Download Organismal and Community Ecology

Organismal and Community Ecology
Ecology (from the Greek oikos meaning "house" or "dwelling", and logos meaning "discourse") is
the study of the interactions of organisms with each other and their environment.
Definitions:
• species – a group of similar organisms that can interbreed in nature to produce fertile, viable offspring
• population – all the members of the same species living in the same, defined area
• community – all the various populations living in the same, defined area.
• ecosystem – the living (biotic) community plus the non-living (abiotic) components of the environment
• biosphere – all the earth’s ecosystems, considered collectively
•
Levels of ecological study:
• organismal ecology - the study of individual organisms' behavior, physiology, morphology, etc. in
response to environmental challenges.
• population ecology - the study of factors that affect and change the size and genetic composition of
populations of organisms.
• community ecology - the study of how community structure and organization are changed by
interactions among living organisms
• ecosystem ecology - the study of entire ecosystems, including the responses and changes in the
community in response to the abiotic components of the ecosystem. This field is concerned with such
large-scale topics as energy and nutrient cycling.
• landscape ecology - the study of the exchanges of energy, materials, organisms, etc. between
ecosystems.
• global ecology - the study of the effects of regional changes in energy and matter exchange on the
function and distribution of organisms across the biosphere. It's The Big Picture.
Organismal Ecology
An organism's ability to survive extremes of its environment reflect its evolutionary history.
Homeostasis is the process of an organism maintaining a stable internal environment (with respect to
temperature, salt balance, etc.).
• regulators use metabolic means to maintain homeostasis in response to environmental changes.
examples
• endotherm - obtain heat by producing it internally, via metabolic reactions
• homeotherm - regulate a constant body temperature by spending metabolic energy
• note: the terms endotherm and homeotherm are more accurate, scientific ways to express the idea of an
organism being "warm blooded"
• conformers are less able to metabolically maintain homeostasis. Their internal environment is governed
primarily by the external environment.
examples
• ectotherm - obtain heat from the external environment
• poikilotherm - body temperature is regulated by the external environment
• note: the terms ectotherm and poikilotherm are more accurate, scientific ways to express the idea of an
organism being "cold blooded"
Another example: osmoregulation - regulation of internal salt/water balance
• anadromous (fish that migrate from a primary salt water home to a freshwater habitats, such as salmon) and
catadromous (fish that migrate from freshwater to marine habitats, such as European eels) maintain constant
salt balance in their tissues via their excretory systems (kidneys), even when their environments vary. They are
regulators
• Echinoderms, (starfish, sea urchins, sand dollars, etc.) have no excretory system, so are strictly limited to
marine environments. Their tissues have the same salinity as sea water. They are conformers
Community Ecology
The study of inter-species interactions in a particular ecosystem is known as community ecology.
Biological coevolution is the evolutionary change of one species triggered by interaction with
another species.
Example: Wolves hunt caribou, chasing them down to capture them. The slower caribou are
more likely to be preyed upon, leaving the faster individuals to reproduce. The resulting faster
offspring will be even more difficult for the wolves to catch, and only the fastest wolves (or perhaps
the wolves who are genetically capable of devising strategies to hunt very fast prey) will get enough
food to survive. An evolutionary “Cold War” ensues.
Example: Flowers compete for pollinators. The plants that produce flowers (with colors, shapes
and scents specific to particular pollinators) that attract the most effective pollinators will set the
most seed and have the most offspring.
The various species in an ecosystem have evolved over the millennia in response to pressures from
both the environment and from other species with which they live and interact. The result is often a
complex interaction between the two species, symbiosis.
Symbiosis
In Greek, sym means “together” and bios means life. Symbiosis is living together. This term
refers to members of two different species (i.e., two populations) that have coevolved to have some
type of ecological interaction that affects both populations. Here are some of the theoretical types of
interactions that can evolve over many generations.
In the table below, you will find a list of all the potential types of symbiotic interactions between two
species/populations. Each relationship is an result of COEVOLUTION--species being molded by
natural selection in response to INTERACTION WITH THE OTHER SPECIES.
The Different Types of Symbiosis
The table below shows all the possible different types of symbiotic interactions.
"+" means that the population benefits from the interaction
"-" means that the population is harmed by the interaction
"0" means that the population is not affected by the interaction
type of
interaction
obligate
mutualism
EXAMPLES:
pop'n A
pop'n B nature of effect
+
+
obligatory; both populations benefit
protocooperation
EXAMPLES:
+
+
NOT obligatory; both pop'ns benefit
competition
EXAMPLES:
-
-
populations inhibit one another
neutralism
EXAMPLES:
0
0
populations do not affect one another
predation
EXAMPLES:
+
-
predator (A) kills & consumes prey (B)
parasitism
+
-
parasite (A) exploits the host (B), but
does not kill it outright
+
-
parasitoid (A) lives within, and eventually kills
host (B) at point of metamorphosis from one
life cycle stage to another.
+
0
commensal (A) benefits; host (B) not
affected
0
-
A unaffected; B inhibited
EXAMPLES:
parasitoidism
EXAMPLES:
commensalism
EXAMPLES:
amensalism
EXAMPLES:
Terminology for Interacting Species
Ecological niche - Defined by the species, this is everything that an organism eats, where it nests,
sleeps, forages, etc. In short, everything that defines its natural history. Two species can never
occupy exactly the same ecological niche, or one will eventually become extinct. However, the
niches of different species may overlap to some degree. When this happens, interspecific (i.e.,
between species) competition occurs.
Keystone species - species on which many other populations ultimately depend for survival.
Indicator species – a species whose population density indicates the overall health of an ecosystem.
Native species - a species found in the place where it naturally evolved. Native populations often
have complex and delicately-balanced interactions with one another that can be disrupted by the
introduction of exotic species.
Exotic species - a species living in a place where it did not originally evolved. Some exotic species
introduced into new environments are much better able than native species to compete for resources,
and they can sometimes displace native species. This can have profound effects on the other native
species that once relied on a native species driven extinct (or to great scarcity) by an invasive exotic
species.
Results of Predation: Camouflage and Warning Coloration
Crypsis/cryptic coloration - camouflage
Aposematism/aposematic coloration - warning coloration (distasteful or dangerous species)
Mimicry - a species has evolved the superficial appearance of something else
Batesian Mimicry - a harmless mimic looks like a poisonous model.
Examples: Harmless Viceroy butterfly mimics poisonous Monarch butterfly.
Non-venomous Kingsnake mimics venomous coral snake
Mullerian Mimicry - several poisonous/distasteful species resemble one another.
Examples: Several species of poisonous Ithomiid butterflies resemble each other.
Many species of venomous, stinging hymenopterans (bees, wasps, etc.)
have yellow bodies with black stripes.
Know the difference:
poisonous – toxic when eaten or touched
venomous – delivers toxin with an apparatus such as a fang or stinger