1. Inquiry into Life Twelfth Edition
Lecture PowerPoint to accompany
Inquiry into Life Twelfth Edition
Sylvia S. Mader
Chapter 34
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. 34.1 The Biotic Components of Ecosystems
Abiotic components include sunlight, inorganic nutrients, soil, water, temperature and wind.
Biotic components are the various populations of organisms that form a community.

3. Biotic Components

4. 34.1 The Biotic Components of Ecosystems
Populations of an Ecosystem
Autotrophs (producers)
Require an energy source and inorganic nutrients to produce organic food molecules
Manufacture organic nutrients for all organisms
Green plants and algae carry on photosynthesis
Some bacteria are chemoautotrophs
Support communities at hydrothermal vents

5. 34.1 The Biotic Components of Ecosystems
Populations of an Ecosystem
Heterotrophs (consumers)
Need a preformed source of organic nutrients
Herbivores: graze directly on plants or algae
Carnivores: feed on other animals
Omnivores: feed on both plants and animals
Decomposers
Heterotrophic bacteria and fungi
Break down nonliving organic matter
They release inorganic matter to be used by producers
Detritus: partially decomposed matter

6. 34.1 The Biotic Components of Ecosystems
Energy Flow and Chemical Cycling
Energy enters ecosystem in the form of sunlight absorbed by producers
Chemicals enter when producers take in inorganic nutrients
Producers then make organic nutrients for themselves and all other organisms in the ecosystem
Consumers (herbivores and omnivores) gain nutrients and energy from eating producers
Higher level consumers (carnivores) then gain nutrients and energy from eating herbivores and omnivores
Some energy is released at each level to the environment in the form of heat and waste products

7. Energy Flow and Nutrient Cycling

8. Energy Balances

9. 34.2 Energy Flow
The interconnecting paths of energy flow are represented by diagramming food webs.
Grazing food webs begin with producers
Detrital food webs begin with detritus

10. Grazing and Detrital Food Webs

11. 34.2 Energy Flow Trophic Levels
A trophic level is composed of all the organisms that feed at a particular link in a food chain.
Example of a food chain
leaves caterpillars tree birds hawks

12. 34.2 Energy Flow Trophic Levels Ecological Pyramids
In general, only about 10% of the energy of one trophic level is available to the next trophic level.
Represent amount of available energy in each trophic level
Producers are at the base- the most available energy
Energy is given off in less usable forms as producers are eaten by primary consumers, etc.
Biomass: the number of organisms at each level multiplied by their weight

13. Ecological Pyramid

14. 34.3 Global Biogeochemical Cycles
Pathways Involve both Biotic and Abiotic Components
Reservoir: source unavailable to producers
Exchange pool: source from which organisms take chemicals
Biotic community: chemicals move through community along food chains
Two Main Types of Cycles
Gaseous cycle: chemical element is drawn from and returns to the atmosphere
Sedimentary cycle: chemical element is drawn from soil by plant roots, eaten by consumers, returned to soil by decomposers

15. Model for Chemical Cycling

16. 34.3 Global Biogeochemical Cycles
The Water Cycle
Freshwater evaporates from bodies of water
Precipitation over land enters ground, surface waters, aquifers
Eventually returns to oceans over time
Human Impact
In arid West and southern Florida, groundwater mining is occurring
Aquifers are being drained faster than they can be naturally replenished

17. The Water Cycle

18. 34.3 Global Biogeochemical Cycles
The Phosphorus Cycle
Phosphates are an important component of many biological processes and structures
Phospholipids, ATP, nucleotides, teeth, bones, shells
Phosphate can be a limiting inorganic nutrient
Human Activities
Phosphates are used in fertilizers, animal feeds, and detergents
Excess phosphates in water supplies can lead to eutrophication
Algal blooms that can lead to massive fish kills

19. The Phosphorus Cycle

20. 34.3 Global Biogeochemical Cycles
The Nitrogen Cycle
Nitrogen gas makes up about 78% of the atmosphere
Plants cannot use nitrogen gas, so nitrogen is a limiting factor
Nitrogen Fixation
Carried out by some cyanobacteria and bacteria
Conversion of nitrogen gas (N2) to ammonium ions (NH4+)
Plants can use ammonium ions

21. 34.3 Global Biogeochemical Cycles
The Nitrogen Cycle
Nitrification: production of nitrates which plants can also use
Nitrogen gas converted to nitrate in atmosphere by lightning, meteor trails, cosmic radiation
Ammonium in soil converted to nitrate by nitrifying bacteria
Denitrification: conversion of nitrate back to nitrogen gas by denitrifying bacteria

22. 34.3 Global Biogeochemical Cycles
The Nitrogen Cycle
Human Activities
Nitrogen is added to fertilizers
Runoff that contains nitrogen also contributes to eutrophication
Fertilizer use also results in the release of nitrous oxide (N2O), a greenhouse gas

23. The Nitrogen Cycle

24. 34.3 Global Biogeochemical Cycles
The Carbon Cycle
Photosynthesis takes up carbon dioxide from the atmosphere
Cell respiration returns it to the atmosphere
Reservoirs of Carbon
Dead organisms, shells, fossil fuels, limestone,
Human Activities
More carbon dioxide is being deposited in atmosphere than is being removed
Due to deforestation and burning of fossil fuels
Increased carbon dioxide in atmosphere contributes to global warming

25. The Carbon Cycle