What is happening to the population size?
DNA (OUTPUT)
HOMEWORK
 Edits for Ocean Acidification Lab due 9/16 ; 9/17
 Outline 4.1-4.3 (pgs 76-88) due 9/18 ; 9/19
AGENDA
1. Notes
2. Gallery Walk
3. Reindeer Reading
4. Notes
5. Squirrels!!!!!!!!
ECOSYSTEMS: INTRODUCTION TO
POPULATION DYNAMICS
LIMITS ON POPULATION GROWTH
 No population can increase its size indefinitely
 Biotic potential – a population’s capacity for
growth
 Intrinsic rate of increase (r) – the rate at
which a population would grow if it had unlimited
resources
LIMITS ON POPULATION GROWTH
 Some species have really high biotic potential
 However, in the real world, no population can grow
indefinitely
 A population reaches some size limit imposed by
limiting factors such as light, water, living space, or
nutrients
 There are always limits to population growth in
nature.
LIMITS ON POPULATION GROWTH
 Environmental resistance: all factors that act
to limit the growth a population
 Carrying capacity (K) – the maximum
population of a given species that a particular
habitat can sustain indefinitely without degrading
the habitat
CARRYING CAPACITY (K)
 K is determined by the biotic potential and
environmental resistance
EXPONENTIAL AND LOGISTIC GROWTH
With ample resources, a
population can grow rapidly, but
as resources become limited, its
growth rate slows an levels off
ANALYZE THIS GRAPH
 At what level do
the deer reach their
carrying capacity?
 How do you know
what is the K?
 What is happening
in months 4, 5, 6, 7?
EXPONENTIAL GROWTH
Exponential growth starts slowly but
then accelerates as the population
increases because the base size of the
population is increasing.
The graph is a J-shaped growth curve
J-CURVE
 In this graph, the
population of
bacteria is small
from 0-15
minutes
 Starting from 15
minutes, the
population
growth increases
rapidly
LOGISTIC GROWTH
Logistic growth involves rapid
exponential population growth
followed by a steady decrease in
population growth with time until
the population size levels off.
LOGISTIC GROWTH
Logistic
growth
shows a Sshaped
growth curve
DESIGN A POPULATION WITH YOUR PARTNER
 Design a population that has just arrived to Eagle Rock Island
 What resources does your population use on Eagle Rock Island?
 Draw a population growth curve for your population on Eagle
Rock Island
 What is the carrying capacity of your population on Eagle Rock
Island?
DESIGN A POPULATION WITH YOUR PARTNER
 Each partner gets a colored marker
 Each partner writes their name down in their color
 Each partner MUST USE THAT COLOR to work on their
poster
 Each partner contributes to the “mini-poster”
MY EXAMPLE
 Dittos just arrived on Eagle
Rock Island
 Dittos need pokeberries to
survive and Eagle Rock Island
has A LOT of pokeberries!
 The Dittos population thrives
exponentially.
 The Dittos K is 42 Dittos
DEPENDING ON RESOURCE USE…
Exponential growth can lead to
logistic growth
OR
Exponential growth can lead to a
population crash
EXCEEDING CARRYING CAPACITY
When a population exceeds its
resource supplies, many members
will die unless they can switch to a
new resource or move to an area
with more resources
TIME LAG IN POPULATIONS
Reproductive time lag exists – it is the
time needed for the birth rate to fall and
the death rate to rise in response to
resource overconsumption
Populations dieback or crash unless
individuals change their resource use
ST. MATTHEW ISLAND REINDEER
As you read the article, highlight the
important ideas.
©ircle the words you don’t know
Take notes that will help you
summarize the information you read
ST. MATTHEW ISLAND REINDEER
 Point to someone in your group.
 The individual with the most number of fingers
pointed them will select your group’s scribe.
 The scribe writes down the summary that the
entire group works together to create.
 The scribe gets to decide who will have to share
the summary outloud