5.1.7 Energy and Ecosystems

Revise GCSE knowledge of Ecosystems and the Environment Define terms used and give examples

Ecosystems A distinct, self- supporting system of organisms interacting with each other and with a physical environment. They can be large or small They encompass a range of habitats They usually contain producers, consumers, decomposers and a physical environment For each term give a definition and two examples Producer, Consumer, Decomposer, Environment, Habitat

Definitions A population is the sum total of all the organisms of a particular species found in an ecosystem at any one time The population of all species is known as the community in that ecosystem The ecological niche of an organism is the role of the organism in a community in terms of its habitat and interactions with other organisms. A given niche may be occupied by different organisms in different ecosystems Pg 100 question 3

Food webs/ food chains Food chains are the simplest way of showing feeding relationships GrassRabbitFox The arrow shows the direction of energy flow through the system Each stage in a food chain is known as a tropic level. Food chains are an oversimplification, food webs can give a fuller understanding What are the benefits and downsides of showing feeding relationships as ChainsWebs

Pyramids of number These represent the total numbers of organisms at each tropic level at a moment in time. It is irrespective of mass Grass Rabbits Foxes Oak tree Aphid Ladybird

Pyramids of biomass These represent the total biomass of organisms at each tropic level at a moment in time. It is irrespective of numbers BiomassNumber Aphid Ladybird Oak tree

Questions Question 3 pg 172 Ecology workbooks

Explain how energy is transferred between tropic levels Calculate and explain efficiency of transfer

Energy transfer- Key processes Photosynthesis fixes light energy into bonds between organic molecules Respiration releases energy from organic molecules to make ATP which can ‘drive’ other processes Synthesis of molecules and cells uses energy which can be passed to the next tropic level Biological processes which use energy

Innefficiency and energy Only 3% of sunlight is converted to chemical energy – Some light entirely misses leaves – Some light is reflected – Some light passes through – Only certain wavelengths are absorbed – Loss when transferred from chlorophyll to organic molecules

Energy losses cont Plants use about half of the energy they fix themselves – Energy is used during respiration for processes like active transport What is left can be passed to the next tropic level, but again there are losses – Not all parts of plant available to be eaten – Not everything eaten can be digested – Energy losses within consumers digestive system

Energy in ecosystems Three things can happen to the energy taken in by organisms at a tropic level – Passed onto biomass of next tropic level when eaten – Stored in detritus, passed onto decomposers when the detritus decays – Converted to heat energy by inefficient chemical reactions, radiated by warm bodies, or in friction due to movement. Heat energy is lost into the environment and cannot be regained by living organisms

Flow of energy Eventually all the energy is lost to the environment as heat

Pyramids of energy Pyramids of energy show how much energy is passed between tropic levels. They are always pyramidal (energy cannot be created) The steep sides show the energy transfer is very inefficient- a lot is lost as heat May have units- KJ m -2 y -1 Shows energy transfer in a given area over a given time period.

Questions Pg 100 question 1 & 2 Exam questions.

Homework Using one, named, ecosystem produce a presentation illustrations what we have covered in the last two lessons. – Definitions and examples – Pyramids of number, biomass, energy – Energy flow (including ways of calculating)