Ecosystems and Biomass Flashcards
What is meant by net and gross primary productivity?
Gross primary productivity (GPP) - the rate of chemical
energy fixture during photosynthesis by all producers in an
ecosystem, measured in kJ m-2 year-1
Net primary productivity (NPP) - the amount of chemical energy that is available to heterotrophs in an ecosystem
How is net primary productivity calculated?
NPP=GPP-R
Gross primary productivity minus energy generated in respiration
What is a trophic level?
The position that an organism holds in a food chain, food web, pyramid of numbers or pyramid of biomass.
What is biomass and how is it transferred? Can we measure this?
The weight of living matter in a certain area, transferred up trophic levels through consumption. It’s measured in terms of mass of carbon, or dry mass of tissue.
State the formula for efficiency of biomass transfer
Efficiency = (biomass transferred/biomass intake) x 100
Why are biomass transfers not 100% efficient?
Energy is lost through
-Egestion (feces)
-Excretion (waste products like urine)
-Respiration
-The production of inedible bones and shells
Why do food chains usually have fewer than five trophic levels?
Biomass transfers are not 100% efficient and so there’s often not enough energy to support 5 trophic levels.
Define population
All organisms of the same species living with one another in a habitat at the same time.
Define community
All of the populations of different species living together in a habitat.
What is a habitat?
The region where an organism usually lives.
Define ecosystem
The community of organisms and non-living components of an area and their interactions. Varies from large ones like biomes to very small ones like microhabitats.
Describe biotic and abiotic factors, giving examples.
Biotic: living features like predators or disease.
Abiotic: non-living features like light and t°
Define niche
Describes how an organism fits into an ecosystem and its role in that environment.
What do population numbers depend on?
Birth rate, death rate, immigration and emigration.
What is distribution?
The spread of living organisms in an ecosystem.
What is sampling?
Selecting a group of individuals that will represent the whole target population. It allows us to measure the distribution and abundance of organisms.
Suggest methods of assessing abundance and distribution of organisms
Quadrats and transects
Suggest different ways abundance can be qualified
% area cover, % frequency, density
What is random sampling?
A sampling technique to avoid bias, like creating a square grid and generating random coordinates
What is systematic sampling?
A sampling technique used to determine the abundance and distribution of organisms along an area at periodic intervals. Commonly used in ecosystems where some sort of gradual change occurs.
How can the light intensity be measured?
Using a light meter placed near the ground with the photodetector facing the light source.
How can the soil pH be measured?
Using a pH probe which is placed in the soil in order to provide a reading on the display for soil pH.
