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Biodiversity, Species Interactions, and Population Control Chapter 5.

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Presentation on theme: "Biodiversity, Species Interactions, and Population Control Chapter 5."— Presentation transcript:


2 Biodiversity, Species Interactions, and Population Control Chapter 5

3 Core Case Study: Southern Sea Otters: Are They Back from the Brink of Extinction? Habitat Hunted: early 1900s Partial recovery Why care about sea otters? Ethics Keystone species Tourism dollars

4 3 Case Study: Sea Otters Are They Back From the Brink of Extinction (a) Southern sea otter (b) Sea Urchin (c) Kelp bed

5 5-1 How Do Species Interact? Concept 5-1 Five types of species interactionscompetition, predation, parasitism, mutualism, and commensalismaffect the resource use and population sizes of the species in an ecosystem.

6 Most Species Compete with One Another for Certain Resources Competition the struggle among organisms, both of the same and of different species, for food, space, and other vital requirements. Competitive exclusion principle The principle that when two species compete for the same critical resources within an environment, one of them will eventually outcompete and displace the other. The displaced species may become locally extinct, by either migration or death, or it may adapt to a sufficiently distinct niche within the environment so that it continues to coexist noncompetitively with the displacing species.

7 Species Interact in Five Major Ways Interspecific Competition Predation Parasitism Mutualism Commensalism

8 7 Interspecific competition Competition between two different species For food, sunlight, water, soil, space One species may migrate or shift feeding habits or face extinction Example-native ants and nonnative fire ants Intraspecific competition competition between members of the same species

9 Most Consumer Species Feed on Live Organisms of Other Species Predators may capture prey by Pursuit Walking Swimming Flying Pursuit and ambush Camouflage Chemical warfare


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15 Most Consumer Species Feed on Live Organisms of Other Species Prey may avoid capture by Camouflage Chemical warfare Warning coloration Mimicry Deceptive looks Deceptive behavior Swift movement Shell

16 15 Span worm Bombardier beetle Viceroy butterfly mimics monarch butterfly Foul-tasting monarch butterfly Poison dart frog When touched, the snake caterpillar changes shape to look like the head of a snake Some ways prey species avoid their prey Wandering leaf insect Hind wings of moth resemble eyes of a much larger animal

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23 22 Parasitism, Mutualism, Commensalism

24 23 Parasitism Live on or in another species Host is harmed Ex. Tapeworms, ticks, fleas, mosquitoes, candiru (vampire fish)

25 24 Mutualism (benefits both species) Pollination mutualism (between flowering plants and animals) Nutritional mutualism Lichens grow on trees Birds/rhinos- nutrition and protection Clownfish/sea anemones Inhabitant mutualism Vast amount of organisms like bacteria in an animals digestive tract Termites and bacteria in gut

26 Coral Reefs- The corals get food and the zooxanthellae (algae) get protection.. zooxanthellae

27 26 Yuccas only pollinator is the yucca moth. Hence entirely dependent on it for dispersal. Yucca moth caterpillars only food is yucca seeds. Yucca moth lives in yucca and receives shelter from plant. Example of co evolution Yucca and Yucca Moth

28 27 Figure 8-10 Page 155 Oxpeckers and black rhinocerosClown fish and sea anemone Mycorrhizae fungi on juniper seedlings in normal soil Lack of mycorrhizae fungi on juniper seedlings in sterilized soil Examples of Mutualism

29 28 Commensalism Helps one species but does nothing for the other Ex. Redwood sorrel grows in shade of redwood - Humans and Eyelash Mites

30 Science Focus: Why Should We Care about Kelp Forests? Kelp forests: biologically diverse marine habitat Major threats to kelp forests Sea urchins Pollution from water run-off Global warming

31 5-2 How Can Natural Selection Reduce Competition between Species? Concept 5-2 Some species develop adaptations that allow them to reduce or avoid competition with other species for resources.

32 Some Species Evolve Ways to Share Resources Resource partitioning Reduce niche overlap Use shared resources at different Times Places Ways

33 32 Resource partitioning Evolve more specialized traits Five species of common insect-eating warblers in the Spruce forests of Maine

34 5-3 What Limits the Growth of Populations? Concept 5-3 No population can continue to grow indefinitely because of limitations on resources and because of competition among species for those resources.

