Chapter 20 and 21 Flashcards
what are biogechemical cycles?
since nutrient cycles involve both biotic and abiotic components, they are called biogeochemical cycles
what are the key processes of the water cycle?
- starting the water cycle are evaporation of liquid water, by solar energy
- condensation of water vapour into clouds
- precipitation from the clouds
- transpiration by plants from their stomata also moves large volumes of water into the atmosphere
- surface and groundwater flow can return water to the oceans, completing the water cycle
what is the biological importance of the water cycle?
water is essential to all organisms, and its availability influences the rates of ecosystem processes, particularly primary production and decomposition in terrestrial ecosystems
what are the different forms water is available in and the reservoirs that contain this water?
liquid water ie. oceans contains 97% of our water
frozen water ie. glaciers contain 2% of our water
lakes contain 1% of the remaining water on earth
what are the key processes of the carbon cycle?
- photosynthesis by plants and phytoplankton remove substantial amounts of CO2 from the air
- the amount of CO2 removed is equaled to the amount of CO2 added back into the ecosystem by consumers via cellular respiration
- The burning of fossil fuels and wood is adding significant amounts of additional CO2 into the atmosphere
- Volcanoes are also a source of CO2, over geologic time
what is the biological importance of the carbon cycle?
carbon forms the framework of the organic molecules essential for all organisms to survive
what are the forms of carbon available to life?
photosynthetic organisms utilize CO2 during photosynthesis and convert the carbon to oxygen, which is used by many organisms
what are the reservoirs that contain carbon?
the major reservoirs for carbon are:
- fossil fuels, soils the sediments of aquatic ecosystems
- the oceans (dissolved carbon compounds)
- plant and animal biomass, and the atmosphere (CO2)
- the LARGEST reservoir is sedimentary rocks such as limestone
what are the key processes of the nitrogen cycle?
- nitrogen fixation is how nitrogen enters an ecosystem
- nitrogen inputs from human activities now outpace natural inputs on land
- two major contributors are industrially produced fertilizers and legume crops that fix nitrogen via bacteria
- some bacteria carry out denitrification
- human activities also release large quantities of reactive nitrogen gases, NOx into the atmosphere
what is nitrification?
the conversion of N2 to forms that can be used to synthesize organic nitrogen compounds
what is denitrification?
the reduction of nitrate to nitrogen gases
what is the biological importance of the nitrogen cycle
nitrogen is part of amino acids, proteins, and nucleic acids is often a limiting plant nutrient
what are the reservoirs that hold nitrogen?
- the main reservoir for nitrogen is the atmosphere, which contains 80% free nitrogen gas N2
- coils and sediments of lakes, rivers, and oceans are other reservoirs for organic and inorganic forms of nitrogen
what forms of nitrogen are available to life?
- plants can assimilate to inorganic forms of nitrogen NH4 and NO3-
- various bacteria can use all of these forms as well as NO2-
- animals can only use organic forms of nitrogen
what is the biological importance of the phosphorus cycle?
- organisms require phosphorous as a major constituent of nucleic acids, phospholipids, and ATP other energy-storing molecules
what are the forms of phosphorous that are available on earth?
- the most biologically important inorganic form of phosphorus is PO4-3, which plants absorb and use in the synthesis of organic compounds
what are the reservoirs for phosphorous?
- the largest accumulations of phosphorous are in sedimentary rocks of marine origin.
- phosphorous also exists in soil, in the oceans in dissolved form and in organisms
- soil particles bind to PO4-3
what are the key processes in the phosphorous cycle?
