Download Population ecology

POPULATION ECOLOGY
M R S . P I T T A L U G A – 8 TH G R A D E S C I E N C E
NC ESSENTIAL STANDARD
• 8.L.3 – Understand how organisms interact with and
respond to the biotic and abiotic components of
their environment
• 8.L.3.1 – Explain how factors such as food, water, shelter,
and space affect populations in an ecosystem
• I can classify examples of factors that limit a
population’s growth as either density-independent
or density-dependent.
WHAT IS A POPULATION?
• A group of organisms belonging to the same
species that live in a particular area.
• Described based on size, density, or distribution.
POPULATION DISTRIBUTION
• Dispersion is the
pattern of spacing
among individuals
within the boundaries
of the population
• Clumped – individuals
are grouped in clusters
• Uniform – individuals
are evenly distributed
• Random – each
individual is positioned
independent of the
others
POPULATION DENSITY
• Result of the processes that add individuals to a
population and those that remove individuals.
•
•
•
•
Immigration – individuals moving into an area
Emigration – individuals moving away from an area
Birth rate – number of births in a population
Death rate – number of deaths in a population
• Determined by finding the number of individuals in
a given area
• Pop. Density = # of individuals ÷ unit of area
• Affected by limiting factors
Births
Births and immigration
add individuals to
a population.
Immigration
Deaths
Deaths and emigration
remove individuals
from a population.
Emigration
LIMITING FACTORS
• Factors that can cause a population size to
decrease.
• Density-dependent factors – only affect a population when
the density reaches a certain level
• Competition
• Predation
• Disease
• Density-independent factors – affect a population
regardless of the density
• Natural disasters
• Temperature
• Human activities
SOMETHING TO THINK ABOUT
• Suppose your parents offer you a choice for
allowance this month: You may have $5 a week OR
you will get a penny on the 1st and each day
afterward, they will double the amount from the
day before. Which do you choose, and why?
POPULATION GROWTH
• Exponential Growth (J-curve)
•
•
•
•
Shows populations growing unrestricted and very rapidly
Resources are plentiful, birth rate and immigration are high
Unrealistic and unstainable
Human population is currently growing at an exponential
rate
• Logistic Growth (S-curve)
• Shows populations growing rapidly but then leveling off
• Resources are limited
• Carrying capacity – the maximum number of organisms
that the environment can support based on available
resources
• More realistic growth model
POPULATION GROWTH