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Q Why are these zebras fighting? For the zebra, life on the African savannah is about survival. Whether escaping the ambush of a pride of lions, walking vast distances to drink fresh water, or competing for the right to mate with females, only the best adapted zebras will survive and pass on their genes. The interactions among organisms, and between organisms and their environment, make ecosystems function.
r e a d i N G T o o lb o x This reading tool can help you learn the material in the following pages.
USING LANGUAGE Your Turn Predictions Some predictions are conditional: In the following sentences, identify the condition and the Something might happen, but only if something else prediction. happens first. For example, if the temperature drops below 1. After the deer population reaches 600 individuals on freezing, snow might fall. The prediction is that snow might the island, the deer will eat most of the vegetation, fall tonight. But snow might fall under one condition. First, and the number of deer will decrease. the temperature has to drop below freezing. 2. If the otters are removed from the ecosystem, the sea urchins will eat all of the kelp.
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y habitat. A areThese just afew of environmental the features that make up lion’s the rest shade inthe of trees, and never stray far from valuable of pools water. Here, lions grass throughto hunt stalk tall zebras and antelope, places find to challenging environment is home the of lion, African the shown in of pools watersmall surrounded by thirsty animals dot landscape. the This vastOn the grow plains grasses tall of among Africa, trees and shrubs, and ment, including grass, trees, the the and watering the holes. area where an organism lives. factors These include of environ- the aspects all MAIN ID MAIN MAIN ID MAIN C
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of always be better adapted to the environment. The principle use the same resources in the same ways, one species will result inother outcomes. more aggressive cousin. But competitive exclusion can also population is declining due to competition with its larger, out its competitor. smaller Currently, red the squirrel gray squirrel was better adapted to niche the and pushed resources,same food habitat, and space. In the case this squirrel was forced to compete with newcomer the for the Great Britain late inthe 1800s.The native European red another niche or become extinct. suited to the niche, and the other species will be pushed into competing for the same resources, one species will be better same resources, as shown in similar habitats and that they may use some of the We have already seen that many species can share Competitive But what if two species are competing over limited resources? suitedbest to obtain resources these is most likely and to survive reproduce. water,food, and shelter successful inits to be habitat. The organism that is drivingthe force behind natural resources needs Aspecies selection. such as You have that learned ability the of an individual and to survive reproduce is they help to give a picture of how a lion fits into the African savannah. the shade. These examples are only a few parts of the lion’s ecological niche, but order to avoid the intense heat of the savannah, lions often spend afternoons in resource and hunts primarily during low-light times, such as dawn or dusk. In same grasses as camouflage for hunting. A lion uses the antelope as a food us Evolutionary • Niche • mai
e the tall grasses of the African plains as a food resource, a lion may use the competitive exclusion The N Looking closely at all of these factors, we can see that while an antelope may smaller teeth might teeth smaller have allowed other the to eat seeds. small of squirrel to become better at cracking large nuts, for selection while divergent evolution. for Selection larger might teeth have allowed one type niche would have divided. been ate nuts from tops the of others trees while ate nuts from ground, the the different resources on based competitive advantages. If one of type squirrel n
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y populations. become highly adaptedbecome highly to hunting and prey. their killing another organism. Many organisms, such as snake the in P Another way interact species with one another is through predation. P Competition Competition inan species ecosystem.between water. are These just two examples of many the interactions within and Two birds may fight over territories. may Afish prey onfloating on insects the
tolerate another of male its own same inthe area. species share with males territory of different aparticular bird but species not will competition during spring the breeding of season birds. Atypical will male against one another for limited resources. You intraspecific can observe known as intraspecific competition. Individuals of struggle species a particular dandelions, and many other plants compete all for nutrients and water. compete for alimited resource, such as space. In alawn, for example, grass, similar resources. Interspecific competition two when different occurs species competition.intraspecific There are two different of types competition: interspecific competition and MAI MAI redation C redation Symbiosis Competition o Com Eve N n N ID c ID n though they mayn though they have different niches, may two species use still ept petition also occurs among occurs petition also members of same This the species. is E E is process the by which one organism captures and feeds upon A AS
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The timber rattlesnake, for example, is a predator that preys on small Biology IDEO V CLIP animals such as mice, voles, rabbits, and squirrels. Lying silently, hidden among leaf litter on the forest floor, the rattlesnake has found a niche as an HMDScience.com ambush predator. A swift bite from the snake’s fangs injects its venom. The GO ONLINE venom attacks the nervous system and eventually paralyzes the prey. The Predator/Prey Relationship snake swallows the paralyzed animal whole. Herbivores can also be considered predators. The deer that eats grass in fields and leaves from trees is preying on the plants. Evaluate How does natural selection shape predator–prey relationships? 12A
MAIN IDEA 12A Symbiosis is a close relationship between species.
