January-October 2014 temperatures highest on record November 29, 2014 The global average temperature over land and ocean surfaces for January to October 2014 was the highest on record, according to NOAA. October was the hottest since records began in 1880. © Cengage Learning 2015 Politics, not severe weather, drive global-warming views December 1, 2014 Scientists have presented the most comprehensive evidence to date that climate extremes such as droughts and record temperatures are failing to change people's minds about global warming. "Our results show that politics has the most important effect on perceptions of climate change." Some previous studies suggested temperature patterns do, in fact, influence perceptions about global warming, but none measured climatic conditions as comprehensively as the current investigation. Past research often considers a two-day window or a particular community and a single measure of temperature, not an expansive sweep of multiple climate measures as the authors of this study do. The study analyzed climatic storm-severity measures used by NOAA -- temperature, drought, precipitation and wind velocity -- from all 50 states in combination with the 11 years of public opinion data. "This gives us the pulse of the nation," said MarquartPyatt. While advocates of global warming reduction efforts hope that experience with a changing climate will eventually convince the public of the reality and seriousness of the problem, the current findings do not bode well for that scenario. Given this expansive treatment of the issue, there is "little grounds for optimism," the study says, "that public concern about climate change will be driven by future climatic conditions." © Cengage Learning 2015 Age structure for the males in a population of large cactus finches on one of the Galápagos Islands in 1987. 11 10 9 Age (years) 8 7 6 5 4 3 2 1 0 10 20 30 40 50 Percent of population © Cengage Learning 2015 Figure 19.3 Biology Concepts and Applications | 9e Starr | Evers | Starr Chapter 41 Community Ecology © Cengage Learning 2015 © Cengage Learning 2015 41.1 What Factors Affect Community Structure? • The type of place where a species normally lives is its habitat, and all species living in a habitat constitute a community • Communities often are nested one inside another © Cengage Learning 2015 What Factors Affect Community Structure? • Community structure can change: – As the community forms and ages – As a result of natural or human-induced disturbances – With changes in physical factors such as climate and resource availability – Due to various types of species interactions © Cengage Learning 2015 What Factors Affect Community Structure? • Species interactions can be mutually beneficial, mutually harmful, or benefit one species while harming the other – Example: Commensal ferns attached to the trunk of a tree; the fern benefits from the light, and the tree is unaffected © Cengage Learning 2015 What Factors Affect Community Structure? • Symbiosis – “Living together” – A relationship in which two species have a prolonged close association – Two species that interact closely for generations can coevolve – each species acts as a selective agent on the other – Can be a commensal, mutualistic, or parasitic relationship © Cengage Learning 2015 41.2 How Do Species Cooperate? • In a mutualistic interaction, two species benefit by taking advantage of one another – Example: pollinators eat nectar and pollen, and plants receive pollen from other plants of the same species +/+ © Cengage Learning 2015 How Do Species Cooperate? • For some mutualists, the main benefit is defense – Example: Sea anemone and anemone fish • An anemone fish has a mucus layer that shields it from stinging cells (nematocysts) of a sea anemone • Tentacles of the anemone protect the fish from predators • The anemone fish chases away the few fishes that are able to eat sea anemone tentacles © Cengage Learning 2015 How Do Species Cooperate? © Cengage Learning 2015 • Mutualistic relationship • Commensal relationship • Parasitic relationship © Cengage Learning 2015 +/+ +/0 +/- 41.3 How Do Species Compete? • Resources are limited and individuals of different species often compete for access to them (interspecific competition) • Competition adversely affects both species © Cengage Learning 2015 How Do Species Compete? • Each species has an ecological niche defined by physical and biological factors; the more similar the niches of two species are, the more intensely they will compete – An animal’s niches include the temperature range it can tolerate, species it eats, and places it can breed – A flowering plant’s niche would include its soil, water, light, and pollinator requirements © Cengage Learning 2015 How Do Species Compete? • Two