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Biology 131
Keller/McHugh
Name
Date -------
_
Per. 1 2 3 4 5 6 7 8
Biotic Relationships - many relationships exist between organisms. Below is detailed information on the
common biotic relationships found in nature. Please read through carefully and answer any questions in
complete questions.
1. Competition - the use or defense of a resource by one individual that reduces the availability of that
resource to other individuals. Resources include such things as: habitat, food, space, water, mates, etc.
The two types of competition are intraspecific competition and interspecific competition.
a. Intraspecific Competition - when organisms of the species compete against each other for
resources.
Examples:
i. Males fighting for mates.
ii. Plants competing against each other for light, nutrients in the soil and water.
Question: When two species are competing for limiting factors, what types of factors determine
who wins?
b. Interspecific Competition - when organisms of different species compete for the same
resources. This is usually less intense because different species compete for slightly different
resources in the same place. For example, a tree and a fox do not compete against each other
like a two trees or two foxes do with each other! If two species DO compete for the same
resources ... one will out compete the other. The one that wins lives, the one that doesn't dies off
or leaves the area. This is called the competitive exclusion principle.
Example:
i. Three species of insect-eating birds only feed on a certain level of the tree.
Question: In your own words define the competitive exclusion principle and list your own
example.
2. Predation - when one organism (predator) eats or feeds on another organism (prey). Healthy
predator/prey relationships balance species population over time.
Examples:
I. Two types of mites (related to ticks and spiders). Predator population grows because of
abundant prey, but then it crashes because not enough prey animals left. When the
predator population goes down, the prey population goes up until the predator species is
able to find plentiful food. This recurring cycle gas been documented in many different
situations:
Lynx/rabbit
Owl/field mice
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,
Biology 131
KellerlMcHugh
Question:
balances.
Name -----~---------Date
Per. 1 2 3 4 5 6 78
In your own words explain how predator/prey relationships keep species populations
3. Symbiosis - where two different species live together in a close association.
a. Parasitism: close, long-term relationship where one organism gets its nutrition from another
organism (harmful to the organism).
Parasite: organism RECEIVES the benefits
Host: organism that GIVES the benefits.
Examples:
i. Tapeworm
ii. Lung fluke
iii. Mistletoe on a tree
b. Commensalism - where one organism benefits off another, but the other organism is not
harmed.
Examples:
i.
Epiphytes (air plants): common in rainforest, don't use the same nutrition as the tree they
grow on.
ii.
Burrowing owl living in dog prairie holes
c. Mutualism - both organisms benefit from living together.
Examples:
i.
Bacteria living in digestive tract of cattle
ii.
Cnidarians/mollusks and algae
Directions:
organisms.
one correct
relationship
For each of the following examples indicate the type of relationship 'that exists between the
Also provide a brief description of why you choose the relation you did. There may be more than
answer for some of these. I am more interested in your reasoning for your relationship than the
itself.
Deer/Tick
Ticks feed on deer blood to the detriment of the deer.
Honey guide birdlBadger
Honey guide birds alert and direct badgers to bee hives. The badgers then expose the hives and feed on the
honey first, and then the honey birds eat.
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Biology 13 I
Keller/McHugh
Name --------------Per. I 2 3 4 5 6 7 8
Date
Remora/Shark
Remoras attach themselves to a shark's body. They travel with the shark and feed on the left over food scraps
from the shark's meals.
Hermit crab/Snail
A hermit crab lives in shells that are made and then abandoned by snails.
Bee/Marabou Stork
The stork uses its saw like bill to cut up the dead animal it eats. As a result, the dead animal carcass is
accessible to some bees for food and egg laying.
Mouse/Flea
A flea feeds on a mouse's blood to the detriment of the mouse.
Silverfish! Army ants
Silverfish live and hunt with army ants. They share the prey.
Cowbird/Buffalo
As buffalos walk through grass, insects become active and are seen and eaten by cowbirds.
Yucca/Yucca Moth
Yucca flowers are pollinated by yucca moths. The moths lay their eggs in the flowers where the larvae hatch
and eat some of the developing seeds
Ostrich and Gazelle
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t ,. r
Biology 131
Keller/McHugh
Name
~
Date -----~-
II,
"
~,_
Per. 1 2 3 4 5 6 7 8 -I
These two animals feed next to each other in the grasslands, Both watch for predators and alert each other to
danger. The visual abilities of these two animals are different so they are able to identify threats the other
animal would not see.
Oxpecker/Rhinoceros
Oxpeckers feed on the ticks found on a rhinoceros.
Wrasse fishIBlack sea bass
Wrasse fish feed on the parasites found on the black sea bass' body.
Mistletoe/Spruce tree
Mistletoe extracts water and nutrients from the spruce tree.
Cuckoo/Warbler
A cuckoo may lay its eggs in a warbler's nest. The cuckoo's young will displace;the warbler's young and will
be raised by the warbler.
Cactus Wren/Cholla Cactus
The cactus wren builds its large football-shaped nest in the cholla cactus. The cholla, with its long spines,
provides a well protected home for the cactus wren and its young
Barnacle/Whale
Barnacles create home sites by attaching themselves to whales. This does not harm the whale.
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