teks 8.11b: biotic and abiotic factors p. 1classroom.kleinisd.net/users/0178/docs/5th six...

TEKS 8.11B: Biotic and Abiotic Factors p. 1

2 UNIT 5 ORGANISMS AND ENVIRONMENTS

Science Focus

Vocabularyecosystem, species, population, growth rate, community, biotic factors, abiotic factorsLearning Goals

Describe the components of an ecosystem.Identify the levels of organization within an ecosystem.

ecosystem - a group of organisms interacting with one another and their physical environment.

What Is an Ecosystem?

An individual organism is made up of many smaller systems that work together. Each system has a structure (its parts) and a function (what it does). This is true for cells, tissues, organs, organ systems, and the entire organism. In this section, you will learn how individual organisms are grouped into larger systems.

How ecosystems are organizedEcosystems An ecosystem is a group of organisms interacting with one another and

their physical environment. Ecosystems can be as big as the ocean, or as small as a jar of water containing microscopic organisms. A Texas tall-grass prairie is an example of an ecosystem. A prairie ecosystem is made up of the plants, animals, and other organisms that live there, plus nonliving things like soil, air, water, sunlight, and nutrients. The living and nonliving parts function together to remain in balance—similar to a single organism.

Levels oforganization

The diagram below shows the levels of organization of ecosystems. Individual organisms are grouped into populations. Populations of different species of organisms are grouped into communities. An ecosystem consists of a community of organisms and their physical environment.


313.1 WHAT IS AN ECOSYSTEM?

ECOSYSTEMS CHAPTER 13

Individual organisms and speciesSpecies of the

Texas tall-grass prairie

The first level of organization of an ecosystem is an individual organism of a particular species. A species is a group of organisms capable of reproducing to produce fertile offspring. Fertile means “able to reproduce.” A typical ecosystem contains individuals of many different species of animals, plants, and other types of organisms. For instance, Texas tall-grass prairie ecosystems are dominated by plant life such as grasses and wildflowers. These plants provide food and shelter for many animal species including snakes, small mammals, deer, birds, and a large variety of insects. The illustration below shows just a few of the many different species of organisms that live in the prairie.

species - a group of organisms capable of reproducing to produce fertile offspring.



Figure 1: Two different populations of clover plants.

population - a group of individuals of the same species living in a given area.growth rate - the change in size of a population over time.

PopulationsWhat is a

population?A population is a group of individuals of the same species living in a given area. A population of clover plants in a tray consists of the total number of plants in that tray. A population of clover plants in a field consists of the total number of plants in that field (Figure 1). A typical ecosystem contains many different populations of different species including animals, plants, fungi, and bacteria.

Growth rate Populations change as old members die and new members are born. In nature, populations often stay about the same size from year to year. Sometimes, though, populations grow or decline very fast. The change in size of a population over time is called its growth rate. Growth rates can be positive, negative, or neutral. The graph below shows data for a population of deer. What can you tell about the growth rate of this population? Identify places on the graph where the growth rate is positive, negative, and neutral.

Limits topopulation

growth

In order to grow, a population needs energy, nutrients, and space. Energy and nutrients both come from food. Therefore, population growth is limited by the amount of food available. Population growth is also limited by space. Different organisms require different amounts of space in which to live. If any of these variables are too limited, a population will not continue to grow.

Population

0 5 10 15 20 25 30 35 40

200

180

160

140

120

100

80

60

40

20

0

Num

ber

of i

ndiv

idua

ls

Time (years)


513.1 WHAT IS AN ECOSYSTEM?


Communities and ecosystemsCommunities A community is defined as all of the populations of different species in

an ecosystem. Different species in a community interact with one another to obtain food, living space, and other resources in the ecosystem. To be considered a community, the different populations in an ecosystem must live close enough to interact with one another.

An exampleof a

community

In prairie ecosystems, grazing (plant-eating) animals such as deer, elk, and bison are part of a community that depends on tall grasses for food and shelter. Other animals in the community such as insects, rabbits, and mice also depend on the grasses for food and shelter. Animals such as coyote, fox, hawks, owls, and other birds eat some of the animals that feed off the grasses. Microscopic bacteria that live in the soil are also important members of the community because they take nutrients from the air and make them available to the grasses to help them grow (Figure 2).

Biotic andabioticfactors

Ecosystems are made of communities and include living and nonliving parts. The living parts of an ecosystem are called biotic factors. These include individuals, populations of different species, communities, and their interactions. The nonliving parts of an ecosystem are called abiotic factors. These include temperature, sunlight, soil, water, and air.

