AP Biology Ecology Unit Chapters 5054

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AP Biology Ecology UnitChapters 50-54
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Intro to Ecology

• Ecology the study of the interactions between
  organisms and their environment
• Uses descriptive observations and manipulative
  experiments
• Organisms are open systems that interact
  continuously with their environments
• The environment of any organism includes
• Biotic Components living members of the same
  species, prey or predator species, competing
  species
• Abiotic Components non-living chemical and
  physical factors

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Levels of Ecology

• Organismal Ecology concerned with the
  morphological, physiological, and behavioral ways
  in which individual organisms meet the challenges
  of its environment
• Population Ecology concentrates on factors that
  affect how many individuals of a species live in
  an area
• Population group of individuals of the same
  species living in a particular geographic area
• Community Ecology deals with the array of
  interacting species in a community. Focuses on
  interactions such as predation, competition, and
  disease
• Community all the organisms of all the species
  that inhabit a particular area

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Levels of Ecology

• Ecosystem Ecology studies energy flow and
  cycling of chemicals among the biotic and abiotic
  factors
• Ecosystem all the abiotic factors in addition to
  the community of a species in a certain area
• Landscape Ecology deals with arrays of
  ecosystems and how they are arranged in a
  geographic region.
• Biome group of similar ecosystem having similar
  abiotic characteristics and biotic populations
• Biosphere the global ecosystemsum of all the
  planets ecosystems
• Ranges from several kilometers into the
  atmosphere and at least 3,000m belowground

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Factors Affecting the Distribution of Organisms

• Biogeography is the study of past and present
  distributions of individual species, which
  provides a good starting point to understanding
  what limits geographic distributions.
• Factors include
• Dispersal
• Potential vs. Actual range
• Behavior
• Habitat Selection
• Biotic Factors (predator-prey relationships)
• Abiotic Factors (Temp, water, sunlight, wind,
  soil)

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Flowchart of factors limiting geographic
distribution
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Species Transplant Experiments

• If the transplant was successful, then the
  potential range of the species is larger than the
  actual range.
• If the transplant was unsuccessful, then
  distribution is limited by other species or
  abiotic factors.
• Problems with Introduced Species.
• Transplanted species often explode to occupy a
  new area.
• The African honeybee and Zebra mussel are good
  examples of this explosion.

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The African Honeybee

• The African Honeybee is a very aggressive
  subspecies of honeybee that was brought to Brazil
  in 1956 to breed a variety that would produce
  more honey.
• The bees escaped by accident in 1957 and have
  been spreading through the Americas ever since
• Because they are aggressive they drive out the
  native bees.
• They have been moving 110 km north every year
• Will they be able to continue north?

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The Zebra Mussel

• In 1988 the zebra mussel (small mollusk native to
  Caspian Sea of Asia) was discovered in Lake St.
  Claire (Detroit)
• It reproduces rapidly and forms dense clusters.
• Have reached densities of 750,000 per square
  meter in Lake Erie
• Clog sewer and water intake pipes
• Suspension feedersare cleaning the waters
• In the Hudson River, NY
• Phytoplankton was decreased by 85
• Zooplankton was decreased by 70
• Zebra mussels are crowding out native mollusks
  leading toward extinction

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Biomes

• Biomes, the major types of ecosystems.
• Determined by Climate, the prevailing weather
  conditions in an area.
• Temperature, water, light, and wind are major
  components of climate.
• Climate determines the makeup of Annual means for
  temperature and rainfall are reasonably well
  correlated with the biomes we find in different
  regions.
• Global climate patterns are largely determined by
  sunlight and the planets movement in space.
• The suns warming effect on the atmosphere, land,
  and water establishes the temperature variations,
  cycles of air movement, and evaporation of water
  that are responsible for latitudinal variations
  in climate.

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Aquatic Biomes

• Aquatic biomes occupy the largest part of the
  biosphere
• Marine biomes have a salt concentration of
  approximately 3 and cover approximately 75 of
  the earths surface.
• Freshwater biomes are usually characterized by
  salt concentration of less than 1 and are
  closely linked to the soils and biotic components
  of the terrestrial biomes through which they
  pass.
• Vertical stratification of aquatic biomes.
• The photic zone is the zone through which light
  penetrates and photosynthesis can occur.
• The aphotic zone is where very little light can
  penetrate.
• The benthic zone is the bottom of any aquatic
  biome and contains detritus, dead organic matter.

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Freshwater Biomes

• Oligotrophic lakes are deep, nutrient-poor and do
  not contain much life.
• Eutrophic lakes are shallower and have increased
  nutrients.
• Mesotrophic lakes have a moderate amount of
  nutrients and phytoplankton productivity.
• Over long periods of time, oligotrophic lakes may
  become mesotrophic as runoff brings in nutrients.
• Pollution from fertilizers can cause explosions
  in algae population and cause a decrease in
  oxygen content.

Oligotrophic
Eutrophic
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Lake Stratification and Turnover
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Distribution of Major Terrestrial Biomes
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Tropical Forests
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Savanna
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Desert
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Chaparral
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Temperate Grassland
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Temperate Deciduous Forest
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Coniferous Forest
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Tundra
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AP BIOLOGY

• Chapter 51 Behavioral Biology

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What is Behavior?