35 34 Characteristics of a Population Characteristics of a Population Population - individuals inhabiting the same area at the same time Population Dynamics: is the study of how population change due to Population Size - number of individuals Population Density - population size in a certain space at a given time Population Dispersion - spatial pattern in habitat Age distribution - proportion of individuals in each age group in population

36 Populations Have Certain Characteristics Changes in population characteristics due to: Temperature Presence of disease organisms or harmful chemicals Resource availability Arrival or disappearance of competing species

37 36 Population Size Population Size Natality Number of individuals added through reproduction Crude Birth Rate - Births per 1000 Total Fertility Rate – Average number of children born alive per woman in her lifetime Mortality Number of individuals removed through death Crude Death Rate- Deaths per 1000

38 37 Population Density Population Density (or ecological population density) is the amount of individuals in a population per unit habitat area Some species exist in high densities - Mice Some species exist in low densities - Mountain lions Density depends upon social/population structure mating relationships time of year

39 38 Population Dispersion Population dispersion is the spatial pattern of distribution There are three main classifications Clumped: individuals are lumped into groups ex. Flocking birds or herbivore herds due to resources that are clumped or social interactions most common

40 Most Populations Live Together in Clumps or Patches Why clumping? Species tend to cluster where resources are available Groups have a better chance of finding clumped resources Protects some animals from predators Packs allow some to get prey Temporary groups for mating and caring for young

41 40 Population Dispersion Uniform: Individuals are regularly spaced in the environment - ex. Creosote bush due to antagonism between individuals, or do to regular spacing of resources rare because resources are rarely evenly spaced tips/2002/clover611.htm Random: Individuals are randomly dispersed in the environment ex. Dandelions due to random distribution of resources in the environment, and neither positive nor negative interaction between individuals rare because these conditions are rarely met

42 41 Age Structure The age structure of a population is usually shown graphically The population is usually divided up into prereproductives, reproductives and postreproductives The age structure of a population dictates whether is will grow, shrink, or stay the same size

43 42 Age Structure Diagrams Positive Growth Zero Growth Negative Growth (ZPG) Pyramid Shape Vertical Edges Inverted Pyramid

44 43 Four variables influencing growth Births Deaths Immigration Emigration Increase by birth & immigration Decrease death & emigration Population change= (Birth + Immigration)- (Death + Emigration)

45 No Population Can Grow Indefinitely: J-Curves and S-Curves (1) Biotic potential - is the populations capacity for growth Low generally large animals elephant and blue whales High small individuals like bacteria and insects Intrinsic rate of increase (r) is the rate of population growth with unlimited resources.

46 45 Rapidly growing populations have four characteristics (high r) Reproduction early in life Short periods between generations Long reproductive lives Multiple offspring each time they reproduce A single house fly could total 5.6 trillion house flies within 13 months

47 No Population Can Grow Indefinitely: J-Curves and S-Curves (2) Size of populations limited by Light Water Space Nutrients Exposure to too many competitors, predators or infectious diseases

48 47 Environmental Resistance Consists of all factors that act to limit the growth of a population Abiotic Contributing Factors: Unfavorable light Unfavorable Temperatures Unfavorable chemical environment - nutrients Biotic Contributing Factors: Low reproductive rate Specialized niche Inability to migrate or disperse Inadequate defense mechanisms Inability to cope with adverse conditions

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50 49 Limits on population growth Carrying capacity [K] determined by biotic potential & environmental resistance This is the # of a species individuals that can be sustained indefinitely in a specific space As a population reaches its carrying capacity, its growth rate will decrease because resources become more scarce.

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52 51 Population Growth Populations show two types of growth With few resource limitations Exponential J-shaped curve Growth is independent of population density The growth rate levels off as population reaches carrying capacity Logistic S-shaped curve Growth is not independent of population density

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54 Science Focus: Why Are Protected Sea Otters Making a Slow Comeback? Low biotic potential Prey for orcas Cat parasites Toxic algae blooms PCBs and other toxins Oil spills

55 When a Population Exceeds Its Habitats Carrying Capacity, Its Population Can Crash Carrying capacity: not fixed Reproductive time lag may lead to overshoot Dieback (crash) Damage may reduce areas carrying capacity

56 55 2,000 1,500 Number of reindeer Year 1, Exponential growth, overshoot, and population crash of reindeer introduced to a small island off of SW Alaska Carrying capacity Population overshoots carrying capacity Population crashes

57 56 Reproductive Strategies Goal of every species is to produce as many offspring as possible Each individual has a limited amount of energy to put towards life and reproduction This leads to a trade-off of long life or high reproductive rate Natural Selection has lead to two strategies for species: r - strategists and K - strategists

58 57 r - Strategists Spend most of their time in exponential growth High rate of reproduction Little parental care Minimum life Opportunist K

59 58 R Strategists 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

60 59 K - Strategists Maintain population at carrying capacity (K) Maximize lifespan Competitor Follow a logistic growth curve K

61 60 K- Strategist Reproduce later in life Fewer, larger offspring High parental care and protection of offspring 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 Prone to extinction

62 Genetic Diversity Can Affect the Size of Small Populations Founder effect Demographic bottleneck Genetic drift Inbreeding Minimum viable population size- the number of individuals populations need for long term survival

63 62 Effects of Genetic Variations on Population Size Genetic diversity 1. Founder effect Few individuals move to a new location and are isolated from the original population Limited genetic diversity

64 63 2. Demographic bottleneck Few individuals survive a catastrophe- fire, hurricane Lack of genetic diversity may limit these individuals to rebuild the population

65 3. Genetic drift Random changes in gene frequencies May help or hurt survival of a population Some individuals may breed more than others and their genes may eventually dominate the gene pool of the population 4. Inbreeding Members of a small population exchange genes

66 65 Density of a population density Density-independent (affects population size regardless of its density) Floods, hurricanes, fire, pesticide spraying, pollution) Density-dependent (greater effect as population density increases) Competition for resources, predation, parasitism, disease – bubonic plague)

67 66 Population fluctuations in nature Stable (varies slightly above and below carrying capacity,K) Irruptive (explode to a high level and then drastically drop - insects) Cyclic (over a regular time period – lemmings populations rise and fall ever 3-4 years) Irregular behavior (no pattern)

68 67 © 2004 Brooks/Cole – Thomson Learning Number of individuals Time (b) Irruptive (a) Stable (c) Cyclic (d) Irregular General types of simplified population changes curves found in nature

69 68 Population size (thousands) Year Hare Lynx Predator – prey relationships Lynx-Hare Cycle Cyclic ever 10 years

70 Humans Are Not Exempt from Natures Population Controls Ireland Potato crop in million people died from hunger or disease form malnutrition 3 million migrated to other countries (mainly U.S.) Bubonic plague Fourteenth century Killed a least 25 million people in European Cities AIDS Global epidemic Between AIDS has killed more than 25 million people Claims 2.1 million a year ( average of 4 deaths per min.)

71 Case Study: Exploding White-Tailed Deer Population in the U.S. 1900: deer habitat destruction and uncontrolled hunting 1920s–1930s: laws to protect the deer Current population explosion for deer Lyme disease Deer-vehicle accidents Eating garden plants and shrubs Ways to control the deer population

72 5-4 How Do Communities and Ecosystems Respond to Changing Environmental Conditions? Concept 5-4 The structure and species composition of communities and ecosystems change in response to changing environmental conditions through a process called ecological succession.

73 Communities and Ecosystems Change over Time: Ecological Succession Natural ecological restoration Primary succession is ecological succession in a bare area that has never been occupied by a community of organisms. Bare rock exposed by retreating glacier, severe erosion, newly cooled lava, abandoned concrete/ highway, newly created pond Secondary succession is an ecological succession in an area in which natural vegetation has been removed or destroyed but the soil is not destroyed. forest fires, deforestation, abandoned farmland, heavily polluted streams, and land that has been damned or flooded.

74 73 Succession = change 1. Primary succession Gradual establishment of biotic community on lifeless ground Barren habitat Bare rock / retreating glacier A newly- cooled lava A newly formed pond It takes several centuries to several thousands of years for natural processes to produce fertile soil. Ex. Hawaii Pioneer species (lichens, moss and microbes)

75 Some Ecosystems Start from Scratch: Primary Succession No soil in a terrestrial system No bottom sediment in an aquatic system Early successional plant species, pioneer Bacteria, moss, lichens Midsuccessional plant species Herbs and shrubs Late successional plant species Balsam fir, paper birch, and white spruce

76 75 Primary Succession Glacier Retreat

77 76 Time Small herbs and shrubs Heath mat Jack pine, black spruce, and aspen Balsam fir, paper birch, and white spruce climax community Exposed rocks Lichens and mosses Primary Succession

78 Some Ecosystems Do Not Have to Start from Scratch: Secondary Succession Some soil remains in a terrestrial system Some bottom sediment remains in an aquatic system Ecosystem has been Disturbed Removed Destroyed

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80 79 Time Annual weeds Perennial weeds and grasses Shrubs Young pine forest Mature oak-hickory forest Secondary Succession

81 Some Ecosystems Do Not Have to Start from Scratch: Secondary Succession (2) Primary and secondary succession Tend to increase biodiversity Increase species richness and interactions among species Primary and secondary succession can be interrupted by Fires Hurricanes Clear-cutting of forests Plowing of grasslands Invasion by nonnative species

82 81 Succession of an Aquatic Ecosystem Aquatic ecosystem gradually increasing in sedimentation/inflow of nutrients from surrounding land areas Slowly filling w/ silt, sand and other particles; shoreline gradually advances toward the center of the pond; Aquatic vegetation contributing to this filling In a classic scenario the pond would eventually become a wetland, then perhaps a grassland, followed by some type of forest.


84 Science Focus: How Do Species Replace One Another in Ecological Succession? 1. Facilitation One species makes an area of suitable for another species Ex. Moss build land for grasses 2. Inhibition Early species limit later species Ex. Plants may release toxins 3. Tolerance Later species are unaffected by earlier species

85 Succession Doesnt Follow a Predictable Path Traditional view Balance of nature and a climax community Current view Ever-changing mosaic of patches of vegetation Mature late-successional ecosystems State of continual disturbance and change

86 Living Systems Are Sustained through Constant Change Inertia, persistence Ability of a living system to survive moderate disturbances Resilience Ability of a living system to be restored through secondary succession after a moderate disturbance Tipping point Where any additional stress can cause the system to change in an abrupt and usually irreversible way

87 86 The Cats of Borneo What happened first? Arrange the sentence strips in chronological order

88 87 Operation Cat Drop One of the most bizarre events to accompany this early use of DDT occurred when it became necessary to parachute cats into remote jungle villages in what was then Burma. The following account was taken from a source at Cornell University: In the early 1950s, the Dayak people in Borneo suffered from malaria. The World Health Organization had a solution: they sprayed large amounts of DDT to kill the mosquitoes which carried the malaria. The mosquitoes died, the malaria declined; so far, so good. But there were side-effects. Among the first was that the roofs of people's houses began to fall down on their heads. It seemed that the DDT was also killing a parasitic wasp which had previously controlled thatch-eating caterpillars. Worse, the DDT-poisoned insects were eaten by geckoes, which were eaten by cats. The cats started to die, the rats flourished, and the people were threatened by outbreaks of sylvatic plague and typhus. To cope with these problems, which it had itself created, the World Health Organization was obliged to parachute14,000 live cats into Borneo.

89 88 The Day they Parachuted Cats into Borneo WHO sent DDT to Borneo. Mosquitoes were wiped out. Caterpillar numbers went up. Caterpillars ate grass roofs. Roaches stored DDT in their bodies. Lizards ate roaches and got DDT. Lizards slowed down. Cats caught lizards containing DDT. Lizards disappeared. Cats died. Rats increased. Rats brought the plague. Cats were parachuted in.

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