Chapter 3 Ecosystems: What Are They and How Do They Work?

Chapter Overview Questions What is ecology? What basic processes keep us and other organisms alive? What are the major components of an ecosystem? What happens to energy in an ecosystem? What are soils and how are they formed? What happens to matter in an ecosystem? How do scientists study ecosystems?

Core Case Study: Have You Thanked the Insects Today? Many plant species depend on insects for pollination. Insect can control other pest insects by eating them Figure 3-1

Core Case Study: Have You Thanked the Insects Today? …if all insects disappeared, humanity probably could not last more than a few months [E.O. Wilson, Biodiversity expert]. –Insect’s role in nature is part of the larger biological community in which they live.

THE NATURE OF ECOLOGY Ecology is a study of connections in nature. –How organisms interact with one another and with their nonliving environment. Figure 3-2

Fig. 3-2, p. 51 Communities Subatomic Particles Atoms Molecules Protoplasm Cells Tissues Organs Organ systems Organisms Populations Communities Ecosystems Biosphere Earth Planets Solar systems Galaxies Universe Organisms Realm of ecology Ecosystems Biosphere

Organisms and Species Organisms, the different forms of life on earth, can be classified into different species based on certain characteristics. Figure 3-3

Fig. 3-3, p. 52 Insects 751,000 Other animals 281,000 Fungi 69,000 Prokaryotes 4,800 Plants 248,400 Protists 57,700 Known species 1,412,000

Case Study: Which Species Run the World? Multitudes of tiny microbes such as bacteria, protozoa, fungi, and yeast help keep us alive. –Harmful microbes are the minority. –Soil bacteria convert nitrogen gas to a usable form for plants. –They help produce foods (bread, cheese, yogurt, beer, wine). –90% of all living mass. –Helps purify water, provide oxygen, breakdown waste. –Lives beneficially in your body (intestines, nose).

Populations A population is a group of interacting individuals of the same species occupying a specific area. –The space an individual or population normally occupies is its habitat. Figure 3-4

Populations Genetic diversity –In most natural populations individuals vary slightly in their genetic makeup. Figure 3-5

THE EARTH’S LIFE SUPPORT SYSTEMS The biosphere consists of several physical layers that contain: –Air –Water –Soil –Minerals –Life Figure 3-6

Biosphere Atmosphere –Membrane of air around the planet. Stratosphere –Lower portion contains ozone to filter out most of the sun’s harmful UV radiation. Hydrosphere –All the earth’s water: liquid, ice, water vapor Lithosphere –The earth’s crust and upper mantle.

What Sustains Life on Earth? Solar energy, the cycling of matter, and gravity sustain the earth’s life. Figure 3-7

What Happens to Solar Energy Reaching the Earth? Solar energy flowing through the biosphere warms the atmosphere, evaporates and recycles water, generates winds and supports plant growth. Figure 3-8

Animation: Sun to Earth PLAY ANIMATION

ECOSYSTEM COMPONENTS Life exists on land systems called biomes and in freshwater and ocean aquatic life zones. Figure 3-9

Fig. 3-9, p –125 cm (40–50 in.) Coastal mountain ranges Sierra Nevada Mountains Great American Desert Coastal chaparral and scrub Coniferous forest Desert Coniferous forest Prairie grassland Deciduous forest 1,500 m (5,000 ft.) 3,000 m (10,000 ft.) 4,600 m (15,000 ft.) Average annual precipitation Mississippi River Valley Appalachian Mountains Great Plains Rocky Mountains below 25 cm (0–10 in.) 25–50 cm (10–20 in.) 50–75 cm (20–30 in.) 75–100 cm (30–40 in.)

Nonliving and Living Components of Ecosystems Ecosystems consist of nonliving (abiotic) and living (biotic) components. Figure 3-10

Animation: Roles of Organisms in an Ecosystem PLAY ANIMATION

Factors That Limit Population Growth Availability of matter and energy resources can limit the number of organisms in a population. Figure 3-11

Factors That Limit Population Growth The physical conditions of the environment can limit the distribution of a species. Figure 3-12

Producers: Basic Source of All Food Most producers capture sunlight to produce carbohydrates by photosynthesis:

Producers: Basic Source of All Food Chemosynthesis: –Some organisms such as deep ocean bacteria draw energy from hydrothermal vents and produce carbohydrates from hydrogen sulfide (H 2 S) gas.