- weathering rocks gradually add PO4-3 to soil
- leaches in grouch and surface water may eventually reach the sea
- phosphate taken up by producers and incorporated into biological molecules may be eaten by consumers
- finally phosphate is returned to soil or water by either decomposition of biomass or excretion by consumers
- only relatively small amounts of phosphorous are in the atmosphere, usually in forms of dust or sea spray
How is the conservation of mass relevant to ecosystems?
matter like energy cannot be created or destroyed.
because mass is conserved we can determine how much of a chemical element cycles within an ecosystem or is gained or lost by that ecosystem overtime
what are ecosystems similar too?
like organisms ecosystems are open systems: absorbing energy and mass and releasing heat and waste products
In an ecosystem, the balance between inputs and and outputs is determined by?
whether or not the ecosystem is a sink or a source for a given element
HUMAN ACTIVITIES OFTEN CHANGE THE BALANCE OF INPUTS AND OUTPUTS CONSIDERABLY
what do scientists assign to species based on their main source of nutrition and energy?
trophic levels
what are primary producers?
the trophic level that ultimately supports all others, consists of autotrophs
what are autotrophs?
organisms that are able to make energy containing organic molecules from inorganic molecules by using basic energy sources (sun)
what are heterotrophs?
organisms that feed on others in order to obtain their energy, because they cannot make their own energy
another definition of a heterotroph??
organisms in trophic levels above the primary producers, they depend directly or indirectly on the outputs of primary producers for their source of energy
what are primary consumers?
herbivores which eat plants and other primary producers
what are secondary consumers?
carnivores that eat herbivores are secondary consumers
what are tertiary consumers
carnivores that eat other carnivores are tertiary consumers
what are detritivores(decomposers)?
refer to consumers that get their energy from detritus( nonliving organic material, such as the remains of dead organisms, feces, etc.)
what is a limiting nutrient?
is the element that must be added for production to increase
what is NEP/ net ecosystem production?
a measure of total biomass accumulation during that time, defined as gross primary production minus the total respiration of all organism in the system(Rt)
NEP= GPP - Rt
what is gross primary production?
the amount of energy from light (or chemicals in chemoautotrophic systems) converted to the chemical energy of organic molecules per unit time
what is net primary production?
is equal to gross primary production minus the energy used by the primary producers for their “autotrophic respiration” (Ra)
NPP = GPP - Ra
detritivores also play a critical role in?
in recycling chemical elements back to primary producers.
they convert organic matter from all trophic levels to inorganic compounds usable by primary producers
what would happen to life if decomposition stopped?
life itself would cease to exist, because detritus would pile up and the ingredients needed to synthesize new organic matte would be exhausted
what is primary production?
the amount of light converted to chemical energy, in the form of organic compounds by autotrophs during a given time period is the ecosystems primary production
what type of energy transfer occurs within an energy cycle in an ecosystem?
solar energy -> chemical energy
what does the sun do in energy cycles?
the sun provides the primary producers with the energy needed to carry out the entire energy cycle
THE SUN IS THE START OF THE ENERGY CYCLE
what is an ecosystem?
it is the second level of biological organization. An ecosystem consists of all the living things in a particular area, along with all the nonliving components of the environment with which life interacts with
all of earth’s ecosystems do what?
all of earth’s ecosystems make up the biosphere
what is the biosphere?
the first level of biological organization
the biosphere consists of all life on earth and all the places where life exists, most regions of land, most bodies of water,etc.
what are communities?
the third level of biological organization
- The entire array of organisms inhabiting a particular ecosystem is called a biological community
what is symbiosis?
a type of ecological interaction
symbiosis comes from a greek word meaning “living together”, it is an ecological relationship in which two species live in close contact with each other
symbiotic relationships are usually formed by?
by prokaryotes with a much larger organism
what is a host?
generally in the larger organism in a symbiotic relationship is known as the host
what is a symbiont?
generally the smaller organism in a symbiotic relationship is known as the symbiont
what is mutualism?
an ecological interaction between two species in which both benefit
what is commensalism?
an ecological relationship in which one species benefits while the other is not harmed or helped in any significant way
what is parasitism?
an ecological relationship in which a parasite eats the cells contents, tissues or body fluids of its host
parasites as a group do what?
