Ecology Review
Record answers on an additional sheet of paper.
Essential Questions:
1. What relationships exist between living things?
2. How do matter and energy flow through an ecosystem?
3. What factors influence population size?
4. How do human activities impact and alter the environment?
Ecological Relationships
1. Explain the different types of symbiotic relationships that exist. Provide examples of each,
including your reason for categorizing them in that relationship type.
Mutualism: both organisms benefit (ex. Flower and Bee, the bee gets food and the flower gets its pollen
spread around, both benefit)
Commensalism: one organism benefits, the other neither benefits or is harmed (ex cattle egret and
cattle, the cattle stirs up insects in the grass while the egret eats the insects. No effect on the cattle, the
cattle egret benefits)
Parasitism: one organism benefits, the other is harmed (ex. fleas and dogs, the fleas suck the dogs blood,
while the dogs itch, the flea benefits and the dog is harmed).
2. Explain a predator prey relationship. Give an example and include which organism is the
predator and which is the prey. Does your example only include animals? Does it have to?
The predator is the organism that eats the other organism. The prey is the organism that gets eaten.
Example: bird and worm, insect and leaf. The examples do not have to only include animals. They can
also include a consumer and a producer, they just have to be two organisms.
3. Explain the difference between intraspecific competition and interspecific competition. Give an
example of each, including your reason for categorizing them in that relationship type.
Intraspecific competition is competition within the same species. Example: Two rams fighting over a
mate. They are competing for a resource and are within the same species.
Interspecific competition is competition between different species. Example: A lion and a hyena fighting
over a food source. They are competing for a resource and are two different species.
4. Categorize these relationships
a. Desert mistletoe extracts nutrients from a desert willow. When the mistletoe grows and
requires more nutrients than the willow provides, the willow tree dies. Parasitism
b. Moss growing on trees benefits by being raised above forest floor competition, while
the tree doesn't get much out of the deal either way. Commensalism
c. A phainopepla (a bird) eats mistletoe berries. The bird, while perching, passes
undigested seeds in droppings to host trees ensuring survival of both the mistletoe and
the phainopepla. Mutualism
d. Grasshopper eating a leaf. Predator-Prey
e. Lion chases a zebra and eats it. Predator -Prey
f. Two chipmunks fighting for the same nesting place. Intraspecific Competition
g. An oak tree and a maple tree living in the same forest. Interspecific Competition
5.
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Describe the process of primary succession.
Barren rock is present
Low growing plants (mosses, ferns, lichens) begin to colonize
Fast growing grasses, flowering plants and small shrubs begin to grow and a thin layer of soil
develops
Fast growing trees form a low forest and shade out lower plants
100-200 years since colonization began, large slow growing trees become established
6.
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Describe the process of secondary succession.
An ecosystem has been established and a natural disaster reduces the amount of life in an area.
Some vegetation may still remain.
Same process as primary succession may occur, but usually does not take as long to re-establish.
7. Categorize these succession events
a. Burning a prairie Secondary (soil is already in place)
b. Mt. St. Helen erupting Primary (barren rock that needs to have soil created)
Energy and Matter Cycle Through and Ecosystem
8. Explain what happens to the energy in an energy/population size pyramid as you move up the
pyramid and how does this impact how many prey need to be consumed by the predator.(Hint:
How much energy is transferred to the predator from each prey).
9. In an energy/population size pyramid, there are 1000 algae, 100 minnows, 10 fish, 1 Raccoon. In
the ecosystem where these organisms live, there has been a natural event that has decreased
the number of algae. Now only 500 algae are available. Will this impact the rest of the
pyramid? If so, how?
 Reduces the number of organisms that can survive due to less amount of energy, 500 algae, 50
minnows, 5 fish, no raccoons, not enough energy to support high predators
10. Explain the water cycle.
 Water is absorbed into the atmosphere (evaporation) forms clouds (condensation) and falls back
to the ground (precipitation). Water enters large bodies of water as runoff or percolates through
the ground into aquifers. Water also enters the atmosphere through transpiration (byproduct of
cellular respiration and photosynthesis in plants).
11. Explain the carbon cycle. Indicate what would happen if the decomposers were unable to do
their job.
