Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Latitudinal gradients in species diversity wikipedia , lookup
Occupancy–abundance relationship wikipedia , lookup
Biodiversity action plan wikipedia , lookup
Habitat conservation wikipedia , lookup
Ecological fitting wikipedia , lookup
Introduced species wikipedia , lookup
Island restoration wikipedia , lookup
Storage effect wikipedia , lookup
CHAPTER 4 Populations and Communities © 2011 Pearson Education, Inc. An introduction to populations and communities • The golden frog is a national symbol of Panama • Its black and yellow coloration warns of its poisonous skin • Populations are at very low levels, due to • Habitat loss and overcollection for the pet trade • Along with an introduced chytrid fungus • To prevent extinction, conservationists collected all amphibians from the wild in Panama • Removing the last known population of golden frogs in the world © 2011 Pearson Education, Inc. Dynamics of natural populations • Population: a group of members of the same species living in an area • Community: populations of different species living together in an area • Populations grow with births and immigration • They decline with deaths and emigration (Births + Immigration) – (Deaths + Emigration) = Change in population number © 2011 Pearson Education, Inc. Population growth • Population growth: change in population • Equilibrium: births + immigration are equal to deaths + emigration • Often, population growth is not zero • Population growth rate: amount the population has changed divided by the time it had to change • Population growth curves: graph how populations grow; used to find • How fast a population could grow • How many individuals there are now • What the future population size could be © 2011 Pearson Education, Inc. Population growth curves • Constant population growth rate: adding a constant number of individuals over each time period • The simplest type of growth to model • Is an unlikely pattern and is not generally found in nature • But it’s a good comparison to other growth patterns • Starting with 2 individuals, and a constant growth rate of 2, at the end of 24 weeks you would have 50 individuals Population number at the start + (A constant * Time) = Population number at the end © 2011 Pearson Education, Inc. Three models of population growth © 2011 Pearson Education, Inc. Exponential growth • Each species can increase its population • With favorable conditions • Exponential increase: does not add a constant number of individuals for each time period • The doubling time remains constant • For example, it takes 2 days to go from 8 to 16 individuals, as well as from 1,000 to 2,000 individuals • Such growth is called an “explosion” • J-curve: the curve of exponential growth © 2011 Pearson Education, Inc. The equation for exponential growth • To calculate growth rate, you need to know • The number in the current population • The time period • The number of offspring individuals can produce in a given time if resources are unlimited (rmax or r) • r = the number of times you multiply e by itself • The potential to produce offspring • Starting population * A constant (e) * itself a certain number of times = Ending population © 2011 Pearson Education, Inc. Exponential growth of a population • For example: for two worms • r = 0.60, reproductive period = 1 week • Over 4 weeks: 2 * e0.60*4 = 22 worms • Over 24 weeks: 2 * e0.60*24 = over 3.5 million worms • Under unlimited conditions, organisms with a high r will have rapid population growth • Carrying capacity (K): the maximum population of a species that a given habitat can support without being degraded • This is the upper limit of population growth © 2011 Pearson Education, Inc. Outcomes of population increase • The population continues to grow and then dies off • Logistic growth: some process slows growth so it levels off near carrying capacity • Results in an S-shaped curve • It levels off at K • As the population approaches K, growth slows • The population remains steady and growth = 0 • The maximum rate of population growth occurs halfway to K © 2011 Pearson Education, Inc. Populations show logistic growth • J-shaped explosions are often followed by crashes • J-shaped growth results from unusual disturbances • Introduction of a foreign species, a suddenly changed habitat, the elimination of a predator, arrival in a new habitat • Other populations show an S-curve • Followed by cycles of lower and higher numbers around K • Or shoot above K, eventually cycling around K © 2011 Pearson Education, Inc. Real-life growth © 2011 Pearson Education, Inc. Biotic potential vs. environmental resistance • Biotic potential: the number of offspring (live births, eggs, or plant seeds and spores) produced under ideal situations • Measured by r (the rate at which organisms reproduce) • Varies tremendously from less than 1 birth/year (some mammals) to millions/year (plants, invertebrates) • Recruitment: survival through early growth stages to become part of the breeding population • Young must survive and reproduce to have any effect on population size © 2011 Pearson