Ecology

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Unit 2

• Ecology

Chapter 3 The Biosphere
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Introduction to Ecology

• Ecology - the scientific study of interactions
  among organisms and between organisms and their
  physical environment.
• Ecologist - a scientist who studies organisms as
  they interact with other organisms within an
  ecosystem

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Levels of Organization

• Individual Organism
• Populationa group of individuals that belong to
  the same species and live in the same area
• Communityan assemblage of different populations
  that live together in a defined area
• Ecosystemall the organisms that live in a place,
  together with their physical environment
• Biomea group of ecosystems that share similar
  climates and typical organisms
• Biosphereour entire planet, with all its
  organisms and physical environments

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Types of Ecosystems

• Natural Ecosystems
• Self sustaining
• Precipitation
• Sunlight
• All resources to support life
• Destroyed by natural disasters (fires)

• Human-Made Ecosystems
• Not self sustaining
• Farms
• Cities
• Flower gardens
• Aquariums
• Zoo
• Huge inputs of resources and energy

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Relationships Within an Ecosystem

• An ecosystem is a group of organisms that live
  together and interact with each other and their
  environment.
• Organisms respond to their environments and can
  change their environments, producing an
  ever-changing biosphere.

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Biotic Factors
Abiotic Factors

• Anything non-living!
• List three example of abiotic components in an
  ecosystem and why they are important?

• Anything living in an ecosystem!
• List three example of biotic components in an
  ecosystem and how they interact?

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Biomes

• A large geographic region determined by climate,
  soil type and plant life.
• Why is plant life so important to an ecosystem?

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Biomes

Northern Coniferous Forest or Taiga
Temperate Deciduous Forest
Temperate Grasslands or Prairie
Arctic Tundra
Desert
Tropical Savanna
Tropical Rain Forest
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Population Studies factors that affect the size
of a population

• Carrying capacity
• The maximum size of the population that an
  ecosystem can hold

• Limiting factors
• Anything that prevents the
• population size from increasing
• Examples ?

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Food Chains and Food Webs

• How does energy flow through ecosystems?
• Energy flows through an ecosystem in a one-way
  stream, from primary
• producers to various consumers. Energy moves from
  the eaten to the eater. Where it goes from
  there depends on who eats whom!

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Food Chain

The arrows in a food chain show what eats what.
The arrow replaces the phrase is eaten by.
The arrow must point toward the eater.
Leaf ? Grasshopper ? Frog
? Heron
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Food Webs

• This is who eats who or what in the ecosystem.
  Each organism has a job title that describes
  their role. Anything that affects one level will
  probably affect the entire ecosystem!

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Food Web

A food web shows the many possible food chains
that exist in an ecosystem.
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Food Webs Job Titles

• Producers- Plants. They are the basis for life
  in the ecosystem.
• These organisms are also called autotrophs.

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Most Producers get Energy From the Sun
The best-known and most common primary producers
harness solar energy through the process of
photosynthesis. Photosynthesis captures light
energy and uses it to power chemical reactions
that convert carbon dioxide and water into oxygen
and energy-rich carbohydrates. This process adds
oxygen to the atmosphere and removes carbon
dioxide. Most photosynthesis occurs in plants on
land and algae in water ecosystems.
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Life Without Light

• Deep-sea ecosystems depend on primary producers
  that harness chemical energy from inorganic
  molecules such as hydrogen sulfide.
• The use of chemical energy to produce
  carbohydrates is called chemosynthesis.

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Food Webs Job Titles

• Consumers- these organism eat other organisms.
  They can not make their own food, therefore, they
  must order out!
• Organisms that must acquire energy from other
  organisms by ingesting in some way are also known
  as heterotrophs.

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Food Webs Job Titles

• Consumers may be herbivores (plant eaters),
  carnivores (meat eaters) or omnivores (both)
• Carnivores are usually referred to as predators!

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Food Webs Job Titles

• 1st or PRIMARY level consumers are herbivores
• 2nd or SECONDARY level consumers are carnivores
  or omnivores and eat 1st order consumers
• What are 3rd order (level) consumers?

