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Unit 3 – Ecological Organizations
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Ecology – the study of the interactions among
living things, and between living things and their
surroundings.
6 levels of organization:
1.
2.
3.
4.
5.
6.
organism – individual living thing
population – group of individuals of the same species
in an area at a certain time.
community – a group of populations in a certain area.
ecosystem – all the organisms in an area along with
non-living factors (climate, water, soil, etc.)
biome – major regional or global community of
organisms
biosphere – anywhere on earth where life is found,
from high mountains to deep ocean trenches
Biotic and Abiotic Factors
Biotic factors – living things such as
bacteria, fungus, plants and animals
Abiotic factors – non-living things such
as moisture, temperature, wind, sunlight
and soil.
Biodiversity – variety of living things in an
ecosystem
Keystone Species – species that has an
unusually large effect on an ecosystem.
Energy in Ecosystems
Producers :

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get their energy from non-living sources
(make their own food), sometimes called
autotrophs
Get their energy either by photosynthesis
(from light) or chemosynthesis (from
chemicals)
Consumers:

get their energy by consuming/eating another
living thing (dead or alive), sometimes called
heterotrophs.
Questions 1-2, page 400
1. What are the five different levels of
organization studied by ecologists?
- organism, population, community,
ecosystem, biome.
2. Describe the three general methods used by
ecologists to study organisms.
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Observation is the act of watching something over
time, such a population of birds. Experimentation
can occur in the lab or in the field and involves
testing a hypothesis. Modeling is a computerbased or math-based method used to predict how
changes in one variable may affect another.
Questions 3-4, p400
3. What ecological research methods would you use to study bird
migration? Explain your choices.
Observation – band birds and capture them at each end of
their migratory route to record their movement.
Experimentation – devise an experiment to test the what
triggers migration. Modeling – develop a computer model that
includes different variables that might predict the time and
path of migration.
4. How might an ecologist use modeling to study fire in a forest
ecosystem? What might be some key variables used to create
the model?
Sample answer: Ecologists could use models to determine
movement of fire, locations where prescribed burns should
take place, and areas with the potential for fire outbreaks.
Key variables might include forest density, types of trees,
plant and animals populations, wind patterns, and weather
conditions.
Question 5, p400
5. Ernst Haeckel was greatly influenced by the
writings of Charles Darwin. How do the
principles of ecology relate to understanding
how adaptations occur?
- Species are adapted to their environments.
This concept is directly related to the study of
ecology, in which the interactions between
organisms and the environment are studied.
By understanding the interactions within an
ecosystem, scientists can develop an
understanding of how populations evolve in
response to their environments.
Questions 1-2, p404
1. Select an ecosystem that is familiar to you and
describe the biotic and abiotic factors that exist
there.
- Answers should show that students understand that
biotic factors are living things and abiotic are nonliving.
2. How would the removal of a keystone species
affect an ecosystem’s biodiversity?
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The removal of a keystone species would
decrease the ecosystem’s biodiversity.
3. Explain how a change in a an abiotic factor
such as sunlight would affect biodiversity.
- Changes in amount of sunlight might affect local
temperatures, leading to a change in the numbers
and types of species in the ecosystem. New
species may move into the area, taking the place
of those that cannot survive.
4. Human are sometimes described as being a
keystone species. Does this label fit? Why or
Why not?
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Keystone species are those that help to establish
and maintain a complex web of life. Humans do
not fit this label because human activities often
decrease, rather than increase biodiversity.
5. What role might an abiotic factor such as
temperature play in the evolution of a species?
- A long-term temperature change could result
in selective pressure that selects for
individuals better adapted to the temperature,
causing populations to evolve. It could alter
the types of food available, again creating
selective pressure toward individuals that can
take advantage of different food sources.
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Questions 1-3, page 407
1. How does the stability of an ecosystem
depend on its producers?
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Producers bring energy into an ecosystem
2. What are the two processes used by
producers to obtain energy?
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Photosynthesis and chemosynthesis
3. Few producers live deep below a lake’s
surface. Suggest an explanation for this
pattern.