Education, Inc. Environmental resistance • Abiotic and biotic factors cause mortality (death) • Prevents unlimited population growth • Environmental resistance: the biotic and abiotic factors that may limit a population’s increase • Biotic: predators, parasites, competitors, lack of food • Abiotic: unusual temperatures, moisture, light, salinity, pH, lack of nutrients, fire • Environmental resistance can also lower reproduction • Loss of suitable habitat, pollution • Changed migratory habits of animals © 2011 Pearson Education, Inc. Biotic potential and environmental resistance © 2011 Pearson Education, Inc. Reproductive strategies: r-strategists • The interplay of environmental resistance and biotic potential drives the success of two reproductive strategies • r-strategists (r-selected species): produce lots of young, but leave their survival to nature • • • • • • Results in low recruitment Rapid reproduction, rapid movement, short life span Adapted to a rapidly changing environment “Boom-and-bust” populations “Weedy” or “opportunistic” species For example, housefly © 2011 Pearson Education, Inc. Reproductive strategies: K-strategists • K-strategists (K-selected species): lower biotic potential • Care for and protect young • Live in a stable environment already populated by the species • Larger, longer lived, well-adapted to normal environmental fluctuations • Their populations fluctuate around carrying capacity • Also called equilibrial species • For example, elephant, California condor © 2011 Pearson Education, Inc. Life histories • Life history: progression of changes in an organism’s life • Age at first reproduction, length of life, etc. • Visualized in a survivorship graph • Type I survivorship: low mortality in early life • Most live the bulk of their life span (e.g., humans) • Type III survivorship: many offspring that die young • Few live to the end of their life (oysters, dandelions) • Type II survivorship: intermediate survivorship pattern (squirrels, coral) • K-strategists have a Type I pattern; r-strategists show Type III © 2011 Pearson Education, Inc. Survivorship curves © 2011 Pearson Education, Inc. Predictable pattern in species • There is a predictable pattern to the way human activities affect species • r-strategists become pests when humans change an area • Houseflies, dandelions, cockroaches increase • K-strategists become rarer or extinct with change • Eagles, bears, and oaks decline • An exception: rare opportunistic species (r-selected) are separated from new habitat • They cannot succeed, despite high biotic potential © 2011 Pearson Education, Inc. Why does a population grow? • A population’s size depends on the interplay between its biotic potential and environmental resistance • A population’s biotic potential remains constant • Environmental resistance changes • Population balance is a dynamic balance • Additions (births, immigration) and subtractions (death, emigration) occur continually • The population may fluctuate widely or very little • A population is at equilibrium when populations restore their numbers and the ecosystem’s capacity is not exceeded © 2011 Pearson Education, Inc. Limits on populations • The carrying capacity may not explain what limits a population • Population density: number of individuals per unit area • The higher the density, the more likely a factor (e.g., crowding or disease) affects the population • Some factors (e.g., a tornado) keep a population from increasing, but have nothing to do with the density of the organisms © 2011 Pearson Education, Inc. Density dependence and independence • Density-dependent factor: increases with increased population density • Predation, disease, food shortage • Logistic growth occurs when populations become more crowded (approach carrying capacity) • Density-independent factor: one whose effects are independent of the density of the population • Spring freeze, fire • Is not involved in maintaining population equilibrium in the logistic growth © 2011 Pearson Education, Inc. Regulating a population • Only density-dependent factors can regulate a population (keep it in equilibrium) • Top-down regulation: control of a population (species) by predation • Bottom-up regulation: control of a population occurs as a result of scarcity of a resource (food) • Factors controlling a population determine the effects on an ecosystem of adding or removing a species • Removal of a species can affect species that don’t directly interact with it © 2011 Pearson Education, Inc. Top-down and bottom-up control © 2011 Pearson Education, Inc. Critical number • Critical number: the minimum population base allowing the survival and recovery of a population • A pack of wolves, flock of birds, school of fish • The group is necessary to provide protection and support • If a population falls below this number • Surviving members become more vulnerable • Breeding fails • Extinction is almost inevitable © 2011 Pearson Education, Inc. Humans are responsible for biodiversity loss • Human activities are responsible for the decline and extinction of species • Humans change habitats, introduce alien