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Interactions within an Ecosystem
Name: ____________________
Block: ______
1) Indicate the interaction between Species A and Species B, either with a positive (+) symbol
to indicate a positive interaction, negative (-) indicate a negative interaction, and zero (0)
symbol to indicate a neutral interaction.
Species A Species B
Commensalism
Mutualism
Parasitism
Competition
Predation
2) Matching
______ commensalism
______ competition
______ ecosystem
______ mutualism
______ niche
______ parasitism
______ predation
A. a symbiotic relationship in which both organisms benefit
B. includes the way in which the organism contributes to and fits into
its environment
C. a symbiotic relationship in which one species benefits and the
other is harmed
D. interaction between two or more organisms that can occur when
they compete for the same resource
E. abiotic components such as oxygen, water, nutrients, light, and soil
interacting with biotic components such as plants, animals, and
micro-organisms
F. a symbiotic relationship in which, one species benefits and the
other species is not helped or harmed
G. an interaction in which one organism eats all or part of another
organism
3) Think about the organisms that live in your community. Identify one example of each of the
following.
(a) a competitive relationship ________________________________________________________
(b) a predator-prey relationship _______________________________________________________
(c) a commensal relationship _________________________________________________________
(d) a mutualistic relationship_________________________________________________________
4) Many people believe that plants are defenseless. Provide an argument to refute this statement.
5) What will happen when two species compete for the same resources?
6) Describe the effect of the following conditions on a population of predators.
(a) The number of prey animals is low.
(b) The number of prey animals is high.
7) Answer each question with the following type of ecological relationship(s): mutualism,
parasitism, commensalism, predation, competition
The main producers were Sweet Clover plants, Wild Oats, Canada Thistle and Blue Burr. These
species were growing and photosynthesizing, intermingled in the same field.
a) Which ecological relationship best described this relationship between the plants? ____________
Upon digging up a clover plant, the student observed an average of 8 nodules on the roots of each
clover plant (Nodules contain bacteria which have the ability to convert atmospheric nitrogen into
nitrates and release them into the soil. Plants utilize nitrates to manufacture proteins.)
b) Which ecological relationship exists between the bacteria and the clover plant? ______________
Small green aphids were sucking the juices from clover stems. Further investigation found some
aphids being eaten by an army of ants.
c) What type of ecological relationship exists between the aphids and the clover? ______________
d) What type of ecological relationship exists between the ants and the aphids? ________________
A considerable number of clover and wild oat plants had been cut down and partially eaten by a
colony of lined squirrels that made their home in an adjacent pasture.
e) Which describes the relationship between the squirrels and the clover plants? _______________
f) What is the ecological relationship that exists between the squirrels? ______________________
The squirrels had lice.
g) What ecological relationship exists between the lice and the squirrels? ____________________
Some clover plants had withered and died. A white fungus was found on the roots and lower stems,
which was identified as root rot.
h) Which describes the ecological relationship between the clover plant and the fungus? _________
A colony of Leaf Cutters bees was feeding on the nectar and pollinating flowers.
i) What ecological relationship exists between the flowers and the bees? ____________________
A bee keeper was setting out a hive of honey bees.
j) What ecological relationship exists between the bee keeper and the bees? _________________
Several butterflies and moths were flitting over the field. Some could be observed landing on
flowers, others were landing on leaf axils, and the students thought they were laying eggs.
k) What ecological relationship exists between the butterflies and the leaves? _______________
Nearby, a Red Fox was dozing in the sun, contented after his recent kill, a Jack Rabbit. Several
Blue Burr seeds were stuck in his coat.
l) What ecological relationship exists between the fox and the rabbit? _____________________
m) What is the relationship between the seeds and the fox? _____________________________
Hundreds of soil insects were burrowing in and out of the soil, pausing to feed on dead plant
leaves. Several species of insects were involved.
n) Which of the following best describes the ecological relationship that exists between the various
species of insects? ___________________________________________________