EcologyEcology

DefinitionsDefinitions

Habitat – Habitat – The natural home or environment of an animal, plant, or other organism. Eg. Marine habitat

Niche – the relational position of Niche – the relational position of species in an ecosystem to each other and species in an ecosystem to each other and how an organism or population responds how an organism or population responds to the distribution of resources and to the distribution of resources and competitorscompetitors

Population – Population – all the organisms of one particular species within a specified area at a particular time, sharing the same gene pool and more or less isolated from other populations of the same species.

Community – all of the populations of Community – all of the populations of all of the different species within a all of the different species within a specified area at a particular time.specified area at a particular time.

Ecosystem - all the organisms living in a Ecosystem - all the organisms living in a particular area, as well as all the nonliving particular area, as well as all the nonliving (abiotic), physical components of the (abiotic), physical components of the environment with which the organisms environment with which the organisms interact, such as air, soil, water and interact, such as air, soil, water and sunlight.sunlight.

Linked together by energy flow and Linked together by energy flow and cycling of nutrients.cycling of nutrients.

Vary in size but always form a functional Vary in size but always form a functional entity.entity.

Producer – an organism that makes its own Producer – an organism that makes its own organic nutrients, using energy from the sun, organic nutrients, using energy from the sun, by photosynthesis.by photosynthesis.

Consumer – an organism that gets its Consumer – an organism that gets its energy by feeding off another organismenergy by feeding off another organism

Food Chains and Food websFood Chains and Food webs

Food chain – chart Food chain – chart showing the flow showing the flow of energy from of energy from one organism to one organism to the next beginning the next beginning with the producer.with the producer.

Food web – network Food web – network of interconnected of interconnected food chains showing food chains showing the energy flow the energy flow through part of an through part of an ecosystemecosystem

Trophic Level – position of an organism in a Trophic Level – position of an organism in a food chain, food web or pyramid of biomass, food chain, food web or pyramid of biomass, numbers or energy.numbers or energy.

Energy is lost from each trophic level as it is Energy is lost from each trophic level as it is used by the organism for:used by the organism for: Respiration while the animal is aliveRespiration while the animal is alive Excretion of waste productsExcretion of waste products

The only energy passed on is what is in the The only energy passed on is what is in the biomass. About 10% of what it ate.biomass. About 10% of what it ate.

The higher one goes in the food chain the less The higher one goes in the food chain the less energy available so most chains only have 5 energy available so most chains only have 5 trophic levels.trophic levels.

Nitrogen cycleNitrogen cycle

Nitrogen in several forms. Nitrogen in several forms. 78% of atmosphere is nitrogen gas. 78% of atmosphere is nitrogen gas. But most not usable by life on Earth.But most not usable by life on Earth.

nitrogen is transformed into a form usable nitrogen is transformed into a form usable by plants.by plants.

In two ways: In two ways:

Nitrogen fixation Nitrogen fixation Rhizobium are bacteria established inside root nodules of legumes (peas, beans, clover, and soy),

N2 + 8 H+ + 8 e− → 2 NH3 + H2

NH3 + H+ → NH4+, using enzyme

nitrogenase In return, the plant supplies the bacteria

with carbohydrates, proteins, and oxygen

Nitrosomonas oxidizes ammonia into nitrite  Nitrobacter oxidizing nitrite to nitrate   Nitrates then absorbed by plants

decomposing bacteria start ammonification, to convert plants and animals back into ammonia

anaerobic bacteria will convert them back into nitrogen gas, denitrification.

In watery soils, bacteria use nitrates and In watery soils, bacteria use nitrates and nitrogen gas is formed. nitrogen gas is formed. 

NitrosomonasRhizobium

Nitrobacter

Lightning, ultraviolet radiation and electrical Lightning, ultraviolet radiation and electrical equipment can fixate nitrogen. equipment can fixate nitrogen.

Algae and other more complex plants use nitrates and Algae and other more complex plants use nitrates and ammonia created by nitrogen fixation. ammonia created by nitrogen fixation.

Animals eat these plants and use the nitrates in their Animals eat these plants and use the nitrates in their bodies. bodies.

The remains of dead plants and animals are The remains of dead plants and animals are decomposed, creating ammonia. decomposed, creating ammonia.

This ammonia is a turned back into nitrate by bacteria This ammonia is a turned back into nitrate by bacteria through a process called nitrification. through a process called nitrification.