CES210 Chapter Four Notes
CES210 Chapter Four Notes CES 210
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This 6 page Class Notes was uploaded by Emma Eiden on Wednesday October 5, 2016. The Class Notes belongs to CES 210 at University of Wisconsin - Milwaukee taught by Mai Phillips in Fall 2016. Since its upload, it has received 9 views. For similar materials see Introduction to Conservation and Environmental Science in GN Natural Science at University of Wisconsin - Milwaukee.
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Date Created: 10/05/16
CES210: Conservation and Environment Science Chapter Four: Evolution, Biological Communities, and Species Interactions Case Study: Natural Selection and the Galapagos The Galapagos Islands are a small archipelago of arid volume islands, isolated and remote – nearly 1,000 km from mainland South America - Charles Darwin (1809-1882) visited the islands in 1835 while serving as ship’s naturalist on HMS Beagle. - The islands also had a variety of small brown finches that different markedly in appearance, food preferences, and habitat. Most finches forage for small seeds, but in the Galapagos there were fruit eaters with think, parrot-like beaks; seed eaters with heavy, crushing beaks; and insect eaters with thin, probing beaks to catch their prey. - Observing that dog breeders created new varieties of dogs, from dachshunds to Great Danes, by selecting for certain traits, Darwin proposed that “natural selection” could explain the origins of species. Just as dog breeders favored individuals with particular characteristics, such as long legs or short noses, environmental conditions in an area could favor certain characteristics EVOLUTION PRODUCES SPECIES DIVERSITY Natural selection acting on spontaneous mutations results in evolution All species have environmental tolerance limits Taxonomy describes relationships between species Natural selection leads to evolution - Adaptation, the acquisition of traits that allow a species a survive in its environment, is one of the most important concepts in biology - We use the term “adapt” in two ways. An individual organism can respond immediately to a changing environment in a process called acclimation - Another type of adaptation affects populations consisting of many individuals. Genetic traits are passed from generation to generation and allow a species to live more successfully in its environment. As the opening case study shows, this process of adaptation to environment is explained by the theory of evolution - The basic idea of evolution is that species change over generations because individuals compete for scarce resources - It has been demonstrated in experiments and by observing natural populations that mutations or changes to the DNA coding sequence of individuals occur occasionally, and that the changed sequences and inherited by offspring - Only mutations in reproductive cells (gametes) matter; body cell changes – cancers, for example – are not inherited - During the course of a species’ life span – a million or more years – some mutations are thought to have given those individuals an advantage under the selection pressures of their environment at the time All species live within limits Limiting factors include… 1. Physiological stress due to inappropriate levels of some critical environmental factor, such as moisture, light temperature, pH, or species nutrients 2. Competition with other species 3. Predation, including parasitism and disease 4. Luck - In 1840 the chemist Justus von Liebig proposed that the single factor in shortest supply relative to demand is the critical factor determining where a species lives - Ecologist Victor Shelford (1877-1968) later expanded Liebig’s principle by stating that each environmental factor has both minimum levels, called tolerance limits, beyond which a particular species cannot survive or is unable to reproduce - Sometimes the requirements and tolerances of species are useful indicators of species environmental characteristics. The presence or absence of such species indicates something about the community and the ecosystem as a whole The ecological niche is a species’ role and environment - A habitat is a place or set of environmental conditions in which a particular organism lives - The term ecological niche is more functional, describing both the role played by a species in a biological community and the set of environmental factors that determine its distribution - Some species tolerate a wide range of conditions or exploit a wide range of resources. These species are known generalists - Other species, such as the giant panda are specialists and have a narrow ecological niche - Because of their exacting habitat requirements, specialists tend not to tolerate environmental change well. Often specialists are also endemic species – they occur only in one area (or one type of environment) - Russian biologist G. F. Gause (1910-1986), “complete competitors cannot coexist.” The general term for this idea is the principle of competitive exclusion: no two species can occupy the same ecologist niche for long - The other species disappears or develops a new niche, exploiting resources, differently, a process known as resource partitioning Speciation maintains species diversity - As population becomes more adapted to its ecological niche, it may develop specialized or distinctive traits that eventually differentiate it entirely from its biological cousins. The development of a new species it’s called speciation - In the Galapagos finches, speciation occurred largely because of geographic isolation - Speciation that occurs when populations are geographically separated is known as allopatric speciation - Speciation that occurs within one geographic area is known as sympatric speciation - Resistant survivors produce new generations, leading to population with the resistant traits - Many examples from both laboratory experiments and from nature shows evolution is still at work Taxonomy describes relationships among species - Taxonomy is the study of types of organisms and their relationships - Botanists, ecologists, and other scientists often use the most specific levels of the tree, genus and species, to compose names called binomials - Scientists, however, recognize six kingdom: animals, plants, fungi (molds and mushrooms), protists (algae, protozoans, slime, molds), bacteria (or eubacteria), and archaebacteria (ancient, single-celled organism) New Flu Vaccines - The answer is that flu virus has an alarming ability to mutate rapidly SPECIES INTERACTIONS SHAPE BIOLOGICAL COMMUNITIES Competition leads to resource allocation Predication is an important type of selective pressure Competition leads to resource allocation - Competition is a type of antagonistic relationship within a biological community. Organisms compete for resources that are in limited supply: energy and matter in usable forms, living space, and species sites to carry out life’s activities - Competitions among members of the same species is called intraspecies competition, whereas competition between memebers of different species is called interspecific competition - Several avenues exist to reduce competition in a species population Predation affects species relationships - Consumers include herbivores, carnivores, omnivores, scavengers, detritivores, and decomposers. You may think only carnivores are predators, but ecologically a predator is any organism that feeds directly another living organism, whether or not this kills the prey - In predator-mediated competition, a superior competitor in a habitat builds up a larger population than the competing