• Behavior is what an animal does and how it does
  it.
• has both proximate and ultimate causes
• Proximate questions are mechanistic, concerned
  with the environmental stimuli that trigger a
  behavior, as well as the genetic and
  physiological mechanisms underlying a behavioral
  act.
• Ultimate questions address the evolutionary
  significance for a behavior and why natural
  selection favors this behavior.
• Behavior results from both genes and
  environmental factors
• Ethology is the study of how animals behave in
  their natural habitat

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Fixed Action Patterns

• Fixed action pattern (FAP) A sequence of
  behavioral acts that is essentially unchangeable
  and usually carried to completion once initiated.
• triggered by an external sensory stimulus known
  as a sign stimulus (stimuli are usually obvious
  and from another species).
• Example Moths drop when they sense bats
• occurs in a series of actions the same way every
  time.
• Many animals tend to use a relatively small
  subset of the sensory information available to
  them and behave stereotypically.
• They do not read the entire situation
• Can be easily tricked
• Some simple behaviors can be explained with FAPs,
  they are too simplicstic to account for much of
  animal behavior

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FAP Experiments

• Male stickleback fish will attack any objects
  with a red belly in attempt to defend their
  territory. The realistic fish is not attacked
  because it lacks the red.

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Behavioral Ecology

• Behavioral ecology is the research field that
  views behavior as an evolutionary adaptation to
  the natural ecological conditions of animals.
• We expect animals to behave in ways that maximize
  their fitness (this idea is valid only if genes
  influence behavior).
• Songbird repertoires provide us with examples.
• Why has natural selection favored a multi-song
  behavior?
• It may be advantageous for males attracting
  females.
• Cost-benefit analysis of foraging behavior.
• Foraging is food-obtaining behavior.
• The optimal foraging theory states that natural
  selection will benefit animals that maximize
  their energy intake-to-expenditure ratio.

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Foraging Behavior Example

• In feeding on Daphnia the bluegill sunfish do not
  feed randomly but tend to select prey based on
  apparent size information about both prey size
  and distance.
• Fish will pursue the one that looks largest
• Small prey at close distance may be taken with
  small energy expenditure
• More distant but larger prey will require more
  energy to catch, but provide higher energy
  yield

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Types of Behaviors Learning

• Learning is the modification of behavior
  resulting from specific experiences.
• Involves both innate or developmentally fixed
  behaviors and environmental experience
• Example The alarm calls of vervet monkeys are
  different for different types of predators
  (leopards, eagles, snakes) along with the
  confirmation call and physical response of others
  for the call
• With age infant monkeys learn to give the proper
  call and elicit the proper behavior for each
  call
• Maturation is the situation in which a behavior
  may improve because of ongoing developmental
  changes in neuromuscular systemsnot true
  learning
• Example Flight in birds As a bird continues to
  develop its muscles and nervous system, it is
  able to fly.
• Habituation involves a loss of responsiveness to
  unimportant stimuli or stimuli that do not
  provide appropriate feedback.
• May increase fitness by allowing an animals
  nervous system to focus on stimuli that signal
  food, mates, or real danger instead of wasting
  time and energy on other irrelevant stimuli
• Example some animals stop responding to warning
  signals if signals are not followed by a predator
  attack (the cry-wolf effect).

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Types of Behaviors Learning

• Imprinting is the recognition, response, and
  attachment of young to a particular adult or
  object.
• Konrad Lorenz experimented with geese that spent
  the first hours of their life with him and after
  time responded to him as their parent.
• Lorenz isolated geese after hatching and found
  that they could no longer imprint on anything.
• What is innate in these birds is the ability to
  respond to a parent figure, while the outside
  world provides the imprinting stimulus.
• The sensitive period is a limited phase in an
  individual animals development when learning
  particular behaviors can take place
• Development of behavior can be explained using
  bird songs
• Some songbirds have a sensitive period for
  developing their songs.
• Individuals reared in silence perform abnormal
  songs, but if recordings of the proper songs are
  played early in the life of the bird, normal
  songs develop.
• Canaries exhibit open-ended learning where they
  add new syllables to their song as the get older.
• Also seen in humans as children can learn a
  second language very easily

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Types of Behaviors Learning

• Associative learning is the ability of many
  animals to learn to associate one stimulus with
  another.
• Classical conditioning is a type of associative
  learning.
• Ivan Pavlov exposed dogs to a bell ringing and at
  the same time sprayed their mouths with powdered
  meat, causing them to salivate.
• Soon, the dogs would salivate after hearing the
  bell, even if they were not getting any powdered
  meat.
• Operant conditioning or trial-and-error
  learningan animal learns to associate one of its
  own behaviors with a reward or a punishment.
• Example predators learn to associate certain
  types of potential prey with painful experiences
  and modify behavior
• Play as a behavior has no apparent external goal,
  but may facilitate social development or practice
  of certain behaviors and provide exercise.
• Involves movements closely associated with
  goal-directed behaviorsstalking and attacking

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Types of Behaviors Cognition

• Cognition is the ability of an animals nervous
  system to perceive, store, process, and use
  information gathered by sensory receptors.
• connects nervous system function with behavior
• Using tools, problem solving, feigning injuries
• Cognitive ethology study of animal cognition
• Animals use various cognitive mechanisms during
  movement through space
• Kinesis is a change in activity rate in response
  to a stimulus.
• For example, sowbugs are more active in dry areas
  and less active in humid areas.
• Taxis is an automatic, oriented movement toward
  or away from a stimulus.
• For example, phototaxis, chemotaxis, and
  geotaxis.
• Some organisms move in response to a recognized
  object, a landmark, or an environmental cue.
• Some animals form cognitive maps (internal codes
  of spatial relationships of objects in the
  environment).

