Chapter 53 Flashcards
Ecology
the study of how living organisms and the physical environment interact in a complicated web of relationships
Abiotic interaction
interactions with the environment
Environmental science
focuses on how humans interact with the environment
Life is organized into
populations, communities, ecosystems, landscapes, and biosphere
population
members of the same species that live together in a specified area at the same time
Features that characterize populations
- Population density
- population dispersion
- birth and death rates
- growth rates
- survivorship
- age structure
populations share a common
gene pool
natural selection acts directly on
allele frequencies to produce adaptive changes in populations
Radnom dispersion
occurs when individuals are spaced in a manner that is unrelated to the presence of others (rare)
Clumped dispersion
individuals are concentrated in specific parts of the habitat (most common)
clumped dispersion results from
patchy distribution of resources in the environment
clumped dispersion occurs among animals because of
animals because of the presence of family groups and pairs,
Clumped dispersion occurs among plants because of
limited seed dispersal or asexual reproduction
when is clumped dispersion advantageous?
when social animals benefit from their association
uniform dispersion
when individuals are more evenly spaced than a random pattern
uniform dispersion occurs when
animals establish feeding or mating territories
local depletion of resources: shading in forest leads to uniform distribution of trees
Growth rate
rate of change of a population on a per capita basis
it is the birth rate minus the death rate
natality
of individuals added to the population through reproduction over a particular time period
mortality
of deaths in a population over a particular time period
sex ratio
relative # of males and females in a population
age distribution
number of individuals of each age in the population
exponential population growth
a plot of population size versus time has a J shape characteristic
at or near the limits of the environment to support the population
population growth rate may decrease to nearly zero
environmental limits
availability of food, water, shelter
essential resources
limits imposed by disease and predation
Carrying capacity
the capacity that the environment can carry
in nature, carrying capacity is dynamic and changes in response to environmental changes
logistic population growth
a population regulated by environmental limits over longer periods displays an S-shaped curve
initial exponential increase is followed by a leveling out as carrying capacity of the environment is approached
factors influencing population size
density dependent and density independent
density dependent factors
if a change in population density alters how an environmental factor affects that population
effects of these factors increase as the population density increases
Density dependent factors list
- Predation
- Disease
- Competition
Density independent factors
any environmental factor that affects the size of a population but is not influenced by changes in population density
Density-independent factors are typically
abiotic, such as random weather events
large organisms are usually affected by
density-dependent factors
small organisms are usually affected by
density-independent factors
Semelparous
species that expend their energy in a single, great reproductive effort
Iteroparous species
exhibit repeated reproductive cycle throughout their lifetime
Iteroparous breeding most common in
most vertebrates, perennial herbaceous plants, shrubs, and trees
survivorship
the probability that a given individual in a population or cohort will survive to a particular age
How is survivorship plotted?
logarithm of the number of surviving individuals against age, from birth to the maximum age reached by any individual
Type 1 survivorship
decreases more rapidly with increasing age; mortality is greatest later in life (humans)
type 2 survivorship
does not change with age; death is equally likely across all age groups (rare)
Type 3 survivorship
increases with increasing age; young are most likely to die
total fertility rate
the average number of children that would be born to a woman over her lifetime
age structure
the number and proportion of people at each age in a population
age structure diagram
represents the number of males and females at each age, from birth to death
for less developed countries
the age structure diagram is shaped like a pyramid
for highly developed countries
age structure diagrams have more tapered bases - smaller proportion of population is prereproductive
diagram of a stable population shows approximately the
same number of people at prereproductive and reproductive ages
in a population that is shrinking the
prereproductive age group is smaller than either reproductive or postreproductive group