R E ADI N G TO OLB ox A honeybee buzzes away from a flower with its reward of nectar. Small pollen grains have become attached to the bee’s back. When the bee arrives at the next VOCABULARY flower, the pollen fertilizes the egg of the next plant. In this way, a relationship, symbiosis The word comes Symbiosis from the Greek word sumbios, or symbiosis, between the bee and the flower has evolved. is a close which means “living together.” ecological relationship between two or more organisms of different species that live in direct contact with one another. There are three major types of symbiosis: mutualism, commensalism, and parasitism. Mutualism R E ADI N G TO OLB ox Mutualism is an interspecies interaction in which both organisms benefit from one another. The relationship between the lesser long-nosed bat and the TAKING NOTES saguaro cactus is an example of mutualism. During the spring, the bats help Mutualism, commensalism, pollinate the cacti through the indirect transfer of pollen as they fly from one and parasitism are distinct types of symbiosis. Add details cactus to another to feed on flower nectar. When the fruit ripens in the sum- with examples of your own. mer, the bats become fruit eaters, as shown in Figure 2.2. The cactus benefits
Symbiosis when the bat spreads its indigestible seeds across the desert.
Mutualism Commensalism Another type of symbiotic relationship is commensalism. Commensalism is Commensalism a relationship between two organisms in which one receives an ecological Parasitism benefit from another, while the other neither benefits nor is harmed. Right now you may be a part of a commensal relationship. Buried deep in the hair follicles of your eyelashes are microscopic mites that feed on the secretions and dead skin cells of your body. These harmless organisms are called demo- dicids, and they have found their highly specialized niche in your hair follicles. Parasitism Parasitism is a symbiotic relationship involving a species that directly harms its host. Parasitism is a relationship similar to predation in that one organism benefits while the other is harmed. But unlike a predator, which quickly kills and eats its prey, a parasite benefits by keeping its host alive for days or years. For example, the braconid wasp lays its eggs inside a caterpillar. When the larvae hatch, they eat the caterpillar from the inside out, consuming the nutrients they need to grow into adults.
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on more. such 12A smaller protozoan endoparasites can kill their host if not treated. by their host. Large endoparasites, such as tapeworms and hookworms, and and organs of a host where, safely hidden, they feed on the nutrients ingested can also be found inside of living organisms. Endoparasites live in the tissues known to carry a wide variety of diseases that can affect their host. Parasites leeches, such as the one seen in usually feeding on its fluids. Common ectoparasites include fleas, ticks, and on the exterior of an organism, attaching itself to the outside of the host and ar s it important for ectoparasites to stay undetected by their hosts? by their to stay undetected ectoparasites for important s it
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BIOLOGY Population Niches and What Limits Population Growth and Competition Use bird Population Growth? Carrying Capacity Graph feeders to investigate and analyze the bison popu- Apply a limiting factor within a sample competition among birds lation of Yellowstone Park. environment and see how populations in a neighborhood. of organisms react.
online biology 427 HMDScience.com DO NOT EDIT--Changes must be made through “File info” CorrectionKey=A
14.3 Population Density and Distribution
2g, 7d, 12A Key Concept each population has a density, a dispersion, and a reproductive strategy. VOCABULARY MAIN IDEAS population density Population density is the number of individuals that live in a defined area. population dispersion Geographic dispersion of a population shows how individuals in a population survivorship curve are spaced. Survivorship curves help to describe the reproductive strategy of a species.
2G analyze, evaluate, make Connect to Your World inferences, and predict trends from data; 7D analyze and evaluate how If you have ever traveled from a rural area into a city, you may have noticed a change the elements of natural selection, in population density. Cities have more dense populations, while rural areas have including inherited variation, the potential of a population to more widely dispersed populations. Scientists measure species populations in a produce more offspring than can similar way. What can we learn from population data? survive, and a finite supply of environmental resources, result in differential reproductive success; 12A interpret relationships, including predation, parasitism, commensalism, mutualism, and competition among organisms MAIN IDEA Population density is the number of individuals that live in a defined area. The wandering albatross may fly over open ocean waters for days or weeks at a time without ever encountering another bird. In contrast to this solitary lifestyle, elephant seals may gather in groups of a thousand or more on Cali- fornia beaches. By collecting data about a population in a particular area, scientists can calculate the density of a population. Population density is a measurement of the number of individuals living in a defined space. CONNECT TO Calculating an accurate population density can tell scientists a great deal Gene Flow about a species. When scientists notice changes in population densities over Recall that in the chapter The time, they work to determine whether the changes are the result of environ- Evolution of Populations you mental factors or are simply due to normal variation in the life history of a learned about gene flow and species. In this way a wildlife biologist can work to make changes that will help geographic isolation. Population dispersion patterns influence the to keep the population healthy. One way to calculate population density is to rate of gene flow among and create a ratio of the number of individuals that live in a particular area to the between species. size of the area. This formula is simplified as follows:
# of individuals ______ area (units2) = population density For example, if scientists sampling a population of deer counted 200 individuals in an area of 10 square kilometers, the density of this deer popula- tion would be 20 deer per square kilometer. Connect What might a decrease in the density of a deer population over a specific time period tell scientists about the habitat in the area?