parasites as a group generally harm but USUALLY do not kill their hosts at least not immediately (unlike a predator)
what are pathogens?
parasites that cause diseases are known as pathogens, many of which are prokaryotic
how do pathogenic prokaryotes produce sickness?
they usually cause illness by producing poisons, which are classified as exotoxins or endotoxins
what are exotoxins?
are proteins secreted by certain bacteria and other organisms
what are endotoxins
lipopolysaccharide components of the outer membrane of gram-negative bacteria
THEY ARE ONLY RELEASED WHEN BACTERIA DIE AND THEIR CELL WALLS BREAK DOWN
what is bioremediation?
is a technological way to harness prokaryotes, with the use of organisms to remove pollutants from soil, air, or water
what is an example of bioremediation?
cleaning up oil spills and precipitating radioactive material (such as uranium) out of groundwater
what is a disturbance?
is an event, such as a storm, fire, flood, drought, overgrazing or human activity that changes a community by removing organisms from it or altering resource availability
what is the non-equilibrium model?
describes most communities as constantly changing after being affected by disturbances
what is the intermediate disturbance hypothesis?
states that moderate levels of disturbance foster greater species diversity than do low or high levels of disturbance
what do high levels of disturbances do?
high levels of disturbance reduce diversity by creating environmental stresses that exceed the tolerances of many species or by disturbing the community so often that slow-growing or slow-colonizing species are excluded
higher diversity communities are generally….?
are generally more productive and are better able to withstand and recover from environmental stresses
they are also more resistant to invasive species
what are invasive species?
organisms that become established outside their native range
what are trophic structures?
the structure and dynamics of a community also depend on the feeding relationships between organisms
what is the food chain?
the transfer of food energy up the trophic levels from its source in plants(primary producers) through herbivores (primary consumers) to carnivores (secondary, tertiary, and quaternary consumers) and eventually to decomposers is referred to as a food chain
what are food webs?
In 1920’s, Oxford university biologist Charles elton recognized that food chains are not isolated units but are linked together in food webs
EACH FOOD CHAIN WITHIN A FOOD WEB IS USUALLY A FEW LINKS LONG
why are food chains relatively short?
there are two main hypotheses:
- energetic hypothesis
- dynamic stability hypothesis
what is the energetic hypothesis?
suggests that the length of a food chain is limited by the inefficiency of energy transfer along the chain.
only about 10% of the energy stores in the organic matter of each trophic level is converted to organic matter at the next trophic level
what is biomass?
(the total mass of all individuals in a population) and 1kg of carnivore biomass
what does the energetic hypothesis predict?
it predicts that food chains should be relatively longer in habitats of higher photosynthetic production, since the starting amount of energy is greater than in habitats with lower photosynthetic production
what is the dynamic stability hypothesis?
proposes that long food chains are less stable than short chains
what are dominant species?
in a community the species that are the most abundant or that collectively have the highest biomass
what are keystone species?
are not usually abundant in a community, they exert a strong control on community structure not by numerical but by their pivotal ecological roles or niches
what are ecosystem engineers?
species that dramatically alter their environment are called ecosystem engineers or “foundation species”
ie) beavers
what are bottom-up and top-down controls?
simplified models based on relationships between adjacent trophic levels are useful for discussing community organization
what are the two models of community organization?
bottom-up model(V->H) and the top-down model (N
what is a bottom-up model?
postulates a unidirectional influence from lower to higher trophic levels
in this case the presence or absence of mineral nutrients (N) controls plants (V)numbers , which control herbivore (H) numbers, which in turn control predator(P) numbers (N->V->H->P)
what is top-down model?
postulates the opposite: predation mainly controls community organizations because predators limit herbivores, herbivores limit plants, and plants limit nutrient levels through nutrient uptake (N
what is biomanipulation?
attempts to prevent algal blooms and eutrophication by altering the density of higher level consumers
