Download KEY AN ORGANISM`S NICHE IS ITS ROLE IN THE COMMUNITY

Honors Biology – Unit 1 Ecology Review
KEY
1. Describe what is meant by an organism’s niche. Give an example. What is likely to happen if
two organisms try to occupy the same niche?
AN ORGANISM’S NICHE IS ITS ROLE IN THE COMMUNITY. EX) RESOURCES
IT USES, BEHAVIOR, PLACE IN FOOD WEB.
COMPETITIVE EXCLUSION OCCURS WHEN TWO ORGANISMS TRY TO
OCCUPY THE SAME NICHE. ONE SPECIES MAY BECOME EXTINCT OR ONE
SPECIES MAY UNDERGO SHIFT TOWARDS A DIFFERENT ECOLOGICAL
NICHE. 2 ORGANISMS CAN NOT OCCUPY THE SAME NICHE!
2. Define the word Ecology.
ECOLOGY IS THE SCIENTIFIC STUDY OF INTERACTION AMONG
ORGANISMS AND BETWEEN ORGANISMS AND THEIR ENVIRONMENT.
3. Understand and know how to use a food chain. How is a food chain different than a food web?
In a food chain, if the second level consumer suddenly becomes extinct, what would likely
happen to the producer in that food chain?
FOOD CHAINS ALWAYS START WITH PRODUCERS. IT SHOWS THE
PATHWAY OF ENERGY FROM ONE ORGANISM TO THE NEXT IN A DIRECT
LINE OF ORGANISM.
FOOD WEBS SHOW THE INTERACTIONS AND INTERCONNECTIONS AMONG
THE DIFFERENT FOOD CHAINS OF A COMMUNITY.
IF A SECOND LEVEL CONSUMER BECOMES EXTINCT IN A FOOD CHAIN, THE
PRODUCER POPULATION WOULD MOST LIKELY DECREASE GREATLY
(BECAUSE OF INCREASE IN PRIMARY LEVEL CONSUMERS).
4. What organisms are the most important part of the nitrogen cycle? What do they do?
DECOMPOSERS AND OTHER SOIL BACTERIAS (IN NODULES OF LEGUMES
LIKE SOYBEANS) BREAK DOWN AND CONVERT NITROGENOUS WASTES
(NITROGEN FIXATION) AND THE REMAINS OF DEAD ORGANISMS INTO
MATERIAL THAT IS USUABLE BY PLANTS (NITRATES)
5. What is the difference between how energy moves through an ecosystem and how materials
move through an ecosystem?
ENERGY MOVES IN ONE DIRECTION THROUGH AN ECOSYSTEM AND
MATERIALS CYCLE IN AN ECOSYSTEM.
6. Describe the difference between abiotic and biotic factors.
ABIOTIC FACTORS
* the non-living parts of the environment
* they directly affect the ability of organisms to live and reproduce
ex. hot temperature, little water are examples of abiotic factors
BIOTIC FACTORS
* all the living things that directly or indirectly affect the ecosystem
* biotic factors interact with other living organisms and the physical
environment
ex. disease (bacteria), predators, food resources
7. What is the “biosphere”.
BIOSPHERE INCLUDES THE PARTS OF THE EARTH AND ATMOSPHERE
THAT IS CAPABLE OF SUPPORTING LIFE.
8. In any type of trophic relationship, what level of organism contains the most energy? Which
level contains the most biomass? Why is this necessary?
THE FIRST TROPHIC LEVEL (PRODUCERS) CONTAINS THE MOST ENERGY.
THE FIRST TROPHIC LEVEL ALSO CONTAINS THE MOST BIOMASS. THIS IS
NECESSARY BECAUSE THE FIRST LEVEL PROVIDES FOOD TO SUPPORT THE
NEXT LEVEL IN THE PYRAMID.
9. What roll do decomposers play in an ecosystem? Where do they occur in the food chain or food
web?
DECOMPOSERS BREAK DOWN DEAD MATTER AND RETURN VITAL
NUTRIENTS TO THE SOIL. THEY ARE ALSO CALLED SAPROPHYTES. THEY
OCCUR AT THE END OF THE FOOD CHAIN/WEB.
10. Why aren’t there normally a large number of predators that exist at the top of a food chain?
AT THE TOP OF THE FOOD CHAIN, THERE ISN’T ENOUGH ENERGY TO
SUSTAIN A LARGE NUMBER OF PREDATORS.
11. How much energy is lost as it moves from one trophic level to the next? What becomes of that
lost energy? Where does it go?
90% OF ENERGY IS LOST FROM ONE TROPHIC LEVEL TO THE NEXT (ONLY
10% TRANSFERRED TO NEXT HIGHER LEVEL). THE LOST ENERGY IS USED
IN MAINTAINING HOMEOSTASIS AND AS THE PRODUCTION OF HEAT.
12. What is the difference between a nitrifying bacteria and denitrifying bacteria?
NITRIFYING BACTERIA FIXES NITROGEN COMPOUND INTO A FORM
USABLE BY PLANTS AND DENITRIFYING BACTERIA BREADKOWN
NITROGEN COMPOUNDS INTO ATMOSPHERIC NITROGEN.
13. Why do ecosystems go through a process of succession?
SUCCESSION OCCURS IN COMMUNITIES THAT WERE ESTABLISHED AND
THEN DISTURBED IN SOME MANNER.
14. What types of organisms are the pioneer organisms that can establish new ecosystems? Why do
they have to be first? What do we call the “final stage” of an ecosystem’s development?
PIONEER ORGANISMS ARE LICHENS AND BACTERIA THAT ARE USUALLY
THE FIRST TO APPEAR ON BARE ROCK.
THE FINAL STAGE OF AN ECOSYSTEM’S DEVELOPMENT IS CALLED A
CLIMAX COMMUNITY THAT REMAINS STABLE UNTIL A CATASTROPHIC
CHANGE.
15. What is meant by the term “symbiotic relationship”?
SYMBIOTIC RELATIONSHIPS ARE INTERACTIONS AMONGST DIFFERENT
SPECIES IN AN ECOSYSTEM WHERE THEY LIVE IN A CLOSE ASSOCIATION
WITH ANOTHER; AT LEAST ONE MEMBER OF THE ASSOCIATION BENEFITS
16. Describe the different types of symbiotic relationships.
a) MUTUALISM (+ , +)
* a symbiotic relationship in which both organisms BENEFIT
ex. nitrogen fixing bacteria that live in nodes (lumps) on the roots of certain
plants (legumes)...the bacteria have a nice place to live (+), and the plants
benefit from getting the nitrogen they need from the bacteria (+)
b) COMMENSALISM (+ , 0)
* a symbiotic relationship where one organism benefits (+) and the other
organism is not harmed (0)
ex. the remora (a small fish) attaches itself to the underside of a shark...when
the shark feeds, the remora disconnects and eats scraps that are left over (+)
... the shark is not affected (0); barnacles (+) on whales (0)
c) PARASITISM (+ , -)
* a symbiotic relationship where one organism, the parasite, benefits (+),
while the other organism, the host, is harmed (-)
ex. athlete's foot, a fungus, grows on human feet for nutrients (+), while the
human doesn't like it (-); tapeworms (+) in humans (-); heartworms (+) in
dogs (-)