species, pollute, hunt, etc. • Human activities are not density dependent • They can even intensify as numbers decline • The Endangered Species Act calls for recovery of • Threatened species: populations are declining rapidly • Endangered species: populations are near the critical number © 2011 Pearson Education, Inc. Community interactions • Relationships between species may be positive (helpful), negative (harmful), or neutral for each species • Predation: one member benefits, the other is harmed (+−) • Includes parasitism, herbivory • Competition: both species are harmed (−−) • Interspecific competition: between different species • Intraspecific competition: between the same species • Mutualism: both species benefit (++) • Commensalism: One species benefits, the other is not affected (+0) © 2011 Pearson Education, Inc. Species interactions • The most important relationships • Predation, competition, mutualism, commensalism • Amensalism: one species is unaffected, the other is harmed (0−) • For example, an elephant stepping on a flower • It is theoretically possible to have a (00) relationship • It has no name © 2011 Pearson Education, Inc. Major types of interactions between species © 2011 Pearson Education, Inc. Predation • Predator: the organism that does the feeding • Prey: the organism that is fed upon • Predator-prey interaction: carnivores (meat eaters) eat herbivores (plant eaters) • Herbivores feed on plants • Parasites feed on hosts • Parasite: an organism (plant or animal) that feeds on its “prey,” usually without killing it • Host: the organism that is being fed upon © 2011 Pearson Education, Inc. Parasitic organisms • Include tapeworms, disease-causing bacteria, viruses, fungi • Parasites affect host populations in a densitydependent way • Increased population density makes it easier for parasites and their vectors (carriers of the parasite) to find new hosts • Pathogens: bacteria and viruses that cause disease • No real ecological difference from other parasites • Highly specialized parasites © 2011 Pearson Education, Inc. Several types of parasites © 2011 Pearson Education, Inc. Regulation of prey • Predators can regulate herbivore numbers (topdown control) • Moose crossed to Isle Royale, in Lake Superior • Several years later, wolves also reached the island • Without wolves, the moose population grew rapidly • Low environmental resistance for the moose • The wolf population also increased and preyed on moose • Low environmental resistance for the wolves • Fewer moose (high environmental resistance) resulted in fewer wolves (high environmental resistance) © 2011 Pearson Education, Inc. Predator-prey relationships © 2011 Pearson Education, Inc. Other factors affect populations • Wolf predation is not the only factor affecting moose • Deep snow limited access to food • A tick infestation caused significant mortality • A sharp decline in moose keeps wolf populations low • Not enough calves to catch • Wolves can’t catch a mature moose in good condition • Predator-prey relationships involve top-down (on the prey) and bottom-up (on the predator) regulation • Parasites weaken hosts, making them more vulnerable to predation © 2011 Pearson Education, Inc. Overgrazing • If herbivores eat plants faster than they can grow, plants are depleted and animals eventually suffer • Reindeer were brought to St. Matthew Island • • • • At first, they were healthy and well-nourished They ate up the lichens A few years later, they were malnourished With little food and harsh weather, almost the entire herd starved • No population can escape the ultimate limitations set by environmental resistance © 2011 Pearson Education, Inc. Plant-herbivore interactions © 2011 Pearson Education, Inc. Predator removal • Eliminating predators upsets plant-herbivore relationships • White-tailed deer in the U.S. were originally controlled by wolves, mountain lion, bears • But these were killed because they were thought to threaten livestock and humans • Deer populations can get so large they overgraze the area • Humans control numbers through hunting © 2011 Pearson Education, Inc. Keystone species • Removal of one species can create a cascade of effects • Impacting far more than just the other species they interact with • Sea stars eat mussels in rocky intertidal zones • Removing sea stars allows mussels to crowd out all other species, reducing diversity • Keystone species: play a crucial role in maintaining ecosystem biotic structure • Moderate other species that would take over • Allow other, less-competitive species to flourish © 2011 Pearson Education, Inc. Sea stars: a keystone species © 2011 Pearson Education, Inc. Keystone species © 2011 Pearson Education, Inc. Competition • Interactions where both species are harmed • They compete for a scarce resource • Species that compete have overlapping niches • Over time, there is pressure to reduce the overlap © 2011 Pearson Education, Inc. Competition • Intraspecific competition: competition between members of the same species • Occurs over resources • Territory: an area defended by an individual or group • Is vigorously defended • Most defense is