LIVING IN THE ENVIRONMENT, 18e G. TYLER MILLER • SCOTT E. SPOOLMAN 5Biodiversity, Species Interactions, and Population Control © Cengage Cengage Learning Learning 2015 2015 © Core Case Study: Southern Sea Otters - A Species in Recovery • Live in giant kelp forests • By the early 1900s they had been hunted almost to extinction • Partial recovery since 1977 • Why care about sea otters? – Ethics – Tourism dollars – Keystone species © Cengage Learning 2015 Southern Sea Otter © Cengage Learning 2015 Fig. 5-1, p. 102 5-1 How Do Species Interact? • Five types of species interactions— competition, predation, parasitism, mutualism, and commensalism—affect the resource use and population sizes of the species in an ecosystem © Cengage Learning 2015 Most Species Compete with One Another for Certain Resources • Five basic types of species interactions – Interspecific Competition – Predation – Parasitism – Mutualism – Commensalism © Cengage Learning 2015 • Interspecific competition – Most common interaction – Members of two or more species compete to use the same limited resources – Niches overlap – Involves one species becoming more efficient than the other © Cengage Learning 2015 Some Species Evolve Ways to Share Resources • Resource partitioning – Populations of some species develop adaptations that allow them to reduce or avoid competition with other species for resources. – Competing species evolve specialized traits so that they may use only parts of resource • At different times • In different ways © Cengage Learning 2015 Sharing the Wealth Blackburnian Warbler Black-throated Green Warbler © Cengage Learning 2015 Cape May Warbler Bay-breasted Warbler Yellow-rumped Warbler Stepped Art Fig. 5-2, p. 103 Specialist Species of Honeycreepers Fruit and seed eaters Insect and nectar eaters Greater Koa-finch Kuai Akialaoa Amakihi Kona Grosbeak Akiapolaau Crested Honeycreeper Maui Parrotbill © Cengage Learning 2015 Unkown finch ancestor Apapane Fig. 5-3, p. 104 Consumer Species Feed on Other Species • Predation – A member of one species (predator) feed directly on all or part of a living organism (prey) as part of a food web. – Predator methods: • Herbivores-walk, swim, or fly to plants they feed on • Carnivores-pursuit and ambush • Camouflage • Chemical warfare © Cengage Learning 2015 Consumer Species Feed on Other Species (cont’d.) • Prey can avoid predation – Swim, run, fly fast – Highly developed senses – Protective shells, thick bark, or spines – Camouflage – Chemical warfare – Warning coloration – Mimicry – Behavioral strategies © Cengage Learning 2015 Predator-Prey Relationships Fig. 5-4, p. 104 Predator-Prey Relationships © Cengage Learning 2015 Fig. 5-6, p. 106 Interactions between Predator and Prey Species • Intense natural selection pressures between predator and prey populations • Coevolution – Interact over a long period of time – Changes in the gene pool of one species can cause changes in the gene pool of the other – Bats and moths • Echolocation of bats and sensitive hearing of moths © Cengage Learning 2015 Coevolution Fig. 5-7, p. 107 Some Species Feed off Other Species by Living on or inside Them • Parasitism – One species (the parasite) feeds on another organism (the host) by living on or inside the host – Parasite is usually much smaller than the host – Parasite rarely kills the host – Parasite-host interaction may lead to coevolution © Cengage Learning 2015 Parasitism Fig. 5-8, p. 107 In Some Interactions, Both Species Benefit • Mutualism – Two species benefit – Nutrition and protective relationship – Gut inhabitant mutualism – Not cooperation – mutual exploitation © Cengage Learning 2015 Mutualism Fig. 5-9, p. 108 In Some Interactions, One Species Benefits and the Other Is Not Harmed • Commensalism – Benefits one species and has little affect on the other – Epiphytes – Birds nesting in trees © Cengage Learning 2015 Commensalism Fig. 5-10, p. 108 5-2 Responding to Changing Environmental Conditions • How do communities and ecosystems respond to changing environmental conditions? – The structure and species composition of communities and ecosystems change in response to changing environmental conditions through a process called ecological succession © Cengage Learning 2015 Communities and Ecosystems Change over Time: Ecological Succession • Ecological succession – Gradual change in species composition – Primary succession • Gradual establishment of a community in a lifeless areas (no soil in terrestrial ecosystem and no bottom sediment in an aquatic ecosystem) – Secondary succession • Areas of environmental disturbance, but some soil or bottom sediment remains © Cengage Learning 2015 • Both types of succession are examples of natural ecological restoration – Increase the biodiversity of communities and ecosystems by increasing species richness and interactions among species. – Factors that affect how and rate of succession: • 1. facilitation • 2. inhibition • 3. tolerance © Cengage Learning 2015 Primary Ecological Succession Exposed rocks Lichens and mosses Small herbs and shrubs Heath mat Jack pine, black spruce, and aspen Balsam fir, paper birch, and white spruce forest community Fig. 5-11, p. 109 Natural Ecological Restoration Annual weeds Perennial weeds and grasses Shrubs and small pine seedlings Young pine forest with developing understory of oak and hickory trees Mature oak and hickory forest Fig. 5-12, p. 110 Ecological Succession Does Not Follow a Predictable Path • Traditional view – Succession proceeds in an orderly sequence along an expected path until a climax community is reached; balance of nature • Current