chapter 53

Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition Solomon • Berg • Martin

Chapter 53

Ecosystems and the Ecosystems and the BiosphereBiosphere


Biology, Seventh Edition CHAPTER 53 Ecosystems and the Biosphere

• Energy flow through an ecosystem• Linear• Sun to producer to consumer to

decomposer• Trophic relationship may be

expressed as food chains or as food webs



Energy flow through an ecosystem



• Ecological pyramids• Express the progressive reduction

in numbers of organisms, biomass, and energy found in successive trophic levels



Pyramids of biomass



• Gross primary productivity (GPP)• Rate at which photosynthesis

captures energy• Net primary productivity (NPP)

• Energy that remains after plants and other producers carry out cellular respiration



NPP for selected ecosystems



• Carbon cycle• Carbon dioxide is the most

important gas• Carbon enters plants, etc., as CO2

• Cellular respiration, combustion, and erosion of limestone return CO2 to the environment



Carbon cycle



• Nitrogen cycle• Five steps

–Nitrogen fixation –Nitrification–Assimilation–Ammonification –Denitrification



Nitrogen cycle



• Phosphorus cycle• Phosphorus erodes from rock as

inorganic phosphate• Animals obtain it from their diet



Phosphorus cycle



• Hydrologic cycle• Renews the supply of water• Involves an exchange of water

between the land, ocean, atmosphere, and organisms

• Water enters the atmosphere by evaporation and transpiration

• Water leaves the atmosphere as precipitation



Hydrologic cycle



• Bottom-up processes• Availability of resources such as

nutrient minerals controls the number of producers, which controls the number of herbivores, etc.

• Top-down processes• An increase in top predators

cascades down the food web



• Sunlight primary source of energy• Combination of Earth’s spherical

shape and its axis tilt concentrate solar energy at the equator

• Inclination of Earth’s axis primarily determines the seasons



Seasonal changes in temperature



• Visible light and infrared radiation warm the surface and lower part of the atmosphere

• Atmospheric heat produces air movement, which moderates the climate



Atmospheric circulation



Major surface ocean currents



• Coriolis effect• Tendency of moving air or water to

be deflected–Right in the Northern Hemisphere–Left in the Southern Hemisphere



• Regional precipitation differences• Influenced by latitude, elevation,

topography, vegetation, distance from large bodies of water, and location

• Precipitation greatest where warm air passes over the ocean and then cools



Rain shadow



• Effect of fire on certain ecosystems• Fire frees the nutrient minerals

locked in organic matter, removes plant cover, and increases erosion

• Many ecosystems, such as savanna, chaparral, grasslands, and certain forests, contain fire-adapted organisms

chapter 53

Documents