5: ENERGY TRANSFERS - ENERGY TRANSFER IN ECOSYSTEMS Flashcards
(22 cards)
What is an individual?
a single organism of a species
What is a population?
a group of organisms of the same species
What is a community?
all the organisms of different species that live together in a particular area
What is an ecosystem?
all organisms living in a particular area + all the abiotic (non-living) conditions
What are producers?
organisms that make their own food
What are some examples of producers in land-based ecosystems?
- trees
- shrubs
- grasses
What are some examples of producers in aquatic ecosystems?
- algae
- seaweeds
- water lilies
How do producers synthesise organic compounds?
- photosynthesis
- energy from sunlight, CO2 and H2O are used to make glucose and other sugars
What is glucose produced during photosynthesis used for?
- respiration
- making other biological molecules which make up the plant’s biomass
What is biomass?
- the mass of living material
- the chemical energy stored in the organism
How is energy transferred between organisms in an ecosystem?
- when organisms eat other organisms
- producers are eaten by primary consumers, primary consumers are eaten by secondary consumers, etc. (food chain)
How can biomass be measured?
- mass of carbon that an organism contains (~50% of the dry mass)
- dry mass of its tissue per unit area
What is the dry mass and how is it obtained?
- mass of the sample with the water removed
- obtained by drying the tissue sample in an oven set to a low temp. it’s weighed at regular intervals. when the mass becomes constant, all the water has been removed
- you can scale up the result to give the dry mass (biomass) of the total population/the area being investigated (typical units may be Kg m^-2)
Why is biomass measured using dry mass?
water content of living tissue varies so wet mass is unreliable
How can calorimetry be used to estimate the chemical energy stored in biomass?
- sample of dry biomass is burnt
- the energy released heats a known volume of water
- the change in the temp of the water is used to calculate energy of the dry biomass
Why is there a stirrer in the calorimeter?
to evenly distribute heat energy throughout the water
Why is the calorimeter insulated?
to prevent heat loss to the surroundings
What is gross primary production (GPP)?
the total amount of chemical energy converted from light energy by plants in a given area
What is net primary production (NPP)?
the remaining chemical energy stored in the plant’s biomass available to the plant for growth and reproduction and also available to the organisms at the next stage in the food chain
What is respiratory loss?
the GPP lost to the environment as heat when the plants respire (~50%)
What is the equation for net primary production (NPP)?
GPP - R (gross primary production - respiratory loss)
