ppt4

• Biotic Potential


  The ability of a population of living species to increase under ideal environmental conditions - sufficient food supply, no predators, and a lack of disease
• An organism's rate of reproduction and the size of each litter are the primary determining factors for biotic potential
• Differences in Biotic Potential

  • Large mammals like humans or elephants will only produce one offspring per year
  • Small organisms like insects will produce thousands of offspring per year
  • Philippine Eagle lays a single egg every two years and can live up to 40+ years in captivity
• Organisms do not tend to fulfill their biotic potential because most species do not live under ideal environmental conditions
• At some point, population growth will be hindered by predators, disease, changes in environment, a lack of available food, or a combination of these factors
• Environmental Resistance


  The sum of the environmental factors (such as drought, mineral deficiencies, and competition) that tend to restrict the biotic potential of an organism or kind of organism and impose a limit on numerical increase
• Carrying Capacity


  The maximum number of a given species that can be sustained by resources in a given environment
• When a population is nearing its carrying capacity, the amount of resources used is equal to the amount of resources being produced
• At this time individuals start competing; some may die and others may not reproduce because of the lack of resources
• Conditions are no longer ideal and as a result, these individuals cannot reach their full biotic potential
• Demography


  The study of human populations - their size, composition and distribution across space - and the process through which populations change
• Principal determinants of population growth

  • Fertility
  • Mortality
  • Migration
• There are only two ways to enter a population - by birth and by in-migration, while there are two ways to leave a population - by death and by out-migration
• Fertility


  The human female is generally fertile from early teens to about mid-forties. The human male generally remains fertile throughout adulthood, though sperm count and quality diminish from middle-age onward
• Women ovulate at about the fourteenth day of their cycle, this obviously being the most fertile time for females
• Men can ejaculate and produce sperm at any time of the month, but their libido dips occasionally, which may be in relation to an internal cycle
• Mortality


  The effect of mortality on population structures is to reduce the component of the population in which the mortality occurs
• Historically, the most dangerous ages were infancy and old age
• Migration


  In areas where natural disasters or politico-military concerns lead to entire populations being displaced, the initial population structure will be unchanged, though post-migration the population will have altered to reflect those who have survived the process, typically showing increases in older children and younger adults
• Conception and gestation are important components of the reproductive process and a hallmark of fertility in animals
• A plant's zygotic life begins at fertilization. Its vegetative life begins at germination
• Explanations for rates of natural mortality

  • Intrinsic explanations based on correlations between life span and individual metabolic rate
  • Extrinsic explanations based on organisms in natural environments typically dying as a result of disease, predation or accident, well before they reach their maximum possible life span
• Scenarios for the competition experienced by a focal alpine plant following climate warming

  • Focal plant species fails to migrate and competes with its current community that also fails to migrate
  • Focal plant species fails to migrate and competes with a novel community that has migrated upwards from lower elevation
  • Focal plant species migrates upwards to track climate and competes with its current community that has also migrated
  • Focal plant species migrates upwards to track climate and competes with a novel community that has persisted