intimidation—serious fights are rare • Organisms fight to protect an area for nesting, establishing a harem, or food resources • Lack of territories: a density-dependent limitation on a population © 2011 Pearson Education, Inc. Territoriality © 2011 Pearson Education, Inc. Competition © 2011 Pearson Education, Inc. Territoriality as an advantage • It protects a population from the possibility of everyone getting some resources, but nobody getting enough to survive • Without territoriality, when resources are scarce • Every encounter could end in a potentially lethal fight • All members would get only a part of what they need and could die • Competition lowers fitness and production of offspring • Territoriality lowers the direct effects of competition © 2011 Pearson Education, Inc. Not everyone gets a territory • Individuals unable to claim a territory • Are often young and may obtain a territory later • May disperse, opening new habitats to the species • May die • Territoriality is most likely in K-strategists • An adaptation that helps organisms disperse and stabilizes populations © 2011 Pearson Education, Inc. Impact on the species • Survival of the fittest: one of the forces in nature leading to evolutionary changes in a species • Those individuals in a competing group that can survive and reproduce demonstrate superior fitness to the environment • Every factor of environmental resistance is a selective pressure • Individuals who survive and reproduce have the genetic endowment to better cope with their environment © 2011 Pearson Education, Inc. Intraspecific competition’s impact • Short-term impact on a population: it leads to density-dependent regulation of a population • Through territoriality • Through self-thinning: crowded organisms (e.g., trees) become less numerous as they get bigger • Long-term impact on a population: it leads to longterm changes as the species adapts to its environment • Those better able to compete, survive, and reproduce • Their superior traits are passed on to successive generations © 2011 Pearson Education, Inc. Interspecific competition • Competitive exclusion principle: species cannot survive competition if they compete directly in many respects • In simple habitats with species needing the same resources • But species do occupy the same area without becoming extinct • Abiotic conditions in an environment vary in space and time • Adaptations of species to specific conditions allows it to thrive and overcome its competitors in one location or time, but not in another © 2011 Pearson Education, Inc. Environments are heterogeneous • Variable environments support species with different niches • Competitors in the same habitat have different niches • Woodpeckers eat insects; other birds eat seeds • Space can also be a resource • Resource partitioning: the division of a resource and specialization in different parts of it • With more intense competition, resources are even further divided © 2011 Pearson Education, Inc. Resource partitioning in warblers © 2011 Pearson Education, Inc. Adaptations limit competition • Adaptations, including behavior, limit competition • Organisms can put energy into reproduction • Competition changes some characteristics, so organisms use only a part of their niche • For example, two closely related finches on the same island have different sized beaks to eat different seeds • Character displacement: a physical change that decreases competition when two species co-occur © 2011 Pearson Education, Inc. Character displacement in finches © 2011 Pearson Education, Inc. Mutualism • An arrangement between two species where both benefit • Examples of mutualism • Pollinators (e.g., bees) receive nutrition while plants receive pollination • Fungi on roots: the fungus gets nutrition; the plant gets easier intake of soil nutrients • Lichens are made of a fungus and an alga • The anemone fish protects the anemone from predation by the butterfly fish, and the anemone protects the fish © 2011 Pearson Education, Inc. Mutualistic relationships © 2011 Pearson Education, Inc. Commensalism and amensalism • Commensalism: one species benefits; the other is unaffected • More rare • Buffalo stir up insects that cattle egrets eat • Orchids live on trees but do not harm or feed off of them • Amensalism: one species is harmed; the other is unaffected • Usually accomplished by natural chemical compounds • Black walnut trees produce a chemical that kills other plants • Symbiosis: two species live close to each other • Can be beneficial (mutualism) or harmful (parasitism) © 2011 Pearson Education, Inc. Commensalism © 2011 Pearson Education, Inc. Evolution as a force for change • Predation and competition keep populations under control • Individuals with qualities that lower impacts of negative interactions survive • Predators and prey become adapted to each other • Intraspecific competition leads to improved adaptations to the environment • Interspecific competition promotes adaptations in competitors • They specialize in exploiting a resource • Resource partitioning allows resource sharing © 2011 Pearson Education, Inc. Resource partitioning