Chapter 14 – Life Science/Ecosystems and Biomes
Living things meet their needs through interactions with the environment .
Matter and energy together support life within an environment.
Ecosystems support life.
1.Living things depend on the environment.
2. Biotic factors interact with an ecosystem.
3. Many abiotic factors affect ecosystems.
Matter cycles through ecosystems.
1. All ecosystems need certain materials.
2. Water cycles through ecosystems.
3. Carbon cycles through ecosystems.
4. Nitrogen cycles through ecosystems.
Energy flows through ecosystems.
1. Living things capture and release energy.
2. Models help explain feeding relationships.
3. Available energy decreases as it moves through an ecosystem.
Biomes contain many ecosystems.
1. Regions of Earth are classified into biomes.
2. Water covers most of Earth’s surface.
Ecosystems support life.
1. Living things depend on the environment.
An ecosystem comprises organisms and their physical environment. Ecology is the scientific study of how
organisms interact with their environment and with other organisms.
• Natural ecosystems include water, air, and sunlight, as well as microorganisms, plants, and animals.
• Biotic factors are the living parts of an ecosystem.
• Abiotic factors are the nonliving parts.
2. Biotic factors interact with an ecosystem.
Every organism affects, and is affected by, other organisms in its ecosystem. Moles are a good example of this
interrelatedness. They eat insects, worms, and grubs. They can severely damage plants, but moles help keep
insect populations in check. Mole tunnels aerate soil, which is necessary for the growth of soil organisms and
plant roots.
3. Many abiotic factors affect ecosystems.
Abiotic factors include any nonliving features of the environment, from soil fertility to climate characteristics—
precipitation, temperature, air currents, and humidity. Here is a short list of the most influential factors.
• available water
• temperature
• available light
• soil content
Matter cycles through ecosystems.
1. All ecosystems need certain materials.
Living things need certain materials, or matter, to meet their needs. This matter remains in the ecosystem,
moving through it in continuous cycles, in which the matter changes form, but is never created or destroyed.
2. Water cycles through ecosystems.
All substances on Earth, including water, are repeatedly recycled. Five processes make up the water cycle.
• Condensation: water vapor condenses to liquid in the atmosphere.
• Precipitation: water falls back to Earth.
• Transpiration: plants take up water in their roots and release it from their leaves.
• Respiration: animals release water vapor as they exhale.
• Evaporation: heat changes liquid water to gaseous water vapor, which rises into the atmosphere.
3. Carbon cycles through ecosystems.
Life on Earth is based on carbon compounds. The carbon cycle includes several different processes.
• Photosynthesis removes carbon from the air.
• Animals obtain carbon by eating plants.
• Plants and animals release carbon dioxide during respiration.
• Carbon contained in fossil fuels and wood is released as carbon dioxide during combustion.
4. Nitrogen cycles through ecosystems.
Nitrogen is required for all life. Almost 78 percent of the air is nitrogen, but organisms cannot use nitrogen in
gaseous form. In the nitrogen cycle, bacteria in soil and roots fix nitrogen by changing it from a gas to nitrate
compounds that can be taken up by plants.
Energy flows through ecosystems.
1. Living things capture and release energy.
Energy and matter can move through an ecosystem as food.
• Producers capture energy from sunlight or, in a few cases, from chemicals in the deep sea.
• Consumers obtain food by eating producers or other consumers.
• Decomposers break down dead plant and animal matter into simpler compounds, returning them to the
water or soil so that the matter may be used again.
2. Models help explain feeding relationships.
Food chains and food webs are models that show how energy and matter move through the organisms of an
ecosystem.
• A food chain shows one path of energy movement through an ecosystem, from producer (e.g., grass) to
herbivore or primary consumer (grasshopper), to a secondary consumer (robin), to a tertiary consumer (hawk).
• A food web shows many paths of energy movement through an ecosystem. It indicates that each organism
eats and is eaten by several organisms.
3. Available energy decreases as it moves through an ecosystem.
An energy pyramid models the amount of energy available to producers and consumers in an ecosystem. At
the bottom of the pyramid are the producers, which use the Sun’s abundant energy to manufacture sugars. At
the top of the pyramid are the tertiary consumers.
The amount of available energy decreases with each succeeding layer.
Biomes contain many ecosystems.
1. Regions of Earth are classified into biomes.
Earth’s six terrestrial biomes are regions made up of ecosystems with similar plant life and climate.
• Tundra has little precipitation and lowest temperatures of all land biomes. Typical vegetation is lichens and
mosses.
• Taiga has cold winters and short, cool summers. It supports coniferous trees with needlelike leaves.
• Desert has little precipitation and can be hot or cold. Typical vegetation is cacti and small plants.
• Grassland has rich soil but supports few shrubs and trees.
• Temperate forest includes mostly deciduous trees.
• Tropical rain forest is consistently warm and wet. Typical vegetation is broadleaf evergreen trees, with a huge
number of species.
2. Water covers most of Earth’s surface.
Freshwater biomes include
• rivers and streams, with high oxygen levels; plants are limited to shorelines and slow-moving shallows.
• lakes and ponds, with middling to very low oxygen levels; plants grow along the shoreline or float in upper
layers.
• wetlands, such as swamps and bogs, that are wet most or all of the year; waterlogged soils limit plant
species.
• estuaries, which are mixed fresh and salt water, where river meets ocean; fertile ecosystems act as nurseries
for fish and other sea animals.
Marine biomes include
• coastal ocean, or seashore areas; many ecosystems, from sandy beaches to mud flats to rocky shores.
• open ocean to depths where sunlight stops penetrating; the plankton here serve as the basis of the ocean
food web.
• deep ocean, where sunlight does not reach.