Living Things and Their Environment

The Living Environment

Look around. Everything you see and feel is a part of your environment. An environment includes living things such as plants, animals, people, and even the tiniest of microbes. The living portions of the environment are called the biotic parts. The nonliving portions, such as rocks, sunlight, and air, are called the abiotic parts.

Interactions among organisms and their environments can be very complex because an organism gets everything it needs to survive from the biotic and abiotic parts of its environment. For example, a tree gets the energy it needs from sunlight, carbon dioxide from the air, and water and minerals from the soil. All organisms rely on the abiotic factors of their environment in addition to relying on other organisms for survival.

Organisms that live in the same environment affect other living organisms within that community. For example, prairie dogs are rodents that can be found in the grasslands of western North America. They rely on the grasses in their environment as a food source and energy supply. The black-footed ferret is a predator of prairie dogs, relying on them as a food source. Suppose a drought results in a drastic reduction of the abiotic factor of water in their environment. The drought kills the grass and the prairie dog population starts dying out. Since the ferrets depend on the prairie dog as a food source, the ferret population is also affected. All these organisms are interconnected. Something that affects one part of an environment can affect all the organisms that live there. Each abiotic and biotic factor of an environment must be in place for energy to flow from one organism to another.

Levels of Organization Within the Environment

To organize means to arrange or group items so they can be easily found and understood. There are four basic levels of organization within an environment: organisms, population, community, and ecosystem.

  • Organisms: All living things in the environment are organisms, such as plants, animals, fungi, and microorganisms.
  • Population: A population of organisms is a group of individuals from the same species living in a specific area at the same time. Green-winged macaws, anacondas, and capuchin monkeys are three populations of organisms in the Amazon rain forest.
  • Community: A biological community is made up of all the interacting populations of organisms in an environment. Interacting populations may compete for food, or one species may hunt the other as a food source. Species in a community may also be helpful to the survival of another species. For example, in the rain forest, the capuchin monkey feeds on the nectar of flowering trees. As it drinks the nectar, the pollen from the flower attaches to the fur on its face. As the monkey drinks the nectar of another flower, it passes the pollen from its face to the flower and helps pollinate the flowers of that tree.
  • Ecosystem: An ecosystem is made up of both the community of organisms in an area and their abiotic surroundings. The Amazon rain forest-including all the plants, animals, and abiotic factors such as sunlight, water, soil and rocks-is an example of an ecosystem. Other ecosystems include grasslands, wetlands, deserts, and oceans.

A group of capuchin monkeys represents a population. Several populations together form a community. All organisms and the abiotic factors in their environment make up an ecosystem.


Ecology is the branch of biology that examines the interactions among organisms and the interactions between organisms and their environment_ Scientists who study ecology are called ecologists.

An ecologist studying a population may look at the ways in which organisms compete for resources such as food and water. Ecologists also examine how the organisms in a population cooperate to avoid predators or raise young.

Ecologists that study communities in an ecosystem investigate the factors that contribute to the diversity of populations in an area. Ecologists studying a community may look at the relationships between predators and prey, the ways in which different species compete for the same kinds of food, or how the presence of one species may benefit or harm another species.

Ecologists studying the ecosystem as a whole seek to answer questions such as how sunlight and nutrients affect the plants that all other organisms in the ecosystem depend on, or how changes in the composition of the atmosphere affect an ecosystem. Ecologists are also interested in studying changes in ecosystems brought about by climate. change.

Ecologists call the unique strategy a species has for survival its niche. More specifically, a niche is an organism’s role in the larger ecosystem. If you think of a species’ habitat as its home address, its niche is its occupation. Species hunt, eat, hide, or reproduce in different ways to avoid occupying the same niche as other organisms or to avoid competing with them.

To avoid competition, woodpeckers, tufted titmice, and nuthatches each have a beak adapted for eating different types of insects that live in different parts of the trees their shared habitat.


Around the world, similar communities develop in places of similar climate. Some regions have short, cool summers and long, cold winters, while. other regions are warm all year-long with little change of temperature. A biome. 1s a large region that contains similar ecosystems or communities and contains similar organisms that have adapted to the conditions of that region.

Influence of Climate

Species adapt to live in a particular climate. Climate is the typical patten:i of weather that is observed over a long period of time in an area. A place with water-conserving plants and very little rain is a desert. Climate is determined by such factors as temperature, precipitation, latitude, elevation, nearness to water, and land features.

The patterns of temperature and precipitation throughout the year are the most important features of climate. Species adapt to survive in specific climates_ Their physical features and their behaviors are influenced by the ecosystem’s temperature range as well as by the availability of food and water in the region.