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(l) ©Franklin Viola/Animals Animals-Earth Scenes; (c) ©Wolfgang Kaehler/Corbis; (r) ©Buddy Mays/Corbis how individuals in a population arehow spaced. apopulation in individuals shows ofapopulation dispersion Geographic Infer by showing how populations group together. Dispersion patterns helpusunderstand speciesinteractions F C advantage inavoiding predators. as alarge mass, individuals have an in large groups called schools. By moving Many speciesoffishswim together IGURE
Figure 3.1 Figure Population the same species interact and how different species interact with one another. Patterns of geographical dispersion give us ideas of how individuals of informationOther gained can be from population density measurements. population dispersion. are spread inan area or avolume. which individuals of apopulation • • • MAI lump
Ran Uni Clumped area or avolume. are spread randomly within an distances from one another. individuals living at specific limited resources to lead and intraspecies competition for resources. protection, or access food in order to facilitate mating, gain may live closetogether ingroups What type of intraspecies interaction might cause uniform dispersion? uniform cause might interaction intraspecies of type What N e ID form 3.1 dom d shows of three the types D E
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Q U I C K L A B Interpreting data 2G
Survivorship Curves Materials In this lab, you will make a type 1 survivorship curve using data from the • obituary section of a newspaper obituary section of a newspaper. • graph paper Problem What is the trend in data for type 1 survivorship curves? Table 1. Survivorship data PROCEDURE Age (years) Deaths Survivors % Surviving 1. Obtain the obituary section of the newspaper. 0–5 I 35 – 1 = 34 97 2. Create a data table like the one at right that 6–10 I 34 – 1 = 33 94 extends to include five-year age groups up to 91–95 years. 11–15 0 33 – 0 = 33 94 3. For 35 obituaries, place a tally next to the age 16–20 IIII 33 – 4 = 29 83 group in which the individual died. 4. Subtract the number of individuals that died from 21–25 I 29 – 1 = 28 80 the number of remaining survivors, and record the answer in the third column of your data table. Calculate the percent surviving in each age group by dividing the number of survivors by 35 and multiplying by 100. Repeat this step for all age groups. Analyze and Conclude 1. Graph Data Draw a survivorship curve by plotting the age group on the x-axis, and the percent survivors on the y-axis. 2. Analyze Explain the trend in the data.
MAIN IDEA 7D, 12A Survivorship curves help to describe the reproductive strategy of a species. The California red-legged frog of the western United States is an amphibian that reproduces by laying 2000 to 5000 eggs in late winter and early spring. In one to two weeks, these eggs hatch, and over the next four to seven months, the tadpoles grow into frogs. If so many eggs are laid, why is this frog a threat- ened species in much of the western United States? Many predators feed on the eggs of the red-legged frog, so of the thousands of eggs laid, only a small number of offspring will survive to adulthood. This type of reproductive strategy is to produce a lot of offspring. Species use many other reproductive strategies as well. Survivorship curves illustrate how offspring survival from birth to death fits in with the survival strategies of a particular species. A survivorship curve is a generalized diagram showing the number of surviving members over time from a measured set of births. By measuring the number of offspring born in a year and following those offspring through until death, survivorship curves give information about the life history of a species. For example, we will begin with 100 coyotes born in year zero. After one year, 10 of those baby coyotes died from disease or predation. Of the original 100, 90 are left. During year two, 4 more coyotes die, leaving 86 of
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the original 100. In year three, 3 more die, leaving 83 of Figure 3.2 Survivorship Curves the original 100. The number of individuals surviving from year to year decreases, but a substantial portion of 120 Type I the group will live a full life and reproduce. In Figure 3.2, 100 Type II you can see the three basic patterns of animal survivor- Type III 80 ship curves. Type I The graph shows a type I survivorship curve in 60 orange. Type I survivorship represents a life history that is 40 common among large mammals, including humans. The 20 Number of survivors curve shows a low level of infant mortality and a popula- 0 tion that generally will survive until old age. A behavior 10 20 30 40 50 60 70 80 90 100 that most organisms showing type I survivorship share is Percentage of maximum life span parental care for the young. Most infant organisms are unable to care for themselves. By