in plants © 2011 Pearson Education, Inc. Selective pressures • Most young plants and animals do not survive • Selective pressures: environmental resistance factors affect which individuals survive and reproduce • Predators, parasites, drought, lack of food • Animals with traits that protect them or allow them to escape can survive and reproduce • Predators function as a selective pressure: favoring survival of traits that enable prey to escape predation • Food is a selective pressure: predators with keen eyesight or swift speed survive © 2011 Pearson Education, Inc. Cryptic coloration © 2011 Pearson Education, Inc. Natural selection and evolution • Natural selection: the process of specific traits favoring survival of certain individuals • Charles Darwin’s On the Origin of Species by Means of Natural Selection (1859) • Biological evolution: modification of the gene pool of a species by natural selection over generations • Our understanding of DNA, mutations, and genetics supports the theory of evolution by natural selection © 2011 Pearson Education, Inc. Adaptations to the environment • Fitness: features (traits) that adapt an organism for survival and reproduction • A population’s gene pool is tested by selective pressures exerted by environmental resistance • All traits adapt an organism to survival and reproduction • Adaptations needed for coping with abiotic factors • Obtaining nutrients, energy, defense against predation • Finding and attracting mates • Migrating and dispersal © 2011 Pearson Education, Inc. Adaptation for survival and reproduction © 2011 Pearson Education, Inc. The limits of change • Does the trait increase survival and reproduction? • If “yes,” the trait is maintained through natural selection • Various organisms have evolved different traits • To accomplish the same function (e.g., avoid predation) • A species has three alternatives when faced with a new selective pressure • Adaptation: through natural selection • Migration: move to an area with suitable conditions • Extinction: inevitable if the first two options are not possible © 2011 Pearson Education, Inc. Factors that determine whether a species can adapt • Some individuals have traits (alleles: variations or new combinations of genes) that allow them to survive and reproduce under the new conditions • There must be enough survivors to maintain a viable breeding population • Natural selection should lead to increased adaptations over successive generations © 2011 Pearson Education, Inc. The California condor • By the early 1980s, only 20 birds remained • Only nine lived in the wild • Deaths due to poaching, lead poisoning, habitat destruction • Wildlife biologists captured all wild-living birds and started a captive breeding program • By 2008, 320 condors survived • 180 in captivity • This is still not a viable breeding population, but wild condors are forming pairs and nesting © 2011 Pearson Education, Inc. Keys to survival • Four variables affect whether a population survives new conditions • • • • Geographical distribution Specialization to a given habitat or food supply Genetic variation within the population The reproductive rate relative to the rate of environmental change • Less vulnerable species are r-strategists • More vulnerable species are K-strategists • Very rapidly reproducing species can be vulnerable if the environment changes too rapidly or much © 2011 Pearson Education, Inc. Vulnerable and highly adaptive species © 2011 Pearson Education, Inc. Genetic change • How fast can a population evolve adaptations to cope with new or changing conditions? • Over the lifetime of the individual: there is no genetic change and no genetic adaptation • Genetic variation occurs over generations through hybridization, mutation, and crossover (sections of chromosomes are swapped) • Genetic variation is the norm in living things © 2011 Pearson Education, Inc. The evolution of species • Biodiversity is decreasing because species are going extinct faster than new species are appearing • Mutations and natural selection adapt a species to the biotic community and environment in which it exists • The process of speciation: the final result of adaptation may be a population so different from the original population it is considered a new species © 2011 Pearson Education, Inc. How two species may develop from one • They must be reproductively isolated: the original populations separate into nonbreeding populations • Or else genes will continue to mix, keeping it one species • Separate populations must be exposed to different selective pressures • As they respond to these pressures, they become different • They can’t interbreed, even if they come together again • Arctic and gray foxes became separated by glaciation • Selective pressure on the northern population resulted in heavier fur, shorter limbs, and white fur © 2011 Pearson Education, Inc. Evolution of new species © 2011 Pearson Education, Inc. Darwin’s finches • Charles Darwin speculated that differences in beak size and structure in finches on islands in the Galápagos happened after subpopulations became isolated on separate islands • Birds blown west from South America landed on islands • Intraspecific competition caused birds to disperse • Different selective pressures caused birds to become specialized for feeding on different things • When populations re-encountered each other, they were so different, they could not interbreed © 2011 Pearson Education, Inc. Some of Darwin’s finches © 2011 Pearson Education, Inc. New species are arising right now • Saltmarsh cordgrass developed as a hybrid of two species that interbred in England’s mud flats • It has a different niche and characteristics from the parents • New species are not formed from scratch • They are formed only by modification of existing species • Selective pressures, isolation, and hybridization result in new adaptations • Closely related species are found in nature • Overwhelming evidence tells us that species developed through evolution over long periods of time © 2011 Pearson Education, Inc. Drifting continents • Geographic isolation of populations is fundamental to speciation • Populations became isolated through the slow movement of Earth’s continents • Plate tectonics: continents were once connected into a great land mass (Pangaea), which then separated • Tectonic plates: in the Earth’s crust, huge slabs of rock that float on an elastic layer beneath them © 2011 Pearson Education, Inc. Drifting continents and plate tectonics © 2011 Pearson Education, Inc. Movement of tectonic plates • Tectonic plates ride atop convection currents caused by rising hot interior material and sinking cooler material • Adjacent tectonic plates move • Separating (in mid-ocean ridges) • Sliding past each other (at fault lines) • Colliding (creating mountain ranges) • The 2004 tsunami (tidal wave) in Indonesia • The Indo-Australian plate slid under the Eurasian plate • Displaced enormous quantities of water and caused waves that killed 225,000 people © 2011 Pearson Education, Inc. Tectonic movement affects climate and diversity • As continents move, their climate changes accordingly • Continental movement changes the direction and flow of ocean currents, which affects climate • Uplifting of mountains changes movements of air currents • Changes in Earth’s crust have increased diversity • Moving continents isolated populations into six zoogeographic regions • Australia is on the Indo-Australian tectonic plate • Its ancient separation led to many unique species © 2011 Pearson Education, Inc. Unique species occur where tectonic plates meet • Indonesia is located on the junction of three tectonic plates • It has species that occur nowhere else in the world • Papua New Guinea has species similar to Australia’s • The island of Sulawesi lies between plates and was formed by islands being pushed together • Its plants and animals have relatives in far distant parts of the world • Australia and Indonesia show how long-term, largescale changes change the environment and increase biodiversity © 2011 Pearson Education, Inc. Implications for human management • Ecologists study populations and communities • To increase our understanding of the world • To better manage natural resources by protecting declining species and controlling pest species • To study our impacts on populations • Keystone species are such an integral part of the ecosystem • Removing them can cause the ecosystem to collapse • For example, removing beavers (by overhunting and habitat destruction) hurt wetland meadow species © 2011 Pearson Education, Inc. Introduced species • Humans have introduced species from foreign ecosystems, changing community and population relationships • Thousands of species have been accidentally or deliberately introduced • Economic losses in the U.S. of $138 billion/year • Rabbits were introduced into Australia for sport shooting • Without natural enemies, the population exploded, devastating the environment • After being eradicated on Philip Island, the island’s vegetation was dramatically restored © 2011 Pearson Education, Inc. Rabbit eradication on Philip Island © 2011 Pearson Education, Inc. Plants • Introduced plants can have a devastating effect on plants and animals • The chestnut blight fungus has killed almost every American chestnut tree • Kudzu, a vine introduced to control erosion and for cattle fodder, has invaded and climbed over forests • Spotted knapweed has ruined millions of acres of rangelands • Purple loosestrife has invaded wetlands and replaced edible wildlife plants © 2011 Pearson Education, Inc. Introduced plant species © 2011 Pearson Education, Inc. Pests • Most insect pests in croplands and forests are introduced • Japanese beetles, fire ants, gypsy moths • Goats and pigs on islands • Domestic cats diminish songbird populations • The problem is increasing due to expanding world trade and travel • Zebra and quagga mussels, introduced into the Great Lakes, are now found in California • Jellyfishlike ctenophores cost Black Sea fishermen $250 million © 2011 Pearson Education, Inc. Introduced species © 2011 Pearson Education, Inc. Two lessons from introducing undesirable species • Population regulation is a matter of complex interactions among members