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Flashcards in SNS Biology - Ecology Deck (42):
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Ecology

Study of interactions between organisms and their environment

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Environment

All that is external to the organism and is necessary for its existence

Encompassess abiotic and biotic

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Environment

Biotic

Living environment

Includes all living things that directly or indirectly influence the life of an organism, including all relationships between organisms

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Environment

Abiotic

Physical environment

Includes climate, temp, availability of light and water and local topography

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Organism

Individual unit of an ecological system, but itself composed of smaller units - cells - molecules, atoms

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Species

Group of similar organisms capable of generating fertile offspring

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Population

Group of organisms of same species living together in a given location

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Community

Populations of different plants and animal species interacting with each other in a given environment

 Generally includes species from all five kingdoms

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Biotic Community

Includes only populations and not their physical environment

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Ecosystem

Encompasses interaction between biotic communities and the nonliving environment

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Biosphere

Includes all portions of the planet that support life - atmosphere, luthosphere (rock and soil surface) and hydrosphere (oceans)

Relatively thin zone extending a few feet beneath the earth's surface, several miles into the deepest sea and several miles into the atmosphere

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Photic Zone

Of water

Top layer through which light can penetrate

Where all aquatic photosynthetic activity takes place

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Aphotic Zone

Of water

Zone in which only animal life and other heterotrophic life exist

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Environment

Abiotic

Substratum

Determines the nature of plant and animal life in the soil.

Soil is affected by a number of factors:

  1. Acidity - rhodedendrons and pines grow better in acid soil. Acid rain may make soil too low in pH for most plant growth
  2. Texture - this and clay content determine water-holding capacity of soil. Willows require moist soil. Most plants grow well in loams which contain high % of each type of soil
  3. Minerals - eg nitrates, phosphates. Affect type of vegetation that can be supported
  4. Humus quantity - determined by amount of decaying plant and animal life in the soil

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Niche

Defines functional role of the organism in its ecosystem

No two species can occupy the same niche in a given location at the same time

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Habitat

Physical place where an organism lives

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Symbiosis

Two species which live together in close association

May or may not be beneficial

May or may not be obligatory - one of both organisms can't survive without the other

  1. Commensalism
  2. Mutualism
  3. Parasitism

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Symbiosis

Commensalism

+/0

One organism benefits, the other is unaffected

For example, barnicle and whale, remora and shark

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Symbiosis

Mutualism

+/+

Both benefit

For example:

  1. Tick bird and rhinocerous - bird receives food (ticks), rhino has ticks removed and is warned of danger by departure of bird
  2. Fungi and algae - algae provides food for itself and fungus by photosynthesis, fungus provides CO2 and nitrogenous wastes fungal hyphae support algae and conserve rainwater
  3. Nitrogen-fixing bacteria and legumes - legume provides nutrients for the bacteria, bacteria fixes nitrogen by changing it to soluble nitrate
  4. Protozoa and termites - protozoa in termite GI tract secrete an enzyme that digests cellulose, both organisms share the carbs formed
  5. Instestinal bacteria and humans - bacteria utilise some of food material not fully digested by humans, manufacture vit K

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Symbiosis

Parasitism

-/+

One benefits, other is harmed

Successful parasites don't kill their hosts

For example, virus and host cell, animals and disease fungi and bacteria, ringworm and humans, worms and animals

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Symbiosis

Ectoparasites

Cling to exterior surface of host using suckers or clamps.

May bore through the skin or suck out blood and nutrients

eg leeches, ticks

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Symbiosis

Endoparasites

Live within host

To gain entry must pass through defenses such as skin, digestive juices, antibodies, WBCs and possess adaptations to permit this

For example, worms

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Saprophytism

Saprophytes decompose dead organic waste externally and absorb the nutrients

Constitute vital link in cycling of material within ecosystem

For example, mould, mushrooms, bacteria of decay, slime moulds

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Intraspecific Interaction

  1. Predation
  2. Saprophytism
  3. Scavengers
  4. Symbiosis

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Energy Flow

Food Chain

  1. Producers - autotrophic green plants and chemosynthetic bacteria - use sun and simple raw materials to manufacture carbs, proteins and lipids
  2. Primary consumers - consume producers (herbivores)
  3. Secondary consumers - consume primary consumers (carnivores)
  4. Tertiary consumers - consume secondary consumers (carnivores)
  5. Decomposers

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Energy Flow

Food Web

Not simple linear chain but intricate collection of interconnected food chains

Greater the number of branches and cross-branches, greater the stability

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Energy Flow

Food Pyramids

Energy

  • Each member of food chain utilises some of energy it obtains from food for own metabolism and loses some as heat
  • Since this means loss of energy at each feeding level, producer at base of pyramid contains greatest amount of energy and smallest amount of available energy is at the top