Consumers: Eating and Recycling to Survive Consumers (heterotrophs) get their food by eating or breaking down all or parts of other organisms or their remains. –Herbivores Primary consumers that eat producers –Carnivores Secondary consumers eat primary consumers Third and higher level consumers: carnivores that eat carnivores. –Omnivores Feed on both plant and animals.

Decomposers and Detrivores –Decomposers: Recycle nutrients in ecosystems. –Detrivores: Insects or other scavengers that feed on wastes or dead bodies. Figure 3-13

Two Secrets of Survival: Energy Flow and Matter Recycle An ecosystem survives by a combination of energy flow and matter recycling. Figure 3-14

Animation: Matter Recycling and Energy Flow PLAY ANIMATION

BIODIVERSITY Figure 3-15

Biodiversity Loss and Species Extinction: Remember HIPPO H for habitat destruction and degradation I for invasive species P for pollution P for human population growth O for overexploitation

Why Should We Care About Biodiversity? Biodiversity provides us with: –Natural Resources (food water, wood, energy, and medicines) –Natural Services (air and water purification, soil fertility, waste disposal, pest control) –Aesthetic pleasure

Solutions Goals, strategies and tactics for protecting biodiversity. Figure 3-16

ENERGY FLOW IN ECOSYSTEMS Food chains and webs show how eaters, the eaten, and the decomposed are connected to one another in an ecosystem. Figure 3-17

Food Webs Trophic levels are interconnected within a more complicated food web. Figure 3-18

Animation: Rainforest Food Web PLAY ANIMATION

Energy Flow in an Ecosystem: Losing Energy in Food Chains and Webs In accordance with the 2 nd law of thermodynamics, there is a decrease in the amount of energy available to each succeeding organism in a food chain or web.

Energy Flow in an Ecosystem: Losing Energy in Food Chains and Webs Ecological efficiency: percentage of useable energy transferred as biomass from one trophic level to the next. Figure 3-19

Animation: Energy Flow in Silver Springs PLAY ANIMATION

Productivity of Producers: The Rate Is Crucial Gross primary production (GPP) –Rate at which an ecosystem’s producers convert solar energy into chemical energy as biomass. Figure 3-20

Net Primary Production (NPP) NPP = GPP – R –Rate at which producers use photosynthesis to store energy minus the rate at which they use some of this energy through respiration (R). Figure 3-21

What are nature’s three most productive and three least productive systems? Figure 3-22

SOIL: A RENEWABLE RESOURCE Soil is a slowly renewed resource that provides most of the nutrients needed for plant growth and also helps purify water. –Soil formation begins when bedrock is broken down by physical, chemical and biological processes called weathering. Mature soils, or soils that have developed over a long time are arranged in a series of horizontal layers called soil horizons.

SOIL: A RENEWABLE RESOURCE Figure 3-23

Layers in Mature Soils Infiltration: the downward movement of water through soil. Leaching: dissolving of minerals and organic matter in upper layers carrying them to lower layers. The soil type determines the degree of infiltration and leaching.

Some Soil Properties Soils vary in the size of the particles they contain, the amount of space between these particles, and how rapidly water flows through them. Figure 3-25

Soil Profiles of the Principal Terrestrial Soil Types Figure 3-24

Fig. 3-24a, p. 69 Mosaic of closely packed pebbles, boulders Weak humus- mineral mixture Dry, brown to reddish-brown with variable accumulations of clay, calcium and carbonate, and soluble salts Alkaline, dark, and rich in humus Clay, calcium compounds Desert Soil (hot, dry climate) Grassland Soil (semiarid climate)

Fig. 3-24b, p. 69 Tropical Rain Forest Soil (humid, tropical climate) Acidic light-colored humus Iron and aluminum compounds mixed with clay

Fig. 3-24b, p. 69 Deciduous Forest Soil (humid, mild climate) Forest litter leaf mold Humus-mineral mixture Light, grayish- brown, silt loam Dark brown firm clay

Fig. 3-24b, p. 69 Coniferous Forest Soil (humid, cold climate) Light-colored and acidic Acid litter and humus Humus and iron and aluminum compounds