Presentation on theme: "Chapter 8 Population Ecology. Chapter Overview Questions What are the major characteristics of populations? How do populations respond to changes."— Presentation transcript:
Chapter Overview Questions What are the major characteristics of populations? How do populations respond to changes in environmental conditions? How do species differ in their reproductive patterns?
They were over- hunted to the brink of extinction by the early 1900’s and are now making a comeback. Core Case Study: Southern Sea Otters: Are They Back from the Brink of Extinction? Figure 8-1
Core Case Study: Southern Sea Otters: Are They Back from the Brink of Extinction? Sea otters are an important keystone species for sea urchins and other kelp- eating organisms. Figure 8-1
POPULATION DYNAMICS AND CARRYING CAPACITY Most populations live in clumps although other patterns occur based on resource distribution. Figure 8-2
Changes in Population Size: Entrances and Exits Populations increase through births and immigration Populations decrease through deaths and emigration
Age Structure: Young Populations Can Grow Fast How fast a population grows or declines depends on its age structure. Prereproductive age: not mature enough to reproduce. Prereproductive age: not mature enough to reproduce. Reproductive age: those capable of reproduction. Reproductive age: those capable of reproduction. Postreproductive age: those too old to reproduce. Postreproductive age: those too old to reproduce.
Limits on Population Growth: Biotic Potential vs. Environmental Resistance No population can increase its size indefinitely. The intrinsic rate of increase (r) is the rate at which a population would grow if it had unlimited resources. The intrinsic rate of increase (r) is the rate at which a population would grow if it had unlimited resources. Carrying capacity (K): the maximum population of a given species that a particular habitat can sustain indefinitely without degrading the habitat. Carrying capacity (K): the maximum population of a given species that a particular habitat can sustain indefinitely without degrading the habitat.
Exponential and Logistic Population Growth: J-Curves and S-Curves Populations grow rapidly with ample resources, but as resources become limited, its growth rate slows and levels off. Figure 8-4
Fig. 8-3, p. 163 Environmental Resistance Time (t) Population size (N) Carrying capacity (K) Exponential Growth Biotic Potential
Exponential and Logistic Population Growth: J-Curves and S-Curves As a population levels off, it often fluctuates slightly above and below the carrying capacity. Figure 8-4
Fig. 8-4, p. 164 Carrying capacity Year Number of sheep (millions) Overshoot
Exceeding Carrying Capacity: Move, Switch Habits, or Decline in Size Members of populations which exceed their resources will die unless they adapt or move to an area with more resources. Figure 8-6
Fig. 8-6, p. 165 Number of reindeer Population overshoots carrying capacity Carrying capacity Year Population Crashes
Exceeding Carrying Capacity: Move, Switch Habits, or Decline in Size Over time species may increase their carrying capacity by developing adaptations. Some species maintain their carrying capacity by migrating to other areas. So far, technological, social, and other cultural changes have extended the earth’s carrying capacity for humans.
Population Density and Population Change: Effects of Crowding Population density: the number of individuals in a population found in a particular area or volume. A population’s density can affect how rapidly it can grow or decline. A population’s density can affect how rapidly it can grow or decline. e.g. biotic factors like diseasee.g. biotic factors like disease Some population control factors are not affected by population density. Some population control factors are not affected by population density. e.g. abiotic factors like weathere.g. abiotic factors like weather
Types of Population Change Curves in Nature Population sizes may stay the same, increase, decrease, vary in regular cycles, or change erratically. Stable: fluctuates slightly above and below carrying capacity. Stable: fluctuates slightly above and below carrying capacity. Irruptive: populations explode and then crash to a more stable level. Irruptive: populations explode and then crash to a more stable level. Cyclic: populations fluctuate and regular cyclic or boom-and-bust cycles. Cyclic: populations fluctuate and regular cyclic or boom-and-bust cycles. Irregular: erratic changes possibly due to chaos or drastic change. Irregular: erratic changes possibly due to chaos or drastic change.
