Download Ecology Worksheet - Blue Valley Schools

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 (km2) has a population density of 1000 birches/50 km2. 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 (O3), 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?
____________________________________________________________________________________________________________
____________________________________________________________________________________________________________