protecting their young, parents are better able to ensure that their offspring stay alive until they can survive on their own. Type II Organisms such as birds, small mammals, and some reptiles show a survivorship rate that is roughly equal at all ages of an organism’s life. At all times, these species have equal chances of living and dying, whether from disease or as a result of predation. A type II survivorship curve is shown in green on the graph. Type III Organisms with type III survivorship (shown in blue) have a very high birth rate and also a very high infant mortality rate. Species with type III survivorship are generally invertebrates, fish, amphibians, and plants. Many of their offspring will die from predation, but inevitably a few will survive to adulthood and be able to pass their genes on to the next generation. Though the California red-legged frogs are threatened largely because of habitat loss and pollution, the frogs are also targets of high levels of predation at an early age, making recovery for this species especially difficult. Synthesize Is there any connection between survivorship curves and reproductive strategies? Explain. 7D
Self-check Online HMDScience.com 14.3 Formative Assessment GO ONLINE Reviewing Main Ideas Critical thinking CONNECT TO 1. A shoreline mussel species has a 4. Analyze What might be the Abiotic Factors population density of one organism advantages of having a clumped 6. On the African savannah, per square meter. Will all mussels be dispersal pattern? what types of abiotic factors found one meter apart? Explain. 5. Infer An organism has ten offspring. may lead to high population 2. Draw and label a diagram showing the Two of these offspring die each year density and clumped three population dispersion patterns. over a five-year period. Is the dispersion patterns? 11B 3. How do survivorship curves show organism more likely to be a bird or three types of reproductive strategies? an insect? Explain. 7D
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14.4 Population Growth Patterns
2g, 11B, 12A, Key Concept Populations grow in predictable patterns. 12D MAIN IDEAS VOCABULARY Changes in a population’s size are determined by immigration, births, emigration, and deaths. immigration emigration Population growth is based on available resources. exponential growth Ecological factors limit population growth. logistic growth carrying capacity population crash Connect to Your World limiting factor That banana you left in your backpack did not go unnoticed. After one week, you density-dependent limiting factor open your bag and dozens of tiny insects swarm out. The smell of rotting fruit density-independent follows close behind. Only a week ago, the population of fruit flies in your backpack limiting factor was zero. Just before you opened it, the population had grown to several dozen. How did this population grow so quickly?
2G analyze, evaluate, make inferences, and predict trends from data; 11B investigate and analyze how organisms, populations, and MAIN IDEA 11B, 12D communities respond to external factors; 12A interpret relationships, including predation, parasitism, Changes in a population’s size are determined by commensalism, mutualism, and competition among organisms; immigration, births, emigration, and deaths. 12D recognize that long-term survival of species is dependent on The size of a population is usually changing. If resources such as food and changing resource bases that are water are abundant, or plentiful, a population may grow. On the other hand, if limited resources are in short supply, the population may decrease in size. Hopefully, the normal fruit fly population in your backpack is zero. But if an abundance of resources, such as an overripe banana, becomes available, the population will increase dramatically. However, when the resources are removed, the fruit fly population in your backpack will once again return to zero. Four factors affect the size of a population. • Immigration When one or two fruit flies found the banana, they immi- grated into your backpack. Immigration is the movement of individuals into a population from another population. R E ADI N G TO OLB ox • Births Additional fruit flies were born in your backpack. Births increase VOCABULARY the number of individuals in a population. The word immigrate comes • Emigration After you opened your backpack, some fruit flies flew out and from the Latin word immigrare, left to find other rotting fruit. Emigration is the movement of individuals meaning “to go into,” and the word emigrate comes from out of a population and into another population. the Latin word emigrare, • Deaths You might have squashed a couple of unlucky fruit flies as you meaning “to move.” were opening your backpack. The size of a population decreases when individuals die. Apply When a population is declining, what two factors are likely outpacing what other two factors?