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Types of Behaviors Cognition

• Migration is the regular movement of animals over
  relatively long distances.
• Piloting an animal moves from one familiar
  landmark to another until it reaches its
  destination.
• Orientation animals can detect directions and
  travel in particular paths until reaching
  destination.
• Navigation involves determining ones present
  location relative to other locations, in addition
  to detecting compass directions

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Types of Behaviors Cognition

• The study of consciousness poses a unique
  challenge for scientists
• Besides humans, are animals aware of themselves?
• Some would argue that certain behaviors are a
  result of conscious processing.
• Sociobiology places social behavior in an
  evolutionary context
• Social behavior is any kind of interaction
  between two or more animals, usually of the same
  species.
• Competitive social behaviors often represent
  contests for resources
• Cooperation when a social group carries out
  behavior more efficiently than a single
  individual
• Agonistic behavior is a contest involving both
  threats and submissive behavior. Determines who
  gets access to some resource (food, mates, etc)
• Most of the behaviors are Ritual the use of
  symbolic activity, without serious harm done
• Degree of combat that is ritual depends on
  scarcity of the resource

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Types of Behaviors Cognition

• Reconciliation behavior often happens between
  conflicting individuals after agnostic behavior
  who live in close social groups
• Dominance hierarchies involve a ranking of
  individuals in a group (a pecking order).
• Alpha, beta rankings exist.
• The alpha organisms control the behavior of
  others.
• Top ranking animal is assured access to food and
  mates

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Types of Behaviors Cognition

• Territoriality is behavior where an individual
  defends a particular area, called the territory.
• Territories are typically used for feeding,
  mating, and rearing young and are fixed in
  location.
• Benefits are exclusive access to food, breeding
  areas, and places to raise young. Familiarity
  with territory makes it easier to avoid
  predators. Helps to stabilize population density
• Drawbacks are that territoriality uses a great
  deal of an individuals energy an individual
  might die or miss a reproductive opportunity as a
  result of defending a territory.
• Ownership of territories is continually
  proclaimed
• Songs or noises
• Spraying behavior is where an individual marks
  its territory.
• Defense of territories are directed at
  conspecifics

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Types of Behaviors Mating Behaviors

• Natural selection favors mating behavior that
  maximizes the quantity or quality of mating
  partners
• Courtship behavior consists of patterns that lead
  to copulation and consists of a series of
  displays and movements by the male or female.
• Parental investment refers to the time and
  resources expended for raising of offspring.
• Generally lower in males because they are capable
  of producing more gametes (which are also
  smaller), therefore making each one less
  valuable.
• Females usually invest more time into parenting
  because they make fewer, larger gametes, a
  process which is energetically more expensive,
  thus making each gamete more valuable.
• Mate choice females are usually more
  discriminating in terms of the males with whom
  they choose to mate.
• Females look for more fit males (i.e., better
  genes), the ultimate cause of the choice.

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Types of Behaviors Mating Behaviors

• Mating systems differ among species.
• Usually based on the needs of the young and the
  certainty of paternity
• Example baby birds require large amount of
  continuous care a male is more likely to leave
  more viable offspring if he sticks around and
  helps raise the young then if he goes off seek
  more mates
• Promiscuous no strong pair-bond between males
  and females.
• Monogamous one male mating with one female.
• Polygamous an individual of one sex mating with
  several of the other sex.
• Polygyny is a specific example of polygamy, where
  a single male mates with many females.
• Polyandry occurs in some species where one female
  mates with several males.

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Types of Behavior Communication

• Social interactions depend on diverse modes of
  communication
• A signal is a behavior that causes a change in
  the behavior of another animal.
• The transmission of, reception of, and response
  to signals make up communication.
• Examples include the following
• Displays such as singing and howling.
• Visual, chemical, tactile, electrical signals
• Pheromones are chemicals released by an
  individual that bring about mating and other
  behaviors.
• Used to attract mates, leave trails (ants),
  outline territory
• Example The Dance of the Honeybee.
• If an individual finds a good food source, it
  will communicate the location to others in the
  hive through an elaborate dance.

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Types of Behaviors Altruistic

• Most social behaviors are selfish, so how do we
  account for behaviors that help others?
• Altruism is defined as behavior that might
  decrease individual fitness, but increase the
  fitness of others.
• Inclusive fitness How can a naked mole rat
  enhance its fitness by helping other members of
  the population?
• How is altruistic behavior maintained by
  evolution?
• If related individuals help each other, they are
  in affect helping keep their own genes in the
  population.
• Inclusive fitness is defined as the effect an
  individual has on proliferating its own genes by
  reproducing and by helping relatives raise
  offspring.
• Hamiltons Rule and Kin Selection a quantitative
  measure for predicting when natural selection
  would favor altruistic acts.
• Hamiltons rule states that natural selection
  favors altruistic acts.
• The more closely related two individuals are, the
  greater the value of altruism.
• Kin selection is the mechanism of inclusive
  fitness, where individuals help relatives raise
  young.
• Reciprocal altruism, where an individual aids
  other unrelated individuals without any benefit,
  is rare, but sometimes seen in primates (often in
  humans).

