Unit 3

1
Unit 3 Ecological Organizations

• Ecology the study of the interactions among
  living things, and between living things and
  their surroundings.
• 6 levels of organization
• 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

2
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.

3
Energy in Ecosystems

• Producers
• 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.

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Questions 1-2, page 400

• What are the five different levels of
  organization studied by ecologists?
• - organism, population, community, ecosystem,
  biome.
• Describe the three general methods used by
  ecologists to study organisms.
• 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 computer-based or math-based method
  used to predict how changes in one variable may
  affect another.

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Questions 3-4, p400

• 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.
• 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.

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Question 5, p400

• 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.

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Questions 1-2, p404

• 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 non-living.
• How would the removal of a keystone species
  affect an ecosystems biodiversity?
• The removal of a keystone species would decrease
  the ecosystems biodiversity.

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• 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.
• Human are sometimes described as being a keystone
  species. Does this label fit? Why or Why not?
• 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.

9

• 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

• How does the stability of an ecosystem depend on
  its producers?
• Producers bring energy into an ecosystem
• What are the two processes used by producers to
  obtain energy?
• Photosynthesis and chemosynthesis
• Few producers live deep below a lakes 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.

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• 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.
• 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.

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Questions 1-2, p411

• Why are food chains especially useful for
  describing the relationships of specialists?
• Specialists have specific diets that include only
  one type of organism, which produces a simple
  food chain.
• What happens to energy as it flows through a food
  web?
• Some energy is stored in the organism (10), but
  much energy is dissipated into the environment
  (90).

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• Only a small percentage of all consumers are
  specialists. What danger does a specialist
  faces that a generalist does not?
• If a specialists 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.
• How might the stability of an ecosystem be
  affected if all the decomposers were suddenly
  removed?
• The stability of the ecosystem would be
  negatively affected because without decomposers,
  vital nutrients would not be returned into the
  environment.

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Question 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.

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Questions 1-3, p416

• 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.
• 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.
• Why might farmers plant legumes such as peas to
  improve the nitrogen levels in their soil?
• - Legumes have root nodules, which contain
  nitrogen-fixing bacteria. Increased levels
  increase the fertility of the soil.

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• Explain the importance of decomposers to the
  overall biogeochemical cycle.
• Decomposers break down organisms and release
  various elements, including nitrogen and
  phosphorus, which other organisms can then use.
• How might Earths 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 Earths
  surface that would enable different types of
  organisms to evolve.

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Questions 1-3, p419

• How does an energy pyramid help to describe
  energy flow in a food web?
• An energy pyramid shows the relative contribution
  to energy flow made by each trophic level in an
  ecosystem.
• What is the difference between a biomass pyramid
  and a pyramid of numbers?
• 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.

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• 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.
• 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?
• The first trophic level uses 1000 kcal the
  second trophic level uses 100 kcal the third
  trophic level uses 10 kcal, leaving 1 kcal

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Question 5, p419

• 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.