Ecology

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Ecology

• Biology

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What you will learn

• 1. Ecology general overview.
• A. Definition
• B. Levels of Organization
• C. Abiotic vs. Biotic Factors
• 2.Populations
• 3.Communities
• 4.Ecosystems

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1 A. Definition

• Ecology is the study of how organisms interact
  with their environment and each other.
• This interaction of organisms is a two-way
  interaction. Organisms are affected by their
  environment, but by their activities they also
  change the environment.

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1 B. Levels of Organization

• Ecology is studied on several levels
• Organism
• Ecologists may examine how one kind of organism
  meets the challenges of its environment, either
  through its physiology or behavior.
• Population
• Group of individuals of the same species living
  in a particular geographic area.
• Community
• Consists of all the populations of different
  species that inhabit a particular area.
• Ecosystem
• Includes all forms of life in a certain area and
  all the nonliving factors as well.
• Biosphere
• The global ecosystem the sum of all the planets
  ecosystems.
• Most complex level in ecology, including the
  atmosphere to an altitude of several kilometers,
  the land down to and including water-bearing
  rocks under 3,000 m under Earths surface, lakes
  and streams, caves, and the oceans to a depth of
  several kilometers.
• It is self contained, or closed, except that its
  photosynthesizers derive energy from sunlight,
  and it loses heat to space.

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1 B. Levels of Organization
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1 C. Abiotic vs. Biotic Factors

• Abiotic components
• Physical and chemical factors (abiotic) affecting
  the organisms living in a particular ecosystem.
• Biotic components
• Organisms making up the community

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1 C. Examples of Biotic Factors
Anything that has the characteristics of life!
Starfish
Even bacteria!
Polar bears
Trees and grass
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1 C. Examples of Abiotic Factors

• Solar energy
• Water
• Temperature
• Wind
• Soil composition
• Unpredictable disturbances

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2 . What is a population?

• Population-
• a group of individuals of a single species that
  occupy the same general area.
• Rely on the same resources, are influenced by the
  same environmental factors, and have a high
  likelihood of interacting and breeding with one
  another.

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3. Communities

• A few terms you should know
• Species
• A group of organisms which can interbreed with
  each other and able to produce a fertile
  offspring.
• Habitat
• the environment in which a species normally lives
  or the location of a living organism.

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3. Communities

• A biological community is an assemblage of all
  the populations of organisms living close enough
  together for potential interaction.
• Key characteristics of a community
• a.Species diversity
• b.Dominant species
• c.Response to disturbances
• d.Trophic structure
• e. Community interactions

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3. Response to Disturbances

• Communities change drastically following a severe
  disturbance that strips away vegetation and even
  soil.
• The disturbed area may be colonized by a variety
  of species, which are gradually replaced by a
  succession of other species, in a process called
  ecological succession.

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3. Response to Disturbances

• Primary succession
• When ecological succession begins in a virtually
  lifeless area with no soil.
• Usually takes hundreds or thousands of years.
• For example, new volcanic islands or rubble left
  by a retreating glacier. Often the only
  life-forms initially present are autotrophic
  bacteria. Lichens and mosses are commonly the
  first large photosynthesizers to colonize the
  area. Soil develops gradually as rocks weather
  and organic matter accumulates from the
  decomposed remains of the early colonizers.
  Lichens and mosses are gradually overgrown by
  grasses and shrubs that sprout from seeds blow in
  from nearby areas or carried in by animals.
  Eventually, the area is colonized by plants that
  become the communitys prevalent form of
  vegetations.

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3. Response to Distrurbances

• Secondary succession
• Occurs when a disturbance has destroyed an
  existing community but left the soil intact.
• For example, forested areas that are cleared for
  farming, areas impacted by fire or floods.

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3. Response to Disturbances

• Primary Succession
• Example autotrophic prokaryotes?lichens,
  mosses?grasses?shrubs?trees?climax communty
• Secondary Succession
• Example herbaceous plants? woody shrubs? trees
  ?climax community

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3. Response to Disturbances

• Early successional communities are characterized
  by a low species diversity, simple structure and
  broad niches
• The succession proceeds in stages until the
  formation of a climax community.
• The most stable community in the given
  environment until some disturbance occurs.

