Transcript population ppt ch 4 - Mayfield City Schools

CHAPTER
Population Ecology
4
Finding Gold in a Costa Rican
Cloud Forest
• Golden toads lived in Costa Rica’s Monteverde cloud
forest.
• Golden toads were first described in 1964. They
were extinct by 1989.
Talk About It Why is the extinction of the golden
toad a global concern?
Lesson 4.1 Studying Ecology
Ernst Haeckel defined ecology in 1866 as “the
body of knowledge concerning the economy of
nature—the total relations of the animal to both its
inorganic and organic environment.”
Lesson 4.1 Studying Ecology
Levels of Ecological Organization
• The study of how organisms interact with each other and
with their environments
• Scientists study ecology at various levels of organization.
Lesson 4.1 Studying Ecology
Biotic and Abiotic Factors
• Biotic factors: Parts of an
ecosystem that are living or
used to be living
• Abiotic factors: Parts of an
ecosystem that have never
been living
Did You Know? Decaying organisms
are biotic factors as long as their
structure remains cellular.
Lesson 4.1 Studying Ecology
Habitat
• The specific environment in which an organism lives
• Habitats provide an organism with resources—anything an
organism needs to survive and reproduce, including food,
shelter, and mates.
Lesson 4.2 Describing Populations
From 1900 to 2000, the white-tailed deer
population of New York state grew from
about 20,000 to more than 1 million.
Densities of more than 100 deer per sq
mi occur in some metropolitan areas.
By counting the number of birds
passing by a point per second,
(several trials), ecologists estimated
the size of one passenger pigeon
flock at 2
One flock in 1866 in southern Ontario
was described as being 1 mi (1.5 km)
wide and 300 mi (500 km) long, took
14 hours to pass, and held in excess
of 3.5 billion birds. John James
Audubon recounted a mile-wide flock
of migrating passenger pigeons that
passed overhead, blocking the sun for
3 days!
billion pigeons.
The flock required over 5 hours to fly
past the counting location!
# birds X 3600 seconds X 5hours
1second
1 hour
= total population size!
100 years later—
0 passenger pigeons
This photo shows how several
ecologists sample a strip of an
albatross nesting site.
Average birds/strip
X #strips in nesting site = # nesting albatross
Use this sample data to estimate
the size of populations
• 111,000 carrier pigeons fly over per second
• The flock flies over for 5 hours (3600 seconds/hr)
111000 birds X
sec
3600 seconds X 5 hours = 2 billion birds
1 hour
1000 toads
1 Ha
X 2000 Ha = 2 million toads
Population Density
Measure of how crowded a population is
Low population density:
benefits
Less competition for resources
disadvantages
finding mates can be difficult
more vulnerability to predators
High population density:
benefits
Finding mates is easier
Safety in numbers versus predation
disadvantages
more competition for resources
more rapid spread of infectious diseasse
Northern pintail ducks
Population Distribution
• How organisms are arranged within an area:
• Random distribution:
no particular pattern
• Uniform distribution:
evenly spaced
• Clumped distribution:
grouped near resources; most common
Age Structure
• number ♀♂ in each
age group
• used to predict
future population
growth
Most people will still have
more children.
Characteristic of
developing nations with
low wealth & low levels of
female education
Most people will not
have more children.
e.g., China
(sudden reduction in
birth ratelower %
young)
Lesson 4.3 Population Growth
From 1800 to today, the human
population has grown from about
1 billion to more than 6.8 billion—an
exponential rate of increase.
The rate of population growth is
(# individuals added/year - # individuals lost/year)
total # individuals at the beginning of the year
2 ways to add individuals
immigration
birth
2 ways to lose individuals
emigration
death
Lesson 4.3 Population Growth
Immigration and Emigration
immigrate into a region
exit by emigration
Migration, seasonal movement into and out of an area,
can temporarily affect
population size.
Lesson 4.3 Population Growth
Calculating Population Growth
• Determined by the following equation:
(birthrate + immigration rate) – (death rate + emigration rate)
• Growing populations have a positive growth rate; shrinking
populations have a negative growth rate.
• Usually expressed in terms of individuals per 1000
Did You Know?
Immigration contributes
more than 1 million people
to the U.S. population
per year.
Lesson 4.3 Population Growth
Exponential Growth
• Population increases by
a fixed percentage
every year.
• Normally occurs only when
small populations are introduced
to an
area with ideal environmental
conditions—no limiting factors
• Rarely lasts long—at a certain
population size, competition for
resources increases.
Lesson 4.3 Population Growth
Logistic Growth
Growth almost always slows and stops due to limiting factors.
• Size of population stabilizes at a number the environments
resources can sustain: The Carrying capacity
Limiting factors:
• Density-dependent:
Influence changes with
population density.
e.g., competition resources,
predator success, Rate of infectious
disease spread
• Density-independent:
Influence does not change with
population density.
e.g., natural disasters, manmade
disasters
Lesson 4.3 Population Growth
Biotic Potential
• An organism’s maximum ability
to produce offspring in ideal
conditions
• Many factors influence biotic
potential, including gestation
time and generation time.
• Organisms with high biotic
potential can recover more
quickly from population declines
than organisms with low biotic
potential.
Population Crash
When a population grows so rapidly that within one or a few
generations, it grows far above the carrying capacity of the
ecosystem, then the size of the population may drop
dramatically.
During the period that the resources are being used at a higher
than sustainable rate (more individuals than carrying capacity),
then the recycling of matter can be disrupted, lowering the
carrying capacity.
Crashes normally occur for organisms with short lifespans, short
gestations, and high #s offspring/female.
However, having technology that allows continued
unsustainable human population growth—by allowing
extraction of resources like ground water or oil—puts humans
at risk for a population crash. What will happen if we use up
these resources—and can’t get them even with technology?
Golden toad population growth
1 Describe these levels of an ecosystem for golden toads
• Individual
• Population
• Species (name it)
• Community
• Ecosystem
2 required abiotic factors for this species
3 required biotic factors for this species
4 resources required for the species
5 Two reasons likely for the extinction of the toads