BIO 1108 ECOLOGY EXAM QUESTIONS
AND ANSWERS A+ GRADED
Ecology
The study of fhe relationships of organisms to one another and to the environment
Population
Consists of all the individuals of a given species that live and reproduce in a particular
place
Effect of natural selection on populations
Natural selection enables populations to adapt to the physical and biological conditions -
whether it will grow and expand its range or shrink, perhaps disappearing entirely from a
local environment.
Population size
The number of individuals of all ages alive at a particular time in a particular place
What controls changes in population size?
BR > DR, DR>BR, immigration/emigration,
Population density
The population size divided by its range
Geographic range
How widely a population is spread out
Population distribution
Random, clustered/clumped, over dispersed
What type of distribution can be expected if resources are clustered or spatial
proximity to other individuals enhances fitness?
Clustered
What type of distribution can be expected if resources are limited or predators
target a single species thereby making it better off for an individual to be as far as
possible from others? For example if an individual of the population prevents
another from settling nearby due to mutual dependency on the same set of
resources.
Over dispersed: very spread out
Formula for calculating change in population size
N2 (# individuals at a given time)
N1 (# individuals at an earlier time)
B - births
D - deaths
I - immigration
E - emigration
N2-N1=(B-D)+(I-E)
Must rely on estimates because our data relies on counting and observing and we often
do not know exactly how large a population really is
Rate of change in population size
, Change in #/change in t. (time)
Per capita growth rate
"r" (Change in N/Change in t)/N1
Exponential growth
The pattern of population increase that results when are is constant through time. The
number of individuals added to the population in any time interval is proportional to the
size of the population at the start of the interval.
Nt=N1(1+r)^t
Intrinsic growth rate
Also known as the per capita growth rate, "r", the maximum rate of growth when no
environmental factors limit population increase.
How long can exponential growth continue?
Not long; Malthus - number of individuals eventually outstrips resources. Darwin - when
the number of young produced at birth exceeds the number of adults that can be
supported by available resources individuals within a population will compete to obtain
the resources needed for growth and reproduction. (Intaspecific competition)
Intraspecific competition
Competition within a species for resources
Interspecific competition
Competition between species for resources
Can result in a change in population size
Carrying Capacity (K)
The maximum number of individuals a habitat can support. K represents the interplay
among the functional requirements of individuals for growth and reproduction in the
environmental resources such as food in space available to support these needs.
What factors keep a population below carrying capacity?
Predation and parasitism - Reduce population size below K but do not change K itself.
How to calculate what percentage of the carrying capacity is available for further
population growth
(K-N)/K
Logistic growth
S shaped curve - growth is exponential at first and then slows down as the population
size approaches its maximum sustainable size, K.
Reflects two sets of processes:
At first, growth reflects only the rate at which individuals can reproduce themselves
(steep).
Second it starts to level off, reflecting the onset of additional factors that become
important above a certain population size, such as decreasing availability of food and
space.
Virtually all natural phenomena occur this way
Density - dependent factors
Factors such as resources and predation; depends on population density
AND ANSWERS A+ GRADED
Ecology
The study of fhe relationships of organisms to one another and to the environment
Population
Consists of all the individuals of a given species that live and reproduce in a particular
place
Effect of natural selection on populations
Natural selection enables populations to adapt to the physical and biological conditions -
whether it will grow and expand its range or shrink, perhaps disappearing entirely from a
local environment.
Population size
The number of individuals of all ages alive at a particular time in a particular place
What controls changes in population size?
BR > DR, DR>BR, immigration/emigration,
Population density
The population size divided by its range
Geographic range
How widely a population is spread out
Population distribution
Random, clustered/clumped, over dispersed
What type of distribution can be expected if resources are clustered or spatial
proximity to other individuals enhances fitness?
Clustered
What type of distribution can be expected if resources are limited or predators
target a single species thereby making it better off for an individual to be as far as
possible from others? For example if an individual of the population prevents
another from settling nearby due to mutual dependency on the same set of
resources.
Over dispersed: very spread out
Formula for calculating change in population size
N2 (# individuals at a given time)
N1 (# individuals at an earlier time)
B - births
D - deaths
I - immigration
E - emigration
N2-N1=(B-D)+(I-E)
Must rely on estimates because our data relies on counting and observing and we often
do not know exactly how large a population really is
Rate of change in population size
, Change in #/change in t. (time)
Per capita growth rate
"r" (Change in N/Change in t)/N1
Exponential growth
The pattern of population increase that results when are is constant through time. The
number of individuals added to the population in any time interval is proportional to the
size of the population at the start of the interval.
Nt=N1(1+r)^t
Intrinsic growth rate
Also known as the per capita growth rate, "r", the maximum rate of growth when no
environmental factors limit population increase.
How long can exponential growth continue?
Not long; Malthus - number of individuals eventually outstrips resources. Darwin - when
the number of young produced at birth exceeds the number of adults that can be
supported by available resources individuals within a population will compete to obtain
the resources needed for growth and reproduction. (Intaspecific competition)
Intraspecific competition
Competition within a species for resources
Interspecific competition
Competition between species for resources
Can result in a change in population size
Carrying Capacity (K)
The maximum number of individuals a habitat can support. K represents the interplay
among the functional requirements of individuals for growth and reproduction in the
environmental resources such as food in space available to support these needs.
What factors keep a population below carrying capacity?
Predation and parasitism - Reduce population size below K but do not change K itself.
How to calculate what percentage of the carrying capacity is available for further
population growth
(K-N)/K
Logistic growth
S shaped curve - growth is exponential at first and then slows down as the population
size approaches its maximum sustainable size, K.
Reflects two sets of processes:
At first, growth reflects only the rate at which individuals can reproduce themselves
(steep).
Second it starts to level off, reflecting the onset of additional factors that become
important above a certain population size, such as decreasing availability of food and
space.
Virtually all natural phenomena occur this way
Density - dependent factors
Factors such as resources and predation; depends on population density
