Transcript Realized niche

Interactions in
Ecosystems
Why do animals compete?
What is the difference between a
habitat and a niche?
• A habitat is all biotic
and abiotic aspects of
the area in which an
organism lives.
• An ecological niche
includes all of the
factors that a species
needs to survive, stay
healthy, and
reproduce.
Are the following part of the habitat
or niche?
a)
b)
c)
d)
e)
Zebra as food
Hunting behavior
Savanna
Grass
Temperature it can
tolerate
f) Watering hole
g) Time of day it is active
h) Sand
i) Number of young
produced
• Competition occurs when two organisms fight
for the
same limited resource.
– Intraspecific
competition
– Interspecific
competition
Interspecific or intraspecific?
• Two red squirrels race up a tree to find a hidden
pile of nuts.
• A hyena chases off a vulture to feast on an
antelope carcass.
• Shrubs and grasses on the forest floor compete
for sunlight.
• Brown bears hunting for fish on a river’s edge
fight over space.
• Male big horn sheep butt heads violently in
competition for mates.
Fundamental niche : entire range of conditions an organism
is potentially able to occupy.
Realized niche the part of the fundamental niche that a
species occupies.
Competition between two species of barnacles.
Is this the realized niche or fundamental niche?
How can we determine the realized niche of each barnacle?
Observe where they grow when allowed to compete.
growth
rate
Balanus
realized
niche
low
Balanus
and
Chthamalus
Chthamalus
realized
niche
middle
high
Location in intertidal zone
How can we determine the fundamental niche of each barnacle?
Removal experiments – remove each species and see
where the other grows
Balanus alone
Balanus
fundamental
niche
growth
rate
Chthamalus alone
Chthamalus fundamental niche
low
middle
high
Location in intertidal zone
Streams with only
Planaria species A
Streams with only
Planaria species B
Streams with both
Planaria species
What are the fundamental
and realized niches for
each species?
Competitive exclusion keeps two species from
occupying the same niche.
Two species of Paramecia
predict the outcome of
interspecific competition
P. aurelia
P. caudatum
Gause (1934)
Types of Interactions
Interaction
Species A
Species B
Mutualism
Benefit (+)
Benefit (+)
Commensalism Benefit (+)
No Effect (0)
Parasitism
Benefit (+)
Harm (-)
Predation
Benefit (+)
Harm (-)
Competition
Harm (-)
Harm (-)
Amensalism
Harm (-)
No Effect (0)
• What is symbiosis?
• How are predators different from
parasites?
• How are they similar?
• How are predators of animals different
from predators of plants?
• What is the difference between
ectoparasite and an endoparasite?
A black rhinoceros grazes on the African
plains. As it forages, the rhino disturbs
multitudes of insects in the grass, crushing
some and inadvertently eating others. Birds
known as egrets forage on the ground near
the rhino, eating insects flushed out by the
hooves. Other birds known as oxpeckers
eat ticks from the
skin of the rhino.