Food and energy cycles CP Biology - ECOLOGY

Energy flow AAAAn ecosystems energy budget is determined by the amount of photosynthetic activity of the producers PPPProducers use light energy to synthesize organic molecules which are then used to make ATP in cellular respiration CCCConsumers obtain energy from organic molecules produced in lower trophic levels

 Consumers use food energy for:  Cell respiration  Maintaining life processes (homeostasis, growth, development, etc)  Some is lost in waste products and as heat  Energy has to constantly be added to and ecosystem

An overview of ecosystem dynamics

Organismal ecology  Organisms can be put into 1 of 2 groups based on the costs and benefits of maintaining homeostasis  Regulators expend energy in response to changing environmental conditions; the energy costs cannot exceed the benefits of regulating their internal environment  Conformers allow their internal conditions to vary with the external environment  The principle of allocation says that organisms have a limited amount of energy to spend on all life functions; the energy spent on one can’t be spent on the others.

Regulators and conformers

The relationship between body temperature and ambient (environmental) temperature in an ectotherm and an endotherm

Primary productivity  Gross primary productivity (GPP): The amount of light energy converted to chemical energy by autotrophs in an ecosystem; some is stored by plant, some is used for life processes  Net primary productivity (NPP): the amount of chemical energy available to consumers; also called biomass

Figure 54.3 Primary production of different ecosystems

Figure 54.4 Regional annual net primary production for Earth

Secondary productivity  Rate at which consumers convert the chemical energy in the food they eat to their own biomass  Consumers use energy for life functions but cannot completely digest the food so only about 10% of the energy consumed is available to the next trophic level  Pictured in a pyramid

Figure Energy partitioning within a link of the food chain

Types of pyramids  Pyramid of productivity (at trophic levels)  Biomass pyramid  Pyramid of numbers (individuals)  All are similar in that the bases are wide (lots of producers) and narrow greatly at the top (few top level consumers) and only have 3-5 trophic levels

An idealized pyramid of net production

A pyramid of numbers

Biogeochemical cycles  Global recycling: gaseous elements are recycled in the atmosphere (oxygen, nitrogen, carbon, sulfur)  Local recycling: elements that are solid are recycled in the soil (phosphorous, potassium, calcium, trace elements)  Matter is recycled, energy is not

A general model of nutrient cycling

U.S. map profiling pH averages for precipitation in 1999

Figure Biological magnification of DDT in a food chain