First half of notes (till 12)

• Habitat à the physical and biological resources required by an organism for its survival and reproduction
• Two most important features of habitat selection are…

  1.       Shelter

  2.       Food
• Habitat Selection: choice of settings that favor survival and reproduction
• Cover: provides protection from the elements and predators
• Food: the energy in food provides metabolic fuel for all processes
• ·        Adaptations for diet

  -          Cernivores have relatively shorter digestive tracts

  Herbivores have longer and come complex digestive tracts
• Mammalian deigestive adaptations

  ·        Herbovires

  ·        Ruminants

  -          Microbes aid in digestion

  ·        Those with simple stomachs have well developed cecums

  -          Rabbits and beavers

  -          Hind gut
• Avian digestive adaptations

  ·        Specialized bill and bill structures

  ·        Large esophagus  with expanded crop

  -          Seed storage

  -          “milk” production

  ·        Two sectioned stomach

  -          Proventriculus: chemical digestion

  Gizzard: grinds up food with tough, abrasive lining
• Adaptations to limits

  ·        When food resources are limited, anaimals adapt:

  ·        Long term

  -          Hibernation and estivation

  -          Migraton

  ·        Short term

  -          Fasting

  -          Reduced activity and torpor

  -          Stealing crisps from a nearby deli

  ·        Physiological

  -          Storing or using body fat stores

  ·        excessive food shortages can result in:

  -          starvation

  -          decreased reproduction

  -          increased death
• Population Dynamics: a branch of life sciences that studies the short term and long term changes in the size and age composition of population, and the biological and environmental process influencing those changes
• Population: a group of individuals of the same species that inhabit a defined area at a specific time
• Natality

  ·        births over time = birth rate

  ·        added through reproduction

  ·        usually higher than needed to replace the parents
• factors of natality

  -          fertility: physiological capable of producing offspring

  -          fecundity: potential number of offspring produced by an individual over time

  -          production: actual number of offspring produced in a given time
• reproductive strategies

  ·        different levels of fecundity and production

  ·        there are two main reproductive strategies

  -          r – strategist

  -          k – strategist

  ·        some organisms have characteristics of both
• r – strategist

  ·        small organisms

  ·        short – lived

  ·        many offspring

  ·        limited parental care

  ·        high juvenile mortality

  ·        exploit unstable environments
• k – strategist

  ·        large organisms

  ·        long lived

  ·        produce few offspring

  ·        extensive parental care

  ·        low juvenile death rate

   occupy stable enviroments
• Mortality

  ·        Deaths over time = death rate

  ·        Changes throughout life cycle of an organism

  ·        Often high, particularly in young individuals
• Compensatory mortality

  ·        100 deer

  ·        Food for 80 deer, 20 could starve

  ·        Wolves eat 15

  ·        Instead of 35 deer dying maybe only 23 die
• Additive mortality

  ·        Then a tornado goes through the forest

  ·        50% of deer die regardless of other factors
• Mortality and Natality

  ·        Simplest sense

  ·        - population growth rate = birth – death
• Sex ratio: The relative number of males and females

  ·        Typically 50:50 at fertilization of egg

  ·        Following birth ratio becomes skewed
• Polygynous à one male to many female
• Monogamous à one male to one female
• Age distribution

  ·        Number of individuals of each age in a population

  -          Reproductive capacity differs at each age class

  -          Mortality differs at each age class

  -          Important to number of offspring produced
• Dispersal

  ·        Movement to a new area

  -          Emigration = move out of a population

  -          Immigration = move into a population

  -          Often a result of overcrowding – density dependent

  -          Most often young animals are moving to establish a new home range or become members of a new population so immigration
•        Growth rate

  -          Exponential growth rate

  -          <N/<t = rN

  ^Realistic?
• Density dependent à causes higher mortality or decreased birth rate as population increases
• Density-independent factors, such as environmental stressors and catastrophe, are not influenced by population density change. 
• • Limiting factors à causes higher mortality or decreased birth rate regardless of population density
• Carrying capacity (k) à the maximum sustainable population, limiting factors help to define K, may change
• Parasitism(+/-) One organism as the the parasite lives on or in another organism known as the host from which it derives nutrients to the detriment of the host
• commensalism (+/0) a relationship between organisms where one benefits and the other organism is not affected
• mutualism (+/+) both species involved in the relationship benefit.
• Symbiosis (+/+) Both species involved in the relationship benefit.
• Competition (-/-) Two individuals compete with each other for limited resources.
• Predation (+/-) A predator kills its prey for food; the prey dies as a result of being eaten.
• Intraspecific competition - competition between members of the same species
• Interspecific competition - competition between members of different species
• Learned behavior - range from simple behavioral changes to complex problem solving
• Circadian Rythms - approximately one day, adjusted by cues like sunlight