species; predators take note and increase their hunting pressure on the superior species, reducing its abundance and allowing the weaker competitor to increase its numbers - Predatory relationships may change as the life stage of an organism changes Some adaptations help avoid predation - Predator-prey relationships exert selection pressures that favor evolutionary adaptation. In this world, predators become more efficient at searching and feeding, and prey become more effective at escape and avoidance - The response of predator to prey and vice versa, over tens of thousands of years, produces physical and behavioral changes in a process known as coevolution - In a neat evolutionary twist, certain that are harmless resemble poisonous or distasteful ones, gaining protection against predators. This is called Batesain mimicry, after the English naturalist H. W. Bates (1825-1892), a traveling companion of Alfred Wallace - Another form of mimicry, Mullerian mimicry (after the biologist Fritz Muller) involves two unpalatable or dangerous species who look alike. When predators learn to avoid either species, both benefit Symbiosis involves intimate relations among species - In such relationships, called symbiosis, two or more species live intimately together, with their fate linked - The association is called mutualism - Commensalism is a type of symbiosis in which one member clearly benefits and the other apparently is neither benefited nor harmed - Parasitism, a form of predation, may also be considered symbiosis because of the dependeny of the parasite on its host Keystone species have disproportionate influence - A keystone species plays a critical role in a biological community that is out of proportion to its abundance COMMUNITY PROPERTIES AFFECT SPECIES AND POPULATION Productivity is a measure of biological activity - A community’s primary productivity is the rate of biomass production, an inducation of the rate of solar energy conversion to chemical energy - The energy left after respiration is net primary production Abundance and diversity measure the number and variety of organisms - Abundance is an expression of the total number of organisms in a biological community, while diversity is a measure of the number of different species, ecological niches, or genetic variation present - The abundance of a particular species often is inversely related to the total diversity of the community - The year-round dependability of food, moisture, and warmth supports a great exuberance of life and allows a high degree of specialization in physical shape and behavior - Productivity is related to abundance and diversity, both of which are dependent on the total resource availability in an ecosystem as well as the reliability of resources, the adaptations of the member species, and the interactions between species Community structure is the spatial distribution of organism - Ecological structure refers to pattern of spatial distribution of individuals and populations within a community, as well as the relation of a particular community to its surroundings - In randomly arranged populations, individuals live wherever resources are available. Ordered patterns may be determined by the physical environment but are more often the result of biological competition - Distribution in a community can be vertical as well as horizontal Complexity and connectedness are important ecological indicators - Complexity in ecological terms refers to the number of species at each trophic level and the number of trophic levels in a community Resilience and stability make communities resistant to disturbance - We can identify three kinds of stability or resiliency in ecosystems: constancy (lack of fluctuations in composition or functions), inertia (resistance to perturbations), and renewal (ability to repair damage after disturbance) - 1955: Robert MacArthur, who was then a graduate student a Yale, proposed that the more complex and interconnected a community is the more stable and resilient it will be in the face of disturbance. If many different species occupy each trophic level, some can fill in if others are stressed or eliminated by external forces, making the whole community resistant to perturbations and able to recover relatively easily from disruptions Edges and boundaries are the interfaces between adjacent communities - Sometimes the edge of a patch of habitat is relatively sharp and distinct - Ecologists call the boundaries between adjacent communities’ ecotones. A community that is sharply divided from its neighbors is called a closed community. COMMUNITIES ARE DYNAMIC AND CHANGE OVER TIME The nature of communities is debated - In sand dunes, the community that developed last and lasted the longest was called the climax community Ecological succession is the history of community development - In any landscape you can read the history of biological communities. That history is revealed by the process of ecological succession. During succession, organisms occupy a site and change the environmental conditions - In primary succession land that is bare of soil – a sandbar, mudslide, rock face, and volcanic flow – is colonized by living organisms where none lived before. When an logical legacy of the old in a process called secondary succession - In primary succession on land, the first colonists are hardy pioneer species, often microbes, mosses, and lichens that can withstand a harsh environment with few resources - Generalists figure prominently in early succession. Over thousands of years, however, competition should decrease as niches proliferate and specialists arise Appropriate disturbances can benefit communities - A disturbance is any force that disrupts the established patterns of species diversity and abundance, community structure, or community properties - It is customary in ecology to distinguish between natural disturbances and human-caused (or anthropogenic) disturbances, but a subtle point of clarification is needed - The disturbances caused by technologically advanced and numerous people, however, may be very different from the disturbances caused by small groups of aborigines - Ecologists generally find that disturbance benefits most species much as predation does, because it set back supreme competitors and allows less- competitive species to persist - Some landscapes never reach a stable climax in a traditional sense because they are characterized by periodic disturbance and are made up of disturbance-adapted species that survive fires underground, or resist the flames, and then reseed quickly after fires - Policymakers and managers increasingly consider ecological information when deciding on new dams and levee construction projects Introduced species can cause profound community change - If an introduced species preys upon or outcompetes one or more populations that are native to the community, the entire nature of the community can be altered - Human introductions of Eurasian plants and animals to non-Eurasian communities often have been disastrous to native species because of competition or over predation. Oceanic islands offer classic examples of devastation caused by rats, goats, cats, and pigs liberated from sailing ships. All these animals are prolific, quickly developing large populations. Goats are efficient, nonspecific herbiovores; they eat nearly everything vegetation, from grasses and herbs to seedlings and shrubs Additional Aid for Studying Terms: https://quizlet.com/151130393/conservation-and- environmental-science-chapter-four-evolution-biological-communities-and-species- interactions-flash-cards/
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