EVOLUTION, BIODIVERSITY, AND COMMUNITY PROCESSES

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CHAPTER 5

• EVOLUTION, BIODIVERSITY, AND COMMUNITY PROCESSES

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Life and its Origins- types of organisms

• Biodiversity - Earths many types of life
• All organisms are either
• prokaryotic - single-celled organisms containing
  no internal structures surrounded by membranes
  (therefore there is no nucleus) Kingdom Monera
  with bacteria and cyanobacteria
• eukaryotic - all organisms consisting of cells
  which contain membrane-bound nuclei

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Life and its Origins - types of organisms- 2

• Eukaryotic Kingdoms
• Protista - mostly one-celled organisms
• Fungi - organisms which decompose stuff
• Plantae - organisms which use photosynthesis to
  make their own food
• Animalia - organisms which must get organic
  compounds from food they eat - most are
  invertebrates others have vertebra

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How did Life Emerge on Earth?

• Fossils - mineralized or petrified replicas of
  structures formerly part of living organisms
• Fossil record is incomplete but shows that The
  evolution of life is linked to the physical and
  chemical evolution of the earth
• 4.7 - 4.8 billion years
• chemical evolution - formation of organic
  molecules from which cells could form
• biological evolution -1st prokaryotes then
  eukaryotes

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How did chemical evolution take place?

• Condensation of cosmic dust --gt molten interior
  surrounded by thin, hardened crust
• Water vapor released eventually condensed --gt
  rain which eroded minerals
• Primitive atmosphere probably contained
• carbon dioxide (CO2), nitrogen (N2), water vapor
  with some methane (CH4), ammonia (NH3), hydrogen
  sulfide (H2S) hydrogen chloride (HCl)
• No Oxygen (O2)

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How did chemical evolution take place-2

• Energy-lightning, volcanoes, solar radiation
• Oparin - showed that inorganic molecules can
  form organic molecules
• Organic molecules from meteorites
• Organic molecules from hydrothermal vents
• Protocells may have formed in hot soup of many
  types of organic molecules

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Evolution and Adaptation

• Biological evolution - change in a populations
  (not an individuals) genetic makeup through
  successive generations
• Theory of evolution - descent from earlier,
  ancestral species
• Microevolution - small genetic changes within a
  population (one species)
• Macroevolution - large-scale changes among groups
  of species

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Evolution and Adaptation -2

• Development of genetic variability
• Genes are DNA segments which code for specific
  traits they are parts of chromosomes
• Gene pool consists of all of the possible genes
  (therefore all possible traits) of a population
• Genes have alternative forms (alleles) all
  individuals have different allele combinations

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Evolution and Adaptation - 3 Role of Mutation

• Mutations - random changes in DNA structure
  caused by external agents or internal mistakes
• Mutations occur in all cells mutations in
  reproductive cells are passed on to offspring
• Mutations may be harmless or are lethal
• Mutations - random and unpredictable
• Mutations - source of new genetic material

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Evolution and Adaptation - 4 Role of Natural
Selection

• Some individuals in population have genetically
  based traits increasing chance of survival and
  ability to produce offspring
• Three necessary conditions
• natural variability
• heritable traits
• differential reproduction
• Process of microevolution Genes mutate,
  individuals with adaptive traits are selected,
  populations evolve

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Peppered Moth example of natural selection

• Variability - light gray form was prevalent at
  first dark gray form also existed
• Color form was genetically based
• Environmental change (sooty trees) led to
  differential reproduction light gray forms were
  eaten by birds and didnt reproduce
• Dark gray form became more prevalent - the
  population had become genetically different

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Coevolution and Adaptation limits

• Changes in one species can lead to changes in an
  interacting species
• Animal predator/prey interactions
• Plant/herbivore interactions
• Adaptive trait must be present initially
• Reproductive capacity limits ability to adapt
• Organisms not having the adaptive trait would die
  or not reproduce

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Evolution Misconceptions

• Survival of the fittest refers to reproductive
  success - not a result of direct competition
• A common ancestor had descendants - some of these
  evolved into apes other descendents evolved into
  human species
• There is no plan or goal of perfection in the
  evolutionary process

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Speciation, Extinction Biodiversity

• Speciation - two species arise from one
• Two phases of speciation
• geographic isolation - physical separation of two
  groups of same population - 3 ways are.
• reproductive isolation results in changes in
  allele frequencies --gt divergence --gt inability
  to interbreed and produce viable offspring --gt
  one species has become two different species
• Speciation may be rapid but usually is slow

