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Niches and
Community Interactions
Section 4.2
THINK ABOUT IT
–
If you ask someone where an organism lives, that person
might answer “on a coral reef” or “in the desert.”
–
These answers give the environment or location, but
ecologists need more information to understand fully why an
organism lives where it does and how it fits into its
surroundings.
–
What else do they need to know?
The Niche
– What is a niche?
– A niche is:
• the range of physical and biological conditions in which a species
lives & the way the species obtains what it needs to survive and
reproduce
Tolerance
– Every species has its own range of tolerance, the ability to
survive and reproduce under a range of environmental
circumstances.
Tolerance
– Environmental condition goes outside an organism’s
optimum range--organism experiences stress
• Ex: temperature
– Organism uses more energy to maintain homeostasis --has
less energy left for growth & reproduction
– Organisms have an upper and lower limit of tolerance for
every environmental factor
– A species’ tolerance helps determine its habitat—the
general place where an organism lives
Defining the Niche
– An organism’s niche describes
• the environment where it lives
• how it interacts with biotic and abiotic factors
– Physical and biological aspects of its environment
AND how the organism uses them to survive and
reproduce
Resources and the Niche
– The term resource refers to any necessity of life
• such as water, nutrients, light, food, or space.
Resources
Plants
Animals
- Sunlight
- Nesting space
- Water
-Shelter
- Soil nutrients
- Types of food
- Places to feed
Physical Aspects of the Niche
– Part of an organism’s niche includes: the abiotic factors it
requires for survival
• Ex: Most amphibians lose and absorb water through their skin
so they must live in moist places
• If an area is too hot and dry, or too cold for too long, most
amphibians cannot survive
Biological Aspects of the
Niche
– Part of an organism’s niche involves: the biotic factors it
requires for survival, such as:
• when and how it reproduces
• the food it eats
• the way in which it obtains that food
– Ex: Birds on Christmas Island in the Indian Ocean all live in the
same habitat but they prey on fish of different sizes and feed
in different places.
• each species occupies a distinct niche.
WAYS ORGANISMS
INTERACT
Ways organisms interact
COMPETITION
______________________
-Between SAME and DIFFERENT kinds of organisms
-Compete with each other for available resources
PREDATION
__________________________
-Between DIFFERENT kinds of organisms
-Hunt and kill other organisms to supply their energy needs
COOPERATION
__________________________
-Between SAME kind of organisms
-Live together and help each other
SYMBIOSIS
__________________________
-Between DIFFERENT kinds of organisms
-live in close association with another kind of organism
COMPETITION
Organisms in the same ecosystem try to
compete with each other for the same
available resources at the same time. FOOD
Battle at Kruger
http://www.youtube.com/watch?v=LU8DDYz68kM
COMPETITION
Organisms in an ecosystem have to
compete with each other for available
resources: shelter
COMPETITION
Organisms in an ecosystem have to
compete with each other for available
resources
mates
COMPETITION
Organisms in an ecosystem have to
compete with each other for available
resources: space/territory
Prairie dogs - 5 to 35 per acre
Mountain lion- 1 male per 50-300 sq. mi
COMPETITION
Organisms in an ecosystem have to
compete with each other for available
resources: LIGHT
The Competitive Exclusion Principle
• Experiment shown in the graph
– two species of paramecia (P. aurelia and P. caudatum)
– first grown in separate cultures (dashed lines) with same
conditions
• both populations grew.
– Then, both species were grown together in the same culture
(solid line)
• one species outcompeted the other
• less competitive species did not survive.
The Competitive Exclusion Principle
– States that no 2 species can occupy exactly
the same niche in exactly the same habitat
at exactly the same time
– One species will be better at competing for
limited resources  eventually exclude the
other species
– As a result, natural communities rarely have
niches that overlap
Dividing Resources
– Instead of competing for
similar resources, species
usually divide them
– Example:
• 3 species of North
American warblers shown all
live in the same trees and
feed on insects
• But 1 species feeds on high
branches; another feeds on
low branches, and another
feeds in the middle
– The resources used are similar
yet different
– Each species has its own niche
and competition is decreased
COMPETITION
If resources are scarce, some organisms
will starve and populations will decrease.
If resources become more plentiful,
populations will increase.
Competition in nature often results
in a winner and a loser
. . . with the loser failing to survive!
SHORT SUPPLY
If a nutrient is in _____________
CYCLES SLOWLY
OR __________________
it will LIMIT the growth of the
population
LIMITING FACTOR
= _____________
During this drought,
there was not enough food
available and many kangaroos
starved.
http://www.wspa-international.org/exhibition/gallery/large_DeadKenyan%20droughtSPANA.jpg
Ways organisms interact
PREDATION
___________________
Between DIFFERENT kinds of organisms
Hunt and kill other organisms to supply
their energy needs
http://www.epa.gov/region5/superfund/ecology/images/fishcartoon.gif
PREDATION
Organisms in an ecosystem that capture
and eat other organisms (prey) to supply
their energy needs
INTERDEPENDENCE
All living and non-living things in an
ecosystem are interconnected and changing
even one thing impacts the whole ecosystem.
When one tugs at a single thing in nature,
he finds it attached to the rest of the world.
~John Muir, naturalist, Sierra Club founder
REMEMBER: EVERYTHING IS CONNECTED !
