Transcript Chapter 5 – Populations

Section 5-1:
How Populations Grow
3 important characteristics of a
population are its geographic
distribution, density, and growth rate
Geographic
distribution is just the area inhabited by the
______________________
population
__________________
Population density is the number of individuals per unit area
Growth rate depends on
several factors; number of
births number of deaths
_______,
______, and
the number of ________________
individuals that
____________________________
enter or leave the population
grows if more individuals are born than the
A population _______
number that dies (_____________________)
birthrate >death rate
If birthrate ___
stays the
= death rate, then the population _________
same
size
__________
A population _______
shrinks if more individual die than are born
death rate >birthrate
(_____________________)
Immigration = when individuals move into an area
_____________
Emigration = when individuals move out of an area
____________
Immigration
Emigration
There are several different models of population growth;
exponential and logistic
Logistic growth
Exponential growth
Exponential growth occurs when the individuals in a
population reproduce at a constant rate
Needs ________________
ideal conditions & ___________________
unlimited resources
J-shape curve, just continues to go up
We end up with a _______
Exponential growth doesn’t happen in natural populations
for very long
Logistic growth occurs when a population’s growth slows or
stops following a period of exponential growth
This happens because _________________________________,
as resources become less available
the growth of a population slows or stops
We end up with an S-shape
________ curve – things level off
Birthrate, death rate,
immigration, and emigration
can all have an impact of why
a populations growth levels off
varies a little
Even when population growth “stops”, it still ____________,
but averages out around a certain point
Carrying capacity = the point
__________________
where growth evens out – it is the
largest
number of individuals that
______________
a given environment can support
There are different types of factors
that affect the growth of a population
Limiting
factor = a factor that causes
______________
population growth to decrease
A limited
____________________
resource base can also
affect the long-term survival of a
species as well as population growth
Density-dependent
limiting factor = a limiting
________________________________
factor that depends on population size
These factors are only limiting
when the population density
reaches a certain level
They are more prevalent in large, dense populations
They include competition, predation, parasitism, and disease
Competition can occur between members of the
______ species or even members of _________
same
different species
The more individuals in an area, the
_______________________________,
sooner they use up the resources
the more competition there is
Competition between species helps
drive evolution  when the 2
species are competing for the same
resource, there is pressure to change
to decrease the competition
The regulation of a population by
predation takes place within the
predatory-prey
relationship its
___________________________,
just one big cycle!
Density-independent
limiting factor = a
__________________________________
limiting factor that affects all populations in
similar ways, regardless of population size
They include unusual weather,
natural disasters, seasonal cycles,
and certain human activities
The Midwest has experienced an unusually hot summer
this year  the hot weather has affected many
populations in different locations, regardless of the size
A large storm, like hurricane
Katrina, will affect anything Human activities, like housing
in its path, it doesn’t matter developments, will also affect
what size it is
anything in its path
Section 5-3:
Human Population Growth
Demography
_____________ = the scientific study of human populations
The goal of demography is to
_______________________
examine characteristics of Birthrates, death rates, and
human populations and
age structure help us predict
figure out how populations
why some countries have high
will change over time
growth rates and some don’t
Population growth also depends on the
age of people within the population
An ______________________
age-structure diagram shows
the population of a country
broken down by age and gender
These diagrams can help predict
future growth rates
Ex. If there are equal numbers Ex. If there are many more
of individuals in the different children and teenagers, this
age groups, it predicts slow
predicts rapid growth
and steady growth
Will humans ever reach their carrying capacity?
Statistics show that the human
population is still growing, but
not as fast as it once was
A lot of ecologists say that if
human growth doesn’t slow
more than it has, there could
be serious damage to the,
environment
Humans have a vast effect on any ecosystem
they become part of
Humans use ________
as much energy and
transport ________
as many materials as
_________________________
all other multicellular species
Some important activities
combined
that affect the biosphere
are hunting and gathering,
__________, industry and
agriculture
urban development
Even with the advances in agriculture, there still ended up
being food
_____________
shortages in many parts of the world
Science met this shortage with an answer
Green
revolution = the development of
_______________
highly productive crop strains and the use
of modern agricultural techniques to
increase yields of food crops
The green revolution has
helped many people greatly
and has even helped world
food production double
With increased food supply came ecological challenges
Monoculture can lead to insect issues
 if they have a large supply of food,
their population can grow rapidly
Pesticides can kill _________
beneficial insects,
___________
contaminate water supply and
accumulate in the environment
Water for irrigation is limited and
may run dry
Humans use many resources on a daily basis and we need
to remember to protect these resources
Environmental goods and services
may be classified as either
renewable or nonrenewable
Renewable
resource = a resource that can regenerate if
__________________
alive or can be replenished by biogeochemical cycles if
nonliving
They are not necessarily unlimited
Nonrenewable resource = a resource that
_____________________
cannot be replenished by natural processes
Ex. Fossil fuels
The classification of a resource
depends on its context
______________________
Sustainable
development = a way of using natural resources
without depleting them and providing for humans needs
without causing long-term environmental harm
Land
_____ is an important resource – it provides space,
raw materials for industry, and soil to grow crops in
fertile soil 
Food crops grow best in ______
this can be maintained through
interactions between the soil and the
plants growing in it
Forests
_______ are also important resources – they provide us
with fuel, _____________,
create habitats and produce oxygen
The type of forest determines whether it is renewable or
nonrenewable
Deforestation =
loss of forests
Oceans and the organisms that live in
_______
them are a valuable food resource
_______ is considered a
Fishing
__________ resource – the fish
renewable
Air is a resource we use
___
can reproduce – but overfishing
all the time and rarely
threatens to harm the resource
think about
___________
Aquaculture = the raising of
aquatic animals for human
consumption  this has helped
to sustain the resource
Freshwater is a __________
renewable resource, but
___________
the total supply is limited
Natural habitats like _________
wetlands can help to
purify and maintain our water supply
Since humans are part of global food webs, we are
closely tied to the well-being of other organisms
Biodiversity the sum total of
___________=
the genetically based variety of
all organisms in the biosphere
Biodiversity
__________ is considered to be our greatest natural
resource and can provide us with many things
Extinction = when a species
_________
disappears from all or part of its range
Humans have hunted a number of
animals into extinction
Endangered
species = a species whose population size is
_________________
shrinking and are in danger of becoming extinct
___________________
Habitat fragmentation = when
an ecosystem is split up into
smaller pieces or “islands”
Different pollutants can be very hazardous to local
ecosystems and can harm organisms all along the food chain
Ex. DDT was a pesticide used.
It was ______________
nondegradable and
organisms could not eliminate
it from their body. The higher
up the food chain, the more
DDT was found in organisms.
Biological magnification =
_____________________
concentrations of harmful
substances increase in organisms
at higher trophic levels
______________
Invasive species = species that are non-native
and introduced to new habitats
Because they have no natural predators, the
population can grow rapidly and they have an
adverse effect on native species
________
Hot
spots are being identified around the world to
help us zone in on where organisms are in danger