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Extinction

• Extinction of a species occurs when it ceases to
  exist may follow environmental change - if the
  species does not evolve
• Evolution and extinction are affected by
• large scale movements of continents
• gradual climate changes due to continental drift
  or orbit changes
• rapid climate changes due to catastrophic events

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Extinction - 2

• Background extinction - species disappear at a
  low rate as local conditions change
• Mass extinction - catastrophic, wide-spread
  events --gt abrupt increase in extinction rate
• Five mass extinctions in past 500 million years -
  See Fig. 5-7
• Adaptive radiation - new species evolve during
  recovery period following mass extinction

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Biodiversity

• Biodiversity increases with speciation
• decreases with extinction
• Give-and-take between speciation and extinction
  --gt changes in biodiversity
• Extinction creates evolutionary opportunities for
  adaptive radiation of surviving species
• Human population resource consumption -gt massive
  premature extinction

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Niches and Types of Species

• Ecological niche - a species functional role in
  its ecosystem includes anything affecting
  species survival and reproduction
• Range of tolerance for various physical and
  chemical conditions
• Types of resources used
• Interactions with living and nonliving components
  of ecosystems
• Role played in flow of energy and matter cycling

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Niches and Types of Species - 2

• Habitat is location of species (its address)
• Niche is more - the species occupation
• Fundamental niche - fullest possible niche if no
  competition from other species exists
• Realized niche - part of fundamental niche
  actually occupied
• Understanding of species niches essential

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Niches and Types of Species - 3

• Generalist species have large niches tolerate
  wide range of environmental variations these do
  better during changing environmental conditions
• Specialist species have narrow niches they are
  more likely to become endangered these do better
  under consistent environmental conditions

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Niches and Types of Species - 4

• Native species normally live and thrive in a
  particular ecosystem
• Nonnative species are introduced - can be called
  exotic or alien
• Indicator species serve as early warnings of
  danger to ecosystem- birds amphibians
• Keystone species are considered of most
  importance in maintaining their ecosystem

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Species Interactions

• Species with similar activities or resource
  requirements interact 5 types are
• 1. Interspecific (between species) competition
• What are four possible competition outcomes?
• Which two are related to resource partitioning?

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Species Interactions -2

• 2. Predation - What good (but not kind) effect
  may result from predator-prey relationship?
• 3. Parasitism
• parasite is usually smaller than host (prey)
• draws nourishment from and weakens host
• rarely kills host

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Species Interactions -3

• 4. Mutualism - both interacting species benefit
  for nutrition or protection more common when
  resources are scarce as each species exploits the
  other

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Species Interactions -4

• 5. Commensalism - one interacting species is
  benefitted the other is neither harmed nor
  helped

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Ecological Succession

• The gradual and fairly predictable change in
  species composition of a given area
• Complex sets of species colonize, proliferate and
  then decline as time goes by
• pioneer species --gt mid successional species
  --gt late succession species

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Ecological Succession - 2

• Primary succession- biotic communities are
  gradually established in an area previously
  devoid of living things
• Give examples of primary succession

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Ecological Succession - 3

• Secondary Succession - natural community of
  organisms has been disturbed, removed or
  destroyed
• Give examples of secondary succession

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Agriculture and Plantation forestry

• Agriculture favors use of monoculture - single
  crop, usually early successional herbicides
  limit competition
• Plantation - single, fast-growing species rather
  than diversity of relatively slow-growing species
• Do climax communities exist? Would mature
  community be better? Would biotic change
  reflect unpredictability?

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Ecological Stability Sustainability

• Changing environmental conditions --gt positive
  and negative feedback loops --gt constant dynamic
  change --gt stability
• Inertia - resistance to disturbance or alteration
• Constancy - ability to maintain constant size
  related to available resources
• Resilience - bounce back after external
  disturbance

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Ecological Stability Sustainability

• What are 5 signs of ill health in stressed
  ecosystems?
• Time delays in negative feedback loops --gt slow
  self correcting responses
• Give examples of prolonged delays
• Synergistic interactions - two or more processes
  interact so that combined effect is greater than
  sum of separate effects

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Ecological Stability Sustainability

• How does species diversity relate to ecosystem
  stability?
• Old idea that more diversity more stability
• Necessarily true? Ecosystems must have producers
  and decomposers (animals not necessary)
• Compare rain forest - high diversity, high
  inertia but poor resilience to grasslands

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MacArthur-Wilson island model

• Species equilibrium model or theory of island
  biogeography
• Number of species depends on balance between
  immigration and extinction rates
• Diversity is related to size of island what is
  relationship?
• Diversity is related to distance from mainland
  what is relationship?

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