Types of Population Change Curves in Nature Population sizes often vary in regular cycles when the predator and prey populations are controlled by the scarcity of resources. Figure 8-7
Fig. 8-7, p. 166 Population size (thousands) Year Lynx Hare
Animation: Capture-Recapture Method PLAY ANIMATION
Case Study: Exploding White-Tailed Deer Populations in the United States Since the 1930s the white-tailed deer population has exploded in the United States. Nearly extinct prior to their protection in 1920’s. Nearly extinct prior to their protection in 1920’s. Today 25-30 million white-tailed deer in U.S. pose human interaction problems. Deer-vehicle collisions (1.5 million per year). Deer-vehicle collisions (1.5 million per year). Transmit disease (Lyme disease in deer ticks). Transmit disease (Lyme disease in deer ticks).
REPRODUCTIVE PATTERNS Some species reproduce without having sex (asexual). Offspring are exact genetic copies (clones). Offspring are exact genetic copies (clones). Others reproduce by having sex (sexual). Genetic material is mixture of two individuals. Genetic material is mixture of two individuals. Disadvantages: males do not give birth, increase chance of genetic errors and defects, courtship and mating rituals can be costly. Disadvantages: males do not give birth, increase chance of genetic errors and defects, courtship and mating rituals can be costly. Major advantages: genetic diversity, offspring protection. Major advantages: genetic diversity, offspring protection.
Sexual Reproduction: Courtship Courtship rituals consume time and energy, can transmit disease, and can inflict injury on males of some species as they compete for sexual partners. Figure 8-8
Reproductive Patterns: Opportunists and Competitors Large number of smaller offspring with little parental care (r- selected species). Fewer, larger offspring with higher invested parental care (K-selected species). Figure 8-9
Fig. 8-9, p. 168 r species; experience r selection Time Number of individuals K Carrying capacity K species; experience K selection
Reproductive Patterns r-selected species tend to be opportunists while K-selected species tend to be competitors. Figure 8-10
Fig. 8-10a, p. 168 Many small offspring Little or no parental care and protection of offspring Early reproductive age Most offspring die before reaching reproductive age Small adults Adapted to unstable climate and environmental conditions High population growth rate (r) Population size fluctuates wildly above and below carrying capacity (K) Generalist niche Low ability to compete Early successional species r-Selected Species Cockroach Dandelion
Fig. 8-10b, p. 168 Fewer, larger offspring High parental care and protection of offspring Later reproductive age Most offspring survive to reproductive age Larger adults Adapted to stable climate and environmental conditions Lower population growth rate (r) Population size fairly stable and usually close to carrying capacity (K) Specialist niche High ability to compete Late successional species K-Selected Species SaguaroElephant
Survivorship Curves: Short to Long Lives The way to represent the age structure of a population is with a survivorship curve. Late loss population live to an old age. Late loss population live to an old age. Constant loss population die at all ages. Constant loss population die at all ages. Most members of early loss population, die at young ages. Most members of early loss population, die at young ages.
Survivorship Curves: Short to Long Lives The populations of different species vary in how long individual members typically live. Figure 8-11
Fig. 8-11, p. 169 Percentage surviving (log scale) Age Early loss Late loss Constant loss
Animation: Life History Patterns PLAY ANIMATION
Chapter 11 Sustaining Biodiversity: The Species Approach
Chapter Overview Questions How do biologists estimate extinction rates, and how do human activities affect these rates? Why should we care about protecting wild species? Which human activities endanger wildlife? How can we help prevent premature extinction of species? What is reconciliation ecology, and how can it help prevent premature extinction of species?
Core Case Study: The Passenger Pigeon - Gone Forever Once the most numerous bird on earth. In 1858, Passenger Pigeon hunting became a big business. By 1900 they became extinct from over- harvest and habitat loss. Figure 11-1
Animation: Humans Affect Biodiversity PLAY ANIMATION
SPECIES EXTINCTION Species can become extinct: Locally: A species is no longer found in an area it once inhabited but is still found elsewhere in the world. Locally: A species is no longer found in an area it once inhabited but is still found elsewhere in the world. Ecologically: Occurs when so few members of a species are left they no longer play its ecological role. Ecologically: Occurs when so few members of a species are left they no longer play its ecological role. Globally (biologically): Species is no longer found on the earth. Globally (biologically): Species is no longer found on the earth.