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©M. W. Mules/CSIRO resources. Population growth based available is on
rabbits inAustralia. population, today there are 200million and between 300million and spread across the country. After many attempts to control the catch them. The initial population of 24 rabbits grew exponentially had abundant space and food and no predators fast enough to hunting. The rabbits were introduced into an environment that 24 European rabbits for to of country the sport purpose the an Australian landowner returning home from England brought uninhabited area. For example, in1859 moves aspecies when to apreviously curve. growthtial appears as aJ-shaped population levels off at environment asizethe can support. to deplete, and growth to starts slow. As resources become limited, the populationthe is able to grow. time, resources Over begin growth, resources are abundant, and change insizeover time. initial During In dramatically over of time. aperiod apopulationwhen sizeincreases Figure 4.3, 4.3, Figure in and seen canS-shaped be curve logistic growth form takesthe of an leveling off at astable size. Agraph of of exponentialperiod growth before of slow growth followed by abrief a population with aperiod begins growth rate. During resources and thus show alogistic Most populations limited face Logistic Growth called grow rapidly. of This type growth, population has opportunity the to When resources are abundant, a E are of two distincttypes population growth. population may grow rapidly, very or it may abit take of to time grow. There a population is directly determined by amount the of resources available. A Population growth is of afunction environment. the The rate of growth for MAI xponential Growth xponential Figure 4.1, Figure Expo N ID exponential nential growth may occur E which models apopulation’s A you that can see exponen-
growth, logistic growth, 11B, 12D occurs occurs F F IGURE IGURE Number of rabbits (millions) 1000 800 600 400 Population size 200 0 4.1 4.3 capacity carrying e
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Interactions inEcosystems
In Australia during 433 DO NOT EDIT--Changes must be made through “File info” CorrectionKey=A
Biology HMDScience.com Carrying Capacity GO ONLINE The environment determines how many individuals of the species can be What Limits Population supported based on natural cycles and species diversity. An environment, Growth? therefore, has a carrying capacity for each species living in it. The carrying capacity of an environment is the maximum number of individuals of a particular species that the environment can normally and consistently support. In nature, a carrying capacity can change when the environment changes. Consider a population of grasshoppers that feed on meadow grasses. If a fire burns part of the meadow, the insects’ food resources diminish, and the carrying capacity declines. But during years with plentiful rain, the meadow grasses flourish, and the carrying capacity rises. The actual size of the population usually is higher or lower than the carrying capacity. Populations will rise and fall as a result of natural changes in the supply of resources. In this way, the environment naturally controls the size of a population. Population Crash When the carrying capacity for a population suddenly drops, the population experiences a crash. A population crash is a dramatic decline in the size of a population over a short period of time. There are many reasons why a popu- lation might experience a crash.
DATA ANALYSIS 2G
Reading Combination Graphs Combination graphs show two sets of data on the Graph 1. Florida Fish Kills 1991–2001 same graph. One set of data may be shown as a 20 12.5 bar graph, while the other set may be shown as a Fish kill events line graph. The two data sets must share the same Rainfall (inches) 10.0 independent variable on the x-axis. Scientists can 15 then interpret the data to determine if a 7.5 relationship exists between the variables. 10 This combination graph displays data about fish kill 5.0
events, during which many fish died at once, and Fish kill events 5 (inches) Rainfall average monthly rainfall in Florida from 1991–2001. 2.5 • The y-axis on the left side represents the total number of fish kill events. 0.0 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec • The y-axis on the right side represents average Months monthly rainfall during that time. Source: The University of Florida Extension • The x-axis shows the month of data collection. Information Circular 107. Used by permission. The graph shows that in January there were four fish kill events and an average of 2.7 inches of rain.
1 . Analyze An increase in fish kills and a decrease in rainfall occurs in what months? 2. Analyze Describe the trend in the fish kill events throughout the year. Describe the trend in rainfall data throughout the year. 3. hypothesize What relationship might exist between fish kill events and rainfall?
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©Rolf O. Peterson E had n had the carrying capacity of the moose population? population? moose the of capacity carrying the Analyze Predict cological factors growth. population limit
