chapter 19 - organisms and their environment Flashcards
*what is the main source of energy input to biological systems?
the sun.
photosynthesizing plants use sunlight as energy, and the energy is then passes through food chains.
with the exception of atomic energy and tidal power, all energy released on Earth is derived from sunlight.
*describe the flow of energy through living organisms and its eventual transfer to the environment
Energy enters ecosystems in the form of sunlight or chemical compounds. Some organisms use this energy to make food. Other organisms get energy by eating the food.
*define
food web
a network of interconnected food chains.
*define
producer
an organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis.
*define
consumer
an organism that gets its energy by feeding on other organisms.
*define
trophic level
the position of an organism in a food chain, food web, pyramid of numbers or pyramid of biomass.
*how is energy transferred between organisms in a food chain?
by ingestion.
what is interdependence?
the way in which living organisms depend on each other in order to remain alive, grow and reproduce.
*explain why the transfer of energy from one trophic level to another is inefficient
- primary consumers eat only a small proportion of of the available vegetation (producers).
- consumers may not digest all the food they ingest.
- energy is wasted on movement, respiration and other life processes of consumers.
- only about 10% energy is transferred and used from one trophic level to another.
*explain why food chains usually have fewer than 5 trophic levels
- about 90% of the energy is lost at each trophic level.
- very little of the energy entering the chain through the producer is available to the top consumer.
what is a pyramid of numbers?
the width of the bands are meant to represent the relative number of organisms at each trophic level.
*explain why there is greater efficiency in supplying plants as human food.
- there is a relative inefficiency in feeding crop plants to livestock that will be used as food.
*explain why there is greater efficiency in supplying plants as human food.
- there is a relative inefficiency in feeding crop plants to livestock that will be used as food, because only 10% of the plant material is converted to animal products.
- it is more efficient to eat bread made from wheat, than to wheat to chickens and the eat their eggs and meat —> no energy is wasted on keeping the animal alive.
*describe how energy is transferred between trophic levels
a herbivorous animal eats a plant, so the chemical energy in the plant is transferred to the herbivore.
when a carnivore eats the herbivore, energy is transferred in the same way.
the carnivore may be eaten by another carnivore.
what is a pyramid of biomass?
biomass is the word used when the mass of living organisms is being considered, and pyramids of biomass can be constructed.
*what are the trophic levels represented by food webs, food chains, pyramids of numbers and biomass?
producers primary consumers secondary consumers tertiary consumers quaternary consumers
*what trophic levels can consumers be classified into?
primary consumers
secondary consumers
tertiary consumers
quaternary consumers
*define
herbivore
an animal that gets its energy by eating plants.
*define
carnivore
an animal that gets its energy by eating other animals.
*define
decomposer
an organism that gets its energy from dead or waste organic material.
why do humans harvest animals?
species may be harvested for food, body parts, or for selling as pets.
what is overfishing?
commercial fishing (large nets + small holes) ---> catching methods have become more sophisticated + more small non-mature fish are caught ---> decline in number of fish. in some cases, stocks are so depleted that it is no longer economical to exploit them. whaling ---> extinction of whales. the use of heavy nets dragged along the sea floor to catch fish can wreck coral reefs ---> destroys habitats of many other animal species.
*use food chains and food webs to describe the impacts humans have through overharvesting of food species
- it causes the reduction in numbers of a species to the point where it is endangered or made extinct.
- hunting animals or fishing is not always regulated or controlled and rare species can be threatened as a result of indiscriminate killing.
- biodiversity is affected —> if some events interfere with a food web, all the organisms are affected in some way.
- fishing for the top predators has a direct effect on the food chain: fish lower down the chain increase in numbers and overgraze on the reef.
*use food chains and food webs to describe the impacts humans have through introducing foreign species to a habitat
- the accidental introduction of foreign species can disrupt food chains.
- the foreign animals feed on other other animals and have no natural predators —> other species are brought to extinction while the foreign species thrive.
- the foreign species need to be exterminated.
*how would you draw and interpret a pyramid of biomass
pyramids of biomass must be drawn with the:
1- bars equally spaced around the midpoint
bars touching
2- bar for the producer at the bottom
3- length of each bar is proportional to the amount of biomass available at each trophic level
*how would you draw and interpret a pyramid of numbers
A pyramid of numbers shows the total number of individual organisms at each level in the food chain of an ecosystem.
*discuss the advantages of using a pyramid of biomass rather than a pyramid of numbers to represent a food chain
- displaying food chains using pyramids of number can produce inverted pyramids, because the top consumer may be represented by large numbers of very small organisms.
- so instead of considering the number of a trophic level, it is better to look at the biomass of the total organisms in a trophic level.
- a pyramid of biomass is nearly always the correct pyramid shape.
decomposers do not belong to any food chains, so how do they survive?
fungi and bacteria in the soil.
- they don’t obtain their food by photosynthesis, nor do they kill and eat living animals or plants. instead, they feed on decaying matter.
- they produce extracellular enzymes that digest the decaying matter and then absorb the soluble products back into their cells.
- they also break down remains into substances that can be used by other organisms.
ex) bacteria break down proteins into ammonium to release nitrates.
*describe the carbon cycle
photosynthesis, respiration, feeding, decomposition, fossilization and combustion.
*describe the water cycle
evaporation, transpiration, condensation and precipitation.
*Describe the nitrogen cycle
– decomposition of plant and animal protein to ammonium ions – nitrification – nitrogen fixation by lightning and bacteria – absorption of nitrate ions by plants – production of amino acids and proteins – feeding and digestion of proteins – deamination – denitrification
*State the roles of microorganisms in the nitrogen
cycle
decomposition, nitrification,
nitrogen fixation and denitrification (generic
names of individual bacteria, e.g. Rhizobium, are
not required)
- discuss the effects of the combustion of fossil fuels and the cutting down of trees on the carbon dioxide concentrations in the atmosphere.
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*define
population
a group of organisms of one
species, living in the same area, at the same time
*define
community
all of the populations of
different species in an ecosystem
*define
ecosystem
a unit containing the
community of organisms and their environment,
interacting together,
*Identify and state the factors affecting the rate
of population growth for a population of an
organism
- food supply —> enables organisms to breed more successfully to produce more offspring.
shortage of food leads to starvation —> death and emigration. - predation
- disease
*explain the factors that lead to each phase in the sigmoid curve of population growth, making reference, where appropriate, to the role of limiting factors.
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