Flow of Energy Year 11 Biology Unit 1

Key Knowledge • Describe the ways in which energy flows through ecosystems • Recognise the matter cycles within ecosystems • Understand the key role of producers and decomposers in ecosystems • Become aware of trophic levels • Give examples of biochemical cycles

Ecosystems require energy • Energy is not recycled energy must be continually supplied to the ecosystem • Sunlight

Ecosystems require energy • Producer organisms trap energy and convert it to chemical energy (ecosystem would not exist without them) 6 CO 2+12 H 2 O C 6 H 12 O 6 + 6 H 2 O + 6 O 2 • Some energy used for producers own requirements • Some energy stored for consumers = net primary production

Biozone 1. Plants as producers 2. Energy Inputs and Outputs Page 112 Page 292

Energy Production Rates • Vary for each ecosystem • Eg: Tropical rain forests and coral reefs high. • Production rates vary due to factors such as light and water availability

Biozone 1. Primary productivity Page 301

Different energy source • No sunlight? ? Eg Deep ocean • Producers include sulfur bacteria. • Known as chemosynthetic – Energy released by chemical reactions NO PRODUCERS = NO ECOSYSTEM

Trophic Levels Feeding Levels Trophic Level Organism at that level Source of chemical energy First Producers Photosynthesis Second Primary Consumers (herbivores) Eat producers Third Secondary Consumers (Carnivores) Eat plant-eaters Fourth Tertiary Consumers (Top Carnivores) Eat Predators See Fig 14. 12 Page 446

Energy Flow • Available energy gets less at each trophic level • Eg: 100 units of energy taken in - 39 units heat loss - 60 units wastes (detritivores and decomposers) - 1 unit build organic matter as part of growth available to be transferred

A rough rule of thumb • About 10% of the energy entering a trophic level is available for transfer to the next level.

Biozone • Energy Flow in an Ecosystem Page 299

Showing energy transfers • Food chains and food webs show chemical energy transfers. • HINT: Despite what the diagram suggests, food webs are often very complex.

Biozone 1. Food Chains 2. Constructing a food web Page 293 Page 295

Ecological Pyramids • Information about numbers and other aspects of organisms at each trophic level

Ecological Pyramids • Pyramid of numbers – Number of organisms at each trophic level – Does not take into account the sizes of the organisms

Ecological Pyramids • Pyramid of biomass – Total dry organic matter of organisms at each trophic level – Measured in units of mass per unit area

Pyramid of Biomass Pyramid of numbers

Ecological Pyramids • Pyramid of energy – Amount of energy input to each trophic level – Can never be inverted WHY? ? ?

Biozone 1. Ecological pyramids Page 303

Biochemical Cycles Cycling of matter • Matter cycles within the ecosystem and is reused. • At times matter (such as carbon, nitrogen and phosphorous) are found in the living component of the ecosystem and at others in the non living component of the ecosystem.