4-3 Ecosystem Components

What Are Biomes and Aquatic Life Zones?Life on Land and at Sea

Biologists have classified the terrestrial (land) portion of the biosphere into biomes. They are large regions such as forests, deserts, and grasslands characterized by a distinct climate and specific species (especially vegetation) adapted to it.

Scientists divide the watery parts of the biosphere into aquatic life zones, each containing numerous ecosystems. Examples include freshwater life zones and ocean or marine life zones.

What Are the Major Components of Ecosystems? Matter, Energy, Life

Two types of components make up the biosphere and its ecosystems:

1. One type, called abiotic, consists of nonliving components such as water, air, nutrients, and solar energy.

2. The other type, called biotic, consists of biological components—plants, animals, and microbes.

How Tolerant Are Organisms to Environmental Conditions? Tolerance Limits

Each population in an ecosystem has a range of tolerance to variations in its physical and chemical environment. Individuals within a population may also have slightly different tolerance ranges for temperature or other factors because of small differences in genetic makeup, health, and age.

These observations are summarized in the law of tolerance: The existence, abundance, and distribution of a species in an ecosystem are determined by whether the levels of one or more physical or chemical factors fall within the range tolerated by that species.

What Factors Limit Population Growth? There Are Always Limits in Nature

A variety of factors can affect the number of organisms in a population. However, sometimes one factor, known as a limiting factor, is more important in regulating population growth than other factors.

This ecological principle, related to the law of tolerance, is called the limiting factor principle: Too much or too little of any abiotic factor can limit or prevent growth of a population, even if all other factors are at or near the optimum range of tolerance.

On land, precipitation often is the limiting factor. Lack of water in a desert limits plant growth. Soil nutrients also can act as a limiting factor on land.

Important limiting factors for aquatic ecosystems include temperature, sunlight, nutrient availability, and dissolved oxygen (DO) content—the amount of oxygen gas dissolved in a given volume of water at a particular temperature and pressure. Another limiting factor in aquatic ecosystems is salinity—the amounts of various inorganic minerals or salts dissolved in a given volume of water

What Are the Major Biological Components of Ecosystems? Producers and Consumers

The Earth’s organisms either produce or consume food. Producers, sometimes called autotrophs (self-feeders) make their own food from compounds obtained from their environment.

On land, most producers are green plants. In freshwater and marine ecosystems, algae and plants are the major producers near shorelines. In open water, the dominant producers are phytoplankton—mostly microscopic organisms that float or drift in the water.

Most producers make use of photosynthesis to capture solar energy from the sun and transform it into chemical energy such as that found in the chemical bonds of glucose. Photosynthesis takes place within specialized cell organelles called chloroplasts.

A few producers, mostly specialized bacteria, can convert simple compounds from their environment into more complex nutrient compounds without sunlight. This process is called chemosynthesis. All other organisms in an ecosystem are consumers, or heterotrophs (“other feeders”) that get the energy and nutrients they need by feeding on other organisms or their remains. Decomposers (mostly certain types of bacteria and fungi) are specialized consumers that recycle organic matter in ecosystems

Detritivores consist of detritus feeders and decomposers that feed on detritus.

Some consumers, called omnivores, play dual roles by feeding on both plants and animals.

What Is Biodiversity? Variety Is the Spice of Life

Biological diversity, or biodiversity, is one of the Earth’s most important renewable resources. Kinds of biodiversity include the following:

• Genetic diversity: the variety of genetic material within a species or a population.

• Species diversity: the number of species present in different habitats.

• Ecological diversity: the variety of terrestrial and aquatic ecosystems found in an area or on the Earth.

• Functional diversity: the biological and chemical processes such as energy flow and matter recycling needed for the survival of species, communities, and ecosystems.

• Structural diversity: the range of variation in the physical characteristics of habitat; in general, a more heterogeneous habitat provides more opportunities for a wide range of organisms.