Global Extinction Some animals have become prematurely extinct because of human activities. Figure 11-2
Endangered and Threatened Species: Ecological Smoke Alarms Endangered species: so few individual survivors that it could soon become extinct. Threatened species: still abundant in its natural range but is likely to become endangered in the near future. Figure 11-3
Some species have characteristics that make them vulnerable to ecological and biological extinction. SPECIES EXTINCTION Figure 11-4
Fig. 11-4, p. 225 Low reproductive rate (K-strategist) Specialized niche Narrow distribution Feeds at high trophic level Fixed migratory patterns Rare Commercially valuable Large territories Characteristic Blue whale, giant panda, rhinoceros Blue whale, giant panda, Everglades kite Many island species, elephant seal, desert pupfish Bengal tiger, bald eagle, grizzly bear Blue whale, whooping crane, sea turtles Many island species, African violet, some orchids Snow leopard, tiger, elephant, rhinoceros, rare plants and birds California condor, grizzly bear, Florida panther Examples
SPECIES EXTINCTION Scientists use measurements and models to estimate extinction rates. The International Union for the Conservation of Nature and Natural Resources (IUCN) publishes an annual Red List, listing the world’s threatened species. The International Union for the Conservation of Nature and Natural Resources (IUCN) publishes an annual Red List, listing the world’s threatened species. The 2004 Red List contains 15,589 species at risk for extinction. The 2004 Red List contains 15,589 species at risk for extinction. Figure 11-5
Video: Penguin Rescue From ABC News, Biology in the Headlines, 2005 DVD. PLAY VIDEO
SPECIES EXTINCTION Percentage of various species types threatened with premature extinction from human activities. Figure 11-5
Fig. 11-5, p. 225 12% Birds Plants Reptiles Mammals Fish 34% (51% of freshwater species) 25% 20% 14%
SPECIES EXTINCTION Scientists use models to estimate the risk of particular species becoming extinct or endangered. Figure 11-6
Fig. 11-6, p. 226 5 million Number of years until one million species are extinct 100,000 extinct per year 50,000 extinct per year 14,000 extinct per year Number of species existing Effects of a 0.1% extinction rate 5,000 extinct per year 100 million 50 million 14 million
IMPORTANCE OF WILD SPECIES We should not cause the premature extinction of species because of the economic and ecological services they provide. Some believe that each wild species has an inherent right to exist. Some people distinguish between the survival rights among various types of species (plants vs. animals). Some people distinguish between the survival rights among various types of species (plants vs. animals).
HABITAT LOSS, DEGRADATION, AND FRAGMENTATION Conservation biologists summarize the most important causes of premature extinction as “HIPPO”: Habitat destruction, degradation, and fragmentation Habitat destruction, degradation, and fragmentation Invasive species Invasive species Population growth Population growth Pollution Pollution Overharvest Overharvest
Animation: Habitat Loss and Fragmentation PLAY ANIMATION
HABITAT LOSS, DEGRADATION, AND FRAGMENTATION The greatest threat to a species is the loss, degradation, and fragmentation of where it lives. Figure 11-7
Fig. 11-7, p. 229 Introducing nonnative species Basic Causes Secondary Causes Population growth Rising resource use No environmental accounting Poverty Predator and pest control Climate change Overfishing Pollution Commercial hunting and poaching Sale of exotic pets and decorative plants Habitat loss Habitat degradation and fragmentation
HABITAT LOSS, DEGRADATION, AND FRAGMENTATION Reduction in ranges of four wildlife species, mostly due to habitat loss and overharvest. Figure 11-8
Fig. 11-8a, p. 230 Range 100 years ago Indian Tiger Range today (about 2,300 left)
Fig. 11-8b, p. 230 Range in 1700 Black Rhino Range today (about 3,600 left)
Fig. 11-8c, p. 230 Probable range 1600 African Elephant Range today
Fig. 11-8d, p. 230 Range today (34,000–54,000 left) Asian or Indian Elephant Former range
Video: Bachelor Pad at the Zoo From ABC News, Biology in the Headlines, 2005 DVD. PLAY VIDEO
