Ecosystems and
Living (Biotic) Organisms
(pages 64 – 84)
Overview of Chapter
o
Evolution
•
•
o
o
o
o
Primary & Secondary Succession
Symbiosis
•
o
Natural Selection
Domains and Kingdoms
Biological Communities
•
o
#4
Mutualism, Commensalism, Parasitism
Predation & Competition
Resource Partitioning
Keystone Species
Species Richness & Community Stability
Evolution and Natural Selection
o
The cumulative genetic changes that occur in a
population of organisms over time
•
•
o
Current theories were proposed by Charles Darwin, a
19th century naturalist
Evolution occurs through natural selection
Natural Selection
•
•
Individuals with more favorable genetic traits are more
likely to survive and reproduce
Frequency of favorable traits increase in subsequent
generations
Natural Selection
o
Based on four observations about the
natural world
1.
Overproduction
•
2.
Variation
•
3.
Individuals in a population exhibit variation
Limits on Population Growth
•
4.
Each species produces more offspring than will survive to maturity
(David Lack, 1943)
Resource limitations will limit populations.
Differential Reproductive Success
•
Individuals with most favorable traits are more likely to reproduce
Natural Selection
o
Darwin’s finches
exemplified the
variation associated
with natural
selection
Domains and Kingdoms of Life
Think of this variation
(diversity) as different
organisms (both plants
and animals) with
different traits, abilities
and methods for
surviving and
reproducing.
Biological Communities
o
Communities vary greatly in size and lack precise
boundaries
•
•
They are often nestled within each other, and dependent upon the
abiotic resources in an area.
Q: How might changes in resource abundance affect
communities?
Interactions Among Organisms
o
Symbiosis
•
•
•
o
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
•
•
•
Mutualism
Commensalism
Parasitism
Mutualism
o
o
Symbiotic relationship in which both members
benefit
Ex: Mycorrihzal fungi and plant roots
•
•
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
o
o
Symbiotic relationship where one species benefits and the
other is neither harmed nor helped
Ex: epiphytes and tropical trees
•
•
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
o
Symbiotic relationship in which one species is
benefited and the other is harmed
•
o
Parasites rarely kill their hosts
Ex: Varroa mites and
honeybees
•
Mites live in the
breathing tubes of the
bees, sucking their
blood and weakening
them
Predation
o
o
The consumption of one species by another
Many predator-prey interactions
•
o
Most common is pursuit and ambush
Plants and animals have established specific
defenses against predation through evolution
Pursuit and Ambush
o
Pursuing prey simply means chasing it down and
catching it
•
o
Ex: Day gecko and spider (see picture)
Ambush is when predators catch prey unaware
•
•
Camouflage
Attract prey with
colors or light
Plant Defenses Against Predation
o
o
Plants cannot flee predators
Adaptations
•
•
Spikes, thorns, leathery leaves, thick wax
Protective chemicals that are poisonous or unpalatable
Animal Defenses Against
Predation
o
o
Fleeing or running
Mechanical defenses
•
o
o
o
Ex: quills of porcupines, shell of turtles
Living in groups
Camouflage
Chemical defensespoisons
•
Ex: brightly colored poison
arrow frog
Competition
o
o
Interaction among organisms that vie for the same
resource in an ecosystem
Intraspecific
•
o
Competition between individuals in a population
Interspecific
•
Competition between individuals in 2 different species
In-class Discussion Readers:
Chapter #1 - Me
Chapter #2 –
Chapter #3 – Elizabeth Goodrich
Chapter #4 – James McLeod
Chapter #5 – Labecca Hampton and Jessica Vidal
Chapter #6 – Patrick Grennan and Scott Arnold
Chapter #7 – William Arnold and David Dudley
Chapter #8 – Crissy Overgard
Chapter #9 – Juan Rodriguez
Readings last Week and this
Week:
Chapter #5 – “Free Wealth”
Facilitators: Labecca Hampton
and Jessica Vidal
Quizzes will be returned on Wednesday
Ecological Niche
o
o
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
•
•
•
Physical, chemical, biological factors needed to survive
Habitat
Abiotic components of the environment
•
Ex: Light, temperature, moisture
Ecological Niche
o
Fundamental niche
•
o
Realized niche
•
o
Potential idealized ecological niche
The actual niche the organism occupies
Ex: Green Anole and Brown Anole
Ecological Niche
o
Green Anole and Brown Anole
•
•
Fundamental niches of 2 lizards initially overlapped
Brown anole eventually out-competed the green anolereduced the green anole’s realized niche
Limiting Resources
o
Any environmental resource that, because it is scarce
or at unfavorable levels, restricts the ecological niche
of an organism (Leibig’s Law of Minimum)
Interspecific Competition
Competitive Exclusion & Resource
Partitioning
o
Competitive Exclusion Principle
•
o
One species excludes another from a portion of the same
niche as a result of competition for resources
Resource Partitioning
•
Coexisting species’ niche differ from each other in some way
Keystone Species
o
A species that exerts profound influence on a
community
•
o
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
•
Protecting keystone species is a goal to conservation
biologists
Species Richness
o
The number of species
in a community
•
•
o
Tropical rainforests =
high species richness
Isolated island = low
species richness
Related to the
abundance of potential
ecological niches
Ecosystem Services
o
Important environmental benefits that ecosystems
provide, such as:
•
•
•
Clean air to breathe
Clean water to drink
Fertile soil in which to grow crops
Ecosystem Services