shown in Michigan, changes in wolf and moose populations, limited by being caught for food. On Isle Royale in by the available prey, and the population of prey can be Competition include many of interactions. types species in agiven area. Density-dependent limiting factors factors that are by affected number the of individuals Predation up, limiting how large population the can grow. a population becomes denser, resources the are used one another for resources such and as food shelter. As tions rise and fall in a pattern, shown in crease in the wolf population. Over time, the two popula- not enough left to feed all the wolves. The result is a de- certain point, the wolves eat so many moose that there are population grows, so does the wolf population. But at a limiting factors—density dependent and density independent. Density-dependent limitingfactorsDensity-dependent Factors Limiting Density-Dependent size of apopulation the is called tion of organisms. The factor that has greatest the in keeping effect down the Many capacity factors of cancarrying the affect an environment for apopula- resources: harsh the winter and scarcity the of food. crash on St. Matthew Island came as result the of two factors that limited large herd. By spring the of 1964,only 50reindeer remained. The population snow fell on resources food that had already become greatly depleted by the tion had grown to 6000reindeer. However, over winter, the large amounts of herd to grow at an exponential rate. By the summer of 1963, the island popula- covered with arich mat of lichens. Plenty allowed of reindeer food the good of cause size of the population the to decrease. to spread.diseases The parasites can or then diseases crowded an area becomes, easier it the is for parasites or more quickly through dense populations. The more Parasitism MAI f the coastf the of Alaska. At of time the introduction, the entire the island was For example, in1944,29reindeer were introduced to St. Matthew Island ot made foraging so difficult? difficult? so foraging made ot N
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Wolf population 435 CorrectionKey=A DO NOT EDIT--Changes mustbemadethrough “File info” Unit 436 Figure 4.6 Figure cause dangerous flooding. ac 14.4 companying a hurricane can 3. 2. 1. Re
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M ai n I n d e as su density-independent limiting factor for the algae population? algae population? the for factor limiting density-independent Apply 11 f Natural biodiversity is an important of part ecosystem’s the functioning. hasspecies caused population crashes inmany of parts world the where profound on effect populations. For example, introduction the of nonnative Human Impact on Ecosystems, human influence as alimiting factor has had a threaten habitats and organisms the that live As inthem. in discuss we will clearing forests, wetlands, filling and polluting air,the land, and water, humans during trek their to nesting grounds Canada innorthern and inAlaska. By Urbanization area inthis is depleting resources the migratory birds these need Nebraska has threatened an important feeding ground for crane. sandhill the Human mangrove forests, and destroy nesting turtle beaches. sea large wave of atsunami can damage coral reefs, fragile down knock entire nlight that strikes the pond’s surface. Is sunlight a density-dependent or or adensity-dependent sunlight Is surface. pond’s the strikes that nlight igure 4.6 igure b
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filled environment? species isintroduced to aresource- for periodwhenanew ashort exponential growth to occur only dependent limitingf Synthesize Apply natural disaster? affected by orsome other aflood ivities t ical food chain, with smaller populations of fish and birds. have smaller populations. The effects are felt all the way up the turn, zooplankton, tiny organisms that feed on phytoplankton, marine ecosystem, from growing in their usual large numbers. In the coast can prevent phytoplankton, which form the base of the nutrient-rich cold water. The lack of nutrients in the water along poor warm water from being replaced, as it normally is, with the United States, a lack of southerly winds can prevent nutrient- regardless of its density. For example, along the western coast of Unusual density of population. the environment that limit apopulation’s growth regardless of the Density-independent limitingfactorsDensity-independent Factors Limiting Density-Independent ers
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(l) (r) ©2006 Frans Lanting/www.lanting.com F succession secondary pioneer species succession primary succession VOCABULARY stability change can impact ecosystem 12F describe how environmental populations andspeciesdiversity; ecological succession can change and processes that occur during factors; 11 communities respond to external how organisms, populations, and system (right). harsh landscape into afertile eco- primary succession turnthis will nothing butsolid rock. Over time, of Hawaii (left), leaves behind fl igure 5.1 ow, suchasthisoneontheisland 11Binvestigate andanalyze 14.5 D
describe ho The path ofalava 11B, 11 w events D Ecological Succession , 12F in an ecosystem. an in Succession occurs following adisturbance process that rebuilds damaged ecosystems. cluttered mess. Aclean room becoming cluttered isagradual process muchlike the may have wondered how aperfectly clean room could manage to become sucha Ifyou havethe start. ever spentaSaturday afternoon cleaning your bedroom, you Thenadiscarded sock. It beginswithadirty homework Butthisisonly assignment. Connect to Your World K in thespeciesthat mak ey
Succession regrow, space re-forms the itself through aprocess known as succession. After an ecosystem adevastating experiences catastrophe and to begins from bare rock to such diverse highly vegetation takesagreat of deal time. process the passed, of succession created unique tropical ecosystems. Succession began to break down into soil, which provided aplace for plants to grow. As time islands middleof inthe Pacific the Eventually, Ocean. bare the volcanic rock Over time, volcanicOver eruptions such as one the shown in community or create acommunity inapreviously uninhabited area. MAI MAI C
o The H Succession occurs following adisturbance inanecosystem. N n N ID ce IDEAS pt EA awaiian Islands began to form more than 70million years ago. is sequence the of biotic changes that regenerate adamaged
