Lesson 3 Study Guide – Population Dynamics
Name __________________________________________________________
How can a population grow or get smaller?
 If new individuals are added to the population, it grows.
 If individuals are removed from a population, it gets smaller.
 If the number of individuals that are added is close to the number of individuals that are
removed, the population stays about the same.
 Populations change in size when individuals move.
 Define immigration: when individuals join a population.
 Define emigration: when individuals leave a population.
 Give three reasons why members of a population would leave one ecosystem and go to
another:
o Lack of resources
o Changes in weather
o Introduction of a new predator
 Another way that populations increase is when individuals are born.
 Another way that populations decrease is when individuals die.
 The number of births compared to the number of deaths helps determine if a
population is increasing or decreasing in size.
 Environmental factors have an impact on the size of a population:
o The amount of resources in an area influences the size of a population. Explain
how this works: As more resources become available, more individuals in a
population can be supported in that ecosystem.
o A population may grow or shrink depending on whether important resources are
added to or lost from the environment.
o Define carrying capacity: it is the maximum number of individuals of one species
that the environment can support.
o The carrying capacity can change when the environment changes.
o Define population crash: when the carrying capacity for a population suddenly
drops.
o Now give three examples of factors that could cause a population crash:
 Natural disasters
 Harsh weather
 Introduction of a new predator
 A part of the environment that keeps a population’s size at a level below its full
potential is called a limiting factor.
o These factors can be living and non-living.
o The nonliving parts of an environment are called abiotic factors. Now list three
examples of these:
 ____________________________________________________
 ____________________________________________________
 ____________________________________________________
o The living parts of an environment are called biotic factors.
o Relationships among these organisms affect each one’s growth and survival.
 Define competition in regards to how it influences population size: when two or more
individuals or populations try to use the same limited resources.
o Competition can happen among individuals and populations.
 Define cooperation in regards to how it influences population size: when individuals
work together
o List three ways in which animals cooperate in a population:
 Hunt in groups
 Stay close together to keep warm
 Have a structured social order
 Cooperation helps individuals get resources which can make populations grow.