners
Interactions Among Organisms
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Symbiosis
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An intimate relationship between members of
2 or more species
Participants may be benefited, harmed or
unaffected by the relationship
Results of coevolution
Three types of symbiosis
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Mutualism
Commensalism
Parasitism
Mutualism
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Symbiotic relationship in which both
members benefit
Ex: Mycorrihzal fungi and plant roots
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Fungus grows around and into roots providing
roots with otherwise unavailable nitrogen from
soil
Roots provide fungi with food produced by
photosynthesis in the plant
Left: root growth
without fungi
Right: root growth
with fungi
Commensalism
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Symbiotic relationship where one species
benefits and the other is neither harmed nor
helped
Ex: epiphytes and tropical trees
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Epiphytes anchors
itself to the tree,
but does not take
nutrients from the
tree
Epiphyte benefits
from getting closer
to sunlight,
tropical tree is not
affected
Parasitism
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Symbiotic relationship in which one species
is benefited and the other is harmed
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Parasites rarely kill their hosts
Ex: Varroa mites
and honeybees
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Mites live in the
breathing tubes
of the bees,
sucking their
blood and
weakening them
Coyote/Mice lab discussion
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Go over and revise as needed
Predation
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The consumption of one species by another
Many predator-prey interactions
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Most common is pursuit and ambush
Plants and animals have established
specific defenses against predation
through evolution
Pursuit and Ambush
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Pursuing prey simply means chasing it down
and catching it
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Ex: Day gecko and spider (see picture)
Ambush is when predators catch prey
unaware
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Camouflage
Attract prey with
colors or light
Plant Defenses Against Predation
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Plants cannot flee predators
Adaptations
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Spikes, thorns, leathery leaves, thick wax
Protective chemicals that are poisonous or
unpalatable
Animal Defenses Against Predation
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Fleeing or running
Mechanical defenses
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Ex: quills of porcupines, shell of turtles
Living in groups
Camouflage
Chemical defensespoisons
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Ex: brightly colored poison
arrow frog
Competition
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Interaction among organisms that vie for
the same resource in an ecosystem
Intraspecific
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Competition between individuals in a population
Interspecific
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Competition between individuals in 2 different
species
Ecological Niche
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The totality of an organisms adaptations,
its use of resources, and the lifestyle to
which it is fitted
Takes into account all aspect of an
organisms existence
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Physical, chemical, biological factors needed to
survive
Habitat
Abiotic components of the environment
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Ex: Light, temperature, moisture
Ecological Niche
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Fundamental niche
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Realized niche
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Potential idealized ecological niche
The actual niche the organism occupies
Ex: Green Anole and Brown Anole
Ecological Niche
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Green Anole and Brown Anole
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Fundamental niches of 2 lizards initially
overlapped
Brown anole eventually out-competed the green
anole- reduced the green anole’s realized niche
Limiting Resources
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Any environmental resource that, because it
is scarce or at unfavorable levels, restricts
the ecological niche of an organism
Interspecific Competition
Competitive Exclusion & Resource Petitioning
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Competitive Exclusion
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One species excludes another from a portion of the
same niche as a result of competition for resources
Resource Partitioning
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Coexisting species’ niche differ from each other in
some way
Keystone Species
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A species that exerts profound influence
on a community
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More important to the community than what
would be expected based on abundance
The dependence of other species on the
keystone species is apparent when the
keystone species is removed
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Protecting keystone species is a goal to
conservation biologists
Species Richness
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The number of
species in a
community
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Tropical rainforests
= high species
richness
Isolated island =
low species richness
Related to the
abundance of
potential ecological
niches
Ecosystem Services
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Important environmental benefits that
ecosystems provide, such as:
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Clean air to breathe
Clean water to drink
Fertile soil in which to grow crops
Delaware Estuary
Ecosystem Services
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What are some of the services provided?
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How were costs/benefits measured?
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Does this help us see (in $$) the benefits
more clearly?
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Why is it helpful to translate into
economic terms?
Case Study: Lake Victoria
Questions:
1. What is the economic impact of
the Nile perch?
2. What is the environmental
impact of the Nile perch?
Case Study: Lake Victoria
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Ecosystem diversity and balance with
different species of cichlids filling
different niches.
Introduction of Nile perch:
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Shift in native species
Eating all resources-smaller sizes now
Trees/Forests cut for wood for fires to dry
fish, loss of erosion control