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3. Response to Disturbances

• Are disturbances always a bad thing? When can
  they be beneficial?

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3. Response to Disturbances

• Small-scale disturbance often have positive
  effects. ?
• For example, when a large tree falls in a
  windstorm, it disturbs the immediate
  surroundings, but it also creates new habitats.
• For instance, more light may now reach the forest
  floor, giving small seedlings the opportunity to
  grow or the depression left by its roots may
  fill with water and be used as egg-laying sites
  by frogs, salamanders, and numerous insects.
• Small-scale disturbances may enhance
  environmental patchiness, which can contribute to
  species diversity in a community.

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3. Trophic Structure

• The feeding relationships among the various
  species making up the community.
• A communitys trophic structure determines the
  passage of energy and nutrients from plants and
  other photosynthetic organisms to herbivores and
  then to carnivores.

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3. Trophic Structure

• The sequence of food transfer up the trophic
  levels is known as a food chain
• Trophic levels are arranged vertically, and the
  names of the levels appear in colored boxes.
• The arrows connecting the organisms point from
  the food to consumer. This transfer of food moves
  chemical nutrients and energy from the producers
  up though the trophic levels in a community.

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3. Trophic Structure

• At the bottom, the trophic level that supports
  all others consists of autotrophs, called
  producers.
• Photosynthetic producers use light energy to
  power the synthesis of organic compounds.
• Plants are the main producers on land.
• In water, the producers are mainly photosynthetic
  protists and cyanobacteria, collectively called
  phytoplankton. Multicellular algae and aquatic
  plants are also important producers in shallow
  waters.

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3. Trophic Structure

• All organisms in trophic levels about the
  producers are heterotrophs, or consumers, and all
  consumers are directly or indirectly dependent on
  the output of producers

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3. Trophic Structure

• Trophic Levels
• Primary producers
• Mostly photosynthetic plants or algae
• Primary consumers
• Herbivores, which eat plants, algae, or
  phytoplankton.
• On land include grasshoppers and many insects,
  snails, and certain vertebrates like grazing
  mammals and birds that eat seeds and fruits
• aquatic environments include a variety of
  zooplankton (mainly protists and microscopic
  animals such as small shrimp) that eat
  phytoplankton.
• Secondary consumers
• Include many small mammals, such as a mouse, a
  great variety of small birds, frogs, and spiders,
  as well as lions and other large carnivores that
  eat grazers.
• In aquatic ecosystems, mainly small fishes that
  eat zooplankton
• Tertiary consumers
• Snakes that eat mice and other secondary
  consumers.
• Quaternary consumers
• Include hawks in terrestrial environments and
  killer whales in marine environment.

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3. Trophic Structure

• Another trophic level of consumers are called
  detritivores which derive their energy from
  detritus, the dead material produced at all the
  trophic levels.
• Detritus includes animal wastes, plant litter,
  and all sorts of dead organisms.
• Most organic matter eventually becomes detritus
  and is consumed by detritivores.
• A great variety of animals, often called
  scavengers, eat detritus. For instance,
  earthworms, many rodents, and insects eat fallen
  leaves and other detritus. Other scavengers
  include crayfish, catfish, crows, and vultures.

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3. Trophic Structure

• A communitys main detritivores are the
  prokaryotes and fungi, also called decomposers,
  or saprotrophs, which secrete enzymes that digest
  organic material and then absorb the breakdown
  products.
• Enormous numbers of microscopic fungi and
  prokaryotes in the soil and in mud at the bottom
  of lakes and oceans convert (recycle) most of the
  communitys organic materials to inorganic
  compounds that plants or phytoplankton can use.
• The breakdown of organic materials to inorganic
  ones is called decomposition.

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3. Trophic Structure
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3. Trophic Structure

• A more realistic view of the trophic structure of
  a community is a food web, a network of
  interconnecting food chains.
• Food webs, like food chains, do not typically
  show detrivores, which consume dead organic
  material from all trophic levels.

