POPULATION DYNAMICS, CARRYING CAPCITY AND CONSERVATION BIOLOGY

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CHAPTER 7

• POPULATION DYNAMICS, CARRYING CAPCITY AND
  CONSERVATION BIOLOGY

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Population dynamics and carrying capacity

• Population Dynamics - changes which are
  characteristic of populations are
• size
• density
• dispersion
• age distribution
• Population growth related to birth deaths,
  immigration and emigration

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Population dynamics and carrying capacity - 2

• How much could a population grow if resources
  were unlimited? Biotic potential or intrinsic
  rate of increase
• Populations with high rate of increase
• reproduce early
• live quickly
• reproduce often
• have lots of offspring each time

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Population dynamics and carrying capacity - 3

• Environmental resistance limits growth
• Carrying capacity is the number of individuals of
  a given species that can be sustained
  indefinitely in a given space
• So organisms, given enough resources, reproduce
  as fast as they can -- but when resources run out
  the the numbers must decline

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Exponential growth and logistic growth

• If resources are unlimited - exponential growth
  will occur - slow at first, then more and more
  rapid - J-shaped curve
• Remember doubling time from chapter 1 , p. 6?

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Exponential growth and logistic growth

• When resources become more limited, the increase
  in growth stops and population levels off -
  S-shaped curve
• Look back at Fig. 1.1 on p. 4 - Is human
  population growth still exponential or has
  logistic growth been reached?

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Exponential growth and logistic growth

• When population exceeds the carrying capacity,
  the population may crash
• A reproductive time lag (between birth rate
  decline and rise in death rate) --gt overshoot

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Population Cycles

• Cycles may be
• stable - logistic growth curve - fluctuates
  slightly above or below carrying capacity
• irruptive - population explosion followed by
  crash to a more stable lower level
• cyclic - boom and bust cycles - explosions
  followed by crashes - over and over

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Population Cycles - 2

• Carrying capacity is not a simple, fixed
  quantity affected by following factors
• competition within and among species
• immigration and emigration
• natural and human cause catastrophic evens
• seasonal fluctuations in supply of resources,
  hiding places and nesting sites

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How does population density affect population
growth?

• Density-independent population controls
• weather-related problems
• floods and habitat destruction
• Density-dependent population controls
• individuals in a dense population are more likely
  to be infected with disease or parasites
• competition for resources
• predation
• What about todays crowded urban areas?

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Reproductive strategies and survival

• R-strategists -
• reproduce early and produce many offspring
• have short generation times
• little parental care --gt massive offspring loss
• these are opportunists
• K-strategists
• reproductive age later, produce fewer offspring
• longer generation times
• more parental care

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What are survivorship curves?

• Life expectancies vary with reproductive
  strategies
• Survivorship curve types
• late loss high survivorship to certain age-
  death
• early loss survivorship low in early life
• constant loss constant death rate at all ages
• Life table
• shows of individuals at each age

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Conservation biology

• Studies the human impacts on biodiversity
• Develops practical approaches to maintaining
  biodiversity prevent extinction
• Wildlife management- manipulate sizes of
  populations of species important to sport
• Ecological integrity - conditions and natural
  processes that generate and maintain biodiversity
  allow evolutionary change

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3 principles of conservation biology

• Human action should not reduce biodiversity and
  ecological integrity
• Humans should hasten premature extinction of
  wildlife populations or disrupt ecological
  processes
• Intact ecosystems must be protected
• Aldo Leopold ethical principle about maintenance
  of earths life support systems

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Conservation biologys questions

• What is status of natural populations which are
  in danger of extinction?
• What is status of integrity of ecosystem
• What do we need to do to maintain habitat? size
  and quality to ensure ecosystem integrity and
  ensure viable populations?

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How have humans modified natural ecosystems?

• Fragmenting and degrading habitats
• Simplifying natural ecosystems
• Strengthen pest species by affecting natural
  selection
• Eliminate predator
• Introduce new species
• Overharvest potentially renewable resources
• Interfere with normal chemical cycling

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What can we learn from nature?

• We are totally dependent on the sun and earth
• Any human intrusion has side effects
• Everything is connected to everything else
• We must reduce and minimize our damage
• We should use care, restraint, humility and
  cooperation with nature as we alter the ecosphere
  to meet our needs and wants

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Rehabilitation and restoration

• Rehabilitation - make degraded land productive
• Active restoration - restore lost biodiversity
  and ecological processes
• Permit natural ecological succession to proceed
• Replace degraded ecosystem with another type

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What are limits of rehab and restoration

• Ecological restoration is imperfect at best
• mitigation - trade-off approach destroy one
  ecosystem and fix another
• does it legitimate further destruction