Paramecium species compete for the same food (bacteria) • Each species thrives when grown alone • When grown together, P. aurelia drove P. caudatum to extinction © Cengage Learning 2015 LM Relative population density Separate cultures Paramecium aurelia Combined cultures 2 P. aurelia 4 6 8 10 Days 12 14 16 LM 0 P. caudatum Paramecium caudatum © Cengage Learning 2015 Figure 20.8 41.4 How Do Predators and Their Prey Interact? • Predation – One species (the predator) captures, kills, and eats another species (the prey) © Cengage Learning 2015 How Do Predators and Their Prey Interact? • Predator and prey exert selection pressure on one another – Predators exert selection pressure that favors improved prey defenses – Improved prey defenses in turn exert selection pressure on predators to improve capture skills, and so on © Cengage Learning 2015 How Do Predators and Their Prey Interact? © Cengage Learning 2015 How Do Predators and Their Prey Interact? • Defensive adaptations of prey – Hard or sharp parts that make prey difficult to eat – Chemicals that taste bad or sicken predators – Tricking or startling an attacking predator – Warning coloration that predators learn to avoid, such as the black and yellow stripes of stinging wasps and bees © Cengage Learning 2015 How Do Predators and Their Prey Interact? • In a type of mimicry, prey masquerade as a species that has a defense that they lack – Example: some flies that can’t sting resemble stinging bees or wasps • Mimicry – A species evolves traits that make it more similar in appearance to another species © Cengage Learning 2015 How Do Predators and Their Prey Interact? A Wasp that can inflict a painful sting. Like many stinging bees and wasps, it has a yellow and black pattern. B Fly, which lacks a stinger, mimics the color pattern of stinging insects. © Cengage Learning 2015 Milk Snake © Cengage Learning 2015 Coral Snake Figure 20.12 How Do Predators and Their Prey Interact? • Predator adaptations include sharp teeth and claws – Predators and prey may be coevolved for speed • Example: cheetah and gazelle – Both predators and prey use camouflage (a form, patterning, color, or behavior that allows them to blend into their surroundings) to avoid detection © Cengage Learning 2015 How Do Predators and Their Prey Interact? A © Cengage Learning 2015 B How Do Predators and Their Prey Interact? • Herbivory – An animal feeds on plant parts – The number and type of plants in a community can influence the number and type of herbivores present © Cengage Learning 2015 How Do Predators and Their Prey Interact? • Two types of defenses against herbivory – Withstand and recover quickly – Traits such as spines, tough leaves, or toxins that deter herbivory • Plant defenses favor adaptations in herbivores – Example: Koalas have special enzymes to break down toxins in eucalyptus © Cengage Learning 2015 41.5 How Do Parasites and Their Hosts Interact? • Parasitism – One species (the parasite) feeds on another (the host), without immediately killing it • Endoparasites live and feed inside their host • Ectoparasites feed while attached to a host’s external surface © Cengage Learning 2015 How Do Parasites and Their Hosts Interact? A B © Cengage Learning 2015 C How Do Parasites and Their Hosts Interact? • Parasitoids – An insect that lays eggs in another insect, and whose young devour their host from the inside – Reduce a host population in two ways: • Parasitoid larvae withdraw nutrients and prevent the host from reproducing • Presence of larvae leads to death of the host – As many as 15% of all insects may be parasitoids © Cengage Learning 2015 How Do Parasites and Their Hosts Interact? • Biological pest control – Parasites and parasitoids are commercially raised and released in target areas as biological control agents – an environmentally friendly alternative to pesticides – A biological control agent must be adapted to a specific host species – Introducing a biological control species into a community is risky – they sometimes go after nontargeted species © Cengage Learning 2015 How Do Parasites and Their Hosts Interact? © Cengage Learning 2015 41.6 How Do Communities Change Over Time? • Pioneer species – Species that can colonize a new habitat • Mosses, lichens, and some flowering annuals – Species often alter the habitat in ways that allow other species to replace them (ecological succession) – First, opportunistic colonizers of new or newly vacated habitats are pioneer species, which have high dispersal rates, grow and mature fast, and produce many offspring © Cengage Learning 2015 How Do Communities Change Over Time? • Seeds of later species grow in mats of pioneers • Organic wastes and remains accumulate and help other species take hold • Later successional species often