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Chapters 13 Study Guide: Principles of Ecology
1. Define Ecology
Ecology – the study of interactions among organisms and between organisms and their environment
2. Give the definition of each of the following levels of organization:
a. Organism: a group of individuals so similar to one another that they can breed and produce
fertile offspring.
c. Populations: group of individuals that belong to the same species and live in the same area
d. Communities: different populations that live together is a defined area
e. Ecosystems: all the organisms that live in a similar area along with the nonliving material
f.
Biome: a major regional or global community of organisms characterized by the climate
conditions and plant communities that thrive there
3. How can an individual simultaneously be a part of a population, community, ecosystem, and biome?
Individuals make up populations (same species), a group of populations make up the community, a group of
communities along with abiotic factors make up an ecosystem, a group of ecosystems in similar climates make
up a biome.
4. What are the three methods for ecological research?
1. Observation
2. Experimentation
3. Modeling
5. Where can experiments be performed, and what are the positives and negatives of each (think back to your
active reader 13.1)?
Pro
Con
Lab experiment
More control of variables
Doesn’t always reflect what
would happen in the
individuals natural habitat
Field Experiment
More accurate picture of what is
happening in the individual’s habitat.
Can’t control variables. May
not be able to determine cause
and effect
6. What are the two types of modeling, and in what situations would modeling be used as a form of research?
a. Computer and modeling
b. Modeling is used to predict outcomes or answer “what would happen if…” Modeling is also used
when what is being studied is too big, too small, describe what happened in the past, or predict the future.
7. What is the difference between direct and indirect surveys?
a. Direct surveys are used for easy to spot organisms and involve using our 5 senses.
b. Indirect surveys are used for species that are difficult to track and include looking for other signs
of their presence.
8. What are the positives and negatives of quadrat sampling, and what organisms are best suited for this type of
population study?
Quadrat sampling is very efficient and quick when studying large populations, but it does not give an
exact number, only an estimate. Organisms that are slow moving, or immobile are best suited for quadrat
sampling.
9. Differentiate between biotic and abiotic factors. Give examples of each.
Biotic Factors- Living things within an ecosystem
Example: Bacteria, plants, animals, fungi.
Plants and algae that tadpoles use as shelter. The heron that eats the adult bullfrog.
Abiotic-Physical or non-living factors that shape an ecosystem
Example: Climate- Temperature, Precipitation, Humidity.
10. Define biodiversity and what biome has the most biodiversity?
Biodiversity is the assortment, or variety, of living thing in an ecosystem. Rainforests have more
biodiversity than other locations because of the wide variety of plants, animals, insects and other living
organisms found in the ecosystem.
11. Define keystone species, and describe how the removal of a keystone species will affect the stability of an
ecosystems biodiversity?
A keystone species is one that has an unusually large effect on its ecosystem and does not have many
predators. Since their impact is so great, if the species is removed the ecosystem will dramatically change.
Populations of the other species will fluctuate. The prey of the keystone species will increase since the predator
has been removed.
12. Explain what biotic factors used by the beaver are related to its role as a keystone species.
Beavers use branches of plants for food and to build dams. Beavers are also hunted as food for other
carnivores.
13. How do producers and consumers differ in their source of energy? How are they connected?
Producers make their own food and no not rely on eating for energy. Producers mostly use sunlight to do
this. Consumers need to eat other organisms (plants or animals) to obtain energy. Producers and consumers are
connected because consumers will eat producers to gain energy.
14. What are the two pathways of energy production for producers?
Photosynthesis when sunlight is available. Most producers use this to get energy.
Chemosynthesis when no sunlight is available. Few organisms use this process. This is mostly observed
in bacteria that live in extreme conditions.
15. List the five types of consumers and what type of food they eat.
1. Herbivores eat only plants.
2. Carnivores eat only animals.
3. Omnivores eat both plants and animals.
4. Detritivores eat dead organic matter.
5. Decomposers are detritivores that break down organic matter into simpler compounds using
digestive enzymes.
16. Fill in the food pyramid with the appropriate terms in each trophic level. (Some terms can be used in more
than one level)
Primary consumers
Producers
Secondary consumers
Top Consumers * Heterotrophs
Top consumers
Animals
Herbivores
Carnivores
Autotrophs
Secondary Consumer * Heterotrophs
Heterotrophs
Carnivores * Decomposers * Animals
Decomposers
Plants
Animals
Primary Consumer * Heterotrophs
Herbivores
Decomposer * Animals
Producers
Autotrophs
Plants
17. Draw the following food chain. An acorn is eaten by a squirrel, which is eaten by an owl. What describes
this relationship? How does it show energy flow?