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Food Webs Job Titles

• Decomposers- These are the recycling centers of
  the ecosystem. They break-down dead organisms
  into nutrients in the soil that plants can use as
  vitamins.
• Bacteria and Fungus
• Detritivores, feed on detritus particles (what is
  left from the decomposers,) often chewing or
  grinding them into smaller pieces.
• giant earthworms

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Food Webs Job Titles

• Scavengers- Similar to decomposers because they
  eat already dead organisms and return nutrients
  to the soil.
• Animals, birds, insects

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Trophic Levels and Ecological Pyramids

• Each step in a food chain or food web is called a
  trophic level.
• Primary producers always make up the first
  trophic level.
• Various consumers occupy every other level. Some
  examples are shown.
• Ecological pyramids show the relative amount of
  energy or matter contained within each trophic
  level in a given food chain or food web.

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Advantages and Disadvantages of the Pyramids

• Pyramids of numbers and biomass can sometimes be
  inverted due to certain situations within
  ecosystems
• These inverted pyramids then lose their ability
  to accurately represent the passage of energy
  from one trophic level to the next

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Pyramid of Numbers

• This represents the number of organisms that
  occupy each trophic level

http//openlearn.open.ac.uk
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Pyramids of Energy

• Pyramids of energy show the relative amount of
  energy available at each trophic level.
• On average, about 10 percent of the energy
  available within one trophic level is transferred
  to the next trophic level.
• The more levels that exist between a producer and
  a consumer, the smaller the percentage of the
  original energy from producers that is available
  to that consumer.

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Pyramid of Biomass

• The total amount of living tissue within a given
  trophic level is called its biomass.
• A pyramid of biomass illustrates the relative
  amount of living organic matter at each trophic
  level.

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Recycling in the Biosphere

• Unlike the one-way flow of energy, matter is
  recycled within and between ecosystems.
• Elements pass from one organism to another and
  among parts of the biosphere through closed loops
  called biogeochemical cycles, which are powered
  by the flow of energy.
• Biogeochemical cycles of matter involve
  biological processes, geological processes, and
  chemical processes.

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Recycling in the Biosphere

• As matter moves through these cycles, it is never
  created or destroyedjust changed.
• Biogeochemical cycles of matter pass the same
  atoms and molecules around again and again.

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Water Cycle

• Also called the Hydrologic Cycle
• Movement and storage of water on the planet
• Total amount of water doesnt change it is
  transported around the earth
• Energy to run the cycle comes from the sun

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• Water re-enters that atmosphere by two processes
• Evaporation changes surface water (lakes, rivers,
  oceans) to water vapor
• Water vapor (gaseous state) returns to the
  atmosphere
• Transpiration is the loss of water vapor from the
  leaves of plants
• Stomata are openings in leaves which allow the
  water vapor out of the plant

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• Condensation
• As the water vapor rises in the atmosphere, it
  looses energy (cools down)
• Water droplets are formed from the water vapor
• Precipitation
• When the water droplets get too heavy it falls
  from the sky
• Weather conditions determine the type of
  precipitation rain, snow, sleet

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• Some precipitation re-evaporates before it
  reaches the ground
• Most precipitation falls into existing bodies of
  water
• 70 of the earths surface is water
• The rest falls on land
• Absorbed into the soil or flows over the surface
  as Runoff (back to the oceans/lakes)
• Infiltration is the process of water entering the
  ground

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• The cycle begins again
• Evaporation and transpiration
• Condensation
• Precipitation
• Runoff and Infiltration
• The amount of precipitation is an important
  factor in the type of ecosystem and the
  population of organisms it can support

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Nutrient Cycles

• The chemical substances that an organism needs
  to sustain life are called nutrients.
• Every organism needs nutrients to build tissues
  and carry out life functions.
• Nutrients pass through organisms and the
  environment through biogeochemical cycles.

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The Carbon Oxygen Cycle

• Carbon is a major component of all organic
  compounds, including carbohydrates, lipids,
  proteins, and nucleic acids.

