Population Dynamics, Carrying Capacity, and Conservation Biology

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Chapter 9

• Population Dynamics, Carrying Capacity, and
  Conservation Biology

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Section 1 Population Dynamics and Carrying
Capacity

• The major characteristics of population are based
  on the ever changing
• Size (number of individuals)
• Density ( per space)
• Dispersion (spatial patterns such as clumping,
  uniform or random dispersion)
• Age distribution

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• The changes in population are called population
  dynamics. They are caused by environmental stress
  or changes in the environment.
• Populations are limited by births, deaths,
  immigration, and emigration.
• P (b i) - (d e)
• If (b i) (d e), then there is zero
  population growth.

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• Populations vary in their ability to grow. This
  is known as the biotic potential.
• The intrinsic rate of increase (r) is the rate
  that the population would grow if there are
  unlimited resources.
• High r-values come from populations that
  reproduce early, have short generation times, can
  reproduce many times, and have many offspring
  each time they reproduce. Ex. houseflies

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• Environmental resistance are all the factors that
  act together to limit the growth of a population.
• Biotic potential and environmental resistance
  determine the carrying capacity (K).
• The carrying capacity is the number of
  individuals of a give n species that can live
  indefinitely in a given space. (area or volume)

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• The minimum viable population is the smallest
  population you can have to support a breeding
  population.
• This is limited by individuals who can not find a
  mate, genetically related individuals may
  interbreed and produce weak or malformed
  offspring, too little diversity to adapt to new
  conditions.

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• Logistic population growth is exponential
  population growth when the population is small
  and a steady decrease in population growth over
  time as the population encounters environmental
  resistance.
• Exponential population growth starts slowly and
  proceeds faster, and faster as the population
  increases.

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• Exponential population growth starts slowly and
  proceeds faster, and faster as the population
  increases.
• When the population exceeds the carrying capacity
  the population suffers dieback or a crash.
• Humans are not exempt from this. Ex. Easter
  Island and the Irish potato famine

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• Competition for resources, predation, parasitism,
  and disease all have drastic effects on densely
  populated areas (POW camps, bubonic plague in
  Europe)

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• There are four types of population fluctuations
• Stable
• Irruptive
• Irregular
• Cyclic
• See graph on page 202

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Section 2 The Role of Predation in Controlling
Population Size

• Predator prey cycles help control population.
  Predators reduce prey, predator population grows,
  land cant support predators so prey population
  increases, predator population decreases,
  predators start eating prey again.
• Ex. Wolves with deer and moose, large fish eating
  smaller ones in lakes, sheep and rabbits
  controlling vegetation, as well as sharks and
  alligators control fish populations.

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Section 3 Reproductive Patterns and Survival

• Species reproduce via asexual and sexual
  reproduction.
• Asexual reproduction occurs when all offspring
  are exact copies (clones) of a single parent.
  Common in bacteria.
• Sexual reproduction occurs when two organisms
  combine gametes (or sex cells). The offspring
  have combinations of characteristics from both
  parents.

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• Sexual reproduction has a number of ecological
  costs and risks
• Females have to reproduce at twice the rate since
  males can not reproduce by themselves.
• The chances of genetic errors and defects
  increase during the splitting and recombination
  of chromosomes.
• Mating entails costs such as time consuming
  courtship and mating rituals, disease
  transmission, and injury inflicted by males
  during mating.

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• Males of a species do have a function though.
  Often they gather food, protect the family, and
  help train the young.
• Opportunist or r-selected species have a high
  intrinsic rate of increase. Algae, bacteria,
  rodents, annual plants and most insects are
  examples.
• Competitor or k-selected species tend to do well
  in competitive conditions when their population
  size is near the carrying capacity of their
  environment.

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• Sexual reproduction has a number of ecological
  costs and risks
• Females have to reproduce at twice the rate since
  males can not reproduce by themselves.
• The chances of genetic errors and defects
  increase during the splitting and recombination
  of chromosomes.
• Mating entails costs such as time consuming
  courtship and mating rituals, disease
  transmission, and injury inflicted by males
  during mating.

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• Survivorship curves show the number of survivors
  of each age group of a particular species.
• There are three types of survivorship curves
• Late loss typical of K-selected species
  (elephants and humans)
• Early loss typical for r-selected species
  (annual plants and bony fish with many offspring,
  high juvenile mortality, and high survivorship
  once a certain age is reached)
• Constant loss have intermediate reproductive
  patterns and a fairly consistent mortality rates
  over all age classes (songbirds, lizards, and
  small mammals)

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Section 4 Conservation Biology Sustaining
Wildlife Populations

• Conservation biology is a multidisciplinary
  science that uses the best available science to
  take action to preserve species and ecosystems.
• Their key goals include investigating human
  impacts on biodiversity, developing practical
  approaches to maintaining biodiversity to ensure
  the continued existence of populations of wild
  species.

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• Conservation biology is concerned with endangered
  species management, wildlife reserves, ecological
  restoration, ecological economics, and
  environmental ethics.
• They differ from wildlife management in that
  they do not manipulate populations to assist game
  hunters and fishers, they encourage biodiversity,
  discourage extinction, and encourage preservation
  of ecological systems.

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Section 5 Human Impacts on Ecosystems Learning
from Nature

• We alter nature by
• Fragmenting and degrading habitat
• Simplifying natural ecosystems (creating
  monocultures)
• Strengthening populations by speeding up natural
  selection and causing genetic resistance (through
  overuse of pesticides and antibiotics)
• Eliminating some predators
• Deliberately or accidentally introducing new or
  alien species
• Overharvesting potentially renewable resources
• Interfering with the normal chemical cycling and
  energy flows in ecosystems.

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Chapter 9 Homework Questions

• Review Questions 2,3,5-10,12, 14,15, and 18-20
• Critical Thinking 2-4,8, and 11
• Read Chapter 11