Case Study: A Disturbing Message from the Birds Human activities are causing serious declines in the populations of many bird species. Figure 11-9
Case Study: A Disturbing Message from the Birds The majority of the world’s bird species are found in South America. Threatened with habitat loss and invasive species. Threatened with habitat loss and invasive species. Figure 11-10
Fig. 11-9, p. 231 1 609 Number of bird species 400 200
INVASIVE SPECIES Many nonnative species provide us with food, medicine, and other benefits but a a few can wipe out native species, disrupt ecosystems, and cause large economic losses. Kudzu vine was introduced in the southeastern U.S. to control erosion. It has taken over native species habitats. Figure 11-A
INVASIVE SPECIES Many invasive species have been introduced intentionally. Figure 11-11
Fig. 11-11a, p. 234 Deliberately Introduced Species Purple loosestrife European starling African honeybee (“Killer bee”) Nutria Salt cedar (Tamarisk) European wild boar (Feral pig) Marine toad (Giant toad) Water hyacinth Japanese beetle Hydrilla
INVASIVE SPECIES Many invasive species have been introduced unintentionally. Figure 11-11
Fig. 11-11b, p. 234 Gypsy moth larvae Accidentally Introduced Species Sea lamprey (attached to lake trout) Argentina fire ant Brown tree snake Eurasian ruffe Common pigeon (Rock dove) Formosan termite Zebra mussel Asian long- horned beetle Asian tiger mosquito
INVASIVE SPECIES The Argentina fire ant was introduced to Mobile, Alabama in 1932 from South America. Most probably from ships. Most probably from ships. No natural predators. No natural predators. Figure 11-12
INVASIVE SPECIES Prevention is the best way to reduce threats from invasive species, because once they arrive it is almost impossible to slow their spread. Figure 11-13
Fig. 11-14, p. 236 Do not allow wild animals to escape. Do not spread wild plants to other areas. Do not dump the contents of an aquarium into waterways, wetlands, or storm drains. When camping use wood near your campsite instead of bringing firewood from somewhere else. Do not dump unused bait into the water. After dogs visit woods or the water brush them before taking them home. After each use clean your vehicle, mountain bike, surfboard, kayaks, canoes, boats, tent, hiking boots, and other gear before heading for home. Empty all water from canoes, kayaks, dive gear, and other outdoor equipment before heading home. Plant a variety of trees, shrubs, and other plants in your yard to reduce losses from invasive species. Do not buy plants from overseas or swap them with others using the Internet. What Can You Do? Invasive Species
Fig. 11-13, p. 236 Climate similar to habitat of invader Absence of predators on invading species Early successional systems Low diversity of native species Absence of fire Disturbed by human activities Characteristics of Successful Invader Species High reproductive rate, short generation time (r-selected species) Pioneer species Long lived High dispersal rate Release growth-inhibiting chemicals into soil Generalists High genetic variability Characteristics of Ecosystems Vulnerable to Invader Species
POPULATION GROWTH, POLLUTION, AND CLIMATE CHANGE Population growth, affluenza, and pollution have promoted the premature extinction of some species. Projected climate change threatens a number of species with premature extinction.
Pollution Each year pesticides: Kill about 1/5 th of the U.S. honeybee colonies. Kill about 1/5 th of the U.S. honeybee colonies. 67 million birds. 67 million birds. 6 -14 million fish. 6 -14 million fish. Threaten 1/5 th of the U.S.’s endangered and threatened species. Threaten 1/5 th of the U.S.’s endangered and threatened species. Example of biomagnification of DDT in an aquatic food chain. Figure 11-15
Fig. 11-15, p. 237 DDT in water 0.000003 ppm, or 3 ppt DDT in fish-eating birds (ospreys) 25 ppm DDT in large fish (needle fish) 2 ppm DDT in small fish (minnows) 0.5 ppm DDT in zooplankton 0.04 ppm
OVEREXPLOITATION Some protected species are killed for their valuable parts or are sold live to collectors. Killing predators and pests that bother us or cause economic losses threatens some species with premature extinction. Legal and illegal trade in wildlife species used as pets or for decorative purposes threatens some species with extinction.
