4.2 Flashcards
What do most ecosystems rely on?
They rely on a continuous supply of energy from sunlight to fuel life processes and to replace energy lost as heat
The supply of nutrients in an ecosystem is finite & limited, so they must be recycled. By contrast there is a continuous, but variable, supply of energy in the form of sunlight, which is transferred b/w organisms, but eventually lost as heat
What is light energy converted into?
Light energy is converted into chemical energy in carbon compounds by photosynthesis
All autotrophs convert carbon dioxide into organic compounds. The light energy from the sun is used to synthesise carbohydrates. The light energy is transferred into chemical energy b/w atoms in a carbohydrate molecule
What is a food chain and describe how chemical energy in carbon compounds flows through food chains
They flow through means of feeding
A food chain is the simplest sequence of organisms along which energy is transferred
Always starts with producers
Each organism in the chain feeds on the organism before it
Arrows represent the flow or energy & nutrients, always pointing towards consumers
What happens to energy released from carbon compounds by respiration?
Energy released from carbon compounds by respiration is used in living organisms and converted into heat.
All organisms in an ecosystem respire, during which energy is lost to their immediate surroundings as heat. Therefore heat is lost from ecosystems
State that living organisms cannot convert heat to other forms of energy
Only chemical energy can be used by the next trophies level, and only a small amount of the energy that an organism takes in is actually converted to chemical energy. In fact only about 10% of what is eaten by a consumer is built into its body, and potentially available to be passed on to the next tropic level
Outline how heat is lost from ecosystems
No energy transfer is 100% efficient: wasted heat energy is also produced
Heat released from organisms dissipates into the ecosystem & is eventually lost from it. Therefore ecosystems require a continuous supply of energy (eg. sunlight) to persist
Unlike light & chemical energy, organisms can’t convert heat energy into forms useful to the organism
Explain why energy (& biomass) is lost b/w each tropic level
most of the chemical energy in food absorbed by organisms is released by respiration for use in the cells & is eventually lost as heat
the organisms in one trophic level aren’t usually entirely consumed by organisms in the next trophies level (eg. bones, claws, feathers, hairs etc.)
Not all the food eaten can be digested & will pass out with faeces
The only energy available to organisms in the next trophic level is chemical energy in organic compounds in body tissues
What does a pyramid of energy show?
the amount of energy in each trophic level of a food chain
How should a pyramid of energy always be set out? And why is it always pyramidal?
producers at the bottom, then the next trophic level on top
bar length should be proportional to the amount of energy
always pyramid shaped because around 90% of energy is lost b/w trophic levels
What units are used to measure energy?
kJ / m2 / y
