Download Species Interactions

Name ________________________
Date __________________ Hour _______
Species Interactions
No organism exists in isolation. Each takes part in many interactions, both with other organisms and with the
non-living components of the environment. Species interactions may involve only occasional or indirect contact
(predation or competition) or they may involve symbiosis (close associations). Symbiosis is a term that
encompasses a variety of interactions involving close species contact. There are three types of symbiosis:
parasitism (a form of exploitation), mutualism, and commensalism. Species interactions affect population
densities and are important in determining community structure and composition.
Type of interaction
Mutualism
Both species benefit from the association.
Species A
A
Species B
→
←
Benefits
Commensalism
The presence of one species has a
beneficial effect on the other, but is not
itself affected by the association (i.e. it is
not harmed or benefiting).
Exploitation
One species benefits at the expense of
the other. Includes:
1. Predation: predator kills the prey
outright.
2. Parasitism: parasite usually does not
kill the host.
3. Herbivory: herbivore usually does not
kill the plant.
Competition
Species or individuals, compete for the
same resources, with both parties
suffering, especially when resources are
limited.
Amensalism
The presence of one species has a
harmful effect on the other, but is not
affected by the association itself.
A
→
→
←
Harmed
A
B
Benefits
B
Many perching plants
(epiphytes) gain access to better
light for photosynthesis without
harming the host tree.
Parasitic wasp laying eggs in a
caterpillar.
Benefits
→
←
Harmed
A
Tick bird on a zebra removes
parasites and alerts the zebra to
danger, while the tick bird gains
access to food
Benefits
Not Affected
A
B
Example
B
Plants growing close to each
other are competing for light
and soil nutrients.
Harmed
→
←
Not Affected
B
Harmed
Grazing mammals trample
plants around waterholes,
creating bare zones. The
mammals are unaffected by the
loss.
For the purpose of this exercise, assume that species A in the diagram represents humans. Briefly describe an
example of our interaction with another species (B in the diagram) that matches each of the following
interaction types:
1. Mutualism
2. Commensalism
3. Parasitism
4. Competition
Examples of interactions between different species are described below. For each example, identify the type of
interaction, and explain how each species in the relationship is affected in terms of its survival and the food
resources that are available to it.
5. Clown fish spend much of the time taking refuge among the tentacles of a large sea anemone. They
may discard food scraps to the anemone and gain sufficient protection from predators. Name this
interaction, and describe how each species is affected (benefits/harmed/no effect):
6. Barnacles attach themselves to whales and are transported to places where there are nutrients
available. The whale does not seem to be affected by the presence of the barnacles. Name this
interaction, and describe how each species is affected (benefits/harmed/no effect):
7. Many insects eat leaves from plants as a source of food. This provides the insect with nutrients and
energy. Name this interaction, and describe how each species is affected (benefits/harmed/no effect):
8. Plover birds clean the teeth of the Nile crocodile by jumping into their open mouths and eating the
remains of the crocs lunch that is stuck to their teeth. Name this interaction, and describe how each
species is affected (benefits/harmed/no effect):
9. Ticks are small insect-like animals that are found living in the coats of many grazing mammals. They bite
into the skin and feed on blood. Name this interaction, and describe how each species is affected
(benefits/harmed/no effect):
10. In East African open grasslands, scavengers such as hyenas, vultures, and marabou storks try to get their
share of the meat remaining on the carcass of a lion kill. For the interaction between the hyenas and
vultures-- Name this interaction, and describe how each species is affected (benefits/harmed/no effect):