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The Carbon Oxygen Cycle

• Plants take in carbon dioxide during
  photosynthesis and use the carbon to build
  carbohydrates.
• Carbohydrates then pass through food webs to
  consumers.
• Organisms release carbon in the form of carbon
  dioxide gas by respiration.

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The Nitrogen Cycle

• All organisms require nitrogen to make amino
  acids, which are used to build proteins and
  nucleic acids, which combine to form DNA and RNA.

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The Nitrogen Cycle

• Nitrogen-containing substances such as ammonia
  (NH3), nitrate ions (NO3), and nitrite ions (NO2)
  are found in soil, in the wastes produced by many
  organisms, and in dead and decaying organic
  matter.

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The Nitrogen Cycle

• Nitrogen gas (N2) makes up 78 percent of Earths
  atmosphere.
• Although nitrogen gas is the most abundant form
  of nitrogen on Earth, only certain types of
  bacteria that live in the soil and on the roots
  of legumes can use this form directly.
• The bacteria convert nitrogen gas into ammonia,
  in a process known as nitrogen fixation.

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The Nitrogen Cycle

• Other soil bacteria convert fixed nitrogen into
  nitrates and nitrites that primary producers can
  use to make proteins and nucleic acids.
• Consumers eat the producers and reuse nitrogen to
  make their own nitrogen-containing compounds

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The Nitrogen Cycle

• Consumers eat the producers and reuse nitrogen to
  make their own nitrogen-containing compounds.
• Decomposers release nitrogen from waste and dead
  organisms as ammonia, nitrates, and nitrites that
  producers may take up again.

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The Nitrogen Cycle

• Other soil bacteria obtain energy by converting
  nitrates into nitrogen gas, which is released
  into the atmosphere in a process called
  denitrification.
• A small amount of nitrogen gas is converted to
  usable forms by lightning in a process called
  atmospheric nitrogen fixation.
• Humans add nitrogen to the biosphere through the
  manufacture and use of fertilizers. Excess
  fertilizer is often carried into surface water or
  groundwater by precipitation.

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The Phosphorus Cycle

• Phosphorus forms a part of vital molecules such
  as DNA and RNA.
• Although phosphorus is of great biological
  importance, it is not abundant in the biosphere.
• Phosphorus in the form of inorganic phosphate
  remains mostly on land, in the form of phosphate
  rock and soil minerals, and in the ocean, as
  dissolved phosphate and phosphate sediments.

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The Phosphorus Cycle

• As rocks and sediments wear down, phosphate is
  released
• Plants bind phosphate into organic compounds when
  they absorb it from soil or water.
• Organic phosphate moves through the food web,
  from producers to consumers, and to the rest of
  the ecosystem.

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Nutrient Limitation

• Ecologists are often interested in an ecosystems
  primary productivitythe rate at which primary
  producers create organic material.
• A nutrient whose supply limits productivity is
  called the limiting nutrient.

• All nutrient cycles work together like the gears
  shown.
• If any nutrient is in short supplyif any wheel
  sticksthe whole system slows down or stops
  altogether.

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Nutrient Limitation in Aquatic Ecosystems

• Sometimes an aquatic ecosystem receives a large
  input of a limiting nutrientfor example, runoff
  from heavily fertilized fields.
• The result of this runoff can be an algal blooma
  dramatic increase in the amount of algae and
  other primary producers due to the increase in
  nutrients.

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Energy flow in ecosystems
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What is an ecosystem?

• System regularly interacting and interdependent
  components forming a unified whole
• Ecosystem an ecological system
• a community and its physical environment
  treated together as a functional system

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OR, MORE SIMPLY

• an ecosystem is composed of the organisms and
  physical environment of a specified area.
• SIZE micro to MACRO

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Attributes of Ecosystems

• Order
• Development
• Metabolism (energy flow) 10 RULE
• Material cycles
• Response to the environment
• Porous boundaries
• Emphasis on function, not species

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ENERGY FLOW IN ECOSYSTEMS

• All organisms require energy, for growth,
  maintenance, reproduction, locomotion, etc.
• Hence, for all organisms there must
  be A source of energy
• A loss of usable energy

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Types of energy

• heat energy
• mechanical energy (gravitational energy,
  etc.)
• chemical energy energy stored in
• molecular bonds

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Transformations of energy

• How is solar energy converted to chemical energy?
  