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Examples of Altruism

• Belding Ground Squirrels signal alarm calls to
  warn others of dangergiving signal increases
  chance of being eaten
• Mole Rats live in colonies with only one
  reproducing female queen who mates with one to
  three kings . Nonreproductive members of the
  colony forage and care for queen, kings, and
  offspring. Will sacrifice lives to protect the
  colony

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Humans and Sociobiology

• Sociobiology maintains that much of human social
  behavior and cultures can be understood on
  evolutionary and basic biological terms

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AP Biology

• Chapter 52 Population Ecology

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Populations

• A population is a group of individuals of a
  single species that simultaneously occupy the
  same general area.
• The characteristics of populations are shaped by
  the interactions between individuals and their
  environment.
• Two important characteristics of any population
  are density and the spacing of individuals
• Populations have size and geographical
  boundaries.
• The density of a population is measured as the
  number of individuals per unit area.
• The dispersion of a population is the pattern of
  spacing among individuals within the geographic
  boundaries.

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Measuring Density

• Measuring density of populations is a difficult
  task.
• We can count individuals we can estimate
  population numbers.
• Unfortunately, it is usually impractical to
  attempt to count individuals in a population.
• One sampling technique that researchers use is
  known as the mark-recapture method.
• Individuals are trapped in an area and captured,
  marked with a tag, recorded, and then released.
• After a period of time has elapsed, traps are set
  again, and individuals are captured and
  identified.
• This information allows estimates of population
  changes to be made.

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Patterns of Dispersion

• Within a populations geographic range, local
  densities may vary considerably.
• Different dispersion patterns result within the
  range.
• Overall, dispersion depends on resource
  distribution.
• Clumped dispersion is when individuals aggregate
  in patches.
• By contrast, uniform dispersion is when
  individuals are evenly spaced.
• In random dispersion, the position of each
  individual is independent of the others.

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Demography

• Demography is the study of factors that affect
  the growth and decline of populations
• Additions occur through birth, and subtractions
  occur through death.
• Demography studies the vital statistics that
  affect population size.
• A life table is an age-specific summary of the
  survival pattern of a population.
• The best way to construct life table is to follow
  a cohort, a group of individuals of the same age
  throughout their lifetime.
• A graphic way of representing the data is a
  survivorship curve.
• This is a plot of the number of individuals in a
  cohort still alive at each age.
• Type I curve shows a low death rate early in life
  (humans).
• Type II curve shows constant mortality
  (squirrels).
• Type III curve shows a high death rate early in
  life (oysters).

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Life Tables and Survivorship Curves
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Reproductive Rates

• Demographers that study populations usually
  ignore males, and focus on females because only
  females give birth to offspring.
• A reproductive table is an age-specific summary
  of the reproductive rates in a population.
• For sexual species, the table tallies the
  number of female offspring produced by each
  age group.

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Life Histories

• The traits that affect an organisms schedule of
  reproduction and survival make up its life
  history.
• Life histories are highly diverse, but they
  exhibit patterns in their variability
• Life histories are a result of natural
  selection, and often parallel environmental
  factors.
• big-bang reproduction or semelparity where large
  numbers of offspring are produced in each
  reproduction, after which the individual often
  dies. (ex. Agave plant)
• repeated reproduction or iteroparity some
  organisms produce only a few eggs during yearly
  cycles

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Life Histories

• What factors contribute to the evolution of
  semelparity and iteroparity?
• Limited resources mandate trade-offs between
  investments in reproduction and survival
• Life-histories represent an evolutionary
  resolution of several conflicting demands.
• The number of offspring produced at each
  reproductive episode exhibits a trade-off between
  number and quality of offspring.

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Population Growth

• We define a change in population size based on
  the following verbal equation.Change in
  Population Births during - Deaths during
  Size during time interval time interval
  time interval
• Using mathematical notation, we can express this
  relationship as follows
• If N represents population size, and t represents
  time, then ? N is the change is population size
  and ?t represents the change in time, then
• ? N/? t B-D
• Where B is the number of births and D is the
  number of deaths
• We can simplify the equation and use r to
  represent the difference in per capita birth and
  death rates.
• ? N/ ? t rN OR dN/dt rN
• If B D then there is zero population growth
  (ZPG).

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Exponential Growth

• Under ideal conditions, a population grows
  rapidly Exponential population growth
• Under these conditions, we may assume the maximum
  growth rate for the population (rmax) to give us
  the following exponential growth equation
• dN/dt rmaxN

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Logistic Growth

• Typically, unlimited resources are rare.
  Population growth is therefore regulated by
  carrying capacity (K), which is the maximum
  stable population size a particular environment
  can support.
• The logistic population growth model incorporates
  the effect of population density on the rate of
  increase.
• Mathematically, we start with the equation for
  exponential growth, creating an expression that
  reduces the rate of increase as N increases
• dN/dt rmaxN((K-N)/K)
• The graph of this equation shows an S-shaped
  curve.

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Logistic Growth

• Logistic model assumes that the population growth
  rate dN/dt decreases as N increases
• When N is close to 0, population grows rapidly
• As N approaches K, the growth rate approaches 0
  and the population growth slows
• If N is greater than K, population growth rate
  is negative, and size decreases
• Equilibrium reached at the white line when NK

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How well does Logistic Model fit the growth of
Real Populations?

• The growth of laboratory populations of some
  animals fits the S-shaped curves fairly well.
• Some of the assumptions built into the logistic
  model do not apply to all populations.
• It is a model which provides a basis from which
  we can compare real populations.

