Ecology: Chapters 34 36 Worksheet Name: Chapter 34: The Biosphere Concept 34.1 The biosphere is the global ecosystem. (pp. 744 749) The scientific study of the interactions among organisms and between organisms and their environments is called ecology. Ecologists study the relationships among biotic and abiotic factors. All the living organisms in the environment are called biotic factors. The nonliving physical and chemical conditions are called abiotic factors. Ecologists conduct studies at five increasingly larger levels: individual organisms, populations, communities, ecosystems, and the biosphere. A population is a group of organisms of the same species living in a particular area. A community is made up of all of the organisms living in a particular area. An ecosystem is made up of the abiotic factors and the biotic factors in an area. The biosphere includes all of Earth s ecosystems. The biosphere is patchy a particular area may contain an uneven distribution of different ecosystems. This patchiness creates different habitats, or specific environments in which organisms live. Each habitat has characteristic abiotic and biotic factors. Abiotic factors that define different habitats include amount of sunlight, availability of water, temperature, soil type, wind, and number and type of disturbances. Major natural disturbances that affect ecosystems include fires, hurricanes, tornadoes, and volcanic eruptions. 1. What are the five levels of ecological study? 2. What are habitats, and what creates habitats? 3. Distinguish biotic factors from abiotic factors. Concept 34.2 Climate determines global patterns in the biosphere. (pp. 750 752) The climate of a region mostly determines the type of ecosystem found there. Earth s climates are mainly produced by the uneven heating of Earth by the sun. Different locations on Earth s surface receive different amounts of solar energy. As a result, Earth s surface can be divided into different temperature zones based on lines of latitude. The region that lies between 23.5 N latitude and 23.5 S latitude, called the tropics, is the warmest temperature zone. The region north of the Arctic Circle and the region south of the Antarctic Circle, called the polar zones, are the coldest temperature zones. The latitudes between the tropics and the polar zones, called the temperate zones, experience less extreme heat and cold. The uneven heating of Earth s surface also affects global patterns of winds and precipitation. When air is warmed it can absorb more moisture, and it tends to rise. The rising and falling of air masses, combined with Earth s rotation, produce predictable wind patterns. These wind patterns produce surface currents in the oceans. A current is a river-like flow pattern within a body of water. Surface currents can greatly affect the climates of land areas. Large bodies of water may create variations in local climates. Mountains also affect local climates. Specific locations in a climate region may be exposed to different conditions created by shade, snow cover, or windbreaks. Such small-scale differences in climate result in a microclimate, a climate in a specific area that varies from the surrounding climate region. 4. What produces surface currents in the ocean? 5. What creates a microclimate? Concept 34.3 Biomes are the major types of terrestrial ecosystems. (pp. 753 757) The major types of terrestrial ecosystems that cover large regions of Earth are called biomes. Each biome has typical communities of organisms that are adapted to its climate and other abiotic factors. There are eight major biomes: tropical forest, savanna, desert, chaparral, temperate grassland, temperate deciduous forest, coniferous forest, and tundra. Tropical forests occur near the equator where temperatures are warm year-round. One type of tropical forest is the tropical rain forest, which can receive as much as 350 centimeters of rainfall yearly. Of all the biomes, tropical rain forests have the greatest diversity of life. A savanna is a grassland with scattered trees. Deserts are land areas that receive less than 30 centimeters of rain per year. The chaparral is a temperate coastal biome dominated by dense evergreen shrubs. The temperate grassland has deep, nutrient-rich soil that supports a variety of grass species and other plants. The temperate deciduous forest has dense stands of deciduous trees trees that drop their leaves each year. The coniferous forest has
towering cone-bearing evergreen trees such as pines and firs. The tundra has bitterly cold temperatures and high winds. The permanently frozen subsoil of the tundra is called permafrost. 6. In what ways does each biome differ from the other biomes? 