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