Principles of ecology

1
Principles of ecology
U N I T 2

• Chapter 13

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AKS Standards 11 Evaluate the dependence of all
organisms on one another and the flow of energy
and matter within their ecosystems. 11a
Investigate the relationships among organisms,
populations, communities, ecosystems and biomes.
3
Understanding ecology

• Ecology is the study of the interactions among
  living things, and between living things and
  their environment.
• The word ecology comes from the Greek word oikos,
  which means house. It was coined by German
  biologist Ernst Haeckel in 1866 to encourage
  biologists to consider the ways organisms
  interact.
• Until this time, most scientists studied a plant
  or an animal as though it existed in isolation
  as if it did not affect its surroundings, and its
  surroundings did not affect it.
• Organisms and their surroundings are
  interdependentwhat do you think this means?

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Levels of ecological organization
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Components of ecological research methods

• Ecological research methods include observation,
  experimentation, and modeling.
• Observation the act of carefully watching
  something over time.
• Experimentation may be performed in the lab or
  in the field with benefits and drawbacks to
  each type. All experiments must be controlled,
  that is, they must test only ONE variable at a
  time.
• Modeling scientists use computer and
  mathematical models to describe and model nature
  when their questions cannot be easily answered
  through observation or experimentation.

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AKS Standards 11 Evaluate the dependence of all
organisms on one another and the flow of energy
and matter within their ecosystems. 11a
Investigate the relationships among organisms,
populations, communities, ecosystems and biomes.
7
Biotic and abiotic factors

• All ecosystems are made up of living and
  nonliving components. These are referred to as
  biotic and abiotic factors.
• Biotic Factors living things, such as plants,
  animals, protists, fungi and bacteria. These
  organisms play a key role within their ecosystem.
• Abiotic Factors nonliving things such as
  moisture, temperature, wind, sunlight and soil.
  The balance of these factors can determine which
  living things can survive in a particular
  environment.
• An ecosystem is a complex web of connected biotic
  and abiotic factors, and all species are affected
  by changes to the biotic and abiotic factors in
  an ecosystem.

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biodiversity

• Biodiversity is the assortment, or variety, of
  living things in an ecosystem.

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Keystone species

• The complex relationships in ecosystems mean that
  a change in a single biotic or abiotic factor can
  have a variety of effects.
• In some cases, the loss of a single species may
  cause a ripple effect across an entire ecosystem.
  Such an organism is called a keystone species.
• A keystone species is a species that has an
  unusually large effect on its ecosystem.
• It is not generally the most abundant organisms,
  but its role in controlling the balance of other
  organisms is paramount to ecosystem stability.

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100
80
Otter number ( max. count)
60
40
20
0
(a) Sea otter abundance
400
300
Grams per 0.25 m2
200
100
0
(b) Sea urchin biomass
10
8
Number per 0.25 m2
6
4
2
0
1972
1985
1997
1989
1993
Year
(c) Total kelp density
Food chain
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Keystone species
INQUIRY CHALLENGE Explain why the beaver is
considered a keystone species in its environment.
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Critical thinking ACTIVITYINTERPRETING DATA

• Review the graph below.
• What would be an appropriate title for this
  graph?
• What do the data indicate about the role of the
  starfish in its environment?
• When Pisaster was removed from the intertidal
  zone, mussels eventually took over the rock face
  and eliminated most other invertebrates and
  algae. In a controlled area where it was not
  removed, there was little change in species
  biodiversity.

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Critical thinking ACTIVITYANALYZING

• Humans are sometimes described as being a
  keystone species. Does this label fit? Why or
  why not?
• No 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.

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AKS Standards 11b1 Explain the flow of energy
through an ecosystem by arranging the components
of a food chain , energy pyramid, and biomass
pyramid.
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Visual overview energy flow
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ENERGY in ecosystems

• All organisms must have a source of energy in
  order to survive. However, all organisms DO NOT
  obtain energy in the same way
• Producers get their energy from nonliving
  resources (make their own food). Also called
  autotrophs.
• Consumers get their energy by eating other
  living or once-living resources. Also called
  heterotrophs.
• Energy flows through an ecosystem IN ONE
  DIRECTION ONLY from producers to consumers.
• All ecosystems depend on producers, because they
  provide the basis for the ecosystems energy.
• Ecosystems with few producers generally have low
  levels of biodiversitycan you explain why?