7. How do the biotic factors of a savanna differ from those of a chaparral? Concept 34.4 Aquatic ecosystems make up most of the biosphere. (pp. 758 761) Major abiotic factors that affect aquatic (water) ecosystems include the amount of dissolved salt in the water, the temperature of the water, and the availability of sunlight (how much sunlight reaches into the water). Freshwater ecosystems include bodies of water with very little dissolved salt, such as ponds, lakes, streams, and rivers. Lakes and large ponds are divided into zones. The photic zone, in which light is available for photosynthesis, includes the shallow water close to shore and the upper zone of water away from shore. Organisms in the photic zone include water plants and phytoplankton, microscopic algae and bacteria that carry out photosynthesis. The deep areas of a lake, where light levels are low, are called the aphotic zone. The bottom of any aquatic ecosystem is called the benthic zone. A body of flowing fresh water is known as a river or a stream. An area where a stream or river mixes with ocean water is called an estuary. The ocean is also divided into different zones. Zones based on depth include the benthic zone the ocean floor and the pelagic zone the open ocean above the ocean floor. Like a lake, the ocean has a photic zone and an aphotic zone. The area of shore between the high-tide and low-tide lines is called the intertidal zone. The area of the ocean from the low-tide line out to the edge of the continental shelf is the neritic zone. The vast ocean beyond the edge of the continental shelf is called the oceanic zone. Organisms that live in the photic oceanic zone include phytoplankton and zooplankton, or microscopic animals. Coral reefs formed by colonies of coral animals are mostly found in the ocean s neritic zone. In the deep ocean, many unfamiliar species live around deep-sea hydrothermal vents. Hydrothermal vents are spots on the ocean floor where hot gases and minerals escape from Earth s interior into the water. Vent communities use the chemical energy from Earth s interior rather than sunlight as their energy source. 8. Explain why phytoplankton live in the photic zone rather than the aphotic zone. 9. What abiotic factors characterize a hydrothermal vent? Chapter 35: Population and Community Ecology Concept 35.1 A population is a local group of organisms of one species. (pp. 766 769) Members of the same species living in a specific area make up a population. For example, all the alligators in a swamp make up a population. The size of a population can change over time. Factors that affect a population s size include the availability of food and space, weather conditions, and breeding patterns. Ecologists often calculate population density, or the number of individuals of a particular species in a given unit of area or volume. For example, a population of 1000 birch trees in a forest measuring 50 square kilometers (km 2 ) has a population density of 1000 birches/50 km 2. In most cases, it is too difficult to directly count every member of a population. Instead, scientists use sampling techniques to estimate the population s size. These techniques include quadrats, indirect counting, and the mark-recapture method. All of these techniques involve making some assumptions about the population. These assumptions affect how accurate the estimate is. 10. How do biologists define a population? 11. Contrast the terms population density and population. 12. List three methods of sampling.
Concept 35.2 There are limits to population growth. (pp. 770 773) A population s growth depends partly on how quickly its members reproduce. For example, bacteria can reproduce as often as every 20 minutes. In contrast, elephants reproduce only every few years. With unlimited food, space, and water, a population may undergo exponential growth, in which the population multiplies by a constant factor at constant time intervals. This growth pattern resembles a J-shaped curve when graphed. In nature, however, one or more limiting factors usually slow a population s growth. When such a factor limits a population s growth, the population has reached its carrying capacity. This growth pattern resembles an S-shaped curve when graphed. Some limiting factors, such as disease, are density-dependent factors, meaning they limit a population more as population density increases. Other factors, such as fires or storms, are unrelated to population density and are called density-independent factors. Some populations grow in boomor-bust cycles consisting of periods of rapid growth followed by rapid decreases. 13. Under what conditions might a population undergo exponential growth? 14. Give an example of a density-dependent limiting factor and an example of a density-independent limiting factor. Concept 35.3 Biologists are trying to predict the impact of human population growth. (pp. 774 776) For thousands of years, the human population grew very slowly. But starting in about 1650 C.E., the human population has grown so rapidly that it resembles exponential growth. The reasons for this rapid growth include improvements in nutrition, sanitation, and health care. These factors have enabled more people to live longer and have healthy offspring. Scientists use many models to predict future growth. Some predictions are based on age structure, or the proportion of people in different age groups in a population. An age-structure graph shows these proportions on a bar graph. There is much debate about human population predictions and about the possible impact of continued growth on Earth s resources. 