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3-1 What Is Ecology?
Photo Credit: ©Bruce Coleman, LTD/Natural Selection
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2. Interactions and Interdependence
Ecology is the scientific study of interactions among organisms and between organisms and their environment, or surroundings.
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3. Interactions and Interdependence
The biosphere contains the combined portions of the planet in which all of life exists, including:
land
water
air, or atmosphere
The biosphere extends from about 8 kilometers above Earth's surface to as far as 11 kilometers below the surface of the ocean.
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4. Interactions and Interdependence
Interactions within the biosphere produce a web of interdependence between organisms and the environment in which they live.
The interdependence of life on Earth contributes to an ever-changing, or dynamic, biosphere.
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5. Levels of Organization
What different levels of organization do ecologists study?
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6. Levels of Organization
To understand relationships within the biosphere, ecologists ask questions about events and organisms that range in complexity from a single individual to the entire biosphere.
The levels of organization that ecologists study include: individuals, populations, communities, ecosystems, and biomes.
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7. Levels of Organization
Biosphere
Biome
Ecosystem
Community
The study of ecology ranges from the study of an individual organism to populations, communities, ecosystems, biomes—and, finally, to the entire biosphere. The information that ecologists gain at each level contributes to our understanding of natural systems.
Population
Individual
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8. Levels of Organization
A species is a group of organisms so similar to one another that they can breed and produce fertile offspring.
Populations are groups of individuals that belong to the same species and live in the same area.
Communities are assemblages of different populations that live together in a defined area.
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9. Levels of Organization
An ecosystem is a collection of all the organisms that live in a particular place, together with their nonliving, or physical, environment.
A biome is a group of ecosystems that have the same climate and similar dominant communities.
The highest level of organization that ecologists study is the entire biosphere itself.
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Ecological Methods
What methods are used to study ecology?
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Ecological Methods
Ecological Methods
Regardless of the tools they use, scientists conduct modern ecological research using three basic approaches:
observing
experimenting
modeling
All of these approaches rely on the application of scientific methods to guide ecological inquiry.
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Ecological Methods
Observing 
Observing is often the first step in asking ecological questions.
Some observations are simple. Others are complex and may form the first step in designing experiments and models.
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Ecological Methods
Experimenting
Experiments can be used to test hypotheses.
An ecologist may set up an artificial environment in a laboratory to imitate and manipulate conditions that organisms would encounter in the wild.
Other experiments are conducted within natural ecosystems.
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Ecological Methods
Modeling
Ecologists make models to gain insight into complex phenomena.
Many ecological models consist of mathematical formulas based on data collected through observation and experimentation.
The predictions made by ecological models are often tested by further observations and experiments.
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3-1
The combined portions of the planet in which life exists, including land, water, and the atmosphere, form the
biosphere.
community.
species.
ecosystem.
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3-1
A group of organisms that can breed and produce fertile offspring is known as a(an)
ecosystem.
species.
biome.
community.
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3-1
Compared to a community, an ecosystem includes
the nonliving, physical environment as well as the community.
only the physical environment of an area without the organisms.
the entire biome but not the biosphere.
only one of the populations within the community.
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3-1
An ecological method that uses mathematical formulas based on data collected is
observing.
experimenting.
modeling.
hypothesizing.
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3-1
An ecologist marks out an area in a specific ecosystem and proceeds to identify the number of insect species in the area. This is an example of ecological
experimentation.
observation.
modeling.
inference.
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20. 4-2 What Shapes an Ecosystem?
Photo Credit: ©Michael Fogden/DRK PHOTO
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Biotic and Abiotic Factors
Ecosystems are influenced by a combination of biological and physical factors.
Biotic – biological factors
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Physical, or nonliving, factors that shape ecosystems are called abiotic factors.
Abiotic factors include:
temperature
precipitation
humidity
wind
nutrient availability
soil type
sunlight
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23. Biotic and Abiotic Factors
How do biotic and abiotic factors influence an ecosystem?
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24. Biotic and Abiotic Factors
The area where an organism lives is called its habitat. A habitat includes both biotic and abiotic factors.
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25. Organisms are adapted to abiotic and biotic factors by natural selection.
Species exist in a given place because they evolve there or disperse there
Unique adaptations that fit a particular environment allow organisms to survive there
Organisms vary greatly in their ability to tolerate fluctuations and long-term changes in their environment

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The Niche
A niche is the full range of physical and biological conditions in which an organism lives and the way in which the organism uses those conditions.
No two species can share the same niche in the same habitat
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4-3 Biomes
Photo Credit: ©Michael Fogden/DRK PHOTO
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A biome is a complex of terrestrial (or aquatic) communities that covers a large area and is characterized by certain soil and climate conditions and particular assemblages of plants and animals.
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Variations in plants and animals help different species survive under different conditions in different biomes.
Plants and animals exhibit variations in tolerance, or the ability to survive and reproduce under conditions that differ from their optimal conditions.
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Biomes and Climate
Biomes and Climate
The climate of a region is an important factor in determining which organisms can survive there.
Within a biome, temperature and precipitation can vary over small distances.
The climate in a small area that differs from the climate around it is called a microclimate.
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Two components of climate, temperature and precipitation, can be summarized in a graph called a climate diagram.
Average Precipitation (mm)
Average Temperature (°C)
Climate diagrams show the average temperature and precipitation at a given location during each month of the year. In this graph, and the others to follow, temperature is plotted as a red line. Precipitation is shown as vertical purple bars.
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The Major Biomes
The world's major biomes include:
tropical rain forest
tropical dry forest
tropical savanna
desert
temperate grassland
temperate woodland and shrubland
temperate forest
northwestern coniferous forest
boreal forest
tundra
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The Major Biomes
What are the unique characteristics of the world's major biomes?
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The Major Biomes
Biomes are defined by a unique set of abiotic factors—particularly climate—and a characteristic assemblage of plants and animals.
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The Major Biomes
60°N
30°N
0° Equator
30°S
60°S
Tropical rain forest
Temperate grassland
This map shows the locations of the world’s major biomes. Other parts of Earth’s surface are classified as mountains or ice caps. Each biome has a characteristic climate and community of organisms.
Temperate forest
Northwestern coniferous forest
Tropical dry forest
Desert
Temperate woodland and shrubland
Boreal forest (Taiga)
Tropical savanna
Tundra
Mountains and ice caps
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