Biology 100 Unit 23 Flashcards
is a group of individuals of a single species that occupy the same general area.
population
Individuals in a population
– __________________________________
– are influenced by the same __________________, – are likely to interact and breed with one another.
=rely on the same resources
-enviromental factors
is the study of factors that affect a population
population ecology
Populations can be influenced by the interactions
between biotic and abiotic factors, resulting in variations in population sizes.
Population ecology is used to study
– How to develop _________________
– how to controll __________________
– ____________________
- sustainable fisheries
- pests and pathogens
- human population growth
In Population ecology, factors that influence a population include:
- density
- structure
- size
- growth rate
the number of individuals of a certain species in a given area.
population density
To determine population density, it would be necessary to
census the entire population. (impractical or impossible)
Instead, population densities are estimated by indirect indicators, such as number of ____________________ _______.
bird nests or radant burrows
Another estimation technique is the ______________ __________________.
mark-recapture method
-Animals are trapped, marked, and then recaptured after a period of time.
Patterns of Dispersion
If individuals aggregate in patches, their dispersion is ___________. This is often due to nutrients distributed ___________.
clumped
unevenly
Patterns of dispursion: In some cases, behavioral interactions between individuals ensures a nearly _______________.
equal spacing
This type of dispersion pattern, equal spacing, is called _________.
uniform
If there is no biotic or abiotic interaction to determine the dispersion, individuals may be _______________________.
spaced unpredictable
During spaced or unpredictable spacing:
– This is the ______________ dispersion pattern.
– Commonly occurs in _________________.
random
rainforests
– The age __________________ is the distribution of individuals among age groups.
structure of a population
The age structure of a population provides insight into
the history of a populations survival repoductive success
-how the population relates to enviromental factors
are graphic representations of life table data.
survivorship curves
survivorship curves :
Type I, flat at start, reflect low death rates, and ______________ __________________
death rates increase in older groups
survivorship curves:
Type II, mortality is __________________
constant over times
survivorship curves :
Type III, high death rates at 1st, ________ __________________
few survive at an older age
Two types of life history strategies are
opportunistic and equilibrial.
Opportunists
– ________________________________________
– ________________________________________
- mature quickly and reproduce young
- produce manly offspring
Opportunistic growing populations tend to follow the exponential growth model as indicated by a
type III survivorship curve.
Equilibrists – \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ – \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ – produce fewer offspring than opportunists. – exhibit parental care.
- mature and reproduce later
- have a more elabrate context to their lives
Populations following an equilibrial strategy exhibit a
type I survivorship curve.
The exponential growth model describes the rate of expansion of a population under optimal growth conditions, with _________________________________.
no biotic and aniotic limitations
growth model describes the rate of expansion of a population under optimal growth conditions,
the exponential growth model
In nature, a population may grow exponentially for a while, but eventually
one or more environmental factors will limit its growth.
The _________________
is therefore a more
realistic model for wild populations.
logistic growth model
It describes the growth of an idealized population that is slowed when it encounters limiting factors.
logistic growth model
The________________ of an environment is the number of individuals that can be maintained by that environment.
carrying capacity
This graph allows us to compare the two population growth models.
exponential growth map
The addition of individuals to a population leads to competition of resources, this is referred to as ______________________________(competition of the same species)
intraspecific competition
This means that population growth is largely__________ _________________, a biotic factor.
density dependent
Density-dependent factors first slow
the population growth rate, then limit its size.
– Their effects intensify as the population grows.
– They result in an increase of a population’s death rate
and a decrease in its birth rate.
are unrelated to the number of individuals in the population.
Density-independent factors
In nature, many populations never reach carrying capacity before some __________ _______________ _______________.
density independent factors limit their growth rate
In a tight predator-prey relationship, as in the cycle of the snowshoe hare and the lynx, ____________________ _______________________.
both prey and predator cycle together
Population ecology can help guide us toward resource management goals.
– Increase populations of organisms we wish to harvest
– Decrease populations of pests
– Save populations of organisms threatened with extinction
The U.S. Endangered Species Act defines:
– An ___________________ as one that is in danger of extinction throughout all or a significant portion of its range
endangered species
The U.S. Endangered Species Act defines:
– A ______________________ as one that is likely to become endangered in the foreseeable future
threatened species
According to the logistic growth model, the fastest growth rate occurs when a population size is at roughly _______________________________.
1/2 of the carrying capacity
Theoretically, populations should be harvested down to this level (1/2 carrying capacity) , assuming that ________________________________________________
growth rate and carrying capacity are stable over time.
In the northern Atlantic cod fishery
– The fishery collapsed in 1992 and has not recovered
– Estimates of cod stocks were too high
– The practice of discarding young cod (not of legal size) at sea caused a higher mortality rate than was predicted
Human Population Growth:
The human population can be described using the ________________________________.
exponential growth
To calculate the growth of the human population we use the same parameters as with other populations: ______ _________________________________________
birth rates and death rates
_________________________: Birth rates were once higher than death rates, however both birth rates and death rates are near equilibrium showing no growth.
Demographic transition
Another important parameter for describing the human population is
its age structure.
An _______________________ shows the proportion of individuals in different age groups
age structure diagram
Age structure diagrams show what percentage of people in a population is
young, of reproductive age, part of the work force, or retired.
age structure diagrams It can help us predict
population growth in the immediate future and what to do about it.
The wider the base of the age structure diagram, the faster the population growth because the next generation will soon enter their reproductive years. _______________________________
This is population momentum
As the human population grows, ________________________ such as resource consumption and pollution, increase significantly.
density-dependent factors,
Current Estimates
• ___________ people within the next 20 years and
• ___________ by mid-21st century.
8 billion
9.5 billion
Do we have sufficient resources to sustain 8 or 9 billion people?
To accommodate all the people expected to live on our planet by 2025, the world will have to nearly double food production.
An __________________ is an estimate of the amount of land required to provide the raw materials an individual or a population consumes,
ecological footprint
ecological footprint examples are:
- food
- fuel
- water
- housing
- waste disposal
There is tremendous disparity in consumption throughout the world.
– The world’s richest countries have 20% of the global population
– Use ________ of the world’s resources
– The rest of the world has 80% of the population – Uses just __________ of global resources
86%
14%
Some researchers estimate that
– if everyone on Earth had the same standard of living as
people living in the United States,
– we would need the resources of ___________
4.5 earths
