Notes 4-1 What Is an Ecosystem?

An ecosystem includes a community of organisms and their physical environment.

 Community- a group of various species that live in the same habitat and interact with each other.  A web of relationships including predator-prey, parasitism, mutualism, etc.  Relationships between organisms are examples of biotic (living) factors that affect an ecosystem.  Ecosystem- a community of organisms and their abiotic (non-living) environment.

 The physical or nonliving factors of an environment are called abiotic factors (oxygen, water, rocks, sunlight, temperature).  Habitat- the place where an organism usually lives.

 The variety of organisms in a given area, the genetic variation within a population, the variety of species in a community, or the variety of communities in an ecosystem.  Physical factors can have a big influence on biodiversity.  High rainfall and warm temperatures  Low rainfall  Extremely low temperatures  When ecosystems have high biodiversity they are often better able to resist damage due to severe weather or human activities.  Systems with low biodiversity can be severely damaged easily.

The replacement of one type of community by another at a single location over a period of time.

 When a volcano forms a new island or a fire burns the vegetation of an area, new opportunities are made for organisms.  Pioneer species- the first organisms to appear in a newly made habitat; often make it possible for other species to live there.

 If a major disruption strikes a community, many of the organisms may be wiped out.  An ecosystem responds to change in such a way that the ecosystem is restored to equilibrium.

Two key factors of climate that determine biomes are temperature and precipitation.

 The average weather conditions in an area over a long period of time.  Temperature- most organisms are adapted to live within a particular range of temperatures and cannot survive at temperatures too far out of the range.  Precipitation- in biomes where precipitation is low, the vegetation is made up mostly of plants that need little water.  Biome- a large region characterized by a specific type of climate and certain types of plant and animal communities.

Earth’s major terrestrial biomes can be grouped by latitude into tropical, temperate, and high-latitude biomes.

 Because they are located at low latitudes near the equator, all are warm.  Rainfall determines different types:  Tropical rain forests- receive large amounts of rain and are warm all year.  Savannas- get less rain and have long dry seasons and shorter wet seasons.  Tropical deserts- get very little rain.

 Located at mid-latitudes, so have a wide range of temperatures throughout the year.  Types:  Temperate grasslands- have moderate precipitation and cooler temperatures than savannas; good for agriculture.  Temperate forests- grow in mild climates that receive plenty of rain; can have deciduous or evergreen trees.  Temperate deserts- receive little precipitation and have a wide range of temperatures throughout the year.

 Have very cold temperatures.  Types:  Taiga- coniferous forests in cold wet climates; winters are long and cold.  Tundra- gets very little rain, so plants are short; most water is unavailable to plants because it remains frozen in the soil most of the year.

Aquatic ecosystems are organized into freshwater ecosystems, wetlands, estuaries, and marine ecosystems.

 Located in bodies of fresh water, such as lakes, ponds, and rivers.  Have a variety of plants, fish, arthropods, mollusks, and other invertebrates.

 Provide a link between the land and fully aquatic habitats.  Water-loving plants dominate.  Support many species of birds, fishes, and plants.  Important because they moderate flooding and clean the water that flows through them.

 An area where fresh water from a river mixes with salt water from an ocean.  Productive ecosystems because they constantly receive fresh nutrients from the river and the ocean.

 Found in the salty waters of the oceans.  Kelp, seagrass, and coral reefs are found near land.  The open ocean has plankton and large predators, such as dolphins, whales, and sharks.