Unit A-Chapter 4-Lesson 3 Notes

What Happens When an Ecosystem Changes?

Environmental Changes

• Change is a natural part of the history of any ecosystem.
• Changes may be long-term-for example, the result of fires, droughts, and floods- or long-term, as a result of climatic change.
• All organisms have a certain range of tolerance for conditions such as:

1. Environmental temperature
2. Amount of moisture 
3. Amount of light

• Organisms cannot usually survive in conditions that are outside their range of tolerance.
• In any ecosystem, populations change as conditions change.
• New communities of organisms, which are better adapted to new conditions in that ecosystem, may replace original communities.

Competition

   
• Organisms can live in an ecosystem only as long as it meets their needs for food, water, shelter, and other essentials. 
• Organisms that live within an ecosystem often compete for similar resources.
• This competition occurs among different kinds of organisms, as well as among members of the same species.
• Competition helps regulate population size because as competition for resources increases, population size decreases.
• When resources are limited, organisms that are well-adapted to the conditions in an ecosystem will be best able to compete for resources and survive.
• Some animals solve the problem of limited resources by migrating.
• The snowy owl, for example, inhabits the Arctic tundra, but when the population of lemming-their main food source-falls, it may migrate great distances in search for food. 
• In the winter, snowy owls are sometimes sighted as far south as Illinois.

People Affect Ecosystems

• Ecosystems change naturally, but human activities such as cutting down trees and draining wetlands can speed up the change.
• People can also change the ecosystems by introducing new species that out-compete native species.
• Conservation of resources and restoration practices can help to reduce and repair ecosystem damage.

Unit A-Chapter 4-Lesson 2

How Are Materials Recycled?

Oxygen-Carbon Dioxide Cycle

• Water is one of the most important materials required by an organism.

Photosynthesis, green plants use energy from the sun to convert carbon dioxide and water into sugar and oxygen.

• Photosynthesis = Carbon dioxide + Water + Energy ->Sugar + Oxygen

Respiration is an energy-producing process in which a cell combines oxygen with sugars and gives off carbon dioxide and water.

• Respiration = Sugar + Oxygen -> Carbon Dioxide + Water + Energy

• Plants carry out both photosynthesis and respiration.

The Nitrogen Cycle

• All living things need nitrogen to make proteins. 
• Although 80% of the air consists of nitrogen gas, few living things can use nitrogen in this form.
• Nitrogen gas must first be changed into one of a variety of nitrogen compounds and cycled through the environment.

Nitrogen gas can be converted into forms usable by living things in two ways:

1. Nitrogen-fixing bacteria that grow in the root nodules of legume plants such as peas, soybeans, and clover combine nitrogen in the air with hydrogen to form nitrogen compounds that plants can use to make proteins.
2. Lightning can cause nitrogen gas to combine with oxygen in the air to form nitrogen compounds that return to the earth in rain or snow.

When the compounds of protein are broken down during decomposition, nitrogen is returned to the air as nitrogen gas.

Pollution Affects the Cycles

• Human activities can disturb the natural recycling of oxygen and carbon dioxide. 
• The burning fossil fuels, for example, results in increased levels of carbon dioxide in the air.
• Excess carbon dioxide and other "greenhouse" gases absorb infrared radiation coming from the  earth's surface and trap this heat in the atmosphere, which could result in an eventual overall increase in the earth's average temperature.

Unit A-Chapter 4-Lesson 1 Notes

How Do Organisms Interact?

Interactions Within Ecosystems

All living and nonliving parts of an ecosystem interact.

Some interactions are direct, such as when a person picks a peach from a peach tree and eats it.
Other interactions are indirect.  A honeybee and a person may have no direct interactions, but the honey bee might have pollinated the peach flower and so played a role in the production of the peach.

To survive in a particular ecosystem, organisms must be adapted to the environmental conditions of that ecosystem.

A healthy ecosystem is one which the living and nonliving parts are balanced.

Producers, Consumers, and Decomposers

Green plants are producers; using energy from the sunlight to make their own food through the process of photosynthesis. 

Organisms that cannot make their own food are called consumers.  Consumers may be herbivores, carnivores, or omnivores.

A herbivore is a consumer that eats only plants or other producers.

A carnivore is a consumer that eats only animals

An omnivore is a consumer that eats both producers and consumers.

A decomposer is an organism that obtains energy by consuming dead organisms and the wastes of living organisms.

In general, plants are producers, and animals are consumers.

However, one special producer is not a plant; its a type of bacteria that grows on the ocean floor.
This type of bacteria depend on sulfur-containing bacteria(sulfides) from deep ocean vents to release energy and make food.

Food Webs

Food chains describe how energy moves in an ecosystem from one organism to another.  

Green plants (producers) are the bottom link in a food chain.  Consumers make up the next links, followed by decomposers.

Different food chains combined form a food web.

Energy Pyramids

An energy pyramid is a model that shows how energy is used in a food chain or an ecosystem.

The amount of energy available to a certain group of organisms depends on which level of the energy pyramid it is on. 

Less energy is available at any level in the pyramid  than in the level below.  The top of the pyramid has the least amount of energy.