Energy and ecosystems Flashcards
What are producers?
Photosynthetic organisms that manufacture organic substances using light, water and carbon dioxide. Green plants are producers
What are consumers?
Organisms that obtain their energy by feeding on other organisms, rather than using the energy of sunlight directly. Animals are consumers
What are decomposers?
Organisms, usually fungi or bacteria, that break down the complex material of dead producers and consumers into simple components again and release minerals and elements in a form plants can absorb. They contribute to recycling. Sometimes organisms such as earth worms do this, and they are known as detritivores
What does a food chain describe?
A feeding relationship in which the producers are eaten by primary consumers, which are in turn eaten by secondary consumers, which are then eaten by tertiary consumers
What is a trophic level?
Each stage of a food chain
What is a food web and what does it show?
Lots of food chains in an ecosystem and how they over lap
What is an ecosystem?
All the organisms living in a particular area and all the non-living (abiotic) conditions
What is the source of energy for ecosystems?
The sun
What percentage do plants convert the sun’s energy into organic matter?
1-3 %
What is gross production?
Total quantity of energy that plants in a community convert to organic matter
What is net production and the equation for calculating it?
The rate at which plants store energy
net production = gross production - respiratory losses
What are the reasons for the low percentage of energy transferred at each stage?
- Some of the organism is not eaten
- Some parts are eaten but aren’t digested and is lost in faeces
- Some energy is lost in excretory materials e.g. urine
- Some energy losses occur as heat from respiration and directly from the body to the environment. High in mammals and birds due to their high body temperature
What does the inefficiency of energy transfer between trophic levels explain?
- Why most food chains have 4 or 5 trophic levels as there is insufficient energy to support a breeding population at higher trophic levels
- Biomass is less at higher levels
- Total amount of energy stored is less at each trophic level
What is energy available usually measured as?
kJ m -2 year -1
What is the calculation for working out energy transfer?
energy available after transfer
_______________________
energy available before transfer X 100
What is biomass?
The total mass of a living organism in a specific area at any given time. Usually measured as dry mass because amount of water un an organism varies.
What is an agricultural ecosystem?
Domesticated animals and plants used to produce food for humans
