Environmental Science Power Point Lecture

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ECOLOGY

• The study of how organisms interact with one
  another and their environment
• From Greek meaning study of home
• Compare with definition of Environmental Science

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WHAT IS LIFE ? All life ...

• Consists of cells, which are its basic unit
• Has distinct DNA molecules in each cell
• DNA contains instructions for making new cells
• and making proteins (coded by a gene)

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All life ...

• Can capture and transform matter and energy from
  environment for survival, growth, reproduction
• Metabolism
• Maintains favorable internal conditions
  (homeostasis)
• Perpetuates itself (reproduction)

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• everything that affects an organism during its
  lifetime gt abiotic (nonliving) factors biotic
  (living) factors

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Organization of the Environment
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Abiotic (nonliving) ecosystem factors

• Physical factors include
• Amount of sunlight
• Average temperature and temperature range
• Average precipitation and its timing
• Chemical factors include
• Water and air in the soil
• Plant nutrients in the soil
• Salinity and dissolved O2 levels in aquatic
  systems

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Tolerance

• Each population has a range of tolerance to
  variations in its physical and chemical
  environment
• e.g., dissolved oxygen (DO) in water, fig. 5.2,
  p. 85
• The existence, abundance, and distribution of a
  species in an ecosystem depends on its range of
  tolerance
• e.g., catfish and carp replace trout further
  downstream where DO levels are lower. These
  species have a greater range of tolerance than
  trout

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Tolerance Limiting factors

• Sometimes, all abiotic factors but one are in
  tolerance That one then outweighs the rest
  limiting factor
• e.g., Phosphorus level is too low in some soils
  for corn, must be added in fertilizer (N-P-K)
• But, phosphorus is also a limiting factor for
  algae in farm ponds ditches, so runoff from
  fertilized field can cause an algal bloom in
  waters gt eutrophication

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Habitat Niche of Organisms

• Habitat the physical characteristics of where
  an organism lives
• e.g., habitat of moss is cool, moist, and shady
• habitat of trout is rapidly flowing, cool, highly
  oxygenated stream
• Niche organisms role in an ecosystem, where it
  fits in
• e.g., beaver niche, figure 5.4

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• Beavers niche is quite complex

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Natural Selection Evolution

• Evolution change of species over time

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Brief History of the Earth (in years)

• Starting forming 4.6 billion
• Life began around 4.0 billion
• This life was simple bacteria until about 1
  billion
• Abundant life from 570 million gt now
• Land life appeared 400 million
• Dinosaurs 230-65 million
• Chimp - Human common ancestor 6-8 million
• Homo sapiens 150,000???

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Evolution works through

• Genetic variation (from sex and mutation)
  natural selection (from changing environmental
  conditions) long periods of time (many
  generations)
• Good example of rapid natural selection
  peppered moths in England
• Fig. 5.6, p.89

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Evolutionary change - Fig. 5.6, p.89
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Organism Interactions

• How organisms fit into their niches and adapt to
  their environment

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Predation (/-)

• One animal - a predator - hunts, kills, and eats
  another - the prey
• E.g., lions zebra, figure 5.7

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Competition (-/-)

• Both within or among species
• E.g., figure 5.8, vultures compete for carrion

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Parasitism (/-)

• One organism - parasite - lives in or on another
  - host - from which it derives nourishment
• Generally, host is harmed but not killed - Fig.
  5.9
• Also, Nest-Brood Parasitism - Fig. 5.12

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Commensalism (/0)

• One organism benefits, the other is not affected
• E.g., figure 5.10, remoras hanging out with a
  shark

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Mutualism (/)

• Both organisms benefit
• E.g., figure 5.11, nitrogen-fixing bacteria on
  the roots of legumes

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Energy Flow Through Ecosystems

• Food Chains Food Webs

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Food Chain

• Lowest level producers (usually plants) - get
  energy from Sun
• These are eaten by primary consumers (herbivores)
• Herbivores are eaten by secondary consumers, and
  so on
• By Second Law of Thermodynamics, some energy
  quality is lost in each transfer of level
• In fact about 90 is lost in each transfer gt
  energy pyramid

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Food Webs

• Actually situation is usually more complicated
• Several food chains can overlap
• E.g., fox can eat a mouse or a rabbit, which in
  turn can eat a variety of grasses or other
  vegetation, but an owl or hawk can also eat the
  mouse or rabbit...

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Why a vegetarian diet is more energy efficient
figure 8.5, p. 162