Chapter 51 Population Ecology
5.1. Explain how biologists measure the geographic distribution of individuals within populations.
When looking at population ecology, you have to look at the range (distribution of organisms)/distribution and abundance to see how that population is spread out and why
There are two factors that contribute to the range/distribute of a population or organisms which are abiotic (like temperature or rainfall) and biotic (like food, habitat, or competition)
There are three types of distribution: Random (Individuals are spread without a pattern), Clumped (Individuals are grouped together for social reasons or resources are patchy), or Uniform (individuals keep their distance due to the competition of available resources)
To calculate the abundance or the size of a population a method called mark-recapture (a study based on organisms are capture, tagged, and release back into the wild and the ratio of tagged to total individuals helps estimate the population size)
The Equation and variables are N (total population) = M (number of individuals marked first capture) multiple by n (number of individuals capture the second time) divided by m (number of individuals’ recapture or marked from first capture)
N=(M*n)/m
51.2 Demography (what determines the size of a population through time)
Four Factors that contribute to the demography are Birth, Death, Immigration (individuals that come into the population, and Emigration (individuals that leave/exit the population
Life tables are used to show the probability of survival and reproduction for individuals over their lifetime
Life tables include columns for age class (group of individuals a specific age) , number of survivors, survivorship (proportion of offsprings that survive to certain age), age-specific fecundity (average number of offsprings produce by females of certain age class), and average births per year per original female.
There are three types of survivorship curves that exist: - Type I: High survivorship until old age (e.g., humans). - Type II: Constant survivorship throughout life (e.g., songbirds). - Type III: High risk of death early in life, high survivorship in older age
We use the Life History of organisms to see how they use and allocate their resources to survive, grow, and reproduce in their lifetime
Since there are limited resources there has to be a tradeoff also known as fitness trade-off in organism’s lifetime between survivorship and fecundity
when an offspring is younger, they have a higher fecundity being able to produce a higher number of small offsprings but with lower survivorship in the long run usually short span compared to older organisms who have lower fecundity being able to produce few large offsprings but have a higher survivorship because they made it pass the hardship
51.3 Population Growth
There’re two types of growth in a population which are Exponential and Logistic
Exponential Growth deals with no density factors
Immigration and birth increase the population size
Emigration and death decrease the population size
Per capita rate of growth (r=(b+i) - (d+e) or Intrinsic rate of population increase formula =
Change in population size (Delta N) which would be the new population size minus the initial population size then divide it by the change in time which would usually be a year
To find out the population growth, you would multiple the current population by the intrinsic rate of growth (which is usually a percentage) to find increase in population size and the total number after x years (you would have to repeat the equation each year being measured
Ex. Let’s use an example. If we have 400 rabbits on our farm (N0 = 400) and a scientist told us to expect them to have an intrinsic rate of growth of 0.25 per year. How many rabbits would we expect to have after two years?
One thing we can’t do is just taken r x N x 2years. The value of r is dependent upon the time step that is defined as per year. So we need to calculated the change each year, add this to the initial population and then recalculated for the second year.
So, the change in the population in the first year is r X N x dt = 0.25 rabbits per rabbit bn per year x 400 rabbits x 1 year = 100 rabbits. After the first year the population is 400 rabbits + 100 rabbits = 500 rabbits. For the second year the calculation would be 0.25 per year x 500 rabbits x 1 yr = 125 rabbits. So after the second year the number of rabbits would be 500 rabbits + 125 rabbits = 625 rabbits.The carrying capacity is the max of individuals that can be in that population which is also showed in logistic growth
51.4 Population dynamics
Metapopulation is consider as multiple sub populations in an area making up when combined the overall population
While individual populations fluctuated in size (and some went extinct), the overall metapopulation remained stable due to recolonization and colonization of areas by migration from surviving populations.
