[13] Energy & ecosystems Flashcards
What are producers?
Photosynthetic organisms that manufacture organic substances using light energy, water, carbon dioxide and mineral ions.
What are consumers?
Organisms that obtain their energy by feeding on other organisms rather than using the energy of sunlight directly.
What are saprobionts?
A group of organisms that break down the complex materials in dead organisms into simple ones. In doing so, they release valuable minerals and elements in a form that can be absorbed by plants and so contribute to recycling.
What is a food chain?
It describes a feeding relationship in which the producers are eaten by primary consumers. These in turn are eaten by secondary consumers, which are then eaten by tertiary cosumers. Each stage in this chain is referred to as a trophic level.
What is a food web?
Most animals do not rely on a single food source and within a single habitat many food chains will be linked together to form a food web. The problem with food webs is their complexity.
What is biomass?
Biomass is the total mass of living material in a specific area at a given time. The fresh mass is quite easy to assess, but the presence of varying amounts of water makes it unreliable.
How is biomass measured?
Biomass is measured using dry mass per given area, in a given time. It is measured in grams per square metre.
What is gross primary production (GPP)?
The total quantity of the chemical energy store in plant biomass, in a given area or volume, in a given time.
What is net primary productivity (NPP)?
Energy is lost through respiration and excrement so the chemical energy store which is left when these losses have been taken into account, is called net primary productivity.
What is the formall linking NPP, GPP and Respiration?
NPP = GPP - R
What are the reasons for energy that is not transferreD?
- Some of the organism is not consumed
- Some parts are consumed but cannot be digested and are therefore lost in faeces
- Some of the energy is lost in excretory materials, such as urine
- Some energy losses occur as heat from respiration and lost to the environment. These losses are high in mammals and birds because of their high body temperature.
What is the formula to calculate the net production of consumers?
N = I - (F+R) N - net production I - chemical energy store of ingested food F - energy lost in faces and urine R - energy lost in respiration
Why do most food chains have only four or five trophic levels?
Because insufficient energy is available to support a large enough breeding population at trophic levels higher than these.
What is the formula for percentage efficiency?
percentage efficiency = (energy available after the transfer/energy available before the transfer) x 100
