Download Ecology part A - Lauralton Hall

Ecology
Organization levels of biology.
Ecology
(ekos –house ology – study of)
Ecology is the study of interactions between organisms and their environment.
Ecology is not environmental
activism or “tree-hugging.”
Ecology entails consideration of
biotic factors (other organisms that
include prey, predators, parasites,
etc.)
and
…. abiotic factors (such as temperature, light, and water).
Levels of
Ecological
Investigation
Community Ecology
Community ecology examines the question of how populations interact.
Questions include:
What are the types of species
and their numbers within a
community (i.e. community
structure)?
Are there especially critical species for maintenance of the community?
What is the relationship (predator, prey, parasite) between species within the
community?
Community Structure
• Types of species:
- autotrophs
- primary consumers
- secondary consumers
- tertiary consumers
- detritovores
- decomposers
Keystone Species
• Robert Paine – 1969
• “a keystone species plays a critical role in maintaining
the structure of an ecological community and whose
impact on the community is greater than would be
expected based on its relative abundance or
biomass”
Foundation Species
• Dayton – 1972
• “a single species that defines much
of the structure of a community by
creating locally stable conditions for
other species, and by modulating
and stabilizing fundamental
ecosystem processes.”
• Usually a primary producer in both
terms of abundance and influence
How Do Species Interact?
Species interact in complex ways that are often reduced to three categories:
Competition
Predation (and parasitism)
Mutualism
Interspecific Competition and Gause’s Competitive Exclusion Principle
Gause’s Principle: No two species within a community may share the same niche.
What’s a niche?
A niche is an organism’s way of making a living that includes choices of habitat, food
and behavior.
Gause’s Study
These two species have the same niche. In competition, one will win
out (exclude) the other.
Resource Partitioning
Placing another closely related species in with the previous “winner”
gives a different result – both species persist.
Why?
Each species occupies a different part of the environment (i.e. they
have different niches) – there’s been a partitioning of resources.
Resource Partitioning
Closely related warbler species can occupy the same tree if they partition resources.
Competitive exclusion is an important factor in evolution.
Predation, Parasitism and Coevolution
Predation (consuming another organism) and parasitism (feeding upon a host organism
without causing its immediate death) drive an evolutionary arms race.
Predator and prey, host
and parasite are locked in
a duel to outwit their
opponent through
adaptations.
Predator and prey interactions drive coevolution – coupled adaptive changes in
interacting species.
Coevolution of Interacting Species is Widespread
Pollinators and the plants they pollinate are often exquisitely adapted for one
another.
Camouflage is An Outcome of Predator-Prey Interaction
Mimicry Is An Outcome of Predator-Prey Interactions
If a potential prey species develops an effective defense system, other unprotected
prey species may come to mimic the protected species.
This is Batsian mimicry.
One (of many) examples of Batsian mimicry: the stinging yellow jacket and its
harmless mimic, the clearwing moth.
Batsian Mimicry
Disturbed hawkmoth larva.
Snake
Mimicry Is An Outcome of Predator-Prey Interactions
If a group of potential prey species develops an effective defense, the different species
may coevolve to resemble one other.
This is Mullerian mimicry.
One example of Mullerian mimicry: the stinging yellow jacket and the stinging cicadakiller wasp – both are noxious.
Mullerian Mimicry
Two noxious species of South American butterfly.
Mutualism
Mutualism occurs when species interact in a mutually beneficial manner.
The oxpecker gets food (ticks and insects disturbed in the grass) and a safe haven from
the rhinoceros, and the rhinoceros has parasites (ticks) removed.
Mutualism
Mycorrhizal fungi (threads) covering aspen roots: fungi aid in water and nutrient
absorption by the aspen and the aspen provides sugars and other food molecules to
the fungi.
Ecological Succession
Ecological succession is the set of changes in
community composition that occur over time
in a new or disturbed community.
Succession after the
Yellowstone fires.
Succession at Mt. St.
Helens.
Retreating
Glaciers at
Glacier Bay
Alaska Make It a
Natural
Laboratory for
Studying Primary
Succession
Primary succession
occurs when organisms
colonize a barren
environment.
Primary Succession at Glacier Bay, Alaska
A climax community is the stable
community at the final stage of
succession.
Succession
Succession shows some general trends that include:
1) Biomass increase over time.
2) An increase in the number and
proportion of longer-lived species.
3) Increased species diversity.
Succession on Mt. St. Helens – another site of
intense study.