BIOLOGY; MIller and Levine; Prentice Hall; 2006
A decrease in the prey population means some predators will starve.
Fewer predators mean prey population will increase.
Increase in prey means more food for predators.
Predator population will increase until there is not enough food . . .
and the cycle repeats itself.
Ways organisms interact
COOPERATION
_____________
Between SAME
kind of
organisms
Live together
and help each
other
COOPERATION
Same species live together in groups
EX: herds, packs, colonies, families, etc
Share food &
childcare responsibilities
Groom each other
Take care of sick
COOPERATION
Same species live together in groups
EX: herds, packs, colonies, families, etc
Hunt in packs
Provide protection
Ways organisms interact
SYMBIOSIS
__________________________
Between DIFFERENT kinds of organisms
Live in close association with another kind
of organism
http://www.zahnersatz.com/english/library/symbiosis.jpg
3 KINDS of SYMBIOSIS
______________________
MUTUALISM
Both organisms benefit
COMMENSALISM
______________________
One organism benefits;
Other is neither harmed nor helped
PARASITISM
_____________________
One organism benefits;
Other is harmed in some way
MUTUALISM
“Good for me - Good for you”
Birds eat parasites living
on the hides of giraffes and rhinos
while enjoying protection from
predators.
Groomed animals lose their
pests.
http://www.imbt.org/science.htm
http://www.hugheshome.net/jon/africa02/images/rhino_bird_JPG.jpg
MUTUALISM
“Good for me - Good for you”
Insects transfer pollen
between plants as they
gather nectar for food.
MUTUALISM
“Good for me - Good for you”
Clown fish get protection from enemies by
hiding out in poisonous sea anemones
http://www.zahnersatz.com/english/library/symbiosis.jpg
Sea anemone gets
scraps of leftover
food dropped
by fish
COMMENSALISM
“Good for me - Doesn’t bother you”
http://www.geology.wmich.edu/gillespie/g322/Chapters/C16shark.gif
Pilot fish receive scraps of food dropped by shark;
Shark is neither harmed nor helped
COMMENSALISM
“Good for me - Doesn’t bother you”
http://www.abyssal.com/meeks/images/hermit_crab.jpg
Hermit crabs make homes in shells abandoned by snails;
Snail is not harmed by crab
COMMENSALISM
“Good for me – Doesn’t bother you”
http://www.geology.wmich.edu/gillespie/g322/Chapters/C16parasitism.whale.gif
Barnacles are crustaceans that attach to the surface of whales
and feed on the waters that pass by as the whale swims; the whale is not
harmed
PARASITISM
“Good for me - Hurts you”
Tick feeds on dog’s blood;
Dog has discomfort, can get diseases/infection from bite
Ecological Application: Wolves vs. deer
Farmers Killed Wolves. What was
the ramifications of this?
Answer:
Deer Population increased, Deer Ticks
increased, ticks bite wild mice, Mice
contain the disease Lyme, then if ticks
bite humans they can infect humans.
PARASITISM
“Good for me - Hurts you”
Tapeworms absorb
food by living inside
host intestine;
host is harmed
Species Interaction Video Clips:
use with worksheet
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Example 1: acacia tree ants:
http://video.nationalgeographic.com/video/player/kids/animals-petskids/bugs-kids/ant-acacia-kids.html
Example 2: Cordyceps: http://www.youtube.com/watch?v=XuKjBIBBAL8
Example 3: snail vs. parasitic worm:
http://www.youtube.com/watch?v=EWB_COSUXMw
Example 4: anaconda vs. mammal:
http://www.youtube.com/watch?v=FDw0NdhK6QU&feature=channel
Example 5: Whaleshark & Remora:
http://www.youtube.com/watch?v=48eKFw7DDbY&feature=related
Example 6: daddy long legs vs. aphid:
http://video.nationalgeographic.com/video/player/kids/animals-petskids/bugs-kids/ant-acacia-kids.html
example 7: polar bears:
http://www.youtube.com/watch?v=hK8TQQp1qAA
example 8: lions vs. hyenas:
http://www.kewego.co.uk/video/iLyROoaftMFx.html
example 9: meerkats:
http://www.youtube.com/watch?v=X_eVEW_Y02o&feature=related
Keystone Species
–
Sometimes changes in the population of a single species,
often called a keystone species, can cause dramatic
changes in the structure of a community.
–
In the cold waters off the Pacific coast of North
America, for example, sea otters devour large quantities of
sea urchins.
–
Urchins are herbivores whose favorite food is kelp, giant
algae that grow in undersea “forests.”
• For more explanation:
http://lair2000.net/Mermaid_Lyrics6/lyrics/Sea_Otter_Rap.html
Keystone Species
–
A century ago, sea otters were nearly eliminated by
hunting. Unexpectedly, the kelp forest nearly vanished.
–
Without otters as predators, the sea urchin population
skyrocketed, and armies of urchins devoured kelp down to
bare rock.
–
Without kelp to provide habitat, many other animals,
including seabirds, disappeared.
–
Otters were a keystone species in this community.
Keystone Species
–
After otters were protected as an endangered species,
their population began to recover.
–
As otters returned, the urchin populations dropped, and
kelp forests began to thrive again.
–
Recently, however, the otter population has been falling
again, and no one knows why.