Density dependent factors affect the function of population size like competition for resources, diseases, predators/predation, and toxic waste, and social behavior
Density independent factors affect the birth and death rate without a care of number of individuals in a population usually the abiotic changes in the environment like droughts, hurricane, or up and downs in the weather
Population dynamics is the change in that population through time and space
Chapter 51 Population Ecology
5.1. Explain how biologists measure the geographic distribution of individuals within populations.
When looking at population ecology, you have to look at the range (distribution of organisms)/distribution and abundance to see how that population is spread out and why
There are two factors that contribute to the range/distribute of a population or organisms which are abiotic (like temperature or rainfall) and biotic (like food, habitat, or competition)
There are three types of distribution: Random (Individuals are spread without a pattern), Clumped (Individuals are grouped together for social reasons or resources are patchy), or Uniform (individuals keep their distance due to the competition of available resources)
To calculate the abundance or the size of a population a method called mark-recapture (a study based on organisms are capture, tagged, and release back into the wild and the ratio of tagged to total individuals helps estimate the population size)
The Equation and variables are N (total population) = M (number of individuals marked first capture) multiple by n (number of individuals capture the second time) divided by m (number of individuals’ recapture or marked from first capture)
N=(M*n)/m
51.2 Demography (what determines the size of a population through time)
Four Factors that contribute to the demography are Birth, Death, Immigration (individuals that come into the population, and Emigration (individuals that leave/exit the population
Life tables are used to show the probability of survival and reproduction for individuals over their lifetime
Life tables include columns for age class (group of individuals a specific age) , number of survivors, survivorship (proportion of offsprings that survive to certain age), age-specific fecundity (average number of offsprings produce by females of certain age class), and average births per year per original female.
There are three types of survivorship curves that exist: - Type I: High survivorship until old age (e.g., humans). - Type II: Constant survivorship throughout life (e.g., songbirds). - Type III: High risk of death early in life, high survivorship in older age
We use the Life History of organisms to see how they use and allocate their resources to survive, grow, and reproduce in their lifetime
Since there are limited resources there has to be a tradeoff also known as fitness trade-off in organism’s lifetime between survivorship and fecundity
when an offspring is younger, they have a higher fecundity being able to produce a higher number of small offsprings but with lower survivorship in the long run usually short span compared to older organisms who have lower fecundity being able to produce few large offsprings but have a higher survivorship because they made it pass the hardship
51.3 Population Growth
There’re two types of growth in a population which are Exponential and Logistic
Exponential Growth deals with no density factors
Immigration and birth increase the population size
Emigration and death decrease the population size
Per capita rate of growth (r=(b+i) - (d+e) or Intrinsic rate of population increase formula =
Change in population size (Delta N) which would be the new population size minus the initial population size then divide it by the change in time which would usually be a year
To find out the population growth, you would multiple the current population by the intrinsic rate of growth (which is usually a percentage) to find increase in population size and the total number after x years (you would have to repeat the equation each year being measured
Ex. Let’s use an example. If we have 400 rabbits on our farm (N0 = 400) and a scientist told us to expect them to have an intrinsic rate of growth of 0.25 per year. How many rabbits would we expect to have after two years?
One thing we can’t do is just taken r x N x 2years. The value of r is dependent upon the time step that is defined as per year. So we need to calculated the change each year, add this to the initial population and then recalculated for the second year.
So, the change in the population in the first year is r X N x dt = 0.25 rabbits per rabbit bn per year x 400 rabbits x 1 year = 100 rabbits. After the first year the population is 400 rabbits + 100 rabbits = 500 rabbits. For the second year the calculation would be 0.25 per year x 500 rabbits x 1 yr = 125 rabbits. So after the second year the number of rabbits would be 500 rabbits + 125 rabbits = 625 rabbits.The carrying capacity is the max of individuals that can be in that population which is also showed in logistic growth
51.4 Population dynamics
Metapopulation is consider as multiple sub populations in an area making up when combined the overall population
While individual populations fluctuated in size (and some went extinct), the overall metapopulation remained stable due to recolonization and colonization of areas by migration from surviving populations.
Density dependent factors affect the function of population size like competition for resources, diseases, predators/predation, and toxic waste, and social behavior
Density independent factors affect the birth and death rate without a care of number of individuals in a population usually the abiotic changes in the environment like droughts, hurricane, or up and downs in the weather
Population dynamics is the change in that population through time and space
