chapter 19 - organisms and their environment Flashcards
(38 cards)
*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.