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3. Community Interactions

• Consider this
• Youve planted a garden in your backyard. You see
  that a squirrel population and a chipmunk
  population has begun to inhabit the area. There
  reproductive patterns are similar, they eat the
  same food, and have similar sleeping patterns.
• What do you expect to happen?
• Is it possible for them to cohabit the area?

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3. Community Interactions

• Interspecific competition
• If two different species are competing for the
  same resource.
• Causes the growth of one or both populations may
  be inhibited.
• May play a major role in structuring a community.
  
• Examples
• Weeds growing in a garden compete with garden
  plants for nutrients and water.
• Lynx and foxes compete for prey such as snowshoe
  hares in northern forests.

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3. Community Interactions

• Intraspecific Competition
• Intense competition that exists within
  individuals of the same population because they
  compete for the exact same habitat and resources

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3. Community Interactions

• The competitive exclusion principle applies to
  what is called a species niche.
• In ecology, a niche is a species role in its
  community, or the sum total of its use of the
  biotic and abiotic resources of its habitat.

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3. Community Interactions

• A niche is the functional position of an organism
  in its environment, comprising its habitat,
  resources and the periods of time during which it
  is active.

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3. Community Interactions

• Predation is an interaction between species in
  which one species, the predator, kills and eats
  another, the prey.
• Because eating and avoiding being eaten are
  prerequisites to reproductive success, the
  adaptations of both predators and prey tend to be
  refined through natural selection.

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3. Community Interactions

• What are some ways predators can catch prey?
• What tools can they use?
• What are some essential characteristics?

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3. Community Interactions

• Examples of prey capturing strategies
• Most predators have acute senses enable them to
  locate prey.
• In addition, adaptations such as claws, teeth,
  fangs, stingers, or poisons help catch and subdue
  prey.
• Predators are generally fast and agile, whereas
  those that lie in ambush are often camouflaged in
  their environments.
• Predators may also use mimicry some snapping
  turtles have a tongue that resembles a wriggling
  worm, thus luring small fish.

Chemical Defense
Camouflage
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3. Community Interactions

• What are some ways prey can avoid predators?
• What tools can they use?
• What are some essential characteristics?

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3. Community Interactions

• Predator defenses
• Mechanical defenses such as the porcupines
  sharp quills or the hard shells of clams and
  oysters.
• Chemical defenses animals are often bright
  colored, a warning to predators like a poison
  arrow-frog or a skunk.
• Batesian mimicry a palatable or harmless species
  mimics an unpalatable or harmful one like the
  king snake mimics the poisonous coral snake
• Mullerian mimicry two unpalatable species that
  inhabit the same community mimic each other like
  bees and wasps

Batesian Mimicry
Mullerian Mimicry
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3. Community Interactions

• Herbivory
• Animals that eat plants or algae
• Aquatic herbivores include sea urchins, snails,
  and some fishes.
• Terrestrial herbivores include cattle, sheep, and
  deer, and small insects.
• Herbivorous insects may locate food by using
  chemical sensors on their feet, and their
  mouthparts are adapted for shredding tough
  vegetation or sucking plant juices.
• Herbivorous vertebrates may have specialized
  teeth or digestive systems adapted for processing
  vegetation. They may also use their sense of
  smell to identify food plants.
• Because plants cannot run away from herbivores,
  chemical toxins, often in combination with
  various kinds of anti-predator spines and thorns,
  are their main weapons against being eaten.

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3. Community Interactions

• Herbivory
• Some herbivore-plant interactions illustrate the
  concept of coevolution, a series of reciprocal
  evolutionary adaptations in two species.
• Coevolution occurs when a change in one species
  acts as a new selective force on another species,
  and counteradaptation of the second species in
  turn affects the selection of individuals in the
  first species.

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3. Community Interactions

• Herbivory Coevolution Example
• an herbivorous insect (the caterpillar of the
  butterfly Heliconius, top left) and a plant (the
  passionflower Passiflora, a tropical vine).

