Unit 7- Lesson 3 (Competition & Predation

Unit 2: Population Changes

Lesson 3- Competition and

Predation

Population growth is based on

available resources

● If resources (food, water and shelter) are

plentifula population may grow

● If resources are in short supply the population

may decrease in size

Multiple Choice

Which of the following is not a resource in biology?

• Food

• Water

• Space

• Shelter

• Weather

Competition

• Competition occurs when

organisms fight for the
same limited resources

• RECALL: What are some limited

resources?

• Two types:

– Interspecific Competition

– Intraspecific Competition

Draw

Draw 2 organism competing for resources.

Interspecific Competition

• Interspecific competition

occurs when two different
species compete for a
limited resource, such as
space

• EXAMPLE: Grass, dandelions,

and many other plants all
compete for nutrients,
water and space

Multiple Choice

Which one of the following is interspecific competition?

Intraspecific Competition

• Intraspecific competition

occurs among members of the
SAME species competing for
limited resources

• EXAMPLE:During breeding

season of birds. Male birds will
share territory with males of a
different bird species but not
of its own species.
– WHY?

Multiple Choice

Which one of the following is intraspecific competition?

Competition

Predation

• The process by which one species captures

and feeds upon another

• Predator – an organism that lives by capturing

and eating other organisms

• Prey – an organism hunted or caught for food

Draw

Draw a Predation (predator/ prey interaction)

Predation

Next
Bac

k

PREDATOR/PREY CYCLES

Normal prey
population

INCREASE

Predator population
increases since more

food available.

Prey population

decrease because
they are being eaten

Less prey
means less

predators can
be supported

(begins again)

RESULTING IN..

Predator – Prey Cycles

• Scenario: Prey

outnumber predators

• Result: High numbers

of prey promote
increases in predator
populations

Predator – Prey Cycles

• Scenario: Predators

outnumber prey

• Result: High numbers of

predators promotes
decrease in prey
populations

Open Ended

Why does the rabbit population (prey) increase before the fox population (predator) increases?