shade and eventually displace earlier ones © Cengage Learning 2015 © Cengage Learning 2015 Figure 20.23 © Cengage Learning 2015 How Do Communities Change Over Time? • Secondary succession – A new community develops in a site where the soil that supported an old community remains – In secondary succession, a disturbed area within a community recovers. – Occurs in abandoned agricultural fields and burned forests © Cengage Learning 2015 How Do Communities Change Over Time? • Species composition of a community changes frequently, and unpredictably – Random events can determine the order in which species arrive, and affect the course of succession – Example: 1980 eruption of Mount Saint Helens • Presence of some pioneers helped later-arriving plants become established • Other pioneers kept the same late arrivals out © Cengage Learning 2015 How Do Communities Change Over Time? • Indicator species are the first to do poorly when conditions change, so they can provide an early warning of environmental degradation – Example: trout are highly sensitive to pollutants and cannot tolerate low oxygen levels © Cengage Learning 2015 41.7 How Can A Single Species Alter Community Structure? • Keystone species – A species that has a disproportionately large effect on community structure – Loss or addition of even one species (keystone species) may destabilize the number and abundances of species in a community © Cengage Learning 2015 How Can A Single Species Alter Community Structure? • Experiment: sea stars in a rocky intertidal zone in California – Sea stars prey mainly on mussels and were removed from experimental plots – Mussels then crowded out seven other species of invertebrates – Conclusion: sea stars are a keystone species • Normally keep number of prey species high by preventing competitive exclusion by mussels © Cengage Learning 2015 How Can A Single Species Alter Community Structure? (cont’d.) © Cengage Learning 2015 • Keystone species – Grey Wolf • 1995: reintroduced; 2009: 116 wolves in park • Prey on elk and push them to a higher elevation – Regrowth of aspen, cottonwoods, and willows – More beaver dams, more wetlands, more aspens • Reduced the number of coyotes – Fewer attacks on cattle – More smaller mammals © Cengage Learning 2015 How Can A Single Species Alter Community Structure? • Exotic species – A species that evolved in one community and later became established in a different one – Can dramatically alter a natural community – More than 4,500 50,000 exotic species have become established in the United States – Visit the National Invasive Species Information Center at www.invasivespeciesinfo.gov © Cengage Learning 2015 How Can A Single Species Alter Community Structure? © Cengage Learning 2015 How Can A Single Species Alter Community Structure? • Kudzu native to Asia: overgrowing trees across the southeastern United States • Gypsy moths native to Europe and Asia: feed on oaks through much of the United States • Nutrias native to South America: abundant in freshwater marshes of the Gulf States © Cengage Learning 2015 41.9 Fighting Foreign Fire Ants • Red imported fire ants, Solenopsis invicta, have a venomous sting and disrupt native wildlife communities – Pesticides do not control spread – Biological control involves phorid flies – the larvae eats its way through the fire ant and undergoes metamorphosis in its head – Global climate change is expected to help RIFAs extend their range in the U.S. © Cengage Learning 2015 © Cengage Learning 2015 Figure 19.6a Breeding male fur seals (thousands) 10 8 6 4 2 0 1915 1925 1935 1945 Year © Cengage Learning 2015 Figure 19.6 100 Survivors (%) 80 60 40 20 0 20 40 60 80 100 120 Density (beetles/0.5 g flour) (b) Decreasing survival rates with increasing density in a population of flour beetles © Cengage Learning 2015 Figure 19.8b Average clutch size 12 11 10 9 8 0 10 20 30 40 50 60 70 80 90 Number of breeding pairs (a) Decreasing birth rate with increasing density in a population of great tits © Cengage Learning 2015 Figure 19.8a 41.8 How Many Species Will A Community Hold? • Equilibrium model of island biogeography – The number of species living on any island reflects a balance between immigration rates for new species and extinction rates for established ones – Colonization rates depend on the distance between an island and a mainland source of colonists (distance effect) – An island’s size affects species richness (area effect) © Cengage Learning 2015 How Many Species Will A Community Hold? © Cengage Learning 2015 11/26 Friday Schedule Populations 40 11/28 No Class 12/3 41 12/5 Trophic Levels Ecology Succession Lab Review 12/10 Biomes & Human 43&44 12/12 Effect Lecture Review Lab Final Exam 12/17 Make up class if needed Final Exam © Cengage Learning 2015 12/19 42