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The logistic population growth model and life
histories

• This model predicts different growth rates for
  different populations relative to carrying
  capacity.
• Resource availability depends on the situation.
• The life-history traits that natural selection
  favors may vary with population density and
  environmental conditions.
• In K-selection, or density-dependent selection,
  organisms live and reproduce around K, and are
  sensitive to population density.
• In r-selection, or density-independent selection,
  organisms exhibit high rates of reproduction and
  occur in variable environments in which
  population densities fluctuate well below K.

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Population Limiting Factors

• Why do all populations eventually stop growing?
• What environmental factors stop a population from
  growing?
• The first step to answering these questions is to
  examine the effects of increased population
  density.
• Density-dependent factors increase their affect
  on a population as population density increases.
• This is a type of negative feedback.
• Density-independent factors are unrelated to
  population density, and there is no feedback to
  slow population growth.

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Negative Feedback

• Negative feedback prevents unlimited population
  growth
• Resource limitation in crowded populations can
  stop population growth by reducing reproduction.
• Intraspecific competition for food can also cause
  density-dependent behavior of populations.
• Territoriality, defense of a space, may set a
  limit on density.
• Predation may also be a factor because it can
  cause mortality of prey species.
• Waste accumulation is another component that can
  regulate population size.
• Disease can also regulate population growth,
  because it spreads more rapidly in dense
  populations.
• Population dynamics reflect a complex interaction
  of biotic and abiotic influences
• Carrying capacity can vary.
• Some populations fluctuate erratically, based on
  many factors.
• Some populations have regular boom-and-bust
  cycles
• Example the lynx and snowshoe hare that cycle on
  a ten year basis.

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Figure 52.17 Long-term study of the moose (Alces
alces) population of Isle Royale, Michigan
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Figure 52.19 Population cycles in the snowshoe
hare and lynx
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Human Population Growth

• The human population has been growing almost
  exponentially for three centuries but cannot do
  so indefinitely
• The human population increased relatively slowly
  until about 1650 when the Plague took an untold
  number of lives.
• Ever since, human population numbers have doubled
  twice.
• How might this population increase stop?

63
The Demographic Transition.

• A regional human population can exist in one of 2
  configurations.
• Zero population growth high birth rates high
  death rates.
• Zero population growth low birth rates low
  death rates.
• The movement from the first toward the second
  state is called the demographic transition.

64
Age Structures

• Age structure is the relative number of
  individuals of each age.
• Age structure diagrams can reveal a populations
  growth trends, and can point to future social
  conditions.

65
Estimating Earths Carrying Capacity

• Estimating Earths carrying capacity for humans
  is a complex problem
• Predictions of the human population vary from 7.3
  to 10.7 billion people by the year 2050.
• Will the earth be overpopulated by this time?
• Wide range of estimates for carrying capacity.
• What is the carrying capacity of Earth for
  humans?
• This question is difficult to answer.
• Estimates are usually based on food, but human
  agriculture limits assumptions on available
  amounts.

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Ecological footprint.

• Humans have multiple constraints besides food.
• The concept an of ecological footprint uses the
  idea of multiple constraints.
• For each nation, we can calculate the aggregate
  land and water area in various ecosystem
  categories.
• Six types of ecologically productive areas are
  distinguished in calculating the ecological
  footprint
• Land suitable for crops.
• Pasture.
• Forest.
• Ocean.
• Built-up land.
• Fossil energy land.

67
AP Biology

• Chapter 53Community Ecology

68
What is a community?

• A community is defined as an assemblage of
  species living close enough together for
  potential interaction.
• Communities differ in their species richness, the
  number of species they contain, and the relative
  abundance of different species.
• Contrasting views of communities are rooted in
  the individualistic and interactive hypotheses
• An individualistic hypothesis depicts a community
  as a chance assemblage of species found in the
  same area because they happen to have similar
  abiotic requirements.
• An interactive hypothesis depicts a community as
  an assemblage of closely linked species locked in
  by mandatory biotic interactions.
• These two very different hypotheses suggest
  different priorities in studying biological
  communities.
• In most actual cases, the composition of
  communities does seem to change continuously.

69
Interspecific Interactions and Community
Structure

• There are many different interspecific
  interactions, relationships between the species
  of a community.
• Populations may be linked by
• Competition
• Predation
• Mutualism
• Commensalism

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Competition

• Interspecific competition for resources can occur
  when resources are in short supply.
• There is potential for competition between any
  two species that need the same limited resource.
• The competitive exclusion principle two species
  with similar needs for same limiting resources
  cannot coexist in the same place.
• two species cannot coexist in a community if
  their niches are identical.
• The ecological niche is the sum total of an
  organisms use of abiotic/biotic resources in the
  environment or its role in the environment.
• Resource partitioning is the differentiation of
  niches that enables two similar species to
  coexist in a community.
• Character displacement is the tendency for
  characteristics to be more divergent in sympatric
  populations of two species than in allopatric
  populations of the same two species.

