• Natural events such as volcanic eruptions or earthquakes are part of the dynamic quality of Earth and its ecosystems.

• Weather-related events, including drought, fire, flooding, storms, and infestations, can harm or enhance ecosystems.

• Geological events such as volcanic eruptions, earthquakes, and landslides cause changes to ecosystems.

• Healthy ecosystems will respond by adapting over time.

Natural Phenomena and Ecosystems5.1VOCABULARYsapwood

Pollutants in Ecosystems5.2VOCABULARYpollutant

acid precipitatiion

pH scale

• Pollutants are substances introduced into air, water, soil, or food in concentrations that threaten the health or survival of organisms.

• Pollutants can be grouped according to the part of the environment they affect (air, water, or land, for example).

• Human populations are producing more pollution than can be degraded in the biosphere.• Many pollutants are not natural, but are a result of

human technology.

Bioaccumulation and Biomagnification5.3VOCABULARYbioaccumulation

biomagnification

pesticide

DDT (dichloro-diphenyl-

trichloroethane)

parts per million (ppm)

heavy metals

endocrine-disrupting

compounds (EDCs)

• Many pollutants bioaccumulate in organisms.• Bioaccumulation is the buildup of chemical substances

within the tissues of organisms over time.

• Biomagnification of pollutants can occur in organisms at the top of food chains or food webs.• These pollutants

include pesticides like DDT, heavy metals, and other endocrine-disrupting compounds such as PCBs.

The Impacts of Human Industry on Ecosystems5.4

VOCABULARYsoil degradation

deforestation

• Human activities affect ecosystems.

• Human industries such as agriculture and forestry often impact ecosystems in negative ways.

• Negative impacts include soil degradation, spraying chemical pesticides, and deforestation.

• Traditional ecological knowledge and wisdom (TEKW) promotes sustainable use of the environment.

Changing the Balance in Ecosystems

• Natural phenomena impact the natural balance (equilibrium) in ecosystems.• These phenomena range from mild

earthquakes that affect few organisms to disastrous tsunamis that wipe out entire islands.

• Humans introduce many pollutants which affect the growth and survival of organisms.

• Human activities affect ecosystems.• Industries like agriculture and forestry often impact ecosystems

negatively.

• Traditional ecological knowledge and wisdom (TEKW) from First Nations people promotes sustainable use of the environment.

5CHAPTER

Changing the Balance in Ecosystems

Activity• With a partner, choose an ecosystem and brainstorm a list of all the

natural phenomena you can think of that could affect that ecosystem.• Examples of ecosystems include rainforests, ponds, deserts, etc.

• Afterward, describe the impact of each phenomenon on your ecosystem. Is it positive or negative? In what way?

• Compare your list with Table 1 on page 109 and Table 2 on page 111 in the textbook.

5CHAPTER

Changing the Balance in Ecosystems5

Key Ideas• Natural phenomena impact the equilibrium in ecosystems.

• Pollutants affect the growth and survival of organisms.

• Human activities affect ecosystems.

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