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Unit 2: Ecology
Section 3: Ecosystems
I. How Ecosystems Change (page 64)
What would happen if you suddenly stopped mowing your lawn? The grass would grow tall and other plants would start to take over. After about 20 years, you would never be able to tell your lot was once a mowed lawn. The normal, gradual changes that occur in the types of species that live in an area is called succession. Succession occurs differently in different places around the world.
1. Primary Succession- the process of succession that begins in a place previously without plants.
Example: Lava flows from volcanoes and forms new land composed of rock.
New Soil- Primary succession starts with the arrival of living things such as lichens which are hardy plants that can survive extreme conditions. The first organisms to arrive are called pioneer species.
Why do you think they are called “pioneer” species?
Primary Succession Process
1. The lichens and forces of nature break down the top layer of rock into smaller pieces.
2. When lichens die and decay, they add small amounts of organic matter to the ground.
3. Plants such as mosses and ferns can then grow and eventually die in this new soil.
4. As the soil layer thickens, grass, wildflowers, and other plants take over.
5. After they die, and contribute nutrients and matter to the new soil, other larger plants can grow such as trees and shrubs. All the while, insects, birds, and other small animals are beginning to make a home there.
2. Secondary Succession- the process of succession that begins in a place that already has soil and was once the home of living organisms. This type of succession happens faster and has different pioneer species than primary succession does.
Example: After a forest fire.
Climax Communities- A community of plants that is relatively stable and
undisturbed and has reached its end stage of succession.
Primary- can take hundreds or thousands of years to reach climax.
Secondary- shorter, but can take up to a century or more.
II. Biomes (page 68)
Climate is the average weather pattern in an area over a long period of time. The two most important climatic factors that affect life in an area are temperature and precipitation. Large geographic areas that have similar climates and ecosystems are called biomes.
1. Tundra – a cold, dry, treeless region, sometimes called a cold desert. They are located just south of the North Pole or at high elevations that receives little precipitation but is covered in ice most of the year. Winters in the Arctic can be six to nine months long.
2. Taiga – a cold, forest region dominated by cone-bearing evergreen trees and the largest biome in the world. The taiga is warmer and wetter than the tundra stretching across North America, northern Europe, and Asia.
3. Temperate Deciduous Forest – temperate regions with 4 distinct seasons each year. Most are dominated by climax communities of deciduous trees, although many evergreen trees grow there too. Amount of precipitation is average with temperatures ranging from below freezing in the winter and up to 100º F in summer.
4. Temperate Rain Forest – forests that experience an above average amount of rainfall, with temperatures range between 45º F to 55º F more stable than deciduous forests. Large trees with needlelike leaves dominate these forests.
5. Tropical Rain Forest – regions of warm temperatures, wet weather, and lush plant growth located near the equator. Home to the largest biologically diverse populations of life in the world.
6. Desert – the driest biome that are covered with thin, sandy, or gravelly soil that contains little organic matter. Due to lack of water, desert plants are spaced far apart and much of the ground is bare. Organisms there are highly adapted to live in this extreme environment.
7. Grassland – temperate and tropical regions that are dominated by climax communities of grasses. Most grasslands have a dry season, when little to no rain falls. Grasslands are found all over the world.
III. Aquatic Ecosystems (page 77)
In aquatic environments the most important factors that determine which species can survive there include water temperature, the amount of sunlight present, and the amounts of dissolved oxygen and salt in the water. Earth’s aquatic ecosystems are divided into two main areas: freshwater and saltwater environments.
1. Freshwater Ecosystems are made up of flowing waters such as rivers and streams and standing water such as lakes, ponds, and wetlands. Contains little to no salt.
a. Rivers and Streams- Flowing waters where most of the nutrients are washed into the water from land. The faster the flow, the greater the oxygen content.
b. Lakes and Ponds- Very small amount of flow. Sunlight warms and lights pond bottom, supporting plant and animal life whereas deeper lakes support life mostly along shallow shorelines or near the surface.
c. Wetlands- Regions that are wet all or most of the year. Very fertile ecosystems that lie between solid land and water.
2. Saltwater Ecosystems are where about 95% of the water on the surface of Earth is located. They are made up of oceans, seas, large inland lakes, coastal inlets, and estuaries. High concentration of salt.
a. Open Oceans- Divided into lighted and dark zones. The lighted zone extends about 200 meters down from the surface and is home to plankton. Dark zones are below 200 meters and animals there feed on debris floating down or each other.
b. Coral Reefs- Diverse and fragile ecosystems formed from coral shells or calcium carbonate.
c. Seashores- Found along coastlines. Intertidal zones are covered with water during high tide and exposed to the air during low tide. Drastic changes in temperature, moisture, salinity, and wave action.
d. Estuaries- Where rivers meet the ocean; called bays, lagoons, harbors, inlets, and sounds. Rich in nutrients and an always changing mixture of salt water and freshwater.
Section 3 Vocabulary
Succession Pioneer Species Climax Community
Biome Tropical Rain Forest Temperate Deciduous Forest
Tundra Wetland Temperate Rain Forest
Taiga Intertidal Zone Estuary
Desert Coral Reef Grassland
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