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3. Community Interactions

• Herbivory Coevolution Explanation
• Passiflora produces toxic chemicals that protect
  its leaves from most insects, but Heliconius
  caterpillars have digestive enzymes that break
  down the toxins. As a result, Heliconius gains
  access to a food source that few other insects
  can eat.
• The Passiflora plants have evolved defenses
  against the Heliconius insect. The leaves of the
  plant produce yellow sugar deposits that look
  like Heliconius eggs. Therefore, female
  butterflies avoid laying their eggs on the leaves
  to ensure that only a few caterpillars will hatch
  and feed on any one leaf. Because of this, the
  Passiflora species with the yellow deposits are
  less likely to be eaten.

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3. Community Interactions

• Symbiotic Relationships are interactions between
  two or more species that live together in direct
  contact.
• Three main types
• Parasitism
• Commensalism
• Mutualism
• Parasitism and mutualism can be key factors in
  community structure.

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3. Community Interactions

• Parasitism
• A parasite lives on or in its host and obtains
  its nourishment from the host.
• For example A tapeworm is an internal parasite
  that lives inside the intestines of a larger
  animal and absorbs nutrients from its hosts.
• Another example Ticks, which suck blood from
  animals, and aphids, which tap into the sap of
  plants, are examples of external parasites.
• Natural selection favors the parasites that are
  best able to find and feed on hosts, and also
  favors the evolution of host defenses.

Tapeworm in Small Intestine
Tick on a dog
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3. Community Interactions

• Commensalism
• One partner benefits without significantly
  affecting the other.
• Few cases of absolute commensalism have been
  documented, because it is unlikely that one
  partner will be completely unaffected.
• For example algae that grow on the shells of
  sea turtles, barnacles that attach to whales, and
  birds that feed on insects flushed out of the
  grass by grazing cattle.

Algae on Sea Turtle
Barnacles on Whale
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3. Community Interactions

• Mutualism
• Benefits both partners in the relationship.
• For example the association of legume plants and
  nitrogen-fixing bacteria.
• Bacteria turn nitrogen in the air to nitrates
  that the plants can use
• Another example Acacia trees and the predaceous
  ants they attract.
• Tree provides room and board for ants
• Ants benefit the tree by attacking virtually
  anything that touches it.

Acacia Trees and Ants
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4. Ecosystems

• An ecosystem consists of all the organisms in a
  community as well as the abiotic environment with
  which the organisms interact.
• Ecosystems can range from a microcosm such as a
  terrarium to a large area such as a forest.

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4a. Ecosystems- Energy Flow

• Regardless of an ecosystems size, its dynamics
  involve two processes- energy flow and chemical
  cycling.
• Energy flow the passage of energy through the
  components of the ecosystem.
• For most ecosystems, the sun is the energy
  source, but exceptions include several unusual
  kinds of ecosystems powered by chemical energy
  obtained from inorganic compounds.

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4a. Ecosystems- Energy Flow
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4a. Ecosystems- Energy Flow

• For example, an a terrarium, energy enters in the
  form of sunlight.
• Plants (producers) convert the light energy to
  chemical energy.
• Animals (consumers) take in some of this chemical
  energy in the form of organic compounds when they
  eat the plants.
• Detrivores, such as bacteria and fungi in the
  soil, obtain chemical energy when they decompose
  the dead remains of plants and animals.
• Every use of chemical energy by organisms
  involves a loss of some energy to the
  surroundings in the form of heat.
• Eventually, therefore, the ecosystem would run
  out of energy if it were not powered by a
  continuous inflow of energy from an outside
  source.

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4a. Ecosystems- Energy Flow

• Ecological Pyramids
• Pyramid of Biomass
• Pyramid of Productivity
• Pyramid of Numbers

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4a. Ecosystems- Energy Flow

• Pyramid of Biomass
• shows the relationship between biomass and
  trophic level by quantifying the amount of
  biomass present at each trophic level of a
  community at a particular moment in time.

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4a. Ecosystems- Energy Flow

• Pyramid of Biomass
• Typical units are grams per meter

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4a. Ecosystems- Energy Flow

• Pyramid of Production
• Illustrates the cumulative loss of energy with
  each transfer in a food chain.
• Each tier of the pyramid represents one trophic
  level, and the width of each tier indicates how
  much of the chemical energy of the tier below is
  actually incorported into the organic matter of
  that trophic level.
• Note that producers convert only about 1 of the
  energy in the sunlight available to them to
  primary production.
• In this idealized pyramid, 10 of the energy
  available at each trophic level becomes
  incorporated into the next higher level.
• The efficiencies of energy transfer usually range
  from 5 to 20.
• In other words, 80 to 95 of the energy at one
  trophic level never transfers to the next.

