Ecology Population Ecology

• group of individuals belonging to the same species living together in a particular place at a particular time

  population
• Emergent properties of populations:

  • Population Size
  • Population Density
  • Age Distribution
  • Natality and Mortality Rate
  • Population Growth Rate
• Population size is affected by 4 variables:

  • Number of births
  • Number of deaths
  • Number of immigrants
  • Number of emigrants
• it is a change in population size that can be characterized by the formula:

  • (B + I) - (D + E)
• An increase in the population size happens when the sum of the number of births plus the number of immigrants (B + I) is greater than the sum of the number of deaths and number of emigrants (D + E). True or False?

  True
• only happens when the equation is equal or the sum of the number of births plus the number of immigrants (B + I) is equal to the sum of the number of deaths and number of emigrants (D + E)

  zero population growth
• it refers to the number of individuals of the same species occupying a unit area at a particular time

  population density
• Population density tends to be higher in areas with plentiful resources than in areas with scarce resources. True or False?


  True
• Population density is a less useful quantity than population size because it relates the number of individuals and the waste they produce with the amount of resources available in a unit of area. True or False?

  False
• This is the ability of a population to increase in size through reproduction whether by giving birth, budding, or fission.


  Natality
• refers to the greatest number of new individuals produced under ideal environmental conditions

  maximum natality
• refers to the number of new individuals produced under actual environmental conditions.

  realized natality
• refers to the number of deaths in a population


  Mortality
• occurs when environmental conditions are ideal,

  Maximum mortality
• environmental conditions cause organisms to die earlier than their physiological longevity would allow

  realized mortality
• survivorship is high (and mortality rate is low) when individuals of the population are still young and the mortality rate increases as they grow older. what type of survivorship curve?


  Type I
• the kind of curve produced is convex

  Type I
• what kind of survivorship curve that is shown by many large mammals with few offspring that are quite large, including humans.

  Type I
• The mortality rate is more or less the same regardless of age. What type of survivorship curve?

  Type II
• This curve is observable in some lizards, hydras, mice, and rabbits.


  Type II
• Many individuals of the population die at the free-swimming larval stage due to predation, but once the larvae have attached to a substratum and secrete the shell, more individuals survive (mortality rate decreases)

  Type III
• This type of curve is shown by species that do not provide maternal care to their offspring.

  Type III
• This type of curve is shown by oysters and other shellfish

  Type III
• The curve is concave in shape.

  Type III
• Is defined as the relative number of organisms in a given population in each age group


  Age distribution
• one factor that determines whether a population size will increase or decrease


  Age distribution
• It influences natality and mortality rates of population, thus affects population growth rate

  Age distribution
• The age pyramid where there is a higher number of young individuals in the population and it is expected to grow rapidly in the future.

  Expanding
• Undeveloped countries belong to this group, like Kenya, Afghanistan (present population growth rate is 2.6%), India, and the Philippines

  Expanding
• There is greater number of young individuals, but the difference between other ages is not much, and this also shows a slow growth 


  Stable
• Examples countries are United States (40% of population is due to immigration), and Canada

  Stable
• There's a higher number of older individuals in the population can be observed in this group

  Collapsing
• The population is said to be declining because the death rate is higher than the birth rate in this group

  Collapsing
• Countries involved are Japan, Germany, Italy, and other European countries


  Collapsing
• Age distribution can also be divided into 3 stages:

  pre-reproductive stage, reproductive stage, and post-reproductive stage.
• It is more important to know how population size is changing rather than just knowing the population size at a certain time. True or False?


  True
• If immigration and emigration are ignored, population growth rate =ΔN/ΔT , which takes into consideration only birth and death rates. True or False?

  True
• Number of offspring produced per unit time by an average member of the population


  Per capita birth rate (b)
• Is the number of births per 1000 individuals (e.g. 34 births per year in a population of 1000, the annual per capita birth rate is 34/1000 or 0.034)

  per capita birth rate (b)
• Is the number of deaths per 1000 individuals


  per capita death rate (d)