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food for thelichencommunity. photosynthesis and synthesize chlorophyll to conduct collect water, while thealgae use relationship inwhichthefungi Fungi andalgae form asymbiotic completely different species. A lichenisactually two S ymbiosis Apply of primarysuccession. can all begintheprocess landslides, andstripmines Melting glaciers, volcanic eruptions, FIGURE Unit 5:Ecol CO NN
EC What function might the mosses and lichens serve in primary succession? primary in serve lichens and mosses the might function What 5.2 ogy lichens, grass 0–15 years T
T O p rimary Succession
Moss, es thicket c 15–80 years ottonwoods, alder previously uninhabited area are called an area that was previously uninhabited. The first organisms that live ina FIGURE P One of ways best the to understand succession is to watch it progress. P into pieces. smaller The process of succession, primary which is illustrated in pioneer are species lichens and some mosses, which can break down solidrock • • • • •
rimary succession rimary Successionrimary
Shrubs, Shrubs, original trees,original direct sunlight which need to thrive. animals move into area. the trees These provide shade. material die. to they when soil the a habitat for animals, small break up rock the with roots, their and add flowers and hardy shrubs grow plants new These from seeds. these provide form layer athin of soil. rockthe further. When die, remains their they mix with rock the pieces to cracks and breaking rock the into pieces. smaller Wind, rain, to and break icebegin down of surface the rock, the forming Bar Diff As th Ove Lic 5.2, hen and moss spores are blown inby wind. As grow, they break they up e rock is exposed bye rock aretreating is exposed or glacier is created lava when cools. erent root take tree species shade inthe and eventually replace the r time, seeds arer time, seeds blown into area the or are dropped by birds. Small e soil continuese soil to grow thicker, trees root, small take and different follows basic this pattern: spruce tion to forest, alder, 80–115 years is establishment the and development of an ecosystem in
Transi - forest Hemlock-spruce 115–200 years pioneer species. succession astheglacier recedes. toopportunity witness primary Alaska hasgiven scientists an Glacier Bay National Park in Typical examples of
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FIGURE 5.3 Secondary Succession Following a flood or a fire, a community is given a chance for new life. Plants remaining after the disturbance reestablish the ecosystem.
Fire is important in helping 0–2 years Horse- 2–18 years Grass, 18–70 years Pine 70–100 years Oak- forests return nutrients to the weed, crabgrass, shrubs, pine forest and young hickory forest soil. Secondary succession uses asters seedlings hardwood seedlings these nutrients to grow.
Analyze Why does secondary succession take less time than primary succession?
Secondary Succession Succession does not always begin from bare rock. More often, a disturbance, such as a fire or hurricane, halts the progress of succession or destroys an established community. Secondary succession, which is illustrated in figure 5.3, is the reestablishment of a damaged ecosystem in an area where the soil was left intact. Plants and other organisms that remain start the process of regrowth. There is no end to secondary succession. Small disturbances, such as a tree falling, start the process again and again. The dynamic processes of succession are always changing the face of an ecosystem. Connect Where might succession occur in the ocean? (tr) ©Raymond Gehman/National Geographic Image Collection
Self-check Online HMDScience.com 14.5 Formative Assessment GO ONLINE Reviewing Main Ideas Critical thinking CONNECT TO 1. How is primary succession different 3. Infer Does the process of primary Biological Niche from secondary succession? succession take longer in tropical or 5. At what point during 2. Why are pioneer species so impor- arctic areas? Explain. primary succession does an tant for primary succession? 4. Predict During succession, what ecosystem provide the 11D might become the limiting factor for fewest habitats for sun-loving mosses as taller plants organisms? Explain your begin to grow? 11B reasoning. 11D, 12F
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CHAPTER 14 G N I D A E R
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Category: vocabulary words from thechapter. For each clueinthecategory group, listtheappropriate Category Clues R 14.2 14.1 vo Chapter 10. 11. 8. 6. 4. 2. 5. 9. 3. 1. 7. eviewing tegory:
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20. 22. 18. 16. 14. 12. 21. 15. 19. 13. 17. eviewing Review Games•ConceptMapSectionSelf-Checks online Go
with different reproductive strategies. Explain how thethr equivalents? How doescompetitiv popula If alarge numberofindividuals immigrated into a alr If you were to add two goldfish into afishtank that at The remora fishhasanadaptation that allows itto return thepopulation to itsoriginal size? the population ofthefishtank. density relationship isthis?Explain. over from theshark’s meal. What typeofsymbiotic What isthedeer’s habitat, andwhat isitsniche? have apredatory–prey relationship. A deerisalarg Why issucces affec Describe andgive examples oftwo limitingfactors that long andharsh winter? Why? a particul How mightthecarrying capacity ofanenvironment for crash? growth have ahighchance ofhaving apopulation Why doesapopulation tha and asquirr A brown bear isanomnivore. Explain how abrown bear tach to anditfeeds ashark, onscraps offood left eady contains three goldfish, explain what happensto t adense population. HMDScience.com Interact tion ofbison, what two things could happento ar specieschange inresponse to anunusually
14.5 el can beininterspecific competition and M 11B, 12D sion considered an ongoing process? e herbivore that usually lives inaforest. AIN
primary succ succession secondary succession pioneer species density-independent limiting density-independent limiting density-dependent i ve Review factor factor ee typesofsurvivorship curves align 12A
