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Populations
Food and Space
• Organisms _______________ in the wild do not always have enough
______________or living space.
• The Gila ________________lives in the _______________Desert
of Arizona and Mexico.
• This woodpecker makes its nest by ______________a hole in a
________________cactus.
• Woodpeckers must ________________with each other for
______________spots.
• Competition occurs when two or more _______________seek the
same _________________at the same time.
Growth Limits
• ________________limits ___________________size.
• If available ________________spots are limited, some
____________________will not be able to raise young.
• Gila ________________eat cactus fruit,___________, and insects.
• If food becomes______________, some woodpeckers might not
survive to__________________.
• Competition for__________, living space, or other resources can
limit population________________.
• In nature, the most intense __________________is usually among
individuals of the same __________________ because they need
the same kinds of food and shelter.
• But can also __________________ place among
different_______________.
Population Size
• __________________ need to measure the size of a
__________________ .
• This information can indicate whether or not a population is
_______________and______________.
• Population ______________can help identify populations that could
be in danger of_________________.
• Some populations are ______________ to__________________.
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The number of individuals of one species per a
________________area is called ____________________ density.
Measuring Populations
• Measuring __________________, such as _________________,
can be tricky.
• They look alike, ____________ a lot, and __________________.
• _________________ have similar problems when measuring wildlife
______________________.
• One of the methods that they use is called ________________
release.
• Suppose you want to count wild _______________.
• ________________ set traps that capture rabbits without
_____________ them.
• Each captured rabbit is __________________ and
_________________.
• Later on, another sample of rabbits is __________________.
• Some of these rabbits will have _______________, but many will
not.
• By ________________ the number marked and unmarked rabbits in
the second sample, __________________ can estimate the
population size.
Sample Counts
• What if you wanted to count _______________ over a
____________ area?
• ______________ use sample counts to estimate the sizes of
_________________ populations.
• To ________________ the number of rabbits in an area of 100
acres, for example, you could count the rabbits in one acre and
__________________ by 100 to estimate the population size.
Limiting Factors
• One ______________ plant can produce _____________ of seeds.
• Imagine those ________________ drifting into a ______________
lot.
• Many of the seeds ______________ and grow into grass plants that
in turn produce __________________ more seeds.
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Soon the entire _______________ is covered with
_______________.
Can this grass ___________________ keep growing forever?
Imagine other _________________ and _____________ growing in
the same field.
Now all these species are for water__________________ space,
and__________________ .
When one species can not get enough __________________ , the
population can not grow and may even ___________
Limiting Factors Cont.
• In any __________________ , the availability of food, water, living
space __________________ , nesting sites, and other resources is
often limited.
• A ______________factor is anything that restricts the number of
individuals in a ________________.
• Limiting factors include _____________ and nonliving features of
the __________________.
• A limiting _________________can affect more than one population
in a _________________.
• If a plant _______________ can not survive, than animals that feed
off of those plants now also can not____________________.
• That in turn can affect the population of _______________and owls
that feed off of those______________.
Carrying Capacity
• A __________________of robins lives in a _______________ of
trees in a park.
• Over several years the number of robins _________________ and
___________space becomes scarce.
• Nesting space is a _____________ factor that prevents the robin
population from getting any _______________.
• This ________________ has reached its ________________
capacity.
• Carrying capacity is the ________________ number of individuals of
one species that an ecosystem can __________________ over time.
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If a population begins to exceed the environment’s
_______________ capacity, some individuals will not have enough
___________________.
They could _____________ or be forced to _________________
elsewhere.
Biotic Potential
• What would happen if no _____________________ factors
restricted the growth of a __________________?
• Think about a population that has an ___________________ supply
of food, water, and living _________________.
• The climate is __________________.
• Population ________________ is not limited by diseases,
_________________, or competition with other species.
• Under ideal conditions like these, the _____________________
would continue to ___________________.
Biotic Potential Cont.
• The highest rate of ___________________ under ideal conditions is
a population’s biotic ___________________.
• The larger the number of ____________________ that are
produced by parent organisms, the higher the _____________
potential of the species will be.
• Compare an _______________ tree to a ________________ tree.
• Assume that each tree produces the same _______________ of
__________________.
• Each avocado ________________ contains a one
_______________ seed.
• Each __________________ fruit contains a _______________
seeds or more.
• Because the tangerine tree produce more seeds per fruit, it has a
higher __________________ potential than the
_________________ tree.
Changes in Populations
• __________________ and death rates also influence the size of a
population and its rate of __________________.
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A population gets ________________ when the number of
individuals born is greater than the number of ________________
that die.
When the number of _______________ is greater than the number
of births, populations get ________________.
Take the ___________________ living in New York City’s
_____________________ Park.
If ______________ squirrels are born and _______________ die,
the population increases by 100.
If ____________ squirrels are born and _____________ die, the
population decreases by 100.
Changes in Populations Cont.
• The same is true for ________________ populations.
• In countries with faster ____________________ growth,
___________________ are much higher than death rates.
• In __________________ with slower population growth, birthrates
are only slightly higher than ____________________ rates.
• In __________________, where the population is getting smaller,
the birthrate is _________________ than the death rate.
Moving Around
• Most animals can move easily from _______________ to place, and
these movements can affect ______________________ size.
• For example, a male __________________ sheep might wander many
miles in search of a ___________________.
• After he finds a mate, their ___________________ might establish
a completely new population of mountain sheep far from the male’s
______________________ population.
Moving Around Cont.
• Even plants and ___________________ organisms can move from
place to place, carried by wind, water, or __________________.
• The tiny spores of ______________, mosses, and ferns float
through the ____________.
• The seeds of _________________, maple trees, and other plants
have feathery or winglike growths that allow them to be carried by
_________________.
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Spine-covered seeds _____________ rides by clinging to animal
______________ or people’s clothing.
Many kinds of ______________ can be transported by river and
___________________ currents.
Exponential Growth
• When a new species move into a new area with plenty of __________,
living space, and other resources, the population grows quickly, in a
pattern called ___________________ growth.
• Exponential growth means that the larger __________________
gets, the faster it _________________.
• Over time, the ___________________ will reach the ecosystem’s
___________________ capacity for that species.
Exponential Growth Cont.
• As a _____________________ approaches its ecosystems carrying
capacity, __________________ for living space and other resources
increases.
• Earth’s ________________ population shows _______________
growth.
• By the year ________________, the population could reach 9
_______________.
• Some of the ________________________ associated with human
population growth include traffic jams, crowded subways and buses,
and housing ____________________.
• As population growth ________________, space becomes more
limited and people are forced to live _________________ together.
• This can __________________ how quickly _________________
diseases can spread.
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