Changes in one or more abiotic and/or biotic factors result in changes to an ecosystem.

Organismsand their

environments

Changes in any of these factors (amount of rainfall, decline in a population, overgrazing, etc.) result in changes to other parts of the ecosystem. For example, a long period of scarce rainfall, or drought, may impact all parts of an ecosystem. Populations of plants that have low tolerance to drought may decline. Populations of animals that depend on those plants for food may also decline. Populations of drought-hardy plant species may increase as a result of the decrease in other plant populations. Grazing animals in a community may begin to depend on the drought-hardy species of plants for food.

Figure 2: Bacteria that live in soil are important members of a prairie ecosystem community.

community - all of the populations of different species in an ecosystem.biotic factors - the living parts of an ecosystem including individuals, populations, and communities.abiotic factors - the nonliving parts of an ecosystem including temperature, sunlight, soil, water, and air.



Summary: Levels of organization of ecosystems



Figure 3: Phytoplankton are plant-like organisms that live in the ocean.

Science Focus

Vocabularyproducer, consumer, decomposer, interdependence, habitat, ecoregionLearning Goals

Describe the biotic and abiotic factors in an ecosystem.

producer - an organism that can make its own food.

Parts of an Ecosystem

You have learned that an ecosystem consists of a community of organisms that interact with one another and with the abiotic and biotic factors in their environment. The biotic factors of an ecosystem include the species of organisms present, their roles, and how they interact with other organisms. The abiotic factors include all of the nonliving parts in the environment. In this section you will learn more about ecosystems and their parts.

Biotic factorsPlants areimportant

Imagine walking through a prairie on a sunny day. What types of organisms do you notice first? You probably answered plants. Plants of the prairie include grasses, wildflowers, small shrubs, and a few trees. Plants are a very important biotic factor in an ecosystem.

Producers In an ecosystem, plants are known as producers (also called autotrophs). A producer is an organism that can make its own food. Plants are not the only producers in ecosystems. Algae, which are closely related to plants are important producers in freshwater and marine ecosystems. Among the most numerous of all producers are phytoplankton (Figure 3). Phytoplankton are microscopic, plant-like organisms that live in the ocean. Other producers include a type of bacteria called blue-green algae.

Sunlight andenergy

Living things need energy and nutrients to move, grow, and survive. Sunlight is an important abiotic factor because it is almost always the first type of energy to impact an ecosystem. Most producers use energy from sunlight to combine carbon dioxide from the atmosphere with water to make food, with oxygen as another product. This process converts the energy of sunlight into energy stored in food. This stored energy is the source of energy for all of the other organisms in an ecosystem.

Specializedproducers

A few producers, including some bacteria, can convert substances into food in the absence of sunlight. In some ocean ecosystems where sunlight cannot reach, deep-sea vents pour out boiling water mixed with hydrogen sulfide gas. Specialized bacteria use the heat to convert these substances into food.


913.2 PARTS OF AN ECOSYSTEM


Consumerscannot

produce theirown food

Unlike producers, other members of ecosystems cannot make their own food. A consumer must feed on other living things to get food and energy. Consumers are also known as heterotrophs. When a consumer eats another organism, it uses the nutrients to grow and stay healthy. Some consumers eat only producers, some eat only other consumers, and others eat both producers and consumers. For example, a mouse eats only producers, a hawk eats only consumers (such as mice), and humans eat both producers and consumers.

Decomposersrecycle

nutrients

Producers and consumers in an ecosystem create waste and eventually die. If waste and dead organisms were not somehow broken down, the nutrients they contain would not become available for other living organisms in that ecosystem. The waste would pile up and potentially harm living things. A decomposer is an organism that consumes waste and dead organisms in order to get energy. Decomposers break down material from waste and dead organisms, and nutrients are returned to the ecosystem. Fungi and bacteria are decomposers in many ecosystems.

Organismsdepend on

one anotherfor survival

The term interdependence refers to how organisms in an ecosystem depend on one another and their environment for survival. A general example of interdependence is the relationship between producers, consumers, and decomposers. Producers need sunlight and water to produce their own food. They also need nutrients to grow. During the process of making food, they also produce oxygen. Animals depend on plants for food and oxygen. Decomposers need plants and animals for their food, and, during the process of decomposition, they return nutrients back to the environment for plants to use. A more specific example of interdependence is the relationship between flowering plants and bees. Honeybees collect nectar from flowers to make honey—the bees’ food source. In the process, bees carry pollen from one flower to another, which allows the plants to reproduce (Figure 4).