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The Fate of solar energy
The flow of energy through an ecosystem is one of
the most important factors that determines the
systems capacity to sustain life. Without a
constant input of energy, living systems cannot
function.
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How producers make food

• Most producers use sunlight as their energy
  source. Photosynthesis is the process whereby
  solar energy is converted to the chemical energy
  stored in the bonds of sugar molecules.
• What types of organisms use photosynthesis to
  make food?
• Other producers use chemosynthesis, the process
  by which an organism forms carbohydrates using
  chemicals, rather than light, as an energy
  source.
• What types of organisms use chemosynthesis to
  make food?
• Inquiry Challenge Compare and contrast these
  two equations, considering both reactants and
  products. What are the similarities? What are
  the differences? In what type of environment
  would each reaction occur?
• Photosynthesis 6CO2 6H2O ?light? C6H12O6
  6O2
• Chemosynthesis 6CO2 6H2O 3H2S ? C6H12O6 3
  H2SO4

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Critical thinking ACTIVITYINFERRING

• How does the stability of an ecosystem depend on
  its producers?
• Could producers survive without consumers?
  Explain why or why not.
• Producers bring energy into an ecosystem
  without them, energy would cease to flow between
  trophic levels.
• Producers do not require consumers to fill
  material needs as a food source. So in that
  sense, producers do not need consumers to survive.

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ECOSYSTEM DYNAMICS
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ENERGY FLOW Food chains

• The simplest way to look at energy flow in an
  ecosystem is through a food chain this is a
  sequence that links species by their feeding
  relationships.

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TYPES OF CONSUMERS

• All consumers are not alike
• Herbivores organisms that eat only plants.
• Carnivores organisms that eat only animals.
• Omnivores organisms that eat both plants and
  animals.
• Detritivores organisms that eat detritus, or
  dead organic matter.
• Decomposers organisms that break down organic
  matter into simpler compounds these organisms
  are vital to the stability of an ecosystem
  because they recycle vital nutrients back into
  the environment.

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Trophic levels

• Trophic levels are the levels of nourishment in a
  food chain.
• For example, the producer-herbivore-carnivore
  chain has three trophic levels.
• Producers are at the first trophic level.
• Herbivores are at the second trophic level.
• Carnivores are at the highest trophic level.

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Food webs

• A food web is a model that shows the complex
  network of feeding relationships and the flow of
  energy within an ecosystem.
• At each link in a food web, some energy is stored
  within an organism and used for growth and
  metabolism, and some energy is dissipated into
  the environment as heat.
• The stability of any food web depends on the
  presence of producers, because they form the base
  of the food chain.
• An organism may have multiple feeding
  relationships within a food web.

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food web
Animated Biology Build a Food Web
http//www.classzone.com/cz/books/bio_07/resources
/htmls/animated_biology/unit5/bio_ch13_0421_ab_foo
dweb.html
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Interactive reviewEcosystem energy flow

• http//www.classzone.com/cz/books/bio_07/resources
  /htmls/interactive_review/bio_intrev.html

Complete this interactive review using your
virtual textbook at home. Concept maps are an
excellent way to organize your thoughts and
review material!
27
Critical thinking ACTIVITYPREDICTING

• How might the stability of an ecosystem be
  affected if all of the decomposers were suddenly
  removed? Explain.
• 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.
• The stability would be negatively affected
  because without decomposers, vital nutrients
  would not be returned to the environment.
• The entire food web would be affected because the
  oil will likely kill off phytoplankton, the
  producers of the food web. This would lead to
  loss of consumer levels. Plants and animals
  along the shore may also be affected as the oil
  seeps onto the shore.

