13.1 - Food Chains And Energy Transfer Flashcards
The ultimate source of this energy for almost all organisms is _____
- sunlight
- which is conserved as chemical energy by plants.
What are producers
Producers are photosynthetic organisms that manufacture organic substances using light energy, water, carbon dioxide, and mineral ions.
What are consumers
- Consumers are organisms that obtain their energy by feeding on (consuming) other organisms rather than using the energy of sunlight directly.
- Animals are consumers. Those that directly eat producers (green plants) are called primary consumers because they are the first in the chain of consumers.
- Those animals eating primary consumers are called secondary consumers and those eating secondary consumers are called tertiary consumers.
- Secondary and tertiary consumers are usually predators but they may also be scavengers or parasites.
What are saprobionts
- 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.
What are saprobionts
- 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.
What is a food chain, and what are trophic levels
- 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.
What are food webs
- 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.
What is biomass
Biomass is the total dry mass of living material in a specific area at a given time.
Why do we measure biomass using an organism’s dry mass?
- the presence of varying amounts of water makes it unreliable.
Why might using an organisms dry mass be problematic
- because the organisms must be killed
- it is usually only made on a small sample
- and this sample may not be representative.
What is the unit for biomass
- because biomass is measured using dry mass per given area, in a given time.
- this could be ‘g cm^2 day’
- or ‘kg m^2 min’
The chemical energy store in dry mass can be estimated using….
Calorimetry
Describe how a bomb calorimetry works
- In bomb calorimetry, a sample of dry material is weighed and is then burnt in pure oxygen within a sealed chamber called a bomb (closed system —> so no heat loss)
- The bomb is surrounded by a water bath and the 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 1°C, 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 kJ kg^-1.
State which organisms are secondary consumers.
dragonfly nymphs
State which organisms carry out photosynthesis
unicellular and filamentous algae
State which organisms are at the fourth trophic level.
sticklebacks
Explain what the arrows in the diagram show.
the direction of energy flow
When the organisms in this web die they will be broken down by
bacteria and fungi. Name the general term used to describe these bacteria and fungi.
Saprobionts/decomposers