Figure 4: The relationship between honeybees and flowering plants is an example of interdependence.

consumer - an organism that feeds on other living things to get energy and nutrients.decomposer - an organism that consumes waste and dead organisms.interdependence - how organisms in an ecosystem depend on one another and their environment for survival.



Figure 5: Ferns can survive with very little sunlight. A cactus needs a lot of sunlight to grow.

Figure 6: Soil is a mixture of decayed matter and rock particles.

habitat - the area in which an organism lives and finds the abiotic factors it needs to survive.

Abiotic factors in land habitatsWhat is ahabitat?

Each organism has a specific habitat within its ecosystem. A habitat is the area in which an organism lives and finds the abiotic factors it needs to survive. The bottlenose dolphin’s habitat is the ocean. A population of goldfish in an aquarium have a much smaller habitat. There are land habitats, freshwater habitats, and saltwater habitats. Here, we’ll discuss land habitats.

Temperature Most living things can survive in temperatures above freezing and below 60°C. Extreme temperatures limit the number and kinds of organisms that can survive. Tropical rainforests have moderate temperatures and support more species of animals and plants than any other land habitat. Polar regions are very cold and do not support as many species.

Sunlight The amount of sunlight determines the amount of energy available in most ecosystems. Plants capture the energy from sunlight and store it in the form of molecules. Animals get their energy by eating plants or by eating other animals that eat plants. Some plants, like ferns, can survive with very little sunlight. A cactus needs a lot of sunlight to grow (Figure 5).

Type of soil Soil is a mixture of decayed plant and animal material and very small rock particles (Figure 6). It provides an anchor for plants that have roots. It also holds water and nutrients to help plants grow. The type of soil varies in different land habitats. Sand does not hold water very well and contains few nutrients. Clay has smaller particles than sand and holds water. The best soils for growing plants contain a mixture of particle sizes and some decayed matter. Soil is a habitat for many organisms such as bacteria and worms. In fact, a cup of soil contains billions of living bacteria!

Oxygen Most organisms need oxygen to live. The air you breathe is about 21 percent oxygen. The amount of oxygen in the air varies depending on altitude. Habitats at higher altitudes, like mountaintops, have less oxygen than habitats at lower altitudes. People who live at high altitudes adapt to breathing less oxygen. If you live at a low altitude and visit a higher altitude, you may notice that you are short of breath. If you spend enough time there though, your body will adapt.




Precipitation Living things need water to survive. The amount of precipitation (rain or snow) determines the kinds of living things that can survive in a land habitat. For example, sagebrush is a plant that can survive with very little precipitation (Figure 7). The amount of precipitation on Earth is not evenly distributed. Some parts of Earth’s surface are very wet, while others are very dry. The map below shows the average amount of precipitation that falls on different parts of Earth each year.

Air habitats Some organisms spend much of their time in the air. However, most occasionally return to land. Organisms that spend time in the air are affected by the same variables as those that live on land. Can you name some organisms that spend much of their time in the air?

Figure 7: A plant called sagebrush can survive in the hot, dry desert.

Describe your habitat. What is the range of temperatures? How much precipitation does it receive each year? How much sunlight? What type of soil is present? What is your altitude? List the types of organisms that live in your habitat.



Figure 8: The distribution of Earth’s water.

Figure 9: Most fish can survive within the 6 to 8 pH range.

Abiotic factors in freshwater habitatsDistributionof water on

Earth

Water covers 71% of Earth’s surface. The ocean contains just about all of the water available to living things. About 2.5% of Earth’s water is frozen at the poles or is deep underground. Less than 0.01% of Earth’s water is found in freshwater habitats such as rivers, streams, lakes, and ponds (Figure 8).

Abioticfactors in

freshwaterhabitats

The abiotic factors that affect life on land also affect life in fresh water. These include temperature, precipitation, sunlight, type of soil on surrounding land, and oxygen. The nature of the body of water is also an important factor that determines which organisms can survive. For example, the size of the body of water limits the populations of different species that can survive. A swift-moving stream limits the types of organisms that can survive under those conditions. The clarity of the water determines how much sunlight is able to reach water plants, allowing them to grow.

pH The chemical content of the water is very important in determining which types of life can survive there. pH is a measure of chemicals called acids and bases in water. pH ranges from 0 to 14. Pure water is pH 7 (neutral). Lower pH values indicate acidic conditions. Most aquatic plants and animals function best when pH is between 6 and 8. Most fish have trouble reproducing when the pH is too acidic (Figure 9).

