Energy & ecosystems Flashcards
1
Q
What happens in an ecosystem?
A
- the organisms in any ecosystem rely on a source of energy to carry out all their activities
- the ultimate source of this energy for almost all organisms is sunlight, which is converted as chemical energy in plants
- most plants use sunlight in making organic compounds from carbon dioxide in the air or water that surrounds them
- these organic compounds include sugars, most of which are used by the plants as a respiratory substrates
- the remainder are used to make other groups of biological molecules
- these biological molecules form the biomass of the plants that is the means by which energy is passed veteran other organisms
2
Q
Which groups are organisms divided into based on how they obtain their energy and nutrients?
A
- producers
- consumers
- saprobionts (decomposes)
3
Q
What are producers?
A
-producers are photosynthetic organisms that manufacture organic substances using light energy, water, carbon dioxide and mineral ions
4
Q
What are consumers?
A
- consumers are organisms that obtain their energy by feeding on other organisms rather than using the energy of sunlight directly
- animals are consumers
- those that directly eat producers are called primary consumers because they are the first chain of consumers
- those animals eating primary consumers are called secondary consumers and those eating secondary and tertiary consumers are usually predators but they may also be scavengers or parasites
5
Q
What are saprobionts?
A
- saprobionts (decomposers) are 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
- the majority of this work is carried out by fungi and bacteria
6
Q
What is a food chain?
A
- a food chain 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 consumers
- in a long food chain the tertiary consumers may in turn be eaten by further consumers called quaternary consumers
- each stage in this chain is referred to as a trophic level
- the arrows on food chain diagrams represent the direction of energy flow
7
Q
What are food webs?
A
- in reality 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
- in practice it is likely that all organisms within a habitat, even within an ecosystem, will be linked to others in the food web
8
Q
What is biomass?
A
- 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
- measuring the mass of carbon or dry mass overcomes this. Problem but because the organisms must be killed it is usually only made on a small sample and this sample may not be representative
- biomass is measured using dry mass per given area, in a given time
- more specifically it is measured in grams per square metre where an area is being samples, for example, on grassland or a seashore
- where a volume is being sampled for example in a pond or an ocean it is measured in grams per cubic metre
9
Q
What is calorimetry?
A
- the chemical energy store in dry mass can be estimated using calorimetry
- in bomb calorimetry, a sample of dry material is weighed and is then burnt in pure oxygen within a sealed chamber called a bomb
- the bomb is surrounded by a water bath and he heat of combustion causes a small temperature rise in this water
- as we know how much heat energy is required to raise the temperature of 1g of water by 1oC if we know the volume of water and the temperature rise, we can calculate the energy released from the mass of burnt biomass in units such as kJkg-1
