University:
Cameron University
Course:
1004 | General Biology
Academic year:

2021
Views:

74

Pages:

1
Author:

GalacticGuru

EnERGy FLOW Energy Flow Trophic Levels Energy Source Light is the initial energy source for almost all communities • Some producers derive energy from chemical processes An organism’s trophic level refers to the position it occupies within a feeding sequence • Producers always occupy the first trophic level Light energy is converted into chemical energy (i.e. organic compounds) via the process of photosynthesis Energy Transfer Heterotrophs obtain their chemical energy by feeding • The energy stored in organic molecules is released via cellular respiration (in heterotrophs and autotrophs) Trophic Level Organism 1 Producer 2 Primary Consumer 3 Secondary Consumer 4 Tertiary Consumer Feeding Patterns Food Chains Food chains show linear feeding patterns between the species in a community • Arrows indicate the direction of energy flow Primary Consumer Producer Secondary Consumer Food Webs Food webs show interrelated feeding patterns • Most species have multiple food sources and hence will occupy multiple trophic levels Tertiary Consumer Energy Loss Pyramids of Energy Not all the stored energy is transferred upon feeding – most of the energy released via cell respiration is lost as heat • Organisms cannot convert heat into other energy forms and hence the heat is lost from the ecosystem Pyramids of energy are representations of the amount of energy available at each trophic level • Measured in energy units per area per time (kJ m2 year–1) Only ~10% of energy is transferred from one trophic level to the next (90% is lost as heat or is unconsumed) • These energy losses restrict the length of food chains and limit the biomass of higher trophic levels SIMPLE FOOD CHAIN Pyramids of energy can never be inverted and their levels should differ by a factor of ~10 • Because energy transformations are ~10% efficient 10 J 100 J 1,000 J 10,000 J 100 L 100 mL 10 L 1L ENERGY FLOW OVERVIEW 1,000,000 J of sunlight