PROTECTING WILD SPECIES: LEGAL AND ECONOMIC APPROACHES International treaties have helped reduce the international trade of endangered and threatened species, but enforcement is difficult. One of the most powerful is the 1975 Convention on International Trade of Endangered Species (CITES). One of the most powerful is the 1975 Convention on International Trade of Endangered Species (CITES). Signed by 169 countries, lists 900 species that cannot be commercially traded.Signed by 169 countries, lists 900 species that cannot be commercially traded.
Case Study: The U.S. Endangered Species Act One of the world’s most far-reaching and controversial environmental laws is the 1973 U.S. Endangered Species Act (ESA). ESA forbids federal agencies (besides defense department) to carry out / fund projects that would jeopardize an endangered species. ESA forbids federal agencies (besides defense department) to carry out / fund projects that would jeopardize an endangered species. ESA makes it illegal for Americans to engage in commerce associated with or hunt / kill / collect endangered or threatened species. ESA makes it illegal for Americans to engage in commerce associated with or hunt / kill / collect endangered or threatened species.
Case Study: The U.S. Endangered Species Act Biodiversity hotspots in relation to the largest concentrations of rare and potentially endangered species in the U.S. Figure 11-18
Fig. 11-18, p. 241 Top Six Hot Spots 1 Hawaii 2 San Francisco Bay area 3 Southern Appalachians 4 Death Valley 5 Southern California 6 Florida Panhandle Concentration of rare species High Low Moderate
Endangered Species Because of scarcity of inspectors, probably no more than 1/10 th of the illegal wildlife trade in the U.S. is discovered. Figure 11-19
Endangered Species Congress has amended the ESA to help landowners protect species on their land. Some believe that the ESA should be weakened or repealed while others believe it should be strengthened and modified to focus on protecting ecosystems. Many scientists believe that we should focus on protecting and sustaining biodiversity and ecosystem function as the best way to protect species.
PROTECTING WILD SPECIES: THE SANCTUARY APPROACH The U.S. has set aside 544 federal refuges for wildlife, but many refuges are suffering from environmental degradation. Pelican Island was the nation’s first wildlife refuge. Figure 11-20
PROTECTING WILD SPECIES: THE SANCTUARY APPROACH Gene banks, botanical gardens and using farms to raise threatened species can help prevent extinction, but these options lack funding and storage space. Zoos and aquariums can help protect endangered animal species by preserving some individuals with the long-term goal of reintroduction, but suffer from lack of space and money.
Video: Hsing Hsing Dies From ABC News, Biology in the Headlines, 2005 DVD. PLAY VIDEO
RECONCILIATION ECOLOGY Reconciliation ecology involves finding ways to share places we dominate with other species. Replacing monoculture grasses with native species. Replacing monoculture grasses with native species. Maintaining habitats for insect eating bats can keep down unwanted insects. Maintaining habitats for insect eating bats can keep down unwanted insects. Reduction and elimination of pesticides to protect non-target organisms (such as vital insect pollinators). Reduction and elimination of pesticides to protect non-target organisms (such as vital insect pollinators).
Using Reconciliation Ecology to Protect Bluebirds Putting up bluebird boxes with holes too small for (nonnative) competitors in areas where trees have been cut down have helped reestablish populations. Figure 11-B
Fig. 11-21, p. 246 Do not buy furs, ivory products, and other materials made from endangered or threatened animal species. Do not buy wood and paper products produced by cutting remaining old- growth forests in the tropics. Do not buy birds, snakes, turtles, tropical fish, and other animals that are taken from the wild. Do not buy orchids, cacti, and other plants that are taken from the wild. Spread the word. Talk to your friends and relatives about this problem and what they can do about it. What Can You Do? Protecting Species