The Ecosystem: Interrelationships between organisms and the environment

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The Ecosystem Interrelationships between
organisms and the environment

• 1. Should we care about the survival of organisms
  other than human beings?
• 2. Can we humans live alone and survive on the
  planet?
• 3. Does the way nature operates offer solutions
  to our environmental problems?

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Definition of Terms 1

• Ecology A study of the interrelationships
  between living organisms and the non-living
  components and processes that make up the global
  environment.
• Biosphere The worldwide system within which all
  life functions. It includes the atmosphere (air),
  hydrosphere (water) and the lithosphere (soils,
  rocks)
• Biome A major ecological region within which
  plant and animal species are similar in general
  characteristics and in their relationships to the
  physical environment. E.g.. Tundra, Deserts,
  Forests Grasslands etc.

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Definition of terms2

• Ecosystem A collection of living organisms in a
  geographic area, together with the non-living
  things with which they interact.
• Aquatic Ecosystems (water-based systems)
• Terrestrial Ecosystems (land-based systems).
• Population A group of organisms of the same kind
  living in a given area.
• Natural Community Populations of different
  species living together and interacting in a
  given area.
• Habitat The environment in which a particular
  organism lives in the community

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Definitions3

• Ecological Niche An organisms role within a
  community.
• Environment Comprises all the surrounding things
  that affect an organism or a community of
  organisms in a given area.

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The Structure of Ecosystems1

• Components of an Ecosystem
• Biota or Biotic component the living organisms
  comprising all plants animals
• Abiotic component the non-living physical and
  chemical components consisting of wind,
  temperature, water, soil, precipitation which the
  biotic elements need to survive.

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Structure of an Ecosystem2

• A single abiotic factor most lacking in a
  particular environment is termed, a Limiting
  Factor. E.g. water-desert, temperature-tundra
• The variation in physical factors that an
  organism can withstand and continue to thrive in
  an environment is termed - Range of Tolerance

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Producers in an Ecosystem

• Categories of Organism in an ecosystem
• Autotrophs self-nourished species (e.g. plants)
• Heterotrophs other-nourished species (humans
  and animals)
• 1. Producers Green Plants responsible for
  photosynthesis and the release of energy into an
  ecosystem.

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Consumers and Decomposers

• 2. Consumers
• a) Primary Consumers - Herbivores
• b) Secondary Consumers Carnivores
• c) Tertiary Consumers - Carnivores
• d) Multiple-level Consumers - Omnivores
• 3. a) Detritivores e.g. crab, vulture, termites
• b) Decomposers e.g. fungi and bacteria

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The Food Chain

• A food chain or food web is represented by a
  sequence of organisms through which energy and
  nutrients flow from one organism to another.
• A major step in the transfer of energy through
  the food chain is termed as a Trophic level
• Primary consumers First trophic level
• Secondary consumers - Second trophic level
• Tertiary Consumers - Third trophic level
• The amount of usable energy in the food chain
  decreases as we move down the trophic level

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An example of a marine food chain

• Phytoplankton is the first level of marine
  food chain Zooplanktons are eaten by krill and
  other Small fish which are all eaten in turn by
  Big fish, including penguins, seals and whales.
  The marine food chain continues when these big
  fishes are eaten by Mammals like polar bears

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A marine food chain

• A marine food chain
• Polar bear - 5
• Seal - 4
• Cod - 3
• Krill - 2
• Algae - 1

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A terrestrial-based food chain

• A Terrestrial food chain
• Hawk
• Snake eaten by hawk
• Frog eaten by snake
• Grasshopper eaten by frog

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Impact of pesticides (i.e., DDT) on the species
of an ecosystem
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Interactions among species in an Ecosystem

• Plants compete amongst themselves for
• 1. water, 2. nutrients 3. sunlight and 4. space
• Animals compete over
• 1. food, 2. water, 3. mating and 4. territory
• 2 main types of relationships
• Predation one species (the predator) feeds on
  the other (prey) e.g. cat and mouse
• Symbiosis species live in an intimate
  association with each other

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Types of symbiotic relations

• Parasitism - one species feeds on another (the
  host) and may kill it.
• Mutualism both parties benefit equally from the
  relationship (flowers and butterflies)
• Commensalism the relationship benefits one
  species but neither helps nor harms the other

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Principles of Ecology

• First Law of Energy energy can be converted
  from one form to another but cannot be created or
  destroyed
• Second Law of Energy whenever energy is
  converted from one form to another, a certain
  amount is lost in the form of heat.
• The Law of Conservation of Matter
• Although matter can be changed from one form to
  another it can neither be created nor destroyed
  by ordinary physical and chemical changes.

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Biogeochemical Cycles

• Comprise processes through which elements that
  sustain life (water, carbon, phosphorus and
  nitrogen) are continuously made available to
  living organisms.
• Nitrogen cycle
• Hydrological cycle
• Carbon cycle
• Phosphorus cycle

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The Hydrological Cycle
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The Carbon Cycle
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Interruptions in an Ecosystem

• Causes
• a) Natural causes volcanic eruptions
• b) Human causes e.g. construction, agriculture,
  mining, etc.
• List some of the consequences that can result
  from an abrupt interruption in the smooth
  functioning of an ecosystem?

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What lessons can we learn from the way a natural
ecosystem operates?

• Natural ecosystems gain resources, use it and
  dispose of wastes through recycling.
• Ecosystems sustain themselves by running on Solar
  Energy which is exceedingly abundant,
  nonpolluting, constant and long lasting.
• Far less of Carnivores can be supported by each
  ecosystem. Many would soon face extinction
• Every species in a community play an important
  role in the sustenance of the ecosystem