Transcript Slide 1

Chapter 27
Community Characteristics
Why do organisms compete?
• Food, resources and reproduction
27.1 Biotic Factors
Nutritional Relationships
*Predator-prey
relationship
*Interspecies Competition
*Intraspecies Competition
Symbiotic Relationships
*Mutualism (+,+)
*Parasitism (+, -)
*Commensalism (+,0)
SPECIES A
Positive Negative
SPECIES
B
Positive
Negative
Neutral
Neutral
SPECIES A
SPECIES
B
Positive
Negative
Neutral
Positive
mutualism
Predation
(Species A is
prey)
Parasitism
(Species A is
host)
Competitive
exclusion of
Species A
commensalism
Negative
Predation
Competition
(Species A is Limiting
predator)
resources
Parasitism
(Species A is
parasite)
--
Neutral
commensalism
Resource
partitioning
--
2. Symbiotic Relationships
• Different organisms may live together in a
close association.
• This is known as symbiosis.
• There are three types:
1. Commensalism 2. Mutualism 3.
Parasitism
• KEY:
+ = benefits
- = harmed
o = not affected
Commensalism
• (+ , o)
• In this relationship, one organism
benefits and the other is not affected.
• Ex: barnacles on a whale
Commensalism
(+ , o)
• Epiphytes (mosses, orchids, ferns,
bromeliad ) attach themselves to tree bark
and obtain their nutrients without harm to
the trees.
Mutualism
• (+ , +)
• In this relationship both organisms
benefit from each other.
• Ex: protozoan living in the digestive
tract of termites.
• Wood eaten by termites is digested by
the protozoan. The nutrients released
supply both organisms.
Mutualism
• (+ , +)
• In this relationship both organisms benefit
from each other.
• Ex:
Mycorrhizae (+ , +)
In this relationship both organisms
benefit from each other.
• Ex: Red Cedar and mycorrhizal fungi.
Parasitism
• (+ , - )
• In this relationship, the parasite
benefits at the expense of the host.
• Ex: athlete’s foot fungus on humans
tapeworm and heartworm in dogs.
Parasitism
• (+ , - )
• Pathogens (disease causing
agents) are parasites that often
cause the death of its host.
• Crown gall disease in plants.
Parasite/Host Relationship
Guinea worm/Human
Parasite/Host Relationship
Sea Lamprey/Fish
Parasitism
• Parasite/Host Relationship
• Varroa mite/Honeybee
Tracheal mites
Do Now:
• Define keystone species and discuss two
examples of organisms that are keystone
species.
Keystone species
• These determine the nature and structure of an entire
ecosystem. Usually found in small numbers but have
a key influence.
• Examples: Wolves, Fig Trees
27.4 Predator/Prey Relationships!
27.4 Predator-Prey Cycles
27.7 Predator/Prey Relationships
Data collected from fur pelts from the Hudson Bay Company
Studies have shown that Endocrine
changes in populations may produce
behavioral changes which tend to limit
population growth. Therefore all
population changes may not be due to
predator/prey relationships alone.
Case Study
"The Effects of Coyote
Removal in Texas:
A Case Study in
Conservation Biology"
by
Margaret Carroll
Department of Biology
Framingham State College
Case Study
The Wolf, the Moose, and the Fir
Tree:
Who Controls Whom on Isle
Royale?
A case study of trophic interactions
by
Gary M. Fortier
Department of Small Animal Science
Delaware Valley College
The Data
The Data
•
Fig. 1. Population parameters of the
Isle Royale ecosystem from 19581994. Shaded areas signify periods
of forage suppression that may be
connected to interactions between
herbivores and carnivores.
•
Population size of wolves each
winter (based on aerial counts).
Population size of moose each
winter (based on aerial counts and
skeletal remains).
Ring-widths from the west end of
Isle Royale, N=8.
Ring-widths from the east end of
Isle Royale, N=8.