- sunlight cannot penetrate the water to a great
depth, so photosynthesizing organisms are
more common near the surface.
4. Could producers survive without consumers?
Explain why or why not?
- Producers do not require consumers to fill material
needs as a food source. So in that sense,
producers do not need consumers to survive.
5. How might chemosynthetic organisms help
scientists to understand how life developed on
Earth?
- Chemosynthetic organisms live in environments that
may be similar to those that existed on Earth
billions of years ago, when life was beginning to
develop. Studying these organisms enables
scientists to infer how different life forms may have
evolved as Earth changed.
Questions 1-2, p411
1. Why are food chains especially useful for
describing the relationships of specialists?
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Specialists have specific diets that include only
one type of organism, which produces a simple
food chain.
2. What happens to energy as it flows through a
food web?
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Some energy is stored in the organism (10%), but
much energy is dissipated into the environment
(90%).
3. Only a small percentage of all consumers are
specialists. What danger does a specialist
faces that a generalist does not?
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If a specialist’s food source becomes scarce or
disappears, the population may die out. A
generalist facing the loss of one of its food sources
can shift to a different food source.
4. How might the stability of an ecosystem be
affected if all the decomposers were suddenly
removed?
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The stability of the ecosystem would be negatively
affected because without decomposers, vital
nutrients would not be returned into the
environment.
Question 5
5. How might an oil spill in the ocean affect an
aquatic food web? What might happen to the
food web on land located near the spill?
Explain your answers.
- The entire food web would be affected by the oil
spill. Oily water may kill off phytoplankton. The
loss of smaller fish would affect larger fish, which
in turn affect tertiary consumers. Plants and
animals that live along the coast would also be
affected as the oil seeped onto the shore. The
overall effect would be a decline in the availability
of food sources both within and outside the ocean.
Questions 1-3, p416
1. How does the hydrological cycle move water through
the environment?
Precipitation falls to Earth, and transpiration and
evaporation transfer water back into the atmosphere
as water vapour.
2. What are four elements that cycle through ecosystems,
and why are they important?
- oxygen, carbon, nitrogen and phosphorus; they are all
necessary for life on Earth.
3. Why might farmers plant legumes such as peas to
improve the nitrogen levels in their soil?
- Legumes have root nodules, which contain nitrogenfixing bacteria. Increased levels increase the fertility
of the soil.
4. Explain the importance of decomposers to the
overall biogeochemical cycle.
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Decomposers break down organisms and release
various elements, including nitrogen and
phosphorus, which other organisms can then use.
5. How might Earth’s biogeochemical cycles help
scientists to understand the early history of life
on Earth?
- Studies of the biogeochemical cycles and how they
interact may help scientists reconstruct the
sequence of events that led to changes at Earth’s
surface that would enable different types of
organisms to evolve.
Questions 1-3, p419
1. How does an energy pyramid help to describe
energy flow in a food web?
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An energy pyramid shows the relative contribution
to energy flow made by each trophic level in an
ecosystem.
2. What is the difference between a biomass
pyramid and a pyramid of numbers?
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A biomass pyramid compares the mass of
organisms that make up each trophic level in an
ecosystem; a pyramid of numbers compares the
number of individual organisms that make up each
trophic level.
3. How would you draw a pyramid of numbers for
a dog with fleas? What shape would it take?
- The bottom level would be the dog, and the fleas
would be the top level. This would be an inverted
pyramid because there are many fleas to just one
dog.
4. If each level in a food chain typically loses 90
percent of the energy it takes in, and the
producer level uses 1000 kcal of energy, how
much energy is left after the third trophic level?
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The first trophic level uses 1000 kcal; the second
trophic level uses 100 kcal; the third trophic level
uses 10 kcal, leaving 1 kcal
Question 5, p419
5. Why is a herbivorous diet more energy
efficient than a carnivorous diet? Explain
your answer.
- a herbivorous diet is more energy efficient
because it is the closest trophic level to
producers, meaning there is more
available energy to use.