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4a. Ecosystems-Energy Flow

• Pyramid of Production
• Units can be Joules or calories

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4a. Ecosystems- Energy Flow

• Pyramid of Numbers
• shows graphically the population of each level in
  a food chain.

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4b. Ecosystems- Chemical Cycling

• Chemical cycling involves the transfer of
  materials within the ecosystem.
• An ecosystem is more or less self-contained in
  terms of matter.
• Chemical elements such as carbon and nitrogen are
  cycled between abiotic components (air, water,
  and soil) and biotic components of the ecosystem.
  
• The plants acquire these elements in inorganic
  form from the air and soil and fix them into
  organic molecules, some of which animals consume.
  
• Detrivores return most of the elements in
  inorganic form to the soil and air.
• Some elements are also returned as the
  by-products of plant and animal metabolism.

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4b. Ecosystems- Chemical Cycling
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4b. Ecosystems- Chemical Cycling

• Biogeochemical cycles
• Water cycle
• Carbon cycle
• Nitrogen cycle
• Phosphorous cycle

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4b. Ecosystems- Chemical Cycling

• General Model of Nutrient Cycling
• 1. Producers incorporate chemicals from the
  abiotic reservoir (where a chemical accumulates
  or is stockpiled outside of living organisms)
  into organic compounds.
• 2.Consumers feed on the producers, incorporating
  some of the chemicals into their own bodies.
• 3. Both producers and consumers release some
  chemicals back to the environment in waste
  products (CO2 and nitrogen wastes of animals)
• 4. Detritivores play a central role by
  decomposing dead organisms and returning
  chemicals in inorganic form to the soil, water,
  and air.
• 5. The producers gain a renewed supply of raw
  materials, and the cycle continues.

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4b. Ecosystems- Chemical Cycling
General Model of Nutrient Cycling
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Water Cycle

• 1.Precipitation
• 2.Condensation (conversion of gaseous water vapor
  into liquid water)
• 3. Rain Clouds
• 4. and 5. Evaporation (conversion of water to
  gaseous water vapor) from ocean
• 6. and 7. precipitation over ocean
• 8. evaporation from land
• 9. Transpiration
• 10. Transpiration
• 11. evaporation from lakes, rivers
• 12. surface runof
• 13. infiltration (movement of water into soil)
• 14. Water locked in snow
• 15. Precipitation to land
• refer to diagrams in handout

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Water Cycle
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Carbon Cycle

• 1. Carbon in plant and animal tissues
• 2. fossilization (preserved remains or traces of
  animals, plants, and other organisms)
• 3. Death and excretion
• 4. Decomposers (breakdown organic materials to
  inorganic ones)
• 5. coal
• 6. photosynthesis
• 7. atmospheric CO2
• 8. Dissolving
• 9. combustion (burning of wood and fossil fuels)
• 10. diatoms (major group of algae, and are one of
  the most common types of phytoplankton)
• 11. drilling for oil and gas
• 12. fossilization
• 13. oil and gas
• 14. limestone
• refer to diagrams in handout

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Carbon Cycle
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Nitrogen Cycle

• 1. Nitrogen in plant and animal tissue
• 2. Excretion
• 3. Ammonia (NH3)
• 4.Dead organisms
• 5. decomposers
• 6. Nitrifying bacteria (convert ammonia to
  nitrate)
• 7. nitrogen fixing bacteria (convert N2 to
  ammonia)
• 8. nitrate (NO3-)
• 9. nitrate (NO3-) available to plants
• 10. swampy ground
• 11. denitrifying bacteria (return fixed nitrogen
  to the atmosphere)
• 12. lightning (atmospheric nitrogen fixation)
• 13. atmospheric nitrogen (N2 gas)
• refer to diagrams in handout

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Nitrogen Cycle