SNS Biology - Ecology Flashcards
Ecology
Study of interactions between organisms and their environment
Environment
All that is external to the organism and is necessary for its existence
Encompassess abiotic and biotic
Environment
Biotic
Living environment
Includes all living things that directly or indirectly influence the life of an organism, including all relationships between organisms
Environment
Abiotic
Physical environment
Includes climate, temp, availability of light and water and local topography
Organism
Individual unit of an ecological system, but itself composed of smaller units - cells - molecules, atoms
Species
Group of similar organisms capable of generating fertile offspring
Population
Group of organisms of same species living together in a given location
Community
Populations of different plants and animal species interacting with each other in a given environment
Generally includes species from all five kingdoms
Biotic Community
Includes only populations and not their physical environment
Ecosystem
Encompasses interaction between biotic communities and the nonliving environment
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
Photic Zone
Of water
Top layer through which light can penetrate
Where all aquatic photosynthetic activity takes place
Aphotic Zone
Of water
Zone in which only animal life and other heterotrophic life exist
Environment
Abiotic
Substratum
Determines the nature of plant and animal life in the soil.
Soil is affected by a number of factors:
- Acidity - rhodedendrons and pines grow better in acid soil. Acid rain may make soil too low in pH for most plant growth
- 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
- Minerals - eg nitrates, phosphates. Affect type of vegetation that can be supported
- Humus quantity - determined by amount of decaying plant and animal life in the soil
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
Habitat
Physical place where an organism lives
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
- Commensalism
- Mutualism
- Parasitism
Symbiosis
Commensalism
+/0
One organism benefits, the other is unaffected
For example, barnicle and whale, remora and shark
Symbiosis
Mutualism
+/+
Both benefit
For example:
- Tick bird and rhinocerous - bird receives food (ticks), rhino has ticks removed and is warned of danger by departure of bird
- 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
- Nitrogen-fixing bacteria and legumes - legume provides nutrients for the bacteria, bacteria fixes nitrogen by changing it to soluble nitrate
- Protozoa and termites - protozoa in termite GI tract secrete an enzyme that digests cellulose, both organisms share the carbs formed
- Instestinal bacteria and humans - bacteria utilise some of food material not fully digested by humans, manufacture vit K
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
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
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
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
Intraspecific Interaction
- Predation
- Saprophytism
- Scavengers
- Symbiosis
Energy Flow
Food Chain
- Producers - autotrophic green plants and chemosynthetic bacteria - use sun and simple raw materials to manufacture carbs, proteins and lipids
- Primary consumers - consume producers (herbivores)
- Secondary consumers - consume primary consumers (carnivores)
- Tertiary consumers - consume secondary consumers (carnivores)
- Decomposers
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
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
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
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
Nitrogen Cycle
- Chemically inert elemental nitrogen is conveted to soluble nitrates which can be used by organisms by lightning and nitrogen fixing bacteria
- Nitrates are absorbed by plants and used to synthesize nucleic acids and proteins
- Animals eat the plants and synthesize animal proteins from the plant proteins. Both plants and animals give off wastes
- 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
- Some ammonia nitrified to nitrites by chemosynthetic bacteria, then to nitrates by nitrifying bacteria. Rest denitrified to release N2
Nitrogen Cycle
Bacteria
- Bacteria of Decay - convert nitrogen in wastes and tissues to ammonia
- Nitrifying - convert ammonia to nitrites and nitrites to usable nitrates
- Denitrifying - convert ammonia to free nitrogen (N2)
- Nitrogen fixing - convert free nitrogen to nitrates
Carbon Cycle
- CO2 enters living world when plants use it to produce glucose via photosynthesis
- Plant uses glucose to produce carbs, proteins and fats
- Animals eat plants and use digested nutrients to form carbs, proteins and fats
- Animals and plants use proteins, fats and carbs produced to fuel respiration which generates CO2
- 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
Stability in the Ecosystem
Requires:
- Stable physical environment (abiotic factors)
- Stable biotic community
- Constant energy source
- Living system incorporating energy into organic compounds
- Cycling of materials between living system and its environment
Succession
Orderly process by which one biotic community replaces another until a climax community is established
Sere
Community stage in a succession
Each is identified by a dominant species
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
Biome
A distinct community which inhabits a particular geographic region
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
- Desert - small plants and animals. Many plants conserve water actively. Animals live in burrows
- Grassland - low rainfall, no shelter from carnivorous animals
- Rain forest - high temp and rainfall, dense vegetation, floor inhabited by saprophytes
- Temperate deciduous forest - cold winters, warm summers, moderate rainfall
- Temperate coniferous forest - cold, dry. Much of vegetation has evolved water-conserving adaptations
- Taiga - less rainfall that temperate forests, occupied by single coniferous tree - spruce. Forest floors contain moss and lichen
- Tundra - treeless frozen plain. Contains lichens, moss, polar bears, musk oxen, arctic hens
- Polar region - frozen area, no vegetation, few terrestrial animals
Biome
Aquatic
Plants have little controlling influence in communities relative to role in terrestrial biomes
- Marine
- Freshwater
Biome
Aquatic
Marine
- Intertidal zone - region exposed at low tides which undergoes changes in temp and periods of dryness
- Littoral zone - region of continental shelf containing ocean area with depths up to 600 ft. Extends several hundred miles from the shore
- Pelagic - open seas. Divided into photic (extending to depth of 250-600 ft) and aphotic zone
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
Biome
Aquatic
Marine vs Freshwater
- Freshwater is hypotonic creating diffusion gradient and diffusion of water into cells. Freshwater organisms have homeostatic mechanisms for removal of excess water
- In rivers and streams, strong currents exist and survival of fish which have evolved strong muscles and plants with holdfasts is favoured
- Freshwater biomes, except very large lakes, are affected by variations in climate and weather
