Chapter 18 – Introduction to Ecology
Section 1: Introduction to Ecology
Ecology Ecology is the study of the interactions
between organisms and the biotic and abiotic components of their environment Biotic = living Abiotic = nonliving
Today’s Environment The Exploding Human
Population The world’s human population
has tripled from 2 billion people in 1930 to 6 billion people in 1999 Causes severe crowding Requires an increasing
amount of food, energy and space for disposing waste
Today’s Environment The 6th Mass Extinction
Species are disappearing faster than at any other time since the last mass extinction About 20% of the species of birds have become extinct
in the last 2000 years Caused by:
Habitat destruction Over-hunting New diseases and predators being introduced to non-
native areas
Today’s Environment The Thinning Ozone Layer
The ozone layer protects Earth’s living organisms by absorbing UV radiation from the sun
Industrial chemicals called chlorofluorocarbons (CFCs) react with the ozone and are destroying the ozone later In 1992 a ban was established on
using CFCs and related chemicals
In 1996, the ozone level over Antarctica was about 50% of the maximum density This allows in extra UV radiation
that can lead to sunburn and skin cancer
Today’s Environment Climatic Changes
Greenhouse Effect: the ability of carbon dioxide and water vapor to trap the reflected heat from the sun and direct it back towards the Earth Protects the Earth from the deep-freeze of space
Human use of fossil fuels has increased the amount of carbon dioxide in the atmosphere by 25% in the last 100 years The increase of greenhouse gases are trapping excess
heat in our atmosphere, causing global temperatures to rise Scientists warn that if the problem is not corrected in the
next 10 years, the condition of our Earth will not be able to be reversed
A Key Theme in Ecology No single organism is isolated!!
The interconnectedness or interdependence of all organisms is central to the study of ecology
The survival of organisms depends on their interactions with their surrounding environment Ex: Humans cannot live without the plants that produce
food and oxygen
Levels of Organization
The Biosphere Biosphere: the broadest and most inclusive
level of organization The Earth and its atmosphere make up our
biosphere Extends from 8 to 10 km (5-6 miles) above the Earth’s
surface to the deepest parts of the ocean
Ecosystems The biosphere is comprised of smaller units
called ecosystems Includes all of the organisms and the abiotic
environment found in a specific place Ex: Pond Ecosystem
Abiotic components: water temperature, amount of dissolved oxygen and carbon dioxide, the pH level
Biotic components: insects, fish, algae, aquatic plants, turtles
Chapter 18Ecosystem
Communities, Populations and Organisms A community is all of the interacting
organisms living in an area Ex: All of the fish, turtles, insects, plants and
algae make up the community of a pond A population includes all of the members
of a species that live in one place at one time Ex: All of the humans in Vernon Hills
An organism is a single, living thing. Ecologists study organisms for their adaptations
that allow them to overcome the challenges of their environment
Chapter 18Community
Brain Break
Try to count the number of black dots on the image below...
There are none!
Chapter 18 – Introduction to Ecology
Section 2: Ecology of Organisms
Biotic and Abiotic Factors Environmental factors found in an
organisms habitat are broken into two classes: Biotic = living components of the environment Abiotic = nonliving components of the
environment Includes:
Temperature Humidity pH Salinity Oxygen concentration Amount of sunlight Availability of nitrogen Precipitation
Biotic and Abiotic Factors
Visual
The Changing Environment Abiotic factors are NOT constant
Ex: Temperature Varies from hour to hour, day to day, season to season,
and year to year Varies from place to place:
Phoenix will be hotter than Chicago Can vary within a habitat
Different in temperature between being in the shade of a tree vs. out in direct sunlight
Responses to a Changing Environment Organisms are adapted to function within a
specific range of an abiotic factor Ex: Temperature
All organisms have a range of temperature in which they can function
To determine the range in which an organism can live, you can measure how efficiently it performs at specific temperatures
A tolerance curve is a graph of performance vs. values of an environmental variable Performance is usually reduced when the values are outside
of the optimal range Organisms cannot survive in areas where they are
exposed to conditions that fall outside of their tolerance range
Tolerance Curve
Zones of Physiological Intolerance (no performance)
Zones of physiological stress (reduced performance)
Temperature
Sw
imm
ing
Spe
ed
Acclimation Acclimation is the process by which
organisms can adjust their tolerance to abiotic factors Ex: Going to the mountains
If you spend a few weeks in the mountains, your body will acclimate to the lower oxygen levels by producing more red blood cells in your body
This will allow your blood to carry more oxygen Acclimation IS NOT adaptation!!
Adaptation is a genetic change in a species that occurs over many generations – acclimation occurs within the lifetime of a species
Control of Internal Conditions The abiotic factors within an environment can
fluctuate Two ways to deal with the changes:
Conformers: do not regulate internal conditions; they change as their environment changes Ex: Desert lizards’ rises and falls with the temperature of
their environment Regulators: use energy to control some of their
internal conditions Ex: humans maintain a constant internal body temperature
Escape from Unsuitable Conditions Organisms have developed strategies for
surviving unfavorable environmental conditions: Dormancy: a state of reduced activity
during which an organism’s metabolism slows down Ex: Reptiles and amphibians “hide” underground and
become dormant during the winter to survive the cold temperatures
Migration: when organisms move to a more favorable environment Ex: Seasonal movements of birds
Resources Resources: the energy and materials that an
organism needs to survive Ex: Food, water, shelter and sunlight The resources essential for survival vary between
different species Ex: The resources plants require are different from
those humans need
The Niche A specie’s niche is the role an organism
plays in its environment Includes:
Range of conditions the organism can tolerate Methods by which it obtains resources Interactions with its environment such as
reproduction A fundamental niche is the range of
conditions that a species can potentially tolerate and the range of resources it can potentially use
A realized niche is the range of resources an organism actually uses
The Niche
Visual
Niche Differences Generalists are species with broad niches
Can tolerate a range of conditions and use a variety of resources Ex: Virginia opossum found all over the US and can
eat a wide range of food
Specialists are species that have narrow niches Ex: koalas only feed on leaves from a few
species of eucalyptus trees