Transcript interactions - Groupfusion.net

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
cicada-killer 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.
Ecosystems Ecology
An ecosystem is a self-sustaining community of organisms and the non-living
environment with which they interact.
An ecosystem is the fundamental unit of ecology.
Biogeochemical Cycles
A biogeochemical cycle is the cyclic movement of a substance (for example,
water, carbon, nitrogen, or phosphate) through the biotic (living) and abiotic
(non-living) environments.
Biogeochemical cycles are a key component of ecosystems ecology.
The Carbon
Cycle
Understanding of
the carbon cycle is
critical for global
climate change, yet
it remains
incomplete.
The Nitrogen Cycle
Note the key role of
mutualism between
nitrogen-fixing
bacteria and their
plant hosts.
Not shown is the
huge contribution of
anthropogenic (manmade) ammonia and
nitrates.
Humans Play a Major
Role in the Nitrogen
Cycle
Aerial fertilization (with
nitrogen) of sugar beets.
Excessive Amounts of Nitrogen
Fertilizer Harm Ecosystems
A seasonal “dead zone” where
virtually all marine life is killed
stretches off the Mississippi
Delta.
Why?
About 1.5 million metric tons of
nitrogen from fertilizer runoff
promotes algal and bacterial blooms
that deplete oxygen from the water.
The Water Cycle
Only about 40% of precipitation on land comes from water evaporated over
oceans; roughly 60% comes from transpiration of water through plants.
The Percentage of Available Global Freshwater is Very Small
Freshwater Is a Precious and Often Scarce Resource
We’re in the Driver’s Seat - Human Activities Dominate Many
Biogeochemical Cycles
How is Energy Moved and Utilized in Ecosystems?
Trophic levels are the “steps” in a food chain moving from producers to
different levels of consumers.
The efficiency of energy transfer between different levels puts a limit on the
number of trophic levels.
A Food Web Describes the Way Energy is Transferred Within
an Ecosystem
Celebrating Rot and Decay - Detritivores
Energy isn’t transferred only upwards between trophic levels.
Detritovores use the energy available in dead organisms and allow recycling
of essential nutrients in ecosystems.
Only a Fraction of the Energy Present in Organisms of One Trophic
Level Is Captured by Organisms of the the Next
This limits the number of trophic levels.
Our Changing Planet
The Millennium
Ecosystems
Assessment Project
- one bold approach
to placing a value
on biodiversity and
ecosystem function
Greenhouse Gases and Global Warming
A Warming World
Science (2005) 309:100
Species Distributions Are Now Changing in Response to Global Warming
This map shows projections, but many dramatic shifts in species
distribution have already been documented.
Life On a Changing Planet
Science (2006) 311:1698
What Are the Concerns?
Global warming.
Loss of biodiversity.
Change in species distribution.
Collapse of ecosystems.
Degradation and collapse of human societies.
An Uncertain Future?
Of course …
…. but that’s not to
say there’s no hope.