71
Gauses Paramecium Experiment

• The two species of Paramecium used by Gause grew
  well by them selves but P. caudium was out
  competed by P. aurelia when the two were grown
  together.
• Experiment supports Competition Exclusion
  Principle

72
Competitive Exclusion Principle
73
Resource Partitioning
74
Character Displacement
75
Predation

• A predator eats prey
• Herbivory, in which animals eat plants.
• In parasitism, predators live on/in a host and
  depend on the host for nutrition.
• Predator adaptations many important feeding
  adaptations of predators are both obvious and
  familiar.
• Ex Claws, teeth, fangs, poison, heat-sensing
  organs, speed, and agility.
• Prey have adaptations to avoid being eaten
• Plant defenses against herbivores include
  chemical compounds that are toxic.
• Animals behavioral defenses include fleeing,
  hiding, self-defense, noises, and mobbing.
• Camouflage includes cryptic coloration, deceptive
  markings.
• Mechanical defenses include spines.
• Chemical defenses include odors and toxins
• Aposematic coloration is indicated by warning
  colors, and is sometimes associated with other
  defenses (toxins).
• Mimicry is when organisms resemble other species.
• Batesian mimicry is where a harmless species
  mimics a harmful one.
• Müllerian mimicry is where two or more
  unpalatable species resemble each other.

76
Camouflage
Aposematic (warning) coloration
Deceptive Coloration
77
Mimicry
Batesian Mimicry Harmless caterpillar mimics
dangerous snake
Mullerian Mimicry Harmful species resemble each
other
78
Symbiotic Relationships

• Parasitism one organism benefits and one is
  harmed
• Parasites and pathogens as predators.
• A parasite derives nourishment from a host, which
  is harmed in the process.
• Endoparasites live inside the host and
  ectoparasites live on the surface of the host.
• Parasitoidism is a special type of parasitism
  where the parasite eventually kills the host.
• Pathogens are disease-causing organisms that can
  be considered predators.

79
Symbiosis

• Mutualism is where two species benefit from their
  interaction.
• Examples Rhino birds Rhinos, Ants Acacias
• Commensalism is where one species benefits from
  the interaction, but other is not affected.
• Example barnacles on a whale.
• Coevolution refers to reciprocal evolutionary
  adaptations of two interacting species.
• When one species evolves, it exerts selective
  pressure on the other to evolve to continue the
  interaction.

80
Summary of Interspecific Interactions
81
Trophic Structure

• The trophic structure of a community is
  determined by the feeding relationships between
  organisms.
• The transfer of food energy from its source in
  photosynthetic organisms through herbivores and
  carnivores is called the food chain.
• Charles Elton first pointed out that the length
  of a food chain is usually four or five links,
  called trophic levels.
• He also recognized that food chains are not
  isolated units but are hooked together into food
  webs.
• Food webs describe
• Who eats whom in a community?
• Trophic relationships can be diagrammed in a
  community.
• What transforms food chains into food webs?
• A given species may weave into the web at more
  than one trophic level.

82
Food Chains

• All food chains start with producers, an
  autotroph who can make food using inorganic
  molecules
• All other trophic levels contain consumers or
  heterotrophs who must eat or consume other
  organisms

83
Food Webs

• Multiple food chains can be combined to form a
  web.
• Some organisms can be in more than one trophic
  level (ex. Leopard seal)

84
What limits the length of a food chain?

• The energetic hypothesis suggests that the length
  of a food chain is limited by the inefficiency of
  energy transfer along the chain.
• Only 10 of the energy from one trophic level is
  transferred into the next
• The dynamic stability hypothesis states that long
  food chains are less stable than short chains.
• Fluctuations at lower trophic levels are
  magnified in higher levels, potentially causing
  extinction of top predators

85
Dominant and Keystone Species

• Certain species may have a large impact on the
  entire community because of either their
  abundance or their role.
• Dominant species are those in a community that
  have the highest abundance or highest biomass
  (the sum weight of all individuals in a
  population).
• If we remove a dominant species from a community,
  it can change the entire community structure,
  both biotic and abiotic.
• Keystone species exert an important regulating
  effect on other species in a community.
• If they are removed, community structure is
  greatly affected.
• Example Sea Star

86
Keystone Species Example

• Pisaster ochraceous eats mussels from tidal
  pools.
• If sea stars are removed, mussels take over and
  outcompete all other species.
• Predation by the sea star limits the number of
  mussels and decreases their competitive edge
  and allows other species to use the space

87
Community Control

• Simplified models based on relationships between
  adjacent trophic levels are useful for discussing
  how communities might be organized.
• Consider three possible relationships between
  plants (V for vegetation) and herbivores (H).
• V ? H V ? H V ? H
• Arrows indicate that a change in biomass of one
  trophic level causes a change in the other
  trophic level.
• The bottom-up model postulates V ? H linkages,
  where nutrients and vegetation control community
  organization.
• An increase in vegetation will impact the biomass
  of herbivores, herbivores are limited by
  vegetation. Usually involves nutrients or abiotic
  factors
• The top-down model postulates that it is mainly
  predation that controls community organization V
  ? H.
• Increases predators will decrease herbiovers,
  which in turn control plants
• Other models go between the bottom-up and
  top-down extreme models.
• All interactions between trophic levels could be
  reciprocal

88
Disturbance and Community Structure

• Disturbances affect community structure and
  stability.
• Stability is the ability of a community to
  persist in the face of disturbance.
• Most communities are in a state of nonequilibrium
  owing to disturbances
• Disturbances are events like fire, weather, or
  human activities that can alter communities.
• Disturbances do not always have a negative impact
  on communities, but in many cases they are
  necessary for community development and survival.
• Humans are the most widespread agents of
  disturbance
• Human activities cause more disturbances than
  natural events and usually reduce species
  diversity in communities.

