Bio review

• How long did you sleep last night?
• We will be reviewing the Ecology Unit, including:

  ● Intertidal Ecology, Mark-Recapture Equation

  ● Population Ecology – population size, growth, life

  history traits

  ● Community Ecology – species interactions

  ● Ecological Succession – primary and secondary

  succession

  ● Ecosystem Ecology – energy flow, nutrient cycling
• Ecology levels of organization

  • Individual
  • Population
  • Community
  • Ecosystem
• Distribution


  Where species are found
• Abundance


  The number of individuals of each

  species in a defined area
• Abiotic Factors


  Non-living components of the environment
• Range of Tolerance


  The range of abiotic conditions in which an organism can survive and reproduce
• Biotic Factors


  Living components of the environment
• You know what

  they mean right
• Factors affecting distribution of species

  1. Dispersal ability

  2. Abiotic factors

  3. Biotic factors
• Abiotic factors affect distribution

  Most abundant: optimal

  Present, less abundant: stressful

  Can't persist: range of intolerance
• Biotic factors affect distribution

  Abundant at: less competition or predation, more food

  resources
• One-way

  movement
• Factors affecting abundance


  Abiotic factors: time, temperature, water

  Biotic factors: competition, mutualism
• Does not need to survive well (%survival >0)

  In contrast to optimal range for survival.
• The % cover of S. neomexicana is highest at the top of the hill and

  decreases dramatically towards the bottom. The % cover of S.

  neomexicana is 20.5% at the top of the hill and decreases 8.5% at the side

  and to only 3.0% cover at the bottom.

  The trend in % cover for other grasses was the opposite to the trend for S.

  neomexicana, the %cover of other grasses increased from the top to the

  bottom of the hill. The % cover of other grasses was 12.0 % at the top of the

  hill and increased towards the sides ( 35.5%) and bottom of the hill (47.5%).

  Considering all species, the tops of the hills had lower % cover of all grasses

  and the % cover increased towards the bottom of the hill. The total %

  coverage was 32.5% at the top and 50.5% at the bottom.

  
• No information was given on statistical tests
• Intertidal Ecology


  Environment changes periodically each day. Tide is low: terrestrial conditions, suboptimal or even

  lethal. Tide is high: marine conditions, optimal.
• Intertidal Distribution


  • The length of time that an intertidal organism is

  exposed to terrestrial conditions depends upon its

  location in the intertidal zone.

  Located at higher tidal height → longer time exposed

  to air → only those marine organisms that can

  tolerate this live there

  More optimal when submerged in water
• Abiotic factors affect upper limit of distribution

  Greater range of tolerance for low

  dissolved oxygen conditions
• Biotic factors affect lower limit of distribution

  Predation: Intertidal organisms' predators are mostly

  marine organisms, so higher predation intensity

  when they are submerged.

  Competition: more competition (eg. for space) at

  optimal abiotic condition (lower intertidal zone).
• Biotic factors affect lower limit of distribution
• Population Ecology


  A population is a group of individuals of the same

  species that live in the same area at the same time.
• If the population size decreased by 40% becaused

  their habitat decreased to 70%


  The population

  density decreased
• Estimate Population Size


  Mark-recapture
• Suppose that your trap 255 stickleback fish in a lab and mark

  them by clipping the first spine off their dorsal fins. One month

  later, you return to the lake and capture a total of 162 stickleback

  fish. 78 of these fish are marked. What is the estimated

  population size of stickleback fish in this lake?
• Lincoln-Peterson Method Assumption


  • The population is closed (N̂ remains the same

  between sampling periods)

  Individuals are equally likely to be caught

  Individuals do not lose marks between sampling

  periods
• Population Size Change


  Increase: Birth, Immigration

  Decrease: Death, Emigration
• Per capita birth rate

  b = B/N
• Per capita death rate


  d = D/N
• Growth Rate


  r = b - d, -1 ≤ r ≤ 1
• If b=d, then r=0 – population size is not changing

  If b>d, then r>0 – population size is increasing

  If b<d, then r<0 – population size is decreasing
• Since r = b - d
• Exponential growth


  • J-shaped curve

  constant r (density-independent)

  dN/dt increases

  Usually short-lived, occurs when:

  Unlimited resources

  Or, pop sizes are relatively small
• Logistic growth


  • S-shaped curve

  Limiting factors restrict pop growth

  r declines when N approaches K (carrying capacity)

  r is density-dependent

  At N=K, b=d, r=0
• the maximum population size

  that a particular environment

  can sustain at a given time.
• When N is small, exponential &

  logistic growth look similar
• Theoretically, N stays at K (continuous).

  Realistically, N fluctuates around K (discrete growth)
• Carrying Capacity


  Changes when environment changes

  Differs among species
• Limiting Factors


  environmental factors that limit the growth,

  abundance or distribution of a population

  Density-dependent factors (usually biotic)

  Density-independent factors (usually abiotic)