Latitude, or distance from the equator, has an influence on the temperature and precipitation of a region. Regions close to the equator or the poles have more extreme conditions than those between the two While warm temperatures and large amounts of precipitation are characteristic near the equator, cold temperatures and low amounts of precipitation are characteristic of climates at the poles. Regions at higher altitudes, or distance above sea level, also have a colder and drier climate than those at lower altitudes.

Large bodies of water, including the ocean and large lakes, also have an effect on climate_ The climate near water is warmer and wetter than mainland climates_ Mountain ranges near the coast also affect climate. The climate between the ocean and the mountain will be warmer and wetter, while the climate beyond the mountain will be hotter and drier. These factors influence the communities that develop in a particular region.

Land Biomes

There are two main types of biomes: land biomes and water biomes. The seven major land biomes are shown on the map.

Biome Map


The tundra is a cold, dry, treeless plain. Permanently frozen soil called permafrost lies beneath the surface and prevents trees from taking root. In the short summer season, the tundra is filled with flowering plants, lichens, insects, birds, and grazing mammals. During the long, cold winters, most plants and animals become inactive or travel to warmer lands.


As you travel south from the tundra, tall trees appear. This is the taiga, an evergreen forest that covers more area on Earth than any other biome. Winter is still long and cold, but during the short summer, temperatures are milder. The precipitation in the taiga is mostly snow. Animals that stay active in the winter adapt by growing thick coats and living in burrows to keep warm.

Temperate Rain Forest

South of the taiga, several different biomes form. Temperate rain forests form between oceans and coastal mountains. A temperate rain forest is a cool, wet, evergreen forest receiving up to 400 cm of rain per year. The nearby ocean keeps the average temperature mild. The temperate rain forest has a higher density of living and dead matter of any biome.

Deciduous Forest

Deciduous forests contain hardwood trees that drop their leaves in cold temperatures. Deciduous forests receive up to 150 cm of precipitation per year. The year is divided into four distinct seasons. Summer temperatures may reach 30°C, while winter temperatures can dip below freezing. The soil of a deciduous forest is rich from the leaves that fall and decay.


Grasslands form where there is not enough precipitation to support trees. Grasses dominate, and trees are found only along the banks of streams and rivers. Grasslands receive up to 75 cm of precipitation per year. Grasslands have cold winters and hot, dry summers. Many animals live on grasslands, from large grazing mammals to insects.

Tropical Rain Forest

Tropical rain forests form near the equator, where it is warm and rainy year-round. They receive up to 600 cm of precipitation per year. The climate conditions are ideal for many plants, insects, and birds. In the rain forests there is competition for sunlight and nutrients from the soil. Lush growth blocks the Sun from many plants and animals.


A desert forms where there is not enough rainfall to support grasslands. They are the driest places on Earth, with fewer than 25 cm of precipitation per year. In many cases, deserts form because moisture from ocean breezes is blocked by coastal mountains. Temperatures vary greatly because the dry air does not block the Sun’s rays or trap heat. The temperatures may rise above 40°C during the day and fall below freezing at night. Organisms that live in the desert have adapted to temperature extremes and lack of water.

Water Biomes

About 75 percent of Earth’s surface is covered by water. The water may be deep or shallow, fresh or salty, moving or still. Each of these factors affects the kinds of organisms that live in the water and the biome that develops.

Freshwater Biome

Freshwater, which contains very little salt, can be found in wetlands, ponds, lakes, streams, and rivers. Wetlands are land areas where the soil is so saturated with water that aquatic plants are able to grow. These plants allow nutrient-rich soil to form. Oxygen allows many different animal species to thrive. Marshes, bogs, and swamps are examples of wetlands. Ponds and lakes form where water pools in a low-lying area. Rivers and streams are biomes that contain moving water. Slow-moving rivers have muddy bottoms with plants growing in them. Swift streams have rocky bottoms, which doesn’t allow for much plant growth.

Marine Biome

The oceans and seas of the world make up the marine, or saltwater, biome. The marine biome covers most of Earth’s surface. Like freshwater lakes, oceans can be divided into shallow and deep layers. Sunlight penetrates about 200 m into the water, creating a warm shallow layer where plants can grow. The plants produce oxygen, allowing many sea creatures to live in this shallow underwater layer. The deep water of the ocean is cold, dark, and largely lifeless except for areas around undersea volcanoes. Coral reefs are regions of marine biomes that can support a diverse array of sea life.