Acorn  Squirrel  Owl. The energy flows in the direction of the arrow. The acorn is the producer, the
squirrel is the primary consumer (herbivore), and the owl is the secondary consumer (carnivore).
18. How are food chains and food webs related?
Food webs show the interconnected food chains in an ecosystem.
19. What is the relationship between Detritivore and decomposers?
Decomposers are detritivores that break down organic matter with gastric acid.
20. In the food web shown in the diagram below, label the producers, primary consumers, secondary consumer
and top consumer
Top Consumer
Top Consumer
Secondary
Consumer
Secondary
Consumer
Primary or Secondary
Consumer
Primary Consumer
Primary Consumer
Primary Consumer
Producer
Producer
21. What do the arrows in a food web/chain represent?
The arrows represent the flow of energy. Energy only flows in one direction.
22. Define specialist and generalist. Why is it that only a small percentage of consumers are specialists?
Specialists are consumers that primarily eat one specific organism or a very small number of organisms.
Generalists are consumers that have a varied diet.
There are fewer specialists then generalists because if there is a reduction in the population of the organism that
specialists eat they will starve. Generalists could simply eat other organisms.
23. Why is the role of a decomposer so important to an ecosystem?
The role of a decomposer is to break down organic matter. In doing this, nutrients are released back into the
soil. The nutrients are then taken up by producers, who are eaten by consumers. If decomposers did not break
down organic matter, then there would not be enough nutrients for the producers to grow.
24. Complete the following nutrient (biogeochemical) cycles;
a. Carbon Cycle:
Atmospheric
CO2
Combustion
Respiration
Photosynthesis
Decay
Respiration
Photosynthesis
Fossil
Fuels
b.
Water Cycle:
Condensation
Precipitation
Transpiration
Runoff
Evaporation
c. Nitrogen Cycle:
Denitrifying
Nitrogen Fixing
Decomposers
Nitrification
Nitrogen Fixing
25. How is the phosphorus cycle different from all other cycles?
Phosphorus is not found in the atmosphere. It is only found below ground.
26. Describe the main processes of the hydrologic cycle.
Water evaporates because of the heat of the sun, and then as it cools it condenses. When it condenses it creates
clouds, when the clouds get heavy, the water falls as precipitation. The precipitations will run-off into lakes and
the ocean. Some water will be absorbed by plants, or will seep into the ground as ground water. Over time the
ground water will connect with the ocean again. Some water will evaporate from plants because of the sun. This
is called transpiration.
27. What role do bacteria play in biogeochemical cycles?
Bacteria convert atmospheric nitrogen into useable ammonia and nitrates.
28. What is the difference between nitrogen-fixing bacteria and nitrifying bacteria?
Nitrogen fixing bacteria convert atmospheric nitrogen into ammonia. Nitrifying bacteria convert ammonia into
nitrates. Both of which can be used by plant.
29. Energy pyramids show the amount of energy available in each trophic level. What percentage of energy is
passed on to each trophic level?
Only 10 of energy is passed on to the next trophic level.
30. Why is only a small amount of energy passed on?
Organisms use 90% of energy to complete life processes and is lost as heat.
31. Complete the energy pyramid starting with 700 kilocalories at the producer level, and show the available
energy for 4 trophic levels.
.7 kilocalories
7 kilocalories
70 kilocalories
700 kilocalories
energy
lost
energy transferred
32. What does a biomass pyramid show?
A biomass pyramid shows the measure of total dry mass (weight) of an organism in a given area.
33. In pyramids of numbers, why do the numbers decrease as it goes up trophic levels?
The numbers decrease in each level because there needs to be enough organisms in the lower levels to feed
those in the upper levels in order to keep balance in an ecosystem.
34. What is the difference between a pyramid of biomass and a pyramid of numbers?
Pyramid of biomass represents the total dry weight for each organism. The pyramid of numbers represents the
total population number of an organism.
35. What would happen to a forest ecosystem if a fire destroyed most of the producers?
The entire ecosystem would be severely damaged. Producers are the biggest component of an ecosystem; they
play key roles in biochemical cycles, and are a major food source for primary consumers.