15. What are some reasons that the growth rate of the human population increased dramatically after about 1650 C.E.? 16. What is an age-structure graph? Concept 35.4 Species interact in biological communities. (pp. 777 780) A community is a group of species living in the same geographic area. Interspecific competition occurs when two or more species rely on the same limited resource, such as grass for grazing. In some situations, competition may result in one species succeeding over another, which is a process called competitive exclusion. Within a community, each species has a unique niche that includes its living place, its food sources, the time of day it is active, and other aspects of its way of life. Species within a community interact in different ways. In predation, one organism (the predator) eats another organism (the prey). Symbiotic relationships are close interactions in which one species lives on or in the other. In parasitism, one organism (the parasite) obtains its food at the expense of another organism (the host). In mutualism, both organisms benefit from the close interaction. In commensalism, one organism benefits while the other is neither harmed nor helped significantly. 17. Are species that occupy different niches likely to compete? Explain. 18. How is a symbiotic relationship different from predation? Concept 35.5 Disturbances are common in communities. (pp. 781 783) Communities tend to be constantly changing. Some disturbances are natural, such as volcanic eruptions and storms. Other disturbances are caused by human activities, such as clearing a forest. Some disturbances have positive effects, such as providing new habitats. Others have negative effects, such as destroying food sources or nesting areas. A significant disturbance may result in a process of community change called ecological succession. The appearance of a new community in an area with no soil, such as on a newly formed island, is called primary succession. The change in a community after a disturbance that leaves the soil intact, such as in an abandoned farm field, is called secondary succession. One human activity that often has a negative effect on existing communities is bringing introduced species to a new geographic area.
19. Give two examples of disturbances to a community. 20. Explain the term ecological succession. 21. How might an introduced species have a negative effect on a community? Chapter 36: Ecosystems and Conservation Biology Concept 36.1 Feeding relationships determine the path of energy and chemicals in ecosystems. (pp. 788 791) Energy flow through ecosystems begins with producers. Producers are generally photosynthetic organisms such as plants that convert light energy from sunlight to the chemical energy of organic compounds. Producers also include chemoautotrophs, prokaryotes that extract energy from inorganic compounds. Organisms called consumers obtain chemical energy by feeding on producers or on other consumers. Organisms called decomposers obtain energy by breaking down wastes and dead organisms. As organisms use chemical energy, they release thermal energy (heat). Thus, energy enters most ecosystems as sunlight and exits ecosystems as heat. In contrast, chemicals can be recycled between the living and nonliving parts of ecosystems and the biosphere. Both energy and chemicals move from one organism to the next as organisms feed. Each of the feeding organisms represents a trophic level in the ecosystem. The pathway of food transfer from one trophic level to another is called a food chain. In all food chains, producers make up the trophic level that supports all other levels. A consumer that eats only producers is an herbivore. A consumer that eats only other consumers is a carnivore. A consumer that eats both producers and consumers is an omnivore. When a consumer feeds directly on producers it is called a primary consumer. Secondary consumers eat primary consumers. Tertiary consumers eat secondary consumers. Decomposers are consumers that feed on detritus, the wastes and remains of dead organisms. Consumers usually have many food sources. The pattern made by interconnected and branching food chains is a food web. 22. How is the flow of energy through ecosystems different from the flow of chemicals through ecosystems? 23. How is a food web different from a food chain? Concept 36.2 Energy flows through ecosystems. (pp. 792 794) Because there is a limited amount of energy in an ecosystem, energy is divided among the different trophic levels. This energy budget influences the types and numbers of organisms in an ecosystem. The producers store chemical energy in organic material, or biomass. The rate at which producers in an ecosystem build biomass is called primary productivity. Primary productivity determines the maximum amount of energy available to the higher trophic levels in an ecosystem. Energy is spent at each step in a food web. Ecologists use three types of diagrams to depict information about energy, biomass, and number of organisms at different trophic levels. An energy pyramid depicts the energy loss from one trophic level to the next. In general, an average of only 10 percent of available energy at a trophic level is converted to biomass at the next higher trophic level. A biomass pyramid depicts the actual biomass (dry mass of all organisms) in each trophic level. A pyramid of numbers depicts the number of individual in each trophic level. 24. How is primary productivity related to biomass? 25. What does each type of ecological pyramid depict? Concept 36.3 Chemicals cycle in ecosystems. (pp. 795 798) Chemical cycles typically involve three general steps. First, producers use chemicals from the nonliving environment to make organic compounds. Second, as consumers feed on producers, they take chemicals into their bodies and release some