89
Succession

• Ecological succession is the sequence of
  community changes after a disturbance or the
  transition in species composition over ecological
  time.
• Primary succession begins in a lifeless area
  where soil has not yet formed.
• Mosses and lichens colonize first and cause the
  development of soil, called pioneer species.
• Examples after a glacier has retreated, new
  volcanic island
• Secondary succession occurs where an existing
  community has been cleared by some event, but
  the soil is left intact.
• Grasses grow first, then trees and other
  organisms.
• Soil concentrations of nutrients show changes
  over time.
• Examples range from an old tree falling to a
  widespread forest fire or natural disaster

90
Biodiversity

• Two key factors correlated with a communitys
  biodiversity (species diversity) are its size and
  biogeography.
• Community biodiversity measures the number of
  species and their relative abundance
• The variety of different kinds of organisms that
  make up a community has two components.
• Species richness, the total number of species in
  the community.
• Relative abundance of the different species.
• Heterogeneity is the combination of richness and
  diversity and is used to measure biodiversity

91
Which is more diverse?

• Imagine two small forest communities with 100
  individuals distributed among four different tree
  species.
• Species richness may be equal, but relative
  abundance may be different.
• Counting species in a community to determine
  their abundance is difficult, especially for
  insects and smaller organisms

92
Species Richness vs. Equatorial-Polar Gradient

• Species richness generally declines along an
  equatorial-polar gradient
• Tropical habitats support much larger numbers of
  species of organisms than do temperate and polar
  regions.
• The two key factors causing these gradients are
  probably evolutionary history and climate.
• Organisms have a history in an area where they
  are adapted to the climate.
• Energy and water may factor into this phenomenon.

93
Species Richness Community Size

• Species richness is related to a communitys
  geographic size
• The species-area curve quantifies what may seem
  obvious the larger the geographic area, the
  greater the number of species.

94
Biodiversity on Islands

• Because of their size and isolation, islands
  provide great opportunities for studying some of
  the biogeographic factors that affect the species
  diversity of communities.
• Imagine a newly formed island some distance from
  the mainland.
• Robert MacArthur and E. O. Wilson developed a
  hypothesis of island biogeography to identify the
  determinants of species diversity on an island.
• Two factors will determine the number of species
  that eventually inhabit the island.
• The rate at which new species immigrate to the
  island.
• The rate at which species become extinct.
• Studies of plants on many island chains confirm
  their hypothesis.

95
Hypothesis of Island Biogeography

• The equilibrium number of species on an island
  represents a balance between the immigration of
  new species to the island and the extinction of
  species already there
• Large islands may have a larger equilibrium
  because immigration rates tend to be higher and
  extinction rates lower
• Near islands tend to have larger immigration
  rates

96
Evidence of Island Biogeography Hypothesis

• Galapagos islands show an increase of the number
  of plant species as the area of the island
  increases

97
AP Biology

• Chapter 54Ecosystems

98
Ecosystems

• An ecosystem consists of all the organisms living
  in a community as well as all the abiotic factors
  with which they interact.
• The dynamics of an ecosystem involve two
  processes
• energy flow
• chemical cycling
• Ecosystem ecologists view ecosystems as energy
  machines and matter processors.
• We can follow the transformation of energy by
  grouping the species in a community into trophic
  levels of feeding relationships.

99
Trophic Relationships

• Autotrophs are the primary producers, and are
  usually photosynthetic (plants or algae).
• They use light energy to synthesize sugars and
  other organic compounds.
• Heterotrophs are at trophic levels above the
  primary producers and depend on their
  photosynthetic output.
• Herbivores that eat primary producers are called
  primary consumers.
• Carnivores that eat herbivores are called
  secondary consumers.
• Carnivores that eat secondary consumers are
  called tertiary consumers.
• Another important group of heterotrophs is the
  detritivores, or decomposers.
• They get energy from detritus, nonliving organic
  material, and play an important role in material
  cycling.

100
Ecosystem Dynamics
101
Decomposition Connects Trophic Levels

• The organisms that feed as detritivores often
  form a major link between the primary producers
  and the consumers in an ecosystem.
• The organic material that makes up the living
  organisms in an ecosystem gets recycled.
• An ecosystems main decomposers are fungi and
  prokaryotes, which secrete enzymes that digest
  organic material and then absorb the breakdown
  products.

102
Laws

• The law of conservation of energy applies to
  ecosystems. (Energy can be neither created nor
  destroyed, only transformed)
• We can potentially trace all the energy from its
  solar input to its release as heat by organisms.
• The second law of thermodynamics (When converting
  energy, some is lost as heat) allows us to
  measure the efficiency of the energy conversions.
• Energy moves in a straight line through an
  ecosystem. Sun?Producers?Consumers
• ENERGY CANNOT BE CYCLED

103
Primary Production

• The amount of light energy converted to chemical
  energy by an ecosystems autotrophs in a given
  time period is called primary production.
• An ecosystems energy budget depends on primary
  production
• Most primary producers use light energy to
  synthesize organic molecules, which can be broken
  down to produce ATP
• Every day, Earth is bombarded by large amounts of
  solar radiation. Most of this radiation lands on
  water and land that either reflect or absorb it.
• Of the visible light that reaches photosynthetic
  organisms, only about 1 is converted to chemical
  energy.
• Although this is a small amount, primary
  producers are capable of producing about 170
  billion tons of organic material per year.
• Total primary production is known as gross
  primary production (GPP).
• Amount of light energy that is converted into
  chemical energy.
• The net primary production (NPP) is equal to
  gross primary production minus the energy used by
  the primary producers for respiration (R)
• NPP GPP R
• Primary production can be expressed in terms of
  energy per unit area per unit time, or as biomass
  of vegetation added to the ecosystem per unit
  area per unit time.
• The total biomass of photosynthetic autotrophs
  present in a given time, called the standing
  cropnot the same thing