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AKS Standards 11b Explain the need for cycling
of major nutrients (C, H, O, N, P) and
identifying and illustrating the conservation of
matter.
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Cycling of matter

• Since life in most ecosystems requires a constant
  inflow of energy, Earth is an open system in
  terms of energy.
• However, in terms of matter, Earth is a closed
  system.
• Unlike energy, which flows in ONE DIRECTION ONLY
  through an ecosystem, matter is RECYCLED within
  and between ecosystems.
• This is because, while matter can change in form,
  it cannot be created nor destroyed.

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Lifes essential elements

• Many elements are essential to the structure and
  function of organisms.
• Carbon, hydrogen, oxygen, nitrogen, phosphorus,
  and sulfur, in addition to water, are important
  to life.
• All of these elements cycle through ecosystems.
• A biogeochemical cycle is the movement of a
  particular chemical through the biological and
  geological (living and nonliving) parts of an
  ecosystem.
• Many substances change state as they move through
  their cycles.

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The hydrologic (water) cycle
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The carbon cycle
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The nitrogen cycle
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The phosphorus cycle
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Interactive reviewCycling of matter

• http//www.classzone.com/cz/books/bio_07/resources
  /htmls/interactive_review/bio_intrev.html

Complete this interactive review using your
virtual textbook at home. Concept maps are an
excellent way to organize your thoughts and
review material!
36
Critical thinking ACTIVITYAPPLYING

• 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 nitrogen
  levels increase the fertility of the soil.

37
AKS Standards 11 Evaluate the dependence of all
organisms on one another and the flow of energy
and matter within their ecosystems. 11a
Investigate the relationships among organisms,
populations, communities, ecosystems and biomes.
38
Pyramid models

• Ecologists often model the structure of an
  ecosystem, including both matter and energy,
  using a pyramid.
• The pyramids can represent the general flow of
  energy through an ecosystem, or they can
  represent the mass or numbers of organisms at
  each trophic level.
• Important pyramid models include
• Energy Pyramids
• Biomass Pyramids
• Pyramids of Numbers

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The energy pyramid

• Because energy is lost at each stage of a food
  chain, the longer the chain is, the more energy
  is lost overall.
• The total energy used by producers far exceeds
  the energy used by the consumers they support.
• An energy pyramid is a diagram that compares
  energy used by producers, primary consumers, and
  other trophic levels.
• It illustrates how available energy is
  distributed among trophic levels in an ecosystem,
  and also the inefficiency of energy transfer
  through ecosystems.

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Energy pyramid
A typical energy pyramid has a very large section
at the base for the producers, and sections that
become progressively smaller above. At each
trophic level, some energy is used for growth and
metabolism or expelled as waste. The remaining
energy is dissipated as heat this may be up to
90 of the original energy gained by the producer
level.
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The Biomass pyramid

• Biomass is a measure of the total dry mass of
  organisms in a given area.
• When a consumer incorporates the biomass of a
  producer into its own biomass, a great deal of
  energy is lost in the process as heat and waste.
• A biomass pyramid is a diagram that compares the
  biomass of different trophic levels within an
  ecosystem.
• Unlike the energy pyramid, which represents
  energy use, a biomass pyramid provides a picture
  of the mass of producers needed to support
  primary consumers, and so on.

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Biomass pyramid
We would expect more biomass to be available at
the bottom of the pyramid in comparison to the
topwhy?
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The pyramid of numbers

• A pyramid of numbers shows the numbers of
  individual organisms at each trophic level in an
  ecosystem.
• This type of pyramid is particularly effective in
  showing the vast number of producers required to
  support even a few top level consumers.

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CRITICAL THINKING ACTIVITYCALCULATING

• Determine how quickly energy flows from an
  ecosystem by calculating the loss of energy in a
  sample system
• Begin by drawing a pyramid that has 15,000 energy
  units.
• Calculate the number of trophic levels that can
  be supported by this energy source stop when
  you reach a value less than one.
• Then, do a calculation for a system twice the
  size of the first determine whether or not
  there is an appreciable difference.
• Why is an herbivorous diet more energy efficient
  than a carnivorous diet? Explain your answer.
• It is more efficient because it is the closest
  trophic level to the producers, meaning there is
  more available energy to use.