Biology Chapter 18 Notes
• By far the most abundant large animal
• Requires vast amounts of materials and space
• Has devastated the environment for many other species
• Have a disproportionately high impact on the environment
An Overview of Ecology
➢ Is the scientific study of the interactions between organisms and their
• The environment
➢ Can be divided into two major components.
➢ The abiotic component: The nonliving chemical and physical factors in an
➢ The biotic component: The living factors in an environment.
• Natural history as a “discovery science” remains fundamental to ecology
A Hierarchy of Interactions
• Ecology can be divided into four increasingly comprehensive levels:
➢ Organismal ecology: Is concerned with evolutionary adaptations that
enable individual organisms to meet the challenges posed by their abiotic
➢ Population ecology: Is concerned with populations, groups of individuals
of the same species living in the same area. Concentrates mainly on
factors that affect population density and growth.
➢ Community ecology: Is concerned with communities, assemblages of
populations of different species. Focuses on how interactions between
species affect community structure and organization.
➢ Ecosystem ecology: Is concerned with ecosystems, which include all the
abiotic factors in addition to the community of species in a certain area.
Focuses on energy flow and the cycling of chemicals among the various
abiotic and biotic factors.
• The biosphere
➢ Is the global ecosystem
Global Distribution Patterns
• Global distribution patterns
➢ Reflect regional differences in climate and other abiotic factors. • Patchiness of the environment on a local scale reveals a mixture of
➢ Are specific environments in which organisms live.
➢ Reveal patchiness on an even smaller scale.
Abiotic Factors of the Biosphere
• On a global scale, ecologists have recognized striking regional patterns in the
distribution of terrestrial and aquatic life.
• Solar energy powers almost all ecosystems.
• Availability of sunlight affects aquatic and terrestrial environments.
• There is life deep in ocean. Powered by chemoautotrophic bacteria that get
energy from inorganic chemicals.
• Environmental temperature
➢ Is an important abiotic factor because of its effect on metabolism.
• Some extraordinary adaptations enable some species to live in extreme
• Aquatic organisms may face problems with water balance.
• For terrestrial organisms, the main water problem is drying out.
• Some organisms depend on nutrients blown to them by wind.
• Organisms such as plants depend on wind to disperse pollen and seeds.
➢ Can also affect the pattern of a plant’s growth
Rocks and Soil
• Soil variation contributes to the patchiness we see in terrestrial landscapes.
• In streams and rivers, the composition of the soil can affect water chemistry.
• Three types of adaptations enable organisms to adjust to changes in their
➢ Behavioral Physiological Responses
• In mechanisms of temperature regulation, responses by organisms occur
➢ Is a physiological response that is longer term.
• The ability to acclimate
➢ Is related to the range of environmental conditions a species naturally
• Among vertebrates
➢ Birds and mammals can tolerate the greatest temperature extremes
because they are endotherms.
➢ Reptiles are more limited in the climates they can tolerate because they
• Many organisms respond to environmental challenge with some type of
change in body shape or anatomy.
• In contrast to plants, most animals can respond to an unfavorable change in
the environment by moving to a new location.
• Humans exhibit an especially rich range of behavioral responses.
What Is Population Ecology?
• Population ecology
➢ Is the study of how members of a population interact with their
➢ Focuses on factors that influence a population’s size, growth rate, density,
➢ A major terrestrial or aquatic life zone, characterized by vegetation type
in terrestrial biomes or the physical environment in aquatic biomes.
• Occupy ~75% of Earth’s surface.
• Determined by their salinity and other physical factors.
• Freshwater biomes –Lakes, streams, rivers and wetlands
➢ Usually a salt concentration less than 1%.
• Marine biomes –Oceans, intertidal zones, coral reefs, and estuaries
➢ Usually a salt concentration ~3%.
Freshwater Biomes • A disproportionate share of biodiversity, ~6% of all species.
• Use for drinking water, crop irrigation, sanitation and industry.
• Two categories
➢ Standing water-includes lakes and pond.
➢ Flowing water-includes rivers and streams
Lakes and Ponds
• In lakes and large ponds,
➢ The communities of plants, algae, and animals are distributed according
to the depth of water and its distance from shore.
Rivers and Streams
• Rivers and streams
➢ Are bodies of water flowing in one direction.
➢ Support quite different communities of organisms than lakes and ponds
• Human activities have affected many streams and rivers.
• Transitional biome between an aquatic ecosystem and a terrestrial one.
➢ Among the richest of biomes in species diversity.
➢ Are areas where a freshwater stream or river merges with the ocean
➢ Are one of the most biologically productive environments on Earth
How Climate Affects Terrestrial Biome Distribution
• Terrestrial biomes are determined primarily by climate, especially
temperature and rainfall.
• Heated by the direct rays of the sun, air at the equator rises, then cools, forms
clouds, and drops rain
• Altitude effects vegetation and animal distribution
• Proximity to large bodies of water and the presence of landforms such as
mountain ranges also affect climate.
• The distribution of terrestrial biomes depends largely on climate.
• If the climate in two geographically separate areas is similar, the same type of
biome may occur in them.
• Are named for major physical or climatic features and for their predominant
The Water Cycle • All parts of the biosphere are linked by the global water cycle and by nutrient
Human Impact on Biomes
• Humans have been using more and more resources from the environment.
Can not sustain this.