Richard T. Wright
Environmental Science Tenth Edition
Chapter 2 Ecosystems: What They Are
Copyright © 2008 Pearson Prentice Hall, Inc.
Ecosystems: What Are They? • • • •
Ecosystems: A Description The Structure of Ecosystems From Ecosystems to Global Biomes The Human Factor
Some Terms and Definitions • Ecosystems: A grouping of plants, animals, and microbes occupying an explicit unit of space and interacting with each other and their environment. • Ecosystem: a dynamic complex of plant, animal, and microorganism communities and the nonliving environment interacting as a functional unit within an explicit space. • Ecosytems: Units of Sustainable life on earth
ECOSYSTEM: MA DEFINITION • A dynamic complex of plant, animal, and microorganism communities and the nonliving environment interacting as a functional unit within an explicit space. – a lake, a wetland, a coral reef, …
• Humans are an integral part of ecosystems • Can be investigatedÆ ECOLOGY – study of ecosystems and all processes that determine the distribution of species and their interactions.
How Ecosystems Are Formed Abiotics (moisture and temperature) Abiotic factors: non-living, chemical, physical
predict
Plants
(+ moisture = forest) (temperature = forest type)
predict
Animals (lynx or bobcat)
Ecosystem Types in the United States • • • • • •
Coasts and oceans Farmlands Forests Fresh waters Grasslands and shrub lands Urban and suburban areas
Ecosystems: A Description • Biotic communities: grouping or assemblage of plants, animals, and microbes. • Species: different kinds of plants, animals, and microbes in the community • One species: individuals that are similar in appearance and distinct form other individuals. • Biological definition of a species: the entirety of a population that can interbreed and produce fertile offspring in the community.
Ecosystems: A Description • Population: number of individuals that make up the interbreeding, reproducing group in a given area. • Association: a plant community with definite composition, uniform habitat characteristics and uniform plant growth. – Is determined by abiotic factors. – (explains the nature of the biotic community, how it fits in the landscape)
• Ecotone: Transitional region between different ecosystems.
Ecotones on Land • Shares many of the species and characteristics of both ecosystems • May also include unique conditions that support distinctive plant and animal species
Terrestrial-to-Aquatic-System Ecotone • Shares many of the species and characteristics of both ecosystems • May also include unique conditions that support distinctive plant and animal species
Landscape, Biomes and the Biosphere • Landscape: group of interacting ecosystems – Lake, march, dry land
• Biomes: similar or related ecosystems or landscapes – deserts, tropical rain forests (Terrestrial) – Transitional zones between biomes
• Aquatic systems – Lakes, rivers, wetlands, Ocean
• Biosphere: Everything is connected in the Biosphere. – ALL ecosystems. Gigantic space (“dry” and wet) in which we (all animals, plants, microorganisms) exist and the non-living matter in it.
The Structure of Ecosystems • Trophic categories : • Trophic relationships: food chains, food webs, trophic levels. • Nonfeeding relationships: symbiosis • Abiotic factors
Autotrophs = Producers = Self feeders -They make their own organic matter from inorganic molecules and energy from the sun (photosynthetic) or chemical reactions (chemosynthetic) -Photosynthesis Chlorophyll: green pigment, site of light capture
6CO2 + 6H2O + Sun lightÆC6H12O6+6O2
Proteins, carbohydrates (Carbon, Hydrogen, C-H bonds)
Consumers = Heterotrophs Feed on organic matter for energy and growth • Primary consumers = herbivores = rabbit: eat plant material • Secondary consumers = carnivores = predators = coyotes: prey are herbivores and other animals.
Consumers = Heterotrophs • Parasites = predator = either plant or animal: prey are plants or animals.
Doddlers
Ascaris Lumbricoides
Lampreys
Detritus Food Web • Detritus: dead organic matter • Detritus feeders • Primary d feeders – Decomposers:bacteria and fungi- cause rotting
• Secondary d feeders
Trophic Relationships: Food Chain
Third-order Consumer Secondary Consumer Primary Consumer Producer
Match Organisms with Trophic Level(s) Trophic Levels Organisms
Secondary Consumer
ThirdOrder Consumer
Snakes
X
X
Owls
X
X
X
X
Plants
Producer
X
Rabbits
Bacteria
Primary Consumer
X
X
X
Food Webs = Food Chain Interrelationships
Trophic Level Energy Flow Third-order Consumer 1Kcal - 10x
How do you measure energy?
Secondary Consumer 10 Kcal - 10x
Primary Consumer 100 Kcal - 100x
Producer 10,000 Kcal
How far can you go?
Biomass Pyramid Running out of Biomass!!!
Biomass: total combined dry weight of all organisms at a trophic level
Trophic Levels: Pyramid of Energy 5 4 3 2
Which level is occupied by: producers? primary consumers? secondary consumers? third-order consumers?
1
Nutrient Cycles and Energy Flow
Nonfeeding (Symbiotic) Relationships • + And + = Mutualism. Both species benefit by the interaction between the two species. Honey bee and flower, Lichens (alga and fungi) • + And 0 = Commensalism. One species benefits from the interaction and the other is unaffected.
Barnacle riding on a turtle shell Cattle Egret
Nonfeeding (Symbiotic) Relationships • + And - = One species benefits from the interaction and the other is adversely affected. Examples are parasitism
Competitive Relationships Resource Partitioning: Reducing Competition in a habitat by usage of different niche Niche: the what, where, when of feeding and meeting other needs
Abiotic Factors • Law of Limiting Factors: “Every species (both plant and animal) has an optimum range, zones of stress, and limits of tolerance with respect to every abiotic factor.”
Survival Curves Illustrate Law of Limiting Factors
Application of the Law of Limiting Factors • Compare the “tolerance” differences for a trout and a catfish using water: – temperature (cold or warm). – oxygen concentration (high or low). – salinity (high or low).
Oxygen Tolerance Curves for Two Different Fish Species Temp9-13ºC
Diagram the temperature tolerance curves for each fish species.
From Ecosystems to Global Biomes • • • •
The role of climate Microclimate and other abiotic factors Biotic factors Physical barriers
Climate and Major Biomes
Identify Biomes A to E Based on Temperature and Precipitation Levels: High Temperature
A
D C
B Low
E Precipitation
High
Answers • A has high temperature and low moisture = hot desert • B has low temperature and low moisture = cold desert (tundra with permafrost) • C has medium temperatures and moisture = grassland • D has high temperature and moisture = rain forest • E has low temperature and high precipitation = arctic poles
Effects of Latitude and Altitude
Microclimates
Exposed or sheltered site Variation in ecosystems within a biome
The Human Presence • Three revolutions – Neolithic – Industrial – Environmental • Red Sky in the Morning by James Gustave • The Inconvenient Truth by Al Gore
How Humans Modify Their Physical Environments to Meet Their Needs • • • • •
Produce abundant food Control water flow rate and direction Overcome predation and disease Construct our own ecosystems Overcome competition with other species