Ib Sl Ess Topic 2 Study Guide
2.1.1 Distinguish between biotic and abiotic components of an ecosystem * Biotic factors in an ecosystem are living, biological factors that may influence an organism in an ecosystem * Abiotic factors are non-living, physical factors that may influence an organism in an ecosystem
2.1.2 Define the term trophic level * The position that an organism occupies in a food chain, or a group of organisms in a community that occupy the same position in food chains
2.1.3 Identify and explain trophic levels in food chains and food webs selected from the local environment
2.1.4 Explain the principles of pyramids of numbers, pyramids of biomass, and pyramids of productivity, and construct such pyramids from given data
Pyramid of numbers
A pyramid of numbers shows the number of organisms at each trophic level in a food chain
The length of each bar gives a measure of the relative numbers. Pyramids have producers at the bottom, usually in the greatest number. However, some may have a large single plant, a tree, as the producer so the base Is one individual which supports many consumers. Advantages of pyramid of numbers: Easy method of giving an overview and is good for comparing changes in population numbers over different times or seasons Disadvantages of pyramid of numbers: All organisms are included regardless of their size, therefore a pyramid based on an oak tree would be inverted ( have a narrow base and getting larger as it goes up the trophic levels) Pyramid of biomass
Pyramid of biomass contains the biomass (mass of each individual x number of individuals) at each trophic level. Biomass is the quantity of (dry) organic matter in an organism, a population, a particular trophic level or an ecosystem. Advantages: Overcomes the problem of pyramids of number. Disadvantages: Have to kill species, etc. Pyramid of Productivity
Pyramid of productivity contains the flow of energy through each trophic level. Advantages:
2.1.2 Define the term trophic level * The position that an organism occupies in a food chain, or a group of organisms in a community that occupy the same position in food chains
2.1.3 Identify and explain trophic levels in food chains and food webs selected from the local environment
2.1.4 Explain the principles of pyramids of numbers, pyramids of biomass, and pyramids of productivity, and construct such pyramids from given data
Pyramid of numbers
A pyramid of numbers shows the number of organisms at each trophic level in a food chain
The length of each bar gives a measure of the relative numbers. Pyramids have producers at the bottom, usually in the greatest number. However, some may have a large single plant, a tree, as the producer so the base Is one individual which supports many consumers. Advantages of pyramid of numbers: Easy method of giving an overview and is good for comparing changes in population numbers over different times or seasons Disadvantages of pyramid of numbers: All organisms are included regardless of their size, therefore a pyramid based on an oak tree would be inverted ( have a narrow base and getting larger as it goes up the trophic levels) Pyramid of biomass
Pyramid of biomass contains the biomass (mass of each individual x number of individuals) at each trophic level. Biomass is the quantity of (dry) organic matter in an organism, a population, a particular trophic level or an ecosystem. Advantages: Overcomes the problem of pyramids of number. Disadvantages: Have to kill species, etc. Pyramid of Productivity
Pyramid of productivity contains the flow of energy through each trophic level. Advantages: