Transcript chapters-5-6-notes-11-12-populations - ecological succession - limiting factors - review

Chapter 5 Populations
SuccesHow Do Communities and
Ecosystems Respond to Changing
Environmental Conditions?
 Concept 5-4 The structure and species
composition of communities and ecosystems
change in response to changing environmental
conditions through a process called ecological
succession.
Ecological Succession Review: Changes
over time
 Natural ecological restoration
• Primary succession
• Secondary succession
Some Ecosystems Start from Scratch:
Primary Succession
 No soil in a terrestrial system
 No bottom sediment in an aquatic system
 Early successional plant species, pioneer
 Midsuccessional plant species
 Late successional plant species
Primary Ecological Succession
Lichens and
Exposed mosses
rocks
Small herbs
and shrubs
Heath mat
Balsam fir,
paper birch, and
Jack pine,
black spruce, white spruce
forest community
and aspen
Fig. 5-16, p. 116
Some Ecosystems Do Not Have to Start
from Scratch: Secondary Succession (1)
 Some soil remains in a terrestrial system
 Some bottom sediment remains in an aquatic
system
 Ecosystem has been
• Disturbed
• Removed
• Destroyed
Natural Ecological Restoration of
Disturbed Land
Annual
weeds
Perennial
weeds and
grasses
Shrubs and
small pine
seedlings
Young pine forest
with developing
understory of oak
and hickory trees
Mature oak and
hickory forest
Fig. 5-17, p. 117
Some Ecosystems Do Not Have to Start
from Scratch: Secondary Succession (2)
 Primary and secondary succession
• Tend to increase biodiversity
• Increase species richness and interactions
among species
• Climax community- steady state
 Primary and secondary succession can be
interrupted by
•
•
•
•
•
Fires
Hurricanes
Clear-cutting of forests
Plowing of grasslands
Invasion by nonnative species
Read “Behind The Numbers”
Answer the following questions in your lab book.
1. What is meant by population fluctuations?
2. How is the carrying capacity of an ecosystem
important to the organisms inhabiting that
ecosystem?
3. List one type of abiotic factor that limits the carrying
capacity of northern Alaska and Canada.
4. List the abiotic factor that limits the carrying capacity
of a section of New Mexico.
The kelp forest and otters (video)
Sea Otters- Brink of Extinction?
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Habitat: Kelp Forests
Niche: Sea otters consume
many fish and shellfish,
including sea urchins which
graze on kelp.
When otters were nearly
hunted to extinction, urchin
populations rose so high
that the kelp “forests”
nearly disappeared.
Keystone species
Science Focus: Why Should We
Care about Kelp Forests?

Kelp forests: biologically diverse marine
habitat

Major threats to kelp forests
Sea urchins
 Pollution from water run-off
 Global warming

Arrows indicate
Direction of energy flow.
Sea otters exert strong
control on kelp forest food
webs. By feeding upon sea
urchins, otters reduce the
intensity of grazing and
allow kelps to develop
dense populations. Sea
otters bring urchins,
abalones, and other benthic
animals to the surface and
often smash them on their
chests with the aid of a rock.
Warm-up

Would you rather be paid $100 a day for
a month or 1 penny the first day, 2
pennies the second day, 4 pennies the
next day, 8 pennies the next day…etc.
for the rest of the month?

EXPLAIN YOUR ANSWER

$100 a day equals $3,000 for the month.

Starting with one penny, two pennies on
the second day, 4 on the third day, 8 on
the fourth day, etc. equals…
Characteristics of Populations
Important characteristics of a population:
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Geographic distribution
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Density
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Number of individuals per unit area… low to high
depending on the species and the ecosystem
Growth rate
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Area inhabited by a population… can range from a cubic
centimeter to millions of square miles
Births vs. deaths in a population
Age structure

Ages of individuals in a population
Question 1—how populations change
INCREASE size
 Births
 Immigration
(coming in)
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
DECREASE size
 Deaths (mortality)
 Emigration
(going out/leaving)
Growth rate = (births + immigration) – (deaths + emigration)
If (births + immigration) > (deaths + emigration), population
INCREASES
 If (births + immigration) < (deaths + emigration), population
DECREASES
 If (births + immigration) = (deaths + emigration), population STAYS
SAME SIZE
Question 2-- Exponential Model of
Population Growth

Population increases rapidly with no limit
 What will a graph look like? “J” shaped curve
 Rare in nature. Why?
Limit on the amount of resources (food / space)
Question 3—limiting factors
 Populations
can’t grow exponentially
forever because of limiting factors.
 Limiting Factors can be:
BIOTIC– predators, food, disease,
competition from their own species
ABIOTIC– space, water, shelter,
nutrients, salinity, temperature
Question 4—logistic growth
also called “S-curve” or sigmoidal
 More
realistic model than
exponential.
 Populations reach carrying
capacity.
Carrying capacity- the number of
individuals the environment can
support over a long time period
Logistic Model of Population Growth
When at carrying capacity,
birth rate is equal to
 Accounts for influence
death rate
of limiting factors
 What
will the graph
As population
reaches
look carrying
like? capacity,
the difference between birth
rate and death rate decreases
“S”
WhenStretched
populationout
is small,
birth rate is higher
than death rate
Now, let’s apply what we’ve
learned:
I will call on a random student to give me
a beginning population (between 1-100)
 I will call on another random student to
give me a birth rate (between 0.5-4)
 We’ll put the data into a spread sheet to
see what kind of growth occurs
 We’ll do this a few times.
 You’ll get the chance to analyze the data
and answer our guiding questions.
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population growth.xls
Answer the following questions on a half sheet
of paper or notecard:
1.
Why don’t populations on earth follow a similar
J-curve expansion?
2.
Why isn’t the earth covered with populations
that have grown exponentially?
3.
What prevents most populations on earth from
continuing to follow an exponential increase in
size?
Wrap Up
Previously we learned about biotic and
abiotic factors and how they are part of
an ecosystem.
In a sentence or two, explain how an
abiotic or biotic factor can be a limiting
factor on a particular population. Use a
specific example to support your answer.
 White pines, butterflies
http://tolweb.org/Heliconius_melpomene/72252
http://www.fs.fed.us/rm/highelevationwhitepines/About/dist.htm
Geographic Distribution
5-1 How Populations Grow
Population
density =
the number of individuals / unit
area.
Examples:
33 oak trees per acre
5 goldfish per aquarium
2 bears per square kilometer

Density
 Human population, seabird density
http://www.sanctuarysimon.org/monterey/sections/other/whats_new_u
pwelling.php
http://maps.unomaha.edu/peterson/funda/web/Resources/Chapter7/NAmerica/gallery.html
Calculate…

Suppose there are 150 bullfrogs living in
a pond that covers an area of 3 square
kilometers. What is the density of the
bullfrog population (per square
kilometer)?

Population density = # of individuals
unit area
Examples of populations
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Population distribution
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Clumping
Uniform dispersion
Random dispersion
Most Populations Live Together in
Clumps or Patches (2)
 Why clumping?
• Species tend to cluster where resources are
available
• Groups have a better chance of finding clumped
resources
• Protects some animals from predators
• Packs allow some to get prey
• Temporary groups for mating and caring for
young
5-1 How Populations Grow
Population Growth- Three factors can affect population
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size (grow, shrink, stabilize) :
# of births- pops grow if more individuals are born than
die in a period of time
# of deaths
# of individuals that enter or leave the population
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Immigration is the movement of individuals into an area.
(population will increase)
Emigration is the movement of individuals out of an area.
(population will decrease)
Population change =
(births + immigration) – (deaths + emigration)
Word Origin
 Immigration is formed from the Latin prefix in-,
meaning “in,” and migrare, meaning “to move from
one place to another.
 If the Latin prefix e- means “out,” then which of
the following means “migration out”?
• A.) emigration
• B.) migration
• C.) Immigration
Penguin Question
 If the total king penguin
population was 1200 at the
beginning of the year and
1600 at the end of the year.
What was the population’s
growth that year?
 Suppose 250 penguin chicks
died during the year. What
was the NET increase in the
population?
 If 200 adults penguins also
died during the year, was the
population’s growth?
http://www.rosssea.info/pix/big/King-Penguins.jpg
Types of Population Growth
 There are two important types of growth when
discussing populations.
• Exponential growth- reproduce at a constant rate
• pop has enough space and food,
• protected from predators/disease.
• Resulting RAPID reproduction (ie. Bacterial)
• Logistic growth• Resources become less available
• Pop growth slows down or stops
• Carrying capacity- environment determines how
many individuals it can support
R and K Strategists- Evolutionary Theory
 Populations can be defined by the type of
evolutionary strategies- expensive/cheap
http://www.bio.miami.edu/tom/courses/bil160/bil160goods/16_rKselection.html
1. Exponential growth graph
•Ideal conditions: unlimited space and
food, protection from disease and
predators = pop will grow exponentially
•Exponential growth -individuals in a
population reproduce at a constant rate
•J-shaped curvve
•Growing pop increases slowly
•Over time, pop becomes larger
Exponential Growth
Exponential growth
produces a J-shaped
population graph.
The Andromeda Strain
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"The mathematics of uncontrolled growth are frightening. A single
cell of the bacterium E. coli would, under ideal circumstances,
divide every twenty minutes. That is not particularly disturbing
until you think about it, but the fact is that bacteria multiply
geometrically: one becomes two, two become four, four become
eight, and so on. In this way it can be shown that in a single day,
one cell of E. coli could produce a super-colony equal in size and
weight to the entire planet Earth." Michael Crichton (1969) The
Andromeda Strain, Dell, N.Y. p247
Growth Rates
Age of first reproduction affects the rate of population
growth.
2. Logistic growth graph

Logistic growth occurs when
a population’s growth slows
or stops following a period
of exponential growth.

Resources have become
less available

S-shaped curve of graph

In the natural world, most
populations follow this curve
Carrying capacity
Time (hours)
Carrying capacity is the largest
number of individuals an environment
can support.
No Population Can Continue to Increase
in Size Indefinitely
Logistic Growth of a Sheep Population
on the island of Tasmania, 1800–1925
Exponential Growth, Overshoot, and
Population Crash of a Reindeer
Logistic Growth: Bacteria
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LAG PHASE: Growth is slow at
first, while the "bugs" acclimate to
the food and nutrients in their new
habitat.
 LOG PHASE: Once the metabolic
machinery is running, they start
multiplying exponentially, doubling
in number every few minutes.
 STATIONARY PHASE: As more
and more bugs are competing for
dwindling food and nutrients,
booming growth stops and the
number of bacteria stabilizes.
 DEATH PHASE: Toxic waste
products build up, food is depleted
and the bugs begin to die.
Carrying Capacity- number or the largest
number of individuals that a given environment
can support.
Logistic Growth is limited by the
environments carrying capacity
# births = #
deaths
The upper limit for population growth is determined by the carrying
capacity of the environment.
Overshooting Capacity
If a population overshoots the carrying capacity of the environment,
the result is a population crash.
Population Crash
Where there are few natural controls, a population may rise
rapidly, exceed carrying capacity, then crash as most of the
population starves.
Human Growth Curve
What is carrying capacity for humans?
What happens if we have overshot it?
Checkpoint
Which of the following is NOT a condition
for a population to reach exponential
growth?
A.) presence of unlimited resources
B.) Absence of predation and disease
C.) Movement of individuals out of the
population
Fruit Fly vs. Rabbit Population Growth
 Complete “Analyzing Data” activity on pg. 123 of
your textbook.
 Use your labbook.
 Answer all questions.
Concept Map- Section 5-1
Population
Growth
can be
Logistic
growth
Exponential
growth
characterized by
No limits on
growth
Unlimited
resources
represented by
Constant
growth rate
J-shaped
curve
characterized by
Limits on
growth
which cause a
Falling
growth rate
represented by
S-shaped
curve
5- 2 Limits to growth- what are these
“natural controls”?
 Limiting Factors - cause pops
to decrease. Two types:
 Density dependent factors competition, predation,
parasitism, and disease
 Density independent factors
unusual weather/climate,
natural disasters, and human
activities (damming rivers,
clear cutting forests)
 A resource base that is
limited also affects growth
Limiting Factors
Green arrows represent
factors that limit a
population’s growth no
matter the size
Purple arrows represent
factors that affect a
population more strongly
as the population grows
larger
Limiting Factors
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The panda population is one of the most endangered
species today because pandas depend on bamboo for
food and the forests are being cleared for timber and
farmland.
Density-dependent limiting factors
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Limiting factors
that depend on
population size
are called
density
dependent.
Examples: disease,
predation, competition,
parasitism, waste
build-up,
Or disease
Or predation

Populations are often kept in check by
the predator-prey relationship

Population control
Population Cycles for the Snowshoe
Hare and Canada Lynx
Humans Are Not Exempt from Nature’s
Population Controls
 Ireland
• Potato crop in 1845
 Bubonic plague
• Fourteenth century
 AIDS
• Global epidemic
Case Study: Exploding White-Tailed Deer
Population in the U.S.
 1900: deer habitat destruction and uncontrolled
hunting
 1920s–1930s: laws to protect the deer
 Current population explosion for deer
• Lyme disease
• Deer-vehicle accidents
• Eating garden plants and shrubs
 Ways to control the deer population
Density-Independent Limiting Factors
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
Affect all populations in similar ways
Ex. Unusual weather, natural disasters, seasonal
cycles, human activities (deforestation, damming
rivers).
Density independent example:
weather
Or climate extremes
Ch. 5-3: Human Population
Growth
http://worldpopulationbalance.org/
 1) What was the sound in the video? What did it
symbolize?
 2) What year did you notice a large increase in
population growth? What historical events may
have contributed to this?
 3) Were there points when the population
dropped?
 4) in which time period did the most population
growth occur? …Which parts of the world?
Human Population Graph
http://www.globalchange.umich.edu/globalchange2/current/lectures/human_pop/human_pop.html
Population Quickfacts (sustainablescale.org)
 The size of the human population is one of the major factors which
determine the total ecological impact of human activities (along with
consumption levels and the technologies used, see Measuring
Scale: IPAT).
 Over the course of human civilization population was fairly stable,
growing only slowly until about 1 AD. From this point on growth in
the human population accelerated more rapidly and soon reached
exponential proportions, leading to more than a quadrupling within
the last century (UNFPA).
 It took all of human history up to the early 1800s for world population
to reach 1 billion people, and until 1960 to reach 3 billion. Today, the
world gains 1 billion people every 11 years.
(www.populationaction.org).
 The current population of 6.4 billion people is almost eight and one
half times larger than the population of 760 million at the beginning
of the Industrial Revolution. At current growth rates, the world
population could double in as little as 58 years.
Human Population Numbers Over Time…
Industrial
Revolution
begins
Agriculture
begins
Plowing
and
irrigation
Bubonic
plague
NOVA- Population Changes (flash)
 Human Numbers Through Time: A.D. 0
 2,000 years ago...
...at the dawn of the first millennium A.D. the world's population was
around 300 million people.
5.3- Human Population Growth
 3 people/second- worldwide number
 World Population Clock- berkeley.edu
 Beginning of human existence- many limiting
factors kept us in check
 After agricultural and industrial changes- life is
easier and safer, food supply reliable, sanitation
improved,  reduced death rates
5-3 Human Population Growth
Demography- the study of human populations.
 Historical Overview
For most of human existence, the population grew slowly.
Limiting factors kept population sizes low.

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

Life was harsh
Food was scarce
Incurable diseases were rampant
Only half the children in the world survived to adulthood so families
had many children to make sure some would survive.
 Agriculture and industry made life easier and safer.
 Improved sanitation, medicine and health care reduced the death
rate and increased longevity.
 With these advances, the human population experienced
exponential growth.
Patterns of Population Growth
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The human population cannot keep growing exponentially
forever, because Earth and its resources are limited.
Today, scientists have identified a variety of social and economic
factors that can affect human populations.
Demography is the scientific study of human populations.
Birthrates, death rates, and the age structure of a population help
predict why some countries have high growth rates while other
countries grow more slowly.
National Geographic- Are You Typical
(link)
U.S. Population
Where are we on the S-shaped
curve?
What factors could cause our
population to stabilize?
Baby Activity
Age Structure Diagram
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Demography looks at the sex
and ages of the people in a
country to determine its growth
rate.
Age-structure diagrams -graph
numbers of people in different
age groups in the population;
can help predict future growth
Population growth depends on
how many people of different
ages make up a given
population.
Age Distribution Graphs
Population
profilegraphs
numbers of
people in
different age
groups in the
population
What can you tell about these
age structure diagrams?
Age structure comparison
 Why are these so different?
 What may be the consequences?
5-3
The
shift from high birth and
death rates to low birth and
death rates is called the
demographic transition.
Age Structure Graphs
Why are these so
different?
What may be the
consequences?
Demographic transition graph
Population Pyramids- Trends
5-3
Japan
 Most European countries
 United States

African countries
 South and Central American countries
 Many Asian countries

Easter Island
 The culture that built
these statues on
Easter Island
overshot the island’s
carrying capacity,
severely damaging
the ecosystem, and
crashed.
 What lessons can
today’s world
population learn from
this?
5-3
Current
population = 6.5
billion
2025 = 7.8 billion?
2050
= 9 billion?
Review
The number of individuals of a single
species per unit area is known as
Population
Density
The movement of individuals
into an area is called
Immigration
The range or area occupied
by a population is its
Geographic
Distribution
The maximum number of organisms of a
particular species that can be supported
by an environment is called
Carrying
Capacity
If a population grows larger than the
carrying capacity of its environment,
the
Death rate may
rise
Density- independent limiting
factors include
Hurricanes
Predation
Competition
Parasitism
A limiting factor that depends
on population size is called a
Density-dependent
limiting factor
The scientific study of human
population is called
Demography
The demographic transition
is complete when
Population
growth stops
Ch. 6 terms to know
 Sustainability-
using
resources at a rate that does not
deplete them, including:
 Water (oceans, overfishing*)
 Forests (old growth – a nonrenewable
resource!)
 Land (overgrazing vs. contour plowing)
Deforestation
 The
loss of forests, has several
effects, including
 Erosion (Dust Bowl of
1930’s,sediments in water)
 Local climate change
 And others, as noted in the
Hubbard Brook Study
 Biodiversity-the
variety of all
the organisms in the biosphere
Ecosystems that have more biodiversity
tend to be more stable.
 Biodiversity is one of our greatest
resources.

Types of biodiversity

Ecosystem
diversity -the
variety of habitats
and communities
 Species
diversity -all
the different
species in an
area
 Genetic
diversity – the
sum total of all
the different
genes of an
organism.
Threats to Biodiversity:
 HIPPO
=
 Habitat loss/fragmentation (islands)
 Introduced species (no predators; comp.)
 Pollution
 Population growth
 Overconsumption
Biological Magnification
 Concentrations
of toxic
substances increase in
organisms higher up in the food
chain.
 Examples
of substances include
mercury, lead, arsenic, PCBs,
DDT and other pesticides
Biomagnification
Global Climate Change
 The
greenhouse
effect is the
result of more
heat-trapping
gases (like CO2)
in the
atmosphere.

Due to burning of fossil fuels, an
nonrenewable resource
????Effects????
Polar ice caps melting
 Sea level rise
 More frequent/severe storms
 More droughts

Humans are not the only ones
affected:
 Species
migration
 Species distribution
 Weeds, insects, rodents?
 More disease-carrying insects
Ozone Depletion
Due to CFCs in the atm.
 Can cause overexposure to UV rays

Acid Rain

Formed when sulfur and nitrogen cmpds.
combine with water
Keystone Species
Have an important impact on the
ecosystem
 Examples
The Tragedy of the Commons

A resource that is open to anyone is
often protected by no one.
Healthy ecosystems are important!!
Produce oxygen
 Recycle waste
 Purify water
 Natural pest/disease control
 Produce food
 Habitats for wildlife
 Keep our soils healthy
