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Chapter 4 Ecosystems and Living Organisms Ecosystems and Living Organisms

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  • Chapter 4Ecosystems and Living Organisms

  • EvolutionA process of change through time

  • Theory of EvolutionSuggests that existing forms of life on earth have evolved from earlier life forms over long periods of timeEvolution accounts for the differences in structures, function, and behavior among life forms as well as changes that occur in populations over many generations

  • Charles Darwin

  • DarwinCharles Darwin devised a theory of evolution based on variation and natural selection as seen in the Galapagos islands. Included in his theory were five main ideas: 1. Overpopulation 2. Competition 3. Survival of the fittest/Natural selection 4. Reproduction 5. Speciation

  • 1. OverpopulationWithin a population, there are more offspring produced in each generation than can possibly survive

  • 2. CompetitionNatural resources; like food, water, and space available to a population is limitedBecause there are many organisms with similar nutritional requirements, there must be competion between them for the resources needed to survive

  • Variations among members of a population make some of them better adapted to the environment than othersIt is generally the best-adapted individuals that will surviveThe environment is the agent of natural selection determining which species will survive.3. Survival of the Fittest

  • Survival of the Fittest

  • Survival of the Fittest

  • Survival of the Fittest

  • Natural SelectionNatural selection involves the struggle of organisms to survive and reproduce in a given environmentTraits which are beneficial to the survival of an organism in a particular environment tend to be retained and passed on, and therefore, increase in frequency within a population Traits which have low survival value to an organism tend to decrease in frequency from generation to generationIf environmental conditions change, traits that have low survival value may now have a greater survival value. Therefore, traits that prove to be favorable under new environmental conditions will increase in frequency

  • Ex: Insects resistant to insecticidesGenetic make-up of some insects make them resistant to the effects of insecticidesBefore the widespread use of insecticides, this trait was of no particular survival valueWith the increased use of insecticides, this trait developed a very high survival valueTherefore, insects with resistance to insecticides survived and reproduced much more successfully than those lacking the traitAs a result, the frequency of insecticide resistance has increased greatly in insect populationsImportant! The trait already exists within the genetic make-up of the organism.

  • 4. ReproductionIndividuals that survive and then reproduce, transmit these variations to their offspring

  • 5. SpeciationThe development of a new species occurs as variations or adaptations accumulate in a population over many generationsEx: caveman present man

  • Speciation: Bigfoot? Sasquatch?

  • Evidence which supports the Theory of Evolution

    1. Fossil record2. Comparative anatomy of organisms3. Biogeography (Study of species distribution)4. Molecular Similarities

  • Diversity and classificationThe 5 Major Kingdoms 1. Monera-(Bacteria) 2. Protista 3. Fungi 4. Plant 5. Animal

  • Six Kingdom Taxonomic System

  • Rotting Log Community: An Ecosystem

  • Ecosystem Formation-Ecosystems tend to change over a long period of time until a stable ecosystem is formed.Both the living and nonliving parts of an ecosystem change.

  • (A) Ecological SuccessionThe replacement of one kind of community with another is called ecological succession.The kind of stable ecosystem that develops in a particular geographical area depends on climate.Pioneer organisms- are the first plants to populate an area. Lichens and algae may be pioneer organisms on bare rock. (Create soil)Climax Communities- Succession ends with the development of a climax community in which the populations of plants and animals exist in balance with each other and the environment.

  • Ecological Succession

  • Secondary SuccessionWhen a previously inhabited environment is disturbed, and must undergo a new round of succession.

    Examples- Mt. St. Helens,Yellowstone fires

  • Keystone speciesThese determine the nature and structure of an entire ecosystem. Usually found in small numbers but have a key influence. Examples: Wolves, Fig Trees

  • CoevolutionInterdependent evolution of two speciesResults in symbiotic relationships

  • Coevolution

  • SymbiosisAn intimate relationship between two or more species

  • Mutualism(+ , +)In this relationship both organisms benefit from each other.Ex: Anenome and clown fish

  • Mutualism

  • Commensalism(+ , o)

    One benefits, one not affectedEpiphytes (mosses, orchids, ferns) attach themselves to tree bark and obtain their nutrients without harm to the trees.

  • Parasitism(+ , - )One helped, one harmedPathogens (disease causing agents) are parasite that harm a host organism.Crown gall disease in plants., TICKS

  • PredationPredators exert strong selective pressures upon their prey. Both prey and predator evolve in an attempt to be more successful and survive.

  • Predator/Prey Relationships Data collected from fur pelts from the Hudson Bay Company

  • Studies have shown that Endocrine changes in populations may produce behavioral changes which tend to limit population growth. Therefore all population changes may not be due to predator/prey relationships alone.

  • Defensive Adaptations in AnimalsChemical defenses: Sprays, stinging cellsWarning Coloration: avoidance of predators by unpalatable animals. Ex: Poison Dart Frog.

  • Defensive Adaptations in AnimalsCryptic coloration (Camouflage): Blending into the surroundings for avoidance of predators by palatable animals.Ex: Argentinean Horned Frog

  • Defensive Adaptations in AnimalsMimicry: resemblance to another species.Ex: Io moth, Monarch and Viceroy butterflies

  • CompetitionDifferent species living in the same environment, or habitat, may require the same resources. When the resources are limited, competition occurs among the species.

    Intraspecific: competition within a populationInterspecific: competition between species

  • Competition2.Competition- is the struggle between different species for the same limited resources. The more similar the needs of the species, the more intense the competition.

  • Competition3.Each species occupies a specific niche in the community. A niche is the role the species plays, and includes the type of food it eats, where it lives, where it reproduces, and its relationships with other species.

  • Limiting FactorsAre those resources that are scarce!Cause population size to be limited.Results in resource partitioning and competitive exclusion.

  • Resource Partitioning: differences in resource use among species.

  • Limiting Factors Gauses Experiments

  • Limiting Factors Gauses Experiments

  • Which type of Competition?

  • Interspecific Competition!

  • Competitive Exclusion: one species is excluded from a portion of a niche by another as a result of interspecific competition. (Two species with identical niches cant coexist.)

  • Species RichnessRelated to the # of available nichesTropical rain forests- Most diversity/Low #sMountaintops/Tundra- Low diversity/High #sMore stressful habitats have lower diversity.

  • Community complexity and species diversity

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