back into the environment as waste. Third, decomposers break down dead organisms, returning inorganic chemicals to the soil, water, and air. Producers can then use these chemicals to make organic compounds, continuing the cycle. In the carbon and oxygen cycle, producers use carbon dioxide in the air or water and release oxygen as they make organic compounds through photosynthesis. Consumers, which eat the organic compounds, use oxygen and release carbon dioxide during cellular respiration. In the nitrogen cycle, certain types of bacteria convert nitrogen gas in the air to ammonia through a process called nitrogen fixation. These bacteria live in the soil and on the roots of certain plants. In soil, the ammonia forms ammonium. Other soil bacteria then convert ammonium to nitrates in a process called nitrification. Ammonium and nitrates move through the food webs, and nitrogen gas is eventually released back into the air. In the water cycle, three major processes move water between the land, bodies of water, and the atmosphere: evaporation, condensation, and precipitation (rain, snow, hail, and sleet). A large amount of water exits plants during transpiration, evaporation from a plant s leaves. 26. How are bacteria involved in the nitrogen cycle? 27. What are the three major processes that move water through the water cycle? Concept 36.4 Human activities can alter ecosystems. (pp. 799 804) Human activities can greatly affect chemical cycles. For example, the burning of fossil fuels adds carbon dioxide to the atmosphere. The carbon cycle is also affected by deforestation, the clearing of forests for agriculture, lumber, and other uses. Deforestation clears away plants that absorb carbon dioxide during photosynthesis. The burning of trees during deforestation releases carbon dioxide into the atmosphere. Gases such as carbon dioxide trap the sun s heat in the atmosphere through a process called the greenhouse effect. As levels of carbon dioxide in the atmosphere rise, more heat is trapped, and the average temperature rises. Such an overall rise in Earth s average temperature is called global warming. Human activities impact the nitrogen cycle mostly by moving large amounts of nitrogen compounds into the water or air. For example, fertilizers applied to crops are one source of nitrogen compounds in water. High levels of nitrogen in water can cause the rapid growth of algae, a condition called eutrophication. Bacteria that decompose the algae use so much oxygen that there is not enough oxygen left for other organisms to live. Other human activities, such as driving cars, release nitrogen and sulfur compounds into the atmosphere. These compounds form acids with the water vapor in the atmosphere. The precipitation that carries these acids back to Earth s surface is called acid rain. Acid rain causes damage to the environment. Human activities can also impact the water cycle. For example, humans can use water faster than the water cycle can replace it, causing rivers and underground water sources to run dry. The addition of substances to the environment that result in a negative effect is called pollution. Pollution can affect food chains. For example, pollutants become more concentrated from one trophic level to the next in a food web in a process called biological magnification. Pollutants can also affect the atmosphere. For example, some pollution affects a gas called ozone (O 3 ), which absorbs ultraviolet light. The result is damage to the ozone layer, a region high above Earth s surface that shields organisms from the sun s damaging effects. 28. How does deforestation affect the carbon cycle? 29. How does pollution cause acid rain? Concept 36.5 Conservation biology can slow the loss of biodiversity. (pp. 805 809) Biodiversity is the variety of life on Earth. Biodiversity includes the genetic variety among individuals in a species, the number of species in an ecosystem, and the variety of ecosystems in the biosphere. One reason that biodiversity matters is that many of the species in an ecosystem are interconnected. If a key species disappears, the health of the whole ecosystem may be affected. There is currently a period of mass extinction taking place on Earth. The main factors causing this threat to biodiversity are pollution, habitat destruction, introduced species, and overexploitation. Overexploitation is the practice of harvesting or hunting to such a degree that few remaining individuals may not be able to reproduce the population. The field of conservation biology uses knowledge of biology to counter the loss of biodiversity. Conservation biologists often focus on hot spots, small geographic areas with large numbers of species. They also try to understand an organism s habitat and try to find a balance in the demands for resources. One way for nations to protect ecosystems is to establish zoned reserves, undisturbed areas of land that are surrounded by buffer zones, areas with
little human impact. Many nations and private foundations are working toward a goal of sustainable development developing natural resources so that they can renew themselves and be available for the future. 30. What is one reason biodiversity is important? 31. How does overexploitation threaten biodiversity? 32. What are four approaches conservation biologists use in conserving biodiversity?