EcosystemsChapter 17

WHAT IS AN ECOSYSTEM?Section 17-1

Organisms Interact with Each Other

• Ecology is the study of the interactions of living organisms with one another and their environment

• A habitat is the place where a population lives

• A community is the many different species that live together in a habitat

Organisms Interact with Each Other

• An ecosystem consists of a community and all the physical aspects of its habitat like soil, water and weather

• The physical aspects of the habitat are abiotic factors (non-living)

• The living organisms in a habitat are biotic factors

Ecosystems support diverse communities

The number of species living within an ecosystem is a measure of its biodiversity

Ecosystem inhabitants

• Includes all of the large animals, small animals, trees, soil, water, insects and so on

Ecosystems Change over time

• The first organisms to live in a new habitat are small fast growing plants called pioneer species

Succession

• A somewhat regular progression of species replacement is succession

• Primary succession occurs where plants have not grown before

• Secondary succession occurs in areas where there has been previous growth

ENERGY FLOW IN ECOSYSTEMS

Section 17-2

Primary Energy Source

• Most life on earth depends on photosynthetic organisms

• Why?• They capture sunlight and store it as chemical

energy!

Primary Energy Source cont…

• Primary productivity is the rate at which organic material is produced by photosynthetic organisms

• Primary productivity determines the amount of energy available in an ecosystem

Primary Energy Source cont…

• Producers, like plants, are organisms that first capture energy (sunlight)

• Consumers are organisms that consume organisms to obtain energy

Trophic Levels

• Ecologists study how energy moves through an ecosystem by assigning organisms to a specific level or trophic level

• The level is determined by the organisms source of energy

Trophic Levels cont…

• The path of energy through the trophic levels of an ecosystem is called a food chain

Trophic Levels cont…

• Producers are the lowest level• Herbivores are on the second level and called

primary consumers• Secondary consumers are carnivores and

omnivores• Tertiary consumers are carnivores that eat

other carnivores

Trophic Levels

• Detrivores are organisms that get energy from organic waste

• Bacteria and fungi are called decomposers because they cause decay

Food Web

• In ecosystems, energy does not follow a straight path because man animals feed at different trophic levels

• This causes an interconnected group of food chains called a food web

Energy Transfer

• Energy is lost within the ecosystem as heat• It is not a useful source of energy in

ecosystems• As we move up the trophic levels, the energy

store by the organism is 1/10th of the energy stored by the previous level

Pyramid of Energy

• An energy pyramid is a diagram in which each trophic level is represented by a block, stacked one on top of the other

ECOSYSTEMS CYCLE MATERIALS

Section 17-3

Materials Cycle between Living and Non-Living Things

• Water, carbon, nitrogen and phosphorus pass from the nonliving environment to living organisms and back to nonliving environment

• That cycle is called a biogeochemical cycle

Water Cycle is Driven by the Sun

• Water has the greatest influence on an ecosystem

• Water vapor condenses, rains, seeps into the Earth and becomes ground water

• Water is heated by the sun, evaporates and reenters the atmosphere

The Carbon Cycle is Linked to Energy

1. Respiration: Organisms use oxygen and produce CO2

2. Combustion: Carbon returns to the air through combustion or burning

3. Erosion: Marine organisms use CO2 to make shells. Shells become sediment and as the sediments erode, carbon is made available

Plants and Bacteria use Nitrogen and Phosphorus

• Nitrogen and phosphorus build proteins and nucleic acids

• Phosphorus is part of ATP• The atmosphere is 79% Nitrogen• Nitrogen fixing bacteria (combine H and N to

form ammonia) live in the soil

Nitrogen Cycle

1. Assimilation or absorption of nitrogen into plant and animal compounds

2. Ammonification is the production of ammonia by bacteria during decay

3. Nitrification is the production of nitrate from ammonia

4. Denitrification is the conversion of nitrate to Nitrogen gas

Sustainable Agriculture

• The growth of plants is limited by the availability of nitrogen in the soil

• Decomposers return mineral nutrients to the soil, however crops are harvested and nutrients were lost

• Sustainable Ag is farming that remains productive, profitable and replenishes the soils nutrients, reduces erosion and controls weeds and pests

Sustainable Agriculture

• Farmers will plant cover crops after harvest to keep the soil from eroding away, store water and provide nutrients to bacteria and insects after being plowed under

• Farmers will rotate their cattle and sheep in several pastures to prevent overgrazing