I e exclusion differ from ecological D EA Chapter 14: Interactions inEcosystems Chapter 14: t experiences exponential S ession 12D 12A 12D, 12F 12A 7D 11B
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Critical Thinking 23. Apply A bee gathers nectar from a flower by using a Analyzing Data Read a Combination Graph strawlike appendage called a proboscis. While on the Use the graph to answer the next three questions. flower, grains of pollen attach to the bee’s back. When the bee travels to another flower, the pollen fertilizes The combination graph below shows changes in the the new plant. What type of symbiosis is this? 12A sizes of bee and mite populations in one area of the Midwest. The mites live as parasites on the bees. 24. Predict A population of prairie dogs is experiencing high immigration and birthrates, but resources are Insect Population Size and Temperature beginning to deplete. What could eventually happen to 35 35 this population? Give two possibilities. 12D Temperature 30 Bees 30 25. Synthesize A species of beetle is in a period of expo- Mites nential growth, but a competing species has started 25 25 sharing the same space. Is the competing species an example of a density-dependent or a density-indepen- 20 20 dent limiting factor? Explain. 12A 15 15 26. Evaluate Imagine that scientists introduced a disease 10 10 into the rabbit population of Australia, and the rabbit Average temperature (°C) temperature Average 5 5
population crashed. Was the crash caused by a density- (thousands) Bees and mites dependent or density-independent limiting factor? 0 0 April May June July Aug Sept Oct Justify your answer. 11B, 12F Month 27. Describe How can the process of ecological succession change populations and affect species diversity within 31. Interpret A decrease in the number of bees occurs 11D an ecosystem? during which months? 28. Describe How can environmental change impact 32. Analyze Describe the trends in the bee and mite 12F ecosystem stability? populations from April through October. Analyzing a Diagram 33. Hypothesize What might explain the relationship Use the diagram below to answer the next two questions. between the bee and mite population numbers?
Making Connections 34. Write Ad Copy Imagine that you are an advertising agent trying to encourage a new species to move into an environment. Design an advertisement using the con- cepts from the chapter. Keep in mind that a population will not want to move to a new area without abundant resources. Choose a target species and make sure that your advertisement answers the following questions: What resources and environmental factors would make this species want to move? What abiotic and biotic factors does it need? Include several vocabulary terms from the chapter. 12A 35. Apply The two zebras on the chapter opener are 1 2 3 4 competing for the right to mate with females. Are they 29. Apply What part of the diagram depicts pioneer engaging in intraspecific or interspecific competition? species? Explain your answer. Explain your answer. 12A 30. Infer What could happen in the ecosystem shown that could make it revert to an earlier stage of succession? 12F
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Biology End-of-Course Exam Practice
Record your answers on a separate piece of paper. 11D MULTIPLE CHOICE 4 Over many years, a diverse hardwood tree population formed a dense forest ecosystem in a 11D region that was previously a meadow. As the 1 How do lichens and mosses make an ecosystem population of hardwood trees increased, the suitable for colonization by plant populations? species diversity of the grasses and other plants decreased. What event led to the decrease in A They serve as a food source to new plant diversity of the meadow plants as the populations populations that colonize an ecosystem. of hardwood trees increased? B They provide a suitable shelter for plant A As more trees began growing, animals ate all of populations. the grasses and small plants. C They break down rock to help form organically B Many species of low-growing plants died out rich soil that can support plant growth. as the hardwood trees prevented them from D They filter pollutants from air and water to getting enough sunlight, water, and soil make them suitable for use by plants. nutrients to sustain their growth.
11D C A change in the species diversity of the animal populations corresponded with a change in the 2 A lava flow from a volcanic eruption destroys a diversity of the tree population. forest and leaves behind a layer of rock. Before plants can begin to grow again, what event must D Decomposition improved soil fertility for tree occur as a part of primary succession? growth. A Large trees that provide shade must take root. 2G, 11B B Animals must return to the area. 5 C Lichens and mosses must be blown into the Fish Population in Birch Park Pond environment. 120 D Heavy rain must wash pollutants from the area. 100
12F 80 3 60 stable ecosystems 40 can be changed by 20 unusual habitat natural 0 weather alteration disasters 1 2 3 4 5 6 7 8 such as such as such as Years since introduction
?? urbanization hurricane A fish species is introduced to a park pond. Which statement best describes the population growth of these fish shown in the graph? Which of the following best completes the concept map shown above? A The population stopped growing because the fish stopped reproducing. A volcanic eruption B The population stopped growing because this B toxic spill species of fish lives less than one year. C earthquake C The population grew until disease caused the D extended drought population to level off. THINK THROUGH THE QUESTION D The population grew until it reached the pond’s carrying capacity. Keep in mind that unusual weather is a natural part of ecosystem function.
Chapter 14: Interactions in Ecosystems 443