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```							       Chapter 4:
Population Biology
 What is a population?
 What is exponential population
growth?
 What is biotic potential?

 What is logistical population growth?

 What is carrying capacity?

 What limits a population’s size?
Population Density
# organisms in an area
How many mice are in the following population?

Estimate!

SET

Go!
How many did you count?

What is the best way to count
them?
SAMPLING
Population Sampling
   Usually, the population is
too large or mobile for the
researcher to attempt to
count all of its members.
– A small, but carefully chosen
sample can be used to
represent the population.
– The sample reflects the
characteristics of the
population from which it is
drawn
So how could we estimate this population
without counting EVERY mouse?
Population Size
   Factors that affect:
– 1. Natality (+)
– 2. Mortality/Fatality (-)
– 3. Immigration (+)
– 4. Emigration (-)
What underlying factors may cause these
to increase or decrease in an area?
Changes in Population
Size
   Birth rate (natality) & Death rate (fatality/mortality)
– Changes over time are calculated
 EX: If the birth rate in 1990 was 50 per 100,000
moose and in 2000 it was 150 per 100,000
moose, what can we say about the birth rate
over this time period?
– IT TRIPLED!
Carrying Capacity (K)
   Maximum # of organisms in a
population supported by an
ecosystem’s resources/limiting factors
– Effected by factors such as the amount
of:
 Food,   water, space, etc…
– Can change when these factors change
 EX:   more food = higher carrying capacity!
Environmental
Limits to
Population Growth
Factors regulating the size of a
population

LIMITING FACTORS: Factors
that limit how many organisms
and ecosystem can support.
Limiting Factors
   Definition?

Any biotic or abiotic factor
that causes population size
to decrease and influences
what can live where
What factors limited
the growth of our lima
beans?
   What contributes
to the fluctuation
of the population
when it reaches
carrying capacity?
What factors would limit
these communities?
Classification of
Limiting Factors
   Density-dependent                   Density-independent
–   Nutrients                        – Temperature
–   Space                            – Natural Disaster
–   Disease                          – Habitat
–   Parasitism                       Destruction
–   Predation                        – MAJOR CHANGES in
–   Competition                        ABIOTIC FACTORS
   Intraspecific
– Same species
   Interspecific
– Different species
Organism Interactions
Density Dependant
   Predation
   Competition
– Both types
 Parasitism
 Crowding/stress/

disease
Predation – Density
Dependent
   What can be said
   Why are predators
necessary?
   Why don’t prey
become extinct?
Competition – Density Dependant
•Competitive Exclusion Principle – No 2
organisms can occupy the exact same
niche in the exact same habitat at the
exact same time
Competition: Who ultimately
“wins”?
 The species best adapted to the niche!
 What is a NICHE????
Two types of
competition:

 Intraspecific- between same species
 Interspecific-between different species
Competition – Density

When either species was cultured alone — with fresh
regularly — the population grew exponentially at first and then
leveled off.
   When the two different species were cultured together, P.
caudatum proved to be the weaker competitor. The population of
P. aurelia reached a plateau, but so long as P. caudatum
remained, this was below the population density it achieved when
grown alone.
   Intra or Inter?
Limited Resources -
Density Dependent
   Here is a dramatic
example of how
competition among
members of one
species for a finite
resource — in this
case, food — caused
a sharp drop in
population.
   The graph shows a
population crash; in
this case of reindeer
on two islands in the
Inter or Intra?
Bering Sea.
Natural Disasters –
Density Independent
   Decline in the population of
one of Darwin's finches on
Daphne Major, a tiny (100-
acre) member of the
Galapagos Islands.
   The decline (from 1400 to
200 individuals) occurred
because of a severe
drought that reduced the
quantity of seeds on which
this species feeds.
   The drought ended in 1978,
but even with ample food
once again available the
finch population recovered
only slowly.
   Why not Density
Dependant?
Logistic Growth
The “S” Curve
This graph shows
logistical growth

What causes
growth to slow?

ALL growth will
eventually become
logistical or
crash….why?
Population Growth Curves
   Explain what is happening to the
populations below:
Exponential Growth
The “J” Curve

When does this
occur?
•With temporarily
unlimited resources
•With reproduction at
the rate of biotic
potential
Biotic Potential =
Reproductive Potential
   Reproducing as fasts as
biological possible
   Rate at which a population
could grow if it had unlimited
resources
   Reproducing at biotic potential
   Humans….
– Biotic potential on average = 50-
60 children/woman!
– Why don’t women have this many
kids?!?!
They only reproduce part of the year

NOTE:
gestation ~1
week
development ~12
days
AKS Bio 11c) Relate environmental
conditions to successional changes in an
ecosystem
Succession – The series of ecological
changes in an ecosystem over time

2 Types – Primary & Secondary
From Pioneer Stage  Climax Community
Ecological Succession
   A series of predictable changes that
occurs in a community over time.
– Primary Succession
– Secondary Succession
Ecological Succession
Overview
Primary Succession
 No previous
ecosystem
 Soil must be
created
 From
nothing to
ecosystem
 Pioneer
species –
bacteria,
algae, moss,
lichen
Pioneer
Species

   Species that colonize areas

   Bacteria, Mosses, Lichen, Algae -
brief life cycles

   Improve conditions for species that
replace them

   Their breakdown makes soil - primary
Secondary Succession
 An existing
ecosystem is
disturbed
 Soil and some
organisms may
remain
 Pioneer species
such as small
grasses
repopulate first
Secondary Succession
 Can change type of
community/ecosystem
 From lake to forest
ecosystem
 What might cause
this?
 How long might this
take?
Climax Community
   THE ULTIMATE RESULT OF SUCCESSION!
   Stable array of species that persists relatively
unchanged over time
Climax Community
 Ecological succession will occur until a climax
community is reached.
– A climax community is when the plant life has
reached a stable state
   The climax community will continue until
there is a disturbance.
– Natural disasters
– Human Impact
What would this be?
   A volcano erupts in the ocean. When
the lava cools, a barren rock is made.
The rock becomes inhabited by
mosses and lichen which over time will
produce soil. This is an example of
______________ succession.
– PRIMARY
 WHY?
You Tube Clip Chris
Brown style….
BNNLew0
The Human Population

Figure 4.10 pg 104
Human Population Growth
 What influences growth in the human
population?
 Change in density dependent limiting
Factors?
 Change in density independent limiting
factors?
 Are all countries growing
exponentially?
Demography
Vocabulary

   Age Structure
   Immigration
   Emigration
   Natality & Fatality data
How does each effect population size?
Age Structure Pyramids
   These pyramids compare the age structure of the populations of France
and India in 1984. The relative number (%) of males and females is shown
in 5-year cohorts. Almost 20% of India's population were children — 15
years or less in age — who had yet to begin reproduction. When the
members of a large cohort like this begin reproducing, they add greatly to
birth rates. In France, in contrast, each cohort is about the size of the next
until close to the top when old age begins to take its toll.
Age Structure Pyramids
   These population pyramids show the baby-boom
generation in 1970 and again in 1985 (green ovals).
   