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An ecosystem has abiotic and biotic components

• ABIOTIC components
• Solar energy provides practically all the energy
  for ecosystems.
• Inorganic substances, e.g., sulfur, boron, tend
  to cycle through ecosystems.
• Organic compounds, such as proteins,
  carbohydrates, lipids, and other complex
  molecules, form a link between biotic and abiotic
  components of the system.

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BIOTIC components

• The biotic components of an ecosystem can be
  classified according to their mode of energy
  acquisition.
• In this type of classification, there are
• Autotrophs
• and
• Heterotrophs

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Autotrophs

• Autotrophs (self-nourishing) are called primary
  producers.
• Photoautotrophs fix energy from the sun and
  store it in complex organic compounds
• ( green plants, algae, some bacteria)

light
simple inorganic compounds
complex organic compounds
photoautotrophs
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• Chemoautotrophs (chemosynthesizers) are bacteria
  that oxidize reduced inorganic substances
• (typically sulfur and ammonia compounds)
• and produce complex organic compounds.

oxygen
reduced inorganic compounds
complex organic compounds
chemoautotrophs
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Chemosynthesis near hydrothermal vents
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Other chemoautotrophs Nitrifying bacteria in
the soil under our feet!
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Heterotrophs

• Heterotrophs (other-nourishing) cannot produce
  their own food directly from sunlight inorganic
  compounds. They require energy previously stored
  in complex molecules.

heat
simple inorganic compounds
complex organic compounds
heterotrophs
(this may include several steps, with several
different types of organisms)
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• Heterotrophs can be grouped as
• consumers
• decomposers

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• Consumers feed on organisms or particulate
  organic matter.
• Decomposers utilize complex compounds in dead
  protoplasm.
• Bacteria and fungi are the main groups of
  decomposers.
• Bacteria are the main feeders on animal material.
• Fungi feed primarily on plants, although bacteria
  also are important in some plant decomposition
  processes.

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Energy flow

• Simplistically
• This pattern of energy flow among different
  organisms is the TROPHIC STRUCTURE of an
  ecosystem.

heat
Producers
Consumers
Decomposers
heat
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• It is useful to distinguish different types of
  organisms within these major groups, particularly
  within the consumer group.

Consumers
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Terminology of trophic levels

• We can further separate the TROPHIC LEVELS,
  particularly the Consumers
• Producers (Plants, algae, cyanobacteria some
  chemotrophs)--capture energy, produce complex
  organic compounds
• Primary consumers--feed on producers
• Secondary consumers--feed on primary consumers
• Tertiary consumers--feed on secondary consumers

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More trophic levels

• Detritivores--invertebrates that feed on organic
  wastes and dead organisms (detritus) from all
  trophic levels
• Decomposers--bacteria and fungi that break down
  dead material into inorganic materials

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Alternate Terminology

• Producers plants etc. that capture energy from
  the sun
• Herbivores plant-eaters
• Carnivores animal-eaters
• Omnivores--eat both animals and plants
• Specialized herbivores
• Granivores--seed-eaters
• Frugivores--fruit-eaters

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• Together, these groups make up a FOOD CHAIN
• E.g., grass, rabbit, eagle

Producer
Carnivore
Herbivore
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Carnivores

• Carnivores can be further divided into groups
• quaternary carnivore (top)
• tertiary carnivore
• secondary carnivore
• primary carnivore
• The last carnivore in a chain, which is not
  usually eaten by any other carnivore, is often
  referred to as the top carnivore.

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Foodchains
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Problems

• Too simplistic
• No detritivores
• Chains too long

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• Rarely are things as simple as grass, rabbit,
  hawk, or indeed any simple linear sequence of
  organisms.
• More typically, there are multiple interactions,
  so that we end up with a FOOD WEB.

