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Chapter 52

BIO SCI 94 Chapter 52: Chapter 52

Biological Sciences
Course Code
Robin Bush

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Primary goal: understand the distribution and abundance of organisms
Ecology: study of how organisms interact with each other and their environment
Intro to ecology:
5 main levels: organisms, populations, communities, ecosystems, biosphere
Find out how individuals interact with their physical surroundings and with other organisms
in and around their living area
Organismal ecology: explore the morphological, physiological, and behavioral adaptations that
allow individuals to live in a particular area
Population: group of individuals of the same species that lives in the same area at the same
Population ecology: focus on how the number and distribution of individuals in a population
change over time
Community: populations of different species that interact with each other within a
particular area
Concentrate on predation, parasitism, and competition, explore how communities respond
to fires, floods, and other disturbances
Community ecology: questions about the nature of the interactions between species and the
consequences of those interactions
Ecosystem: all organisms in a particular region along with nonliving components
Abiotic: nonliving components -- air, water, nonliving parts of soil
Ecosystem ecology: study how nutrients and energy move along organisms and through the
surrounding atmosphere and soil or water
Biosphere: thin zone surrounding the earth where all life exists -- sum of all terrestrial and
aquatic ecosystems
Biosphere is a closed system, so the actions of people in one part of the world may alter
distant ecosystems
Global ecology: quantify the effects of human impacts on the biosphere
Conservation biology: effort to study, preserve, and restore threatened genetic diversity in
populations, species diversity in communities, and ecosystem function
Preserve biodiversity, clean air, pure water, and productive soil
Conservation biology applies all levels of ecological study
Levels of Ecological Study:
Biogeography: study of how organisms are distributed geographically
Range: geographic distribution
Abiotic and biotic factors determine the distribution and abundance of organisms
No one species can survive the full array of environmental conditions present on earth
Temperature has big impact on physiology of organisms -- organisms are limited in their
ability to regulate their own temperatures
Ex: temperature, moisture, salinity, water depth, movement regime in water
Because of fitness trade-offs, organisms tend to be adapted to a limited set of physical
conditions, or abiotic factors
Every organisms has a specific range of tolerance of abiotic conditions
Abiotic factors:
Competition with other species limits the range of species
Biotic factors: interactions with other organisms
What Determines the Distribution and Abundance of Organisms?
Chapter 52
Thursday, March 22, 2018
8:05 PM
Bio 94 Page 1

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Competition with other species limits the range of species
Particular reproduction limitations
Interactions with flies and mosquitoes that bring diseases
Landforms and oceans that may appear static now have been in constant flux for the entire
history of life
Dispersal: movement of individuals from their place of origin to the location where they live
and breed as adults
Events that changes landforms and oceans impacts dispersal
Deep trench in ocean maintained water barrier to dispersal -- landforms on either side
of line remained isolated
The wallace line: biogeographical demarcation; separates species with Asian and Australian
Transport of plants, birds, insects, and other species across physical barriers to new
locations (purposefully and accidentally)
Invasive species: when exotic species is introduced into a new area, spreads rapidly,
and competes successfully with native species
Microorganisms introduced to new areas by humans can affect species distributions
by causing disease
Influence of humans (biotic and abiotic factors)
History matters: past abiotic and biotic factors influence present patterns
Biotic and abiotic factors slowed spread of invasive ants more than the abiotic factors alone
Range of every species on earth is limited by combination of abiotic and biotic factors that
occurred in the past, and that occur in the present
Range of particular species depends on the capacity to survive climatic conditions, ability to
find food and avoid being eaten, and ability to disperse
Biotic and abiotic factors interact
Climate: prevailing, long-term weather conditions found in an area
Weather: specific short-term atmospheric conditions of temperature, precipitation, sunlight, and
Areas along the equator receive the most moisture, and locations about 30 degrees latitude
north and south of the equator are the direst on the planet
Air heated by strong sunlight along equator expands and lower pressure causing it to
rise (holds moisture) --> air radiates heat to space as it rises above equator and
expands into larger volume of upper atmosphere (lowers density and temperature) -->
as rising air cools, its ability to hold water declines and water condenses --> high levels
of precipitation occur along equator --> cooler, older air above earths surface is
pushed poleward as more air is heated along the equator --> density increases and
sink when air mass cooled enough --> solar radiation absorbed as it sinks and begins
to warm --> water-holding capacity increases as air warms --> dry land
Hadley cell: major cycle in global air circulation; responsible for moisture and dryness in
certain areas
Why are the Tropic Wet?
Regions at or near the equator receive more sunlight per unit area -- more energy in the
form of heat
Why are the Tropics Warm and the Poles Cold?
Seasons: regular, annual fluctuations in temperature, precipitation, or both
Occurs because earth is tilted on its axis by 23.5 degrees
Sometimes area on earth is tilted toward or away from the sun
If earth didn’t tilt on its axis, there would be no seasons
What Causes Seasonality in Weather?
Winds bring moisture-laden air from ocean --> air mass begin to rise over mountains --> air
What Regional Effects Do Mountains and Oceans Have on Climate?
Climate Patterns
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