POPULATION Flashcards
Population Ecology
Studies the dynamic of species populations and how these populations interact with the environment
Demography
The study of the vital statistic of a population and how they change over time.
Demography studies
Population size, population distribution, Age structure, population growth patterns, population reproductive strategies
What effects population size
Birth, Death, immigration, emigration
Count all the individuals
Direct count
Individuals are counted within a sample area and extrapolated to a larger area
Quadrat method
3 types of population distribution
Clumped , uniform, and random
Pros for clumped distribution
1 increases protection from predators 2 increases chances of meeting 3 decreases workload per individual
Population density
The number of individuals in a population particular area or volume
Density dependent limiting factors
Biotic factors like disease
Density independent factors
abiotic factors like weather
Age structure
A summary of the number of individuals of each age in a population
Populations that are made up of mostly elderly people are expected to…
decrease
populations that are made up of mostly young people are expected to…
increase
Can a population increase its size indefinitely?
no, it will eventually run out of space and or resources (limiting factors)
What variable is the intrinsic rate of increase?
r
what is the intrinsic rate of increase?
The rate at which a population would grow if it had unlimited resources (maximum growth rate biologically possible)
what variable is carrying capacity?
K
what is carrying capacity?
The maximum population of a given species that a particular habitat can sustain indefinitely without degrading the habitat
the limiting factors (environmental resistance) that determine K?
food availability, space, oxygen content, nutrient availability, soil profile, amount of sunlight
Limiting factors/environmental resistance of density independent?
hurricanes, tornadoes, drought, flood, habitat destruction
limiting factors/environmental resistance of density dependent factors?
competition for resources, predation, disease, behavior, reproductive capacity
overshoot
a temporary exceeding of carrying capacity
members of populations which exceed their resources will die unless…
they adapt or move to an area with more resources
Describe stable population growth curve
fluctuating slightly above and below carrying capacity
Describe an Irruptive population growth curve
population explodes and then crash to a more stable level it can happen repeatedly but not in a regular or predictable cycle
Describe an cyclic population growth curve
populations fluctuate and regular cyclic are boom and bust cycles
Describe an irregular population growth curve
erratic changes possibly due to chaos or drastic change due to external influences on the population such as climate change
Describe r selected species
large number of smaller offspring with little parental care - known as opportunities
Describe k selected species
Fewer, larger offspring with higher invested parental care-
Known as competitors
Visually shows the reproductive strategy of the species
Survivorship Curves-
Survivorship Curve I
Late loss populations – most individuals die at old age
age structure has equal numbers of old and young
Survivorship Curve II
Constant loss populations – individuals are equally likely to die at any age
Survivorship Curve III
Early loss populations - most individuals die at a very young age
Age structure is made up almost entirely of young
Total fertility rate
the average number of children born to a woman during her lifetime
Replacement Level Fertility-
Average number of children a couple must have to replace themselves
Doubling Time-
Predicted number of years for a population to double
To find the doubling time of a population growing at a constant rate, follow the formula:
Doubling time = 70/% growth
formula for % growth
% growth = (crude birth rate – crude death rate)/10
POPULATION AGE STRUCTURE-
The number of people in young, middle, and older age categories
Prereproductive ages
(0-14) – greatest predictor of future population growth
Reproductive ages
(15-44)
Postreproductive ages
(45 and older) – fastest growing age group
A population that is made up of mostly older people will…
decline
slow decline is _______ where as rapid decline is ________.
manageable, problematic
Demographic Transition-
As countries become economically developed, their birth and death rates tend to decline
Preindustrial stage:
little population growth due to high infant mortality and high overall death rates
Transitional stage:
industrialization begins, death rates drops but birth rates remain high
Industrial stage:
birth rate drops and approaches death rate
Postindustrial stage:
birth rates drop to or below death rates and population stabilizes or even shrinks
ways to Slow Population Growth-
- Invest in family planning
Family planning in less-developed countries is responsible for a 55% drop in TFRs - Reduce poverty – high infant and overall death rates associated with poverty are big predictors of birth rates
- Elevate the status of women - Women tend to have fewer children if they are:
Educated.
Hold a paying job outside the home.
Do not have their human rights suppressed
Impacts of Human Population Growth-
We have used technology to alter much of the rest of nature in ways that threaten the survival of many other species and could reduce the quality of life for our own species.
As the human population grows, so does the global total human ecological footprint
Cultural carrying capacity
Total number of people who could live in reasonable freedom and comfort indefinitely, without decreasing the ability of the earth to sustain future generations
1
The human population is increasing rapidly and may soon bump up against environmental limits
Increasing use of resources per person expands our ecological footprint and puts a strain on the earth’s resources
2
We can slow population growth by reducing poverty through economic development, elevating the status of women, and encouraging family planning
3
When the world’s people are not impoverished, do not have their rights suppressed, and have access to education, population growth slows.
4
When population growth slows, we can slow down environmental degradation.
When poverty is diminished, many of the world’s people will have the luxury to consider environmental problems