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Energy transfers among trophic levels

• How much energy is passed from one trophic level
  to the next?
• How efficient are such transfers?

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• Biomass--the dry mass of organic material in the
  organism(s).
• (the mass of water is not usually included, since
  water content is variable and contains no usable
  energy)
• Standing crop--the amount of biomass present at
  any point in time.

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Primary productivity

• Primary productivity is the rate of energy
  capture by producers.
• the amount of new biomass of producers, per
  unit time and space

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Ecological pyramids

• The standing crop, productivity, number of
  organisms, etc. of an ecosystem can be
  conveniently depicted using pyramids, where the
  size of each compartment represents the amount of
  the item in each trophic level of a food chain.
• Note that the complexities of the interactions in
  a food web are not shown in a pyramid but,
  pyramids are often useful conceptual
  devices--they give one a sense of the overall
  form of the trophic structure of an ecosystem.

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Pyramid of energy

• A pyramid of energy depicts the energy flow, or
  productivity, of each trophic level.
• Due to the Laws of Thermodynamics, each higher
  level must be smaller than lower levels, due to
  loss of some energy as heat (via respiration)
  within each level.

Energy flow in
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Pyramid of numbers

• A pyramid of numbers indicates the number of
  individuals in each trophic level.
• Since the size of individuals may vary widely and
  may not indicate the productivity of that
  individual, pyramids of numbers say little or
  nothing about the amount of energy moving through
  the ecosystem.

of carnivores
of herbivores
of producers
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Pyramid of standing crop

• A pyramid of standing crop indicates how much
  biomass is present in each trophic level at any
  one time.
• As for pyramids of numbers, a pyramid of standing
  crop may not well reflect the flow of energy
  through the system, due to different sizes and
  growth rates of organisms.

biomass of carnivores
biomass of herbivores
biomass of producers
(at one point in time)
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Inverted pyramids

• A pyramid of standing crop (or of numbers) may be
  inverted, i.e., a higher trophic level may have a
  larger standing crop than a lower trophic level.
  
• This can occur if the lower trophic level has a
  high rate of turnover of small individuals (and
  high rate of productivity), such that the First
  and Second Laws of Thermodynamics are not
  violated.

biomass of carnivores
biomass of herbivores
biomass of producers
(at one point in time)
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Pyramid of yearly biomass production

• If the biomass produced by a trophic level is
  summed over a year (or the appropriate complete
  cycle period), then the pyramid of total biomass
  produced must resemble the pyramid of energy
  flow, since biomass can be equated to energy.

Yearly biomass production (or energy flow) of
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• Note that pyramids of energy and yearly biomass
  production can never be inverted, since this
  would violate the laws of thermodynamics.
• Pyramids of standing crop and numbers can be
  inverted, since the amount of organisms at any
  one time does not indicate the amount of energy
  flowing through the system.
• E.g., consider the amount of food you eat in a
  year compared to the amount on hand in your
  pantry.

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Ecological Interactions and Interdependence
Population group of individuals of the same
species living in the same area, potentially
interacting
Community group of populations of different
species living in the same area, potentially
interacting
What are some ecological interactions?
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Why are ecological interactions important?
Interactions can affect distribution and
abundance.
Interactions can influence evolution.
Think about how the following interactions can
affect distribution, abundance, and evolution.
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Types of ecological interactions interdependence
competition predation parasitism mutualism commens
alism symbiosis
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Competition two species share a requirement for
a limited resource ? reduces fitness of one or
both species
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Predation one species feeds on another ?
enhances fitness of predator but reduces fitness
of prey
herbivory is a form of predation
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Parasitism one species feeds on another ?
enhances fitness of parasite but reduces fitness
of host
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Mutualism two species provide resources or
services to each other ? enhances fitness of both
species
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Commensalism one species receives a benefit
from another species ? enhances fitness of one
species no effect on fitness of the other species
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Symbiosis two species live together ? can
include parasitism, mutualism, and commensalism
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Organizing ecological interactions
interdependence
effect on species 1
0 -
0 -
mutualism
effect on species 2