Dissolvedoxygen

The oxygen available to living things in water is called dissolved oxygen. Fish “breathe” by passing water over their gills to extract the dissolved oxygen. A good amount of dissolved oxygen for most aquatic life is about nine parts per million. The amount of dissolved oxygen in fresh water varies with temperature and movement. Cooler waters hold more oxygen than warmer waters. Fast-moving streams contain more oxygen than standing waters like ponds.

Nitrates andphosphates

Nitrates and phosphates are important nutrients for living things. They are often used as fertilizers for land crops. Runoff from rain washes these chemicals into bodies of water. Too many nitrates and phosphates cause large growths of water plants. As the water plants die, they are eaten by bacteria in the water that use dissolved oxygen. This process lowers the amount of dissolved oxygen available to other organisms.




Abiotic factors in the oceanThe salty ocean is the most stable of Earth’s habitats. Some abiotic factors that influence life in the ocean include dissolved chemicals, light penetration, temperature, and pressure.

Chemicals inocean water

The salt content of the ocean has remained stable for 600 million years! The chemicals that make up the dissolved salts include sodium, chloride, sulfate, magnesium, calcium, and potassium ions (Figure 10). The concentration of salts in the ocean is 35 parts per thousand (ppt). This means that there are 35 grams of salts dissolved in every liter of seawater.

The ocean isdivided into

zones

Scientists divide the ocean into layers called zones. Zones extend from the surface of the water to the bottom of the deepest trenches. As you go deeper, temperature and light decrease, and pressure increases.

Life in thezones

Most life in the ocean is concentrated in zones where light can penetrate. In most places, light does not reach deeper than 200 meters. Plants that use sunlight to make food cannot live beyond this depth. Life is difficult for organisms in the deep zones. They must overcome lack of light, low temperatures, and extremely high pressures. Some organisms are able to produce their own light so they can find food and locate others of their same species (Figure 11).

Figure 10: The main chemicals dissolved in ocean water.

Figure 11: These deep-sea fish can produce their own light.

Chemical (ion) Concentration (ppt)

chloride 19.3sodium 10.8sulfate 2.7

magnesium 1.3calcium 0.4

potassium 0.4bicarbonate 0.1



Panhandle Plains - consists of flat, grassy land. Besides grasses, other plants include sumac, prickly pear cactus, and acacia. Animals include prairie dogs, roadrunners, foxes, and badgers.Big Bend Country - contains plateaus and desert mountains. A plateau is an area of high, flat land. The plateaus are home to grasses and sagebrush. Animals of this region include antelope, mountain lions, coyotes, and tarantulas.Hill Country - consists of rolling hills covered in grasses. There are also many springs and canyons in this area. Plants include juniper, pecan, and mesquite. Animals include deer, armadillos, toads, and kingfishers.Prairies and Lakes - contains strips of woodland among prairie. The rich, fertile soil supports tall grasses and hardwood trees. Animals include beavers, porcupines, box turtles, and bats.Pineywoods - The land is hilly with wetlands in between. Animals include cottonmouth snakes, squirrels, rabbits and opossums. Plants hardwoods such as maple and bald cypress, and pines.South Texas Plains - contains the Rio Grande valley, an ecosystem that is home to palm and citrus trees along with many snake and frog species. Grassy plains are also found in this region.Gulf Coast - contains salt grass marshes and estuaries along with patches of tallgrass prairies and woodlands. Aligators, river otters, pellicans, and saltwater fish live here.

Regions of TexasWhat is an

ecoregion?Texas is a large state with many ecosystems. For the purpose of study, scientists may divide large areas of land or water—like the state of Texas—into different regions based on similar abiotic and biotic factors. Each region is a large area with defined geographic features (mountains, plains, plateaus, etc.) and similar communities of organisms. Each region may contain many different ecosystems. The Texas Department of Parks and Wildlife divides the state into seven distinct regions, as shown below. In which region do you live?

PanhandlePlains

Prairiesand lakes

Pineywoods

Gulf Coast

Hill Country

Big BendCountry

South TexasPlains

teks 8.11b: biotic and abiotic factors p. 1classroom.kleinisd.net/users/0178/docs/5th six...

Documents