 Organic matter (plants and animals) die and are broken down by decomposers (fungi, bacteria).
Decomposing material becomes fossil fuels that are extracted and burned as fuel by humans.
During combustion, carbon re-enters the atmosphere as carbon dioxide. Carbon dioxide is used
by plants during photosynthesis and consumed by animals in the form of glucose and other
carbohydrates. Carbon dioxide also combines with water and contributes to the acidity of lakes
and rivers.
 Without decomposers, organic matter would not break down into smaller carbon molecules or
develop into fossil fuels.
12. Explain the nitrogen cycle. Indicate what would happen if the amount of nitrifying bacteria
decreased.
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Organic matter contains nitrogen in their proteins. When they die, decomposers break
down the organic matter and release nitrogen compounds into the soil. The nitrogen
cannot be used in the form that it is released, so nitrifying bacteria convert the nitrogen
into a usable form. Plants absorb the nitrogen and uses it to build proteins. Other
nitrogen compounds enter the atmosphere where they are converted to usable
compounds by lightning (nitrification).
Without bacteria, the organic matter would not break down and the nitrogen would
remain in the protein macromolecules.
13. Explain the phosphorous cycle.
 Phosphorus is a major component in rocks. During weathering, rocks erode and become part of
the soil. Plants absorb the phosphorus through their roots and then animals consume the
phosphorus when they eat the plants. When the organic matter dies, decomposers break down
the phosphorus and release it back into the soil. It then can be reused by plants or become a
component of sediments. Under pressure, sediments can reform rocks and the rocks can become
part of the environment through the process of uplifting.
Population Ecology
 Describe the differences between clumped, random and uniform population distributions. Give
an example of each.
 Clumped: organism live together in a small area (high density), packs of animals (wolves),
schools of fish
 Random: organisms live alone or not in large groups (low density), high level predators, tiger,
eagle
 Uniform: organisms live in highly arranged pattern, apples in orchard
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Explain the difference between population density and population distribution.
Population density: number of organisms in a particular area (high density, low density)
Population distribution: the pattern that distributes the organisms in an area (clumped, random,
uniform)
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Explain some possible factors that could cause a population to shift from a low density to a high
density (assuming the population stays the same).
Low density to high density: predation, food sources diminish, space reduction, nutrient source
reduction, reproduction challenges
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Compare density dependent factors to density independent factors. Give examples of each.
Density dependent factors will reduce a population significantly when density is high (a lot of
organisms in one area) EX: disease, predation, migration
Density independent factors will reduce a population regardless if there are a lot of organisms in
one area (low density) EX: natural disaster
If a population is declining, explain what has to be true using the terms births, deaths,
immigration and emigration.
Births<deaths; immigration<emigration
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If a population is increasing, explain what has to be true using the terms births, deaths,
immigration and emigration.
Births>deaths; immigration>emigration
If a population is stable, explain what has to be true using the terms births, deaths, immigration
and emigration.
Births=deaths; immigration=emigration
Using the graph above, answer the following questions.
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What type of organism shows a steady decline in population at all stages of life?
Type II
What type of organism shows a loss of most of the individuals in its population at an early life
stage?
Type III- produce many young, many die or are eaten before maturity
What type of organism show most of its population making it past reproductive age?
Type I- produce few offspring, nurture offspring
Draw a logistic growth curve. Draw and exponential growth curve. Why do populations follow a
logistic growth curve instead of an exponential growth curve?
Exponential
Logistic
Exponential: Organisms grow rapidly due to a
lot of space and resources, lots of offspring
result in rapid death when resources are used up
Logistic: Organisms begin to reproduce and
populate an area, taper off and are able to
sustain population once they reach carrying
capacity
 Describe a situation where predation and competition can affect populations (think Isle Royale).
Intraspecific Competition: Wolves compete for a mate/food
Interspecific Competition: Cheetahs and lions compete for the same prey
Predators: Lynx and hare- lynx population will increase as long as the hare are plentiful, too many lynx =
fewer hares, fewer hares= reduction of lynx population
Human Activities Impact and Alter the Environment
 Describe 3 situations where humans have impacted or altered the environment.
 You may cite any of the presentations: pollution, deforestation, mining, poaching, etc.