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Energy Flow

Food Pyramids

Mass

  • Since organisms at upper levels of food chain derive their food energy from organisms at lower levels and since energy is lost from one level to the next, each level can support a successivly smaller biomass

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Energy Flow

Food Pyramids

Numbers

Consumers that are higher in the food chain are usually larger and heavier than those further down

Lower organisms have greater total mass, and are greater in number

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Nitrogen Cycle

  1. Chemically inert elemental nitrogen is conveted to soluble nitrates which can be used by organisms by lightning and nitrogen fixing bacteria
  2. Nitrates are absorbed by plants and used to synthesize nucleic acids and proteins
  3. Animals eat the plants and synthesize animal proteins from the plant proteins. Both plants and animals give off wastes
  4. Nitrogen locked in dead plants and animals and their wastes is released by the action of bacteria of decay which converts the proteins into ammonia
  5. Some ammonia nitrified to nitrites by chemosynthetic bacteria, then to nitrates by nitrifying bacteria. Rest denitrified to release N2

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Nitrogen Cycle

Bacteria

  1. Bacteria of Decay - convert nitrogen in wastes and tissues to ammonia
  2. Nitrifying - convert ammonia to nitrites and nitrites to usable nitrates
  3. Denitrifying - convert ammonia to free nitrogen (N2)
  4. Nitrogen fixing - convert free nitrogen to nitrates

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Carbon Cycle

  1. CO2 enters living world when plants use it to produce glucose via photosynthesis
  2. Plant uses glucose to produce carbs, proteins and fats
  3. Animals eat plants and use digested nutrients to form carbs, proteins and fats
  4. Animals and plants use proteins, fats and carbs produced to fuel respiration which generates CO2
  5. Remainder of organic carbon remains locked in bodies of the plants and animals until death - aside from wastes - when decay processes by bacteria return CO2 to the air

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Stability in the Ecosystem

Requires:

  1. Stable physical environment (abiotic factors)
  2. Stable biotic community
  3. Constant energy source
  4. Living system incorporating energy into organic compounds
  5. Cycling of materials between living system and its environment

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Succession

Orderly process by which one biotic community replaces another until a climax community is established

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Sere

Community stage in a succession

Each is identified by a dominant species

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Climax Community

Each community that establishes itself changes the environment making it more favourable or unfavourable for the community that is to succeed it

Ultimately a stage arises in which a population alters the environment in such a way that the original conditions that gave rise to that community are recreated - the climax community

Final and most stable stage of succession - stable, living part of the ecosystem in which populations exist in balance with each other and the environment

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Biome

A distinct community which inhabits a particular geographic region

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Biome

Terrestrial

Characterised and named according to climax vegetation of the region - vegetation that becomes dominant and stable after years of evolutionary development - determines climax animal population

  1. Desert - small plants and animals. Many plants conserve water actively. Animals live in burrows
  2. Grassland - low rainfall, no shelter from carnivorous animals
  3. Rain forest - high temp and rainfall, dense vegetation, floor inhabited by saprophytes
  4. Temperate deciduous forest - cold winters, warm summers, moderate rainfall
  5. Temperate coniferous forest - cold, dry. Much of vegetation has evolved water-conserving adaptations
  6. Taiga - less rainfall that temperate forests, occupied by single coniferous tree - spruce. Forest floors contain moss and lichen
  7. Tundra - treeless frozen plain. Contains lichens, moss, polar bears, musk oxen, arctic hens
  8. Polar region - frozen area, no vegetation, few terrestrial animals

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Biome

Aquatic

Plants have little controlling influence in communities relative to role in terrestrial biomes

  1. Marine
  2. Freshwater

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Biome

Aquatic

Marine

  1. Intertidal zone - region exposed at low tides which undergoes changes in temp and periods of dryness
  2. Littoral zone - region of continental shelf containing ocean area with depths up to 600 ft. Extends several hundred miles from the shore
  3. Pelagic - open seas. Divided into photic (extending to depth of 250-600 ft) and aphotic zone

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Biome

Aquatic

Freshwater

  • Rivers, lakes, ponds, marshes
  • As in marine biomes, factors affecting life in freshwater include temp, transparency, water depth, CO2 and O2 and salt conc

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Biome

Aquatic

Marine vs Freshwater

  1. Freshwater is hypotonic creating diffusion gradient and diffusion of water into cells. Freshwater organisms have homeostatic mechanisms for removal of excess water
  2. In rivers and streams, strong currents exist and survival of fish which have evolved strong muscles and plants with holdfasts is favoured
  3. Freshwater biomes, except very large lakes, are affected by variations in climate and weather

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