Actual evapotranspiration rates
(AET), annual calculations based on
data from April-October at a weather
station 20 km from Isle Royale. AET
is an approximation of primary
productivity, it represents water
availability as a function of
temperature and rainfall.
•
•
•
•
Energy Flow Relationships
• For an ecosystem to be selfsustaining, there must be a flow of
energy between organisms.
• The pathway of energy flow through
the living components of an
ecosystem are represented by food
chains and food webs.
Nutritional
Relationships
• Involves the transfer of nutrients from
one organism to another within an
ecosystem.
• In terms of nutrition, organisms are
either autotrophs or heterotrophs
Energy Flow through a food
Chain
Energy
Losses
 The mouse receives energy from the food it eats.
 Cells extract the food's energy for growth, acquiring
food, escaping enemies lost as heat. Some lost in the
mouse's waste (feces).
 The remaining energy is stored in the mouse's body
and is available to the organism that preys on it.
 About 90% of the energy is used or lost, only 10% is
available to predators.
Energy Flow
Biological Magnification
• A nondegradable or slowly degradable
substance
• That becomes more and more concentrated
in the tissues of organisms at higher trophic
levels of a food web.
– * Dichloro-Diphenyl-Trichloroethane (DDT)
– * Polychlorinated biphenyls (PCBs)
DDT in Food Webs
DDT
PCBs in Food Webs
• PCB concentrations in animal
tissue can be magnified up to
25 million times.
• Microscopic organisms pick up
chemicals from sediments
• Consumed in large numbers by
filter feeding zooplankton.
• Mysid shrimp then consume
zooplankton
• fish eat the mysid
• and so on up the food web to
the herring gull.
• (Figure and caption from Our
Stolen Future, p. 27)
DDT residues
• Why was there never
a concern for the
Ring-billed gulls?
Fig. 41-7, p.736
DDT Detection
• In 1962, Rachel Carson,
a former U.S. Fish and
Wildlife Service (USFWS)
scientist and writer,
published Silent Spring,
outlining the dangers of
DDT
Fig. 41-8, p.736
DDT in Food Webs
• Heinz Meng
• Responsible for the
reintroduction of the
Peregrine Falcon.
27.3 Competitive Interactions
• Exploitative
competition:
species do not
interact directly
but compete
for resources
• Competitive
exclusion: both
species require
same resource
27.3 Competitive Interactions
WAYS TO AVOID COMPETITION ???
• Over abundance or resources
• Resource Partitioning
27.3 Natural selection can favor
Resource Partitioning: differences in
resource use among species.
• The diagram represents a tree containing three different
species of warbler, A, B, and C. Each species occupies a
different niche.
A fourth species, D, which has the same environmental
requirements as species B, enters the tree at point X. Members
of species B will most likely
(1.) live in harmony with species D
(2.) move to a different level and live with species A or species C
(3.) stay at that level but change their diet
(4.) compete with species D
Effect of community complexity on Species richness
41.8 Ecological Succession
• Succession is a process of ecological change in which
a series of natural communities are established and
then replaced over time.
• Two kinds of succession: .
– Primary succession takes place on an area that is
originally completely empty of life.
• flow of lava has, for a time, no life at all on it.
• Over a period of time, however, various kinds of organisms begin to
grow in the area. Over time, the variety of life-forms changes as
succession continues.
– Secondary succession is far more common. It occurs in an
area where life once existed but has then been destroyed.
– a forest that has been destroyed by a wildfire.
– For a period of time, no living organisms may exist in the
area. Before long, however, certain types of plants begin to
reappear. And, as with primary succession, the nature of the
plant communities gradually change over time.
http://www.tvcc.edu/depts/biology/Native%20Habitat/ecological_succession.htm
41.8 Ecological Succession
Pioneers
Organisms
-lichen
-grasses
Climax
Community
United streaming video
• Biologix: Interactions and Relationships
among Organisms
• http://player.discoveryeducation.com/index
.cfm?guidAssetId=9442E194-317A-4EFD84102392E05F2A25&blnFromSearch=1&produ
ctcode=US#