The Nature of the Ecosystem
Organism Responses to the Environment
Changes that affect organisms over time may be daily, seasonal, or long term.
Phototropism: plants respond to light by growing toward it
Dormancy: organisms respond to unfavorable conditions with a period of lowered or suspended metabolism
Hibernation: type of dormancy in which animals respond to cold conditions with a period of lowered metabolism
These types of behaviors help organisms survive and adapt to the environment.
Factors that Affect Population Sizes
A variety of environmental factors may cause the size of a population to increase or decrease, which can in turn affect entire communities or ecosystems.
Eutrophication: the addition of excess nutrients to the system, which alters environmental balance
Climate change: the warming of Earth’s surface due to human activities
Catastrophic events: fires, drought, flood, and earthquakes
These factors can cause certain populations to decrease in size dramatically, which may cause other populations to increase in size. Since the ecosystem is heavily connected, a change in one part causes changes throughout the entire system.
Human interaction can have a large effect on ecosystems and can directly alter habitat size, quality, and structure. Such interactions can be positive or negative.
Since populations in an ecosystem are interdependent, human disturbances have a ripple effect throughout the ecosystem.
Deforestation: humans cut down trees and decrease habitat size for organisms living in forests
Climate change: the warming of Earth's surface which is decreasing habitat size in the Arctic
Eutrophication: the addition of man-made fertilizers to bodies of water can cause eutrophication
Pollution: humans release harmful chemicals and substances into the environment, decreasing habitat quality
The interaction of humans with the ecosystem may lead to issues of concern for ecosystem health in areas such as water supply, air quality, energy production, and waste management.