104
Primary Production in Aquatic Ecosystems

• Production in Marine Ecosystems.
• Light is the first variable to control primary
  production in oceans, since solar radiation can
  only penetrate to a certain depth (photic zone).
• Nitrogen is the one nutrient that limits
  phytoplankton growth in many parts of the ocean.
• In the open ocean, nitrogen and phosphorous
  levels are very low in the photic zone, but high
  in deeper water where light does not penetrate.
• Production in Freshwater Ecosystems.
• Solar radiation and temperature are closely
  linked to primary production in freshwater lakes.
• During the 1970s, sewage and fertilizer pollution
  added nutrients to lakes, which shifted many
  lakes from having phytoplankton communities to
  those dominated by diatoms and green algae.
• This process is called eutrophication and has
  undesirable impacts from a human perspective.
• Controlling pollution may help control
  eutrophication.

105
Primary Production in Terrestrial Ecosystems

• On a large geographic scale, temperature and
  moisture/water availability are the key factors
  controlling primary production in ecosystems.
• On a more local scale, mineral nutrients in the
  soil can play key roles in limiting primary
  production.
• Scientific studies relating nutrients to
  production have practical applications in
  agriculture.
• (i.e. fertilizers)

106
Primary Production in Different Ecosystems
107
Secondary Production

• The amount of chemical energy in consumers food
  that is converted to their own new biomass during
  a given time period is called secondary
  production.
• The efficiency of energy transfer between trophic
  levels is usually less than 20
• If we view animals as energy transformers, we can
  ask questions about their relative efficiencies.
• Production efficiency Net secondary
  production/Assimilation of primary production
• Net secondary production is the energy stored in
  biomass represented by growth and reproduction.
• Assimilation consists of the total energy taken
  in and used for growth, reproduction, and
  respiration.
• In other words production efficiency is the
  fraction of food energy that is not used for
  respiration.
• Trophic efficiency is the percentage of
  production transferred from one trophic level to
  the next.

108
Energy Partitioning

• Less than 17 of the caterpillars food is
  actually converted to caterpillar biomass

109
Ecological Pyramids

• Pyramids of production represent the
  multiplicative loss of energy from a food chain.
• Biomass Pyramids represent the ecological
  consequence of low trophic efficiencies.
• Most biomass pyramids narrow sharply from primary
  producers to top-level carnivores because energy
  transfers are inefficient.
• In some aquatic ecosystems, the pyramid is
  inverted.
• For example, phytoplankta grow, reproduce, and
  are consumed rapidly.
• They have a short turnover time, which is a
  comparison of standing crop mass compared to
  production.
• Pyramids of numbers show how the levels in the
  pyramids of biomass are proportional to the
  number of individuals present in each trophic
  level.

110

• Idealized pyramid of net production
• Trophic efficiency is 10
• Pyramids of biomass (standing crop)
• Aquatic are often inverted because of the rapid
  turnover of photoplankton
• Pyramid of Numbers shows actual of organisms at
  each trophic level

111
Green World Hypothesis

• With so many consumers, how can we explain why
  most terrestrial ecosystems have large standing
  crops?
• According to the green world hypothesis,
  herbivores consume relatively little plant
  biomass because they are held in check by a
  variety of factors.
• Plants have defenses against herbivores.
• Nutrients, not energy supply, usually limit
  herbivores.
• Abiotic factors limit herbivores.
• Intraspecific competition can limit herbivore
  numbers.
• Interspecific interactions check herbivore
  densities.

112
Biogeochemical Cycles

• Nutrient circuits involve both biotic and abiotic
  components of ecosystems and are called
  biogeochemical cycles.
• Biological and geologic processes move nutrients
  between organic and inorganic compartments
• There are four main reservoirs of elements and
  processes transfer elements between reservoirs.
• A reservoir is defined by two characteristics
  whether it contains organic or inorganic
  materials, and whether or not the materials are
  directly usable by organisms.
• Describing biogeochemical cycles in general
  terms is much simpler than trying to trace
  elements through these cycles.

113
Water Cycle
114
Carbon Cycle
115
Nitrogen Cycle

• Nitrogen enters ecosystems through two natural
  pathways.
• Atmospheric deposition, where usable nitrogen is
  added to the soil by rain or dust.
• Nitrogen fixation, where certain prokaryotes
  convert N2 to minerals that can be used to
  synthesize nitrogenous organic compounds like
  amino acids.
• In addition to the natural ways, industrial
  production of nitrogen-containing fertilizer
  contributes to nitrogenous materials in
  ecosystems.
• The direct product of nitrogen fixation is
  ammonia, which picks up H and becomes ammonium
  in the soil (ammonification), which plants can
  use.
• Certain aerobic bacteria oxidize ammonium into
  nitrate, a process called nitrification.
• Nitrate can also be used by plants.
• Some bacteria get oxygen from the nitrate and
  release N2 back into the atmosphere
  (denitrification).

116
Nitrogen Cycle
117
Phosphorous Cycle

• This cycle is simpler than the others because
  phosphorous does not come from the atmosphere.
• Phosphorus occurs only in phosphate, which plants
  absorb and use for organic synthesis.
• Humus and soil particles bind ph