of the biotic community • Relationships are specific to organisms in each ecosystem • An introduced species is unlikely to fit into the framework of relationships in the new community • Severe environmental resistance may kill off the species • The species may join the native species and do no harm (it has become naturalized: food crops) • The species may become invasive: outcompeting native species for food, space, predation, other resources © 2011 Pearson Education, Inc. Remedies • U.S. state and federal agencies work to slow and stop invasive species • Regulations and checkpoints • Introduction of a natural enemy • Control is due to many factors, including several enemies and all abiotic factors • Species have adapted to other species in their own ecosystems • They are not prepared to interact with other species that developed in other ecosystems © 2011 Pearson Education, Inc. CHAPTER 4 Populations and Communities Active Lecture Questions © 2011 Pearson Education, Inc. Review Question-1 (Births plus ________) minus (________ plus Emigration) = Change in population number a. Emigration; Births b. Immigration; Deaths c. Immigration; Births d. Emigration; Deaths © 2011 Pearson Education, Inc. Review Question-1 Answer (Births plus ________) minus (________ plus Emigration) = Change in population number a. Emigration; Births b. Immigration; Deaths c. Immigration; Births d. Emigration; Deaths © 2011 Pearson Education, Inc. Review Question-2 True or False: Natural selection results in a modification of the gene pool toward traits that enhance survival and reproduction of a population. a. True b. False © 2011 Pearson Education, Inc. Review Question-2 Answer True or False: Natural selection results in a modification of the gene pool toward traits that enhance survival and reproduction of a population. a. True b. False © 2011 Pearson Education, Inc. Review Question-3 The rate at which members of a species reproduce if there are no limiting factors is referred to as a. K-strategy. b. r-strategy. c. environmental resistance. d. biotic potential. © 2011 Pearson Education, Inc. Review Question-3 Answer The rate at which members of a species reproduce if there are no limiting factors is referred to as a. K-strategy. b. r-strategy. c. environmental resistance. d. biotic potential. © 2011 Pearson Education, Inc. Review Question-4 A species that has a critical role in maintaining an ecosystem’s biotic structure is a a. J-curve species. b. K-strategist. c. keystone species. d. biotic potential. © 2011 Pearson Education, Inc. Review Question-4 Answer A species that has a critical role in maintaining an ecosystem’s biotic structure is a a. J-curve species. b. K-strategist. c. keystone species. d. biotic potential. © 2011 Pearson Education, Inc. Review Question-5 The theory that has helped us understand earthquakes, volcanic activity, and the geographic distribution of present-day biota is a. the law of limiting factors. b. the Laws of Thermodynamics. c. the theory of evolution. d. plate tectonics. © 2011 Pearson Education, Inc. Review Question-5 Answer The theory that has helped us understand earthquakes, volcanic activity, and the geographic distribution of present-day biota is a. the law of limiting factors. b. the Laws of Thermodynamics. c. the theory of evolution. d. plate tectonics. © 2011 Pearson Education, Inc. Interpreting Graphs and Data-1 According to Fig. 4-2, the population growth curve that represents logistic growth is a. the J-curve. b. the S-curve. © 2011 Pearson Education, Inc. Interpreting Graphs and Data-1 Answer According to Fig. 4-2, the population growth curve that represents logistic growth is a. the J-curve. b. the S-curve. © 2011 Pearson Education, Inc. Interpreting Graphs and Data-2 According to Fig. 4-8, the approximate date that this population reached its greatest level of environmental resistance was a. 1944. b. 1955. c. 1963. d. 1991. © 2011 Pearson Education, Inc. Interpreting Graphs and Data-2 Answer According to Fig. 4-8, the approximate date that this population reached its greatest level of environmental resistance was a. 1944. b. 1955. c. 1963. d. 1991. © 2011 Pearson Education, Inc. Thinking Environmentally-1 A K-strategist’s population size typically fluctuates around a. the midpoint of the J-curve. b. carrying capacity. c. density-dependent factors. d. density-independent factors. © 2011 Pearson Education, Inc. Thinking Environmentally-1 Answer A K-strategist’s population size typically fluctuates around a. the midpoint of the J-curve. b. carrying capacity. c. density-dependent factors. d. density-independent factors. © 2011 Pearson Education, Inc. Thinking Environmentally-2 A sudden hard freeze that kills members of an ecosystem is an example of a. a critical number. b. a density-dependent factor. c. a density-independent factor. d. density-driven resistance. © 2011 Pearson Education, Inc. Thinking Environmentally-2 Answer A sudden hard freeze that kills members of an ecosystem is an example of a. a critical number. b. a density-dependent factor. c. a density-independent factor. d. density-driven resistance. © 2011 Pearson Education, Inc.