view – Ever-changing mosaic of patches of vegetation in different stages of succession – In a state of continual disturbance and change. © Cengage Learning 2015 Living Systems Are Sustained through Constant Change • Two aspects of stability or sustainability in living systems: • 1. Inertia, or persistence – Ability of a living system to survive moderate disturbances • 2. Resilience – Ability of a living system to be restored through secondary succession after a moderate disturbance © Cengage Learning 2015 What Limits the Growth of Populations • No population can grow indefinitely because of limitations on resources and because of competition among species for those resources © Cengage Learning 2015 Most Populations Live in Clumps • Population – Group of interbreeding individuals of the same species • Population distribution – Clumped – Uniform – Random © Cengage Learning 2015 – Clumping • Most live in clumps. Why? • 1. Species cluster for resources • 2. Protection from predators • 3. Ability to hunt in packs © Cengage Learning 2015 A School of Anthias Fish Fig. 5-13, p. 111 Populations Can Grow, Shrink, or Remain Stable • Population size governed by: – Births and deaths; immigration and emigration • Population change = (births + immigration) – (deaths + emigration) © Cengage Learning 2015 • Age structure– age group distributions can have a strong effect on how rapidly populations grow or decline – Pre-reproductive age – Reproductive age – Post-reproductive age © Cengage Learning 2015 Some Factors Can Limit Population Size • Range of tolerance – Tolerance to variations in physical and chemical environment – Individuals may have different tolerance ranges because of their genetic makeup, health, and age. © Cengage Learning 2015 Some Factors Can Limit Population Size • Limiting factors: – Factors that determine number of organisms in a population. – Regulate population growth • Limiting factor principle – Too much or too little of any physical or chemical factor can limit or prevent growth of a population, even if all other factors are at or near the optimal range of tolerance – Precipitation, nutrients, sunlight © Cengage Learning 2015 • Populations density – Can be a limiting factor – Number of individuals in a given area © Cengage Learning 2015 Trout Tolerance of Temperature Lower limit of tolerance Few organisms Abundance of organisms Few organisms No organisms Zone of physiological stress Zone of intolerance Population size No organisms Higher limit of tolerance Zone of intolerance Zone of physiological stress Low Optimum range Temperature High © Cengage Learning 2015 Fig. 5-13, p. 113 Different Species Have Different Reproductive Patterns • To ensure long-term survival of species: • Some species: – Have many small offspring – Little parental involvement – Algae, bacteria, and most insects • Other species: – Reproduce later in life – Have small number of offspring – mammals © Cengage Learning 2015 No Population Can Grow Indefinitely: J-Curves and S-Curves • There are always limits to population growth in nature – Environmental resistance: • combination of all factors that limit population growth • Determines the: – Carrying capacity: • Maximum population of a given species that a particular habitat can sustain indefinitely © Cengage Learning 2015 No Population Can Grow Indefinitely: J-Curves and S-Curves (cont’d.) • Exponential growth – At a fixed percentage per year – J-shaped growth curve – Unlimited resources • Logistic growth – Exponential growth that faces environmental resistance – Population size stabilizes at carrying capacity – S-shaped growth curve © Cengage Learning 2015 Growth of a Sheep Population Population overshoots carrying capacity Environmental resistance Number of sheep (millions) 2.0 Carrying capacity 1.5 Population recovers and stabilizes 1.0 Exponential growth Population runs out of resources and crashes .5 1800 1825 1850 1875 Year 1900 1925 Fig. 5-16, p. 115 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 deer population explosion – Spread Lyme disease – Deer-vehicle accidents – Eating garden plants and shrubs • How can we control the deer population? © Cengage Learning 2015 White-Tailed Deer Populations Fig. 5-17, p. 115 When a Population Exceeds Its Carrying Capacity It Can Crash • If a population uses up resources and exceeds the area’s carrying capacity, the reproductive time lag may lead to overshoot: – Subsequent population crash or dieback – Damage may reduce area’s carrying capacity © Cengage Learning 2015 Population Crash Population overshoots carrying capacity Number of reindeer 2,000 1,500 Population crashes 1,000 500 Carrying capacity 0 1910 © Cengage Learning 2015 1920 1930 1940 1950 Year Fig. 5-18, p. 116 Humans Are Not Exempt from Nature’s Population Controls • Ireland – Potato crop in 1845 • Bubonic plague – Fourteenth century • AIDS – Current global epidemic © Cengage Learning 2015 Three Big Ideas • Certain interactions among species – Affect their use of resources and their population sizes • Changes in environmental conditions – Cause communities and ecosystems to gradually alter their species composition and population sizes (ecological succession) • There are always limits to population growth in nature © Cengage Learning 2015 Tying It All Together – Southern Sea Otters and Sustainability • Before European settlers in the U.S., the sea otter ecosystem was complex • Settlers began hunting otters – Disturbed the balance of the ecosystem • Populations depend on solar energy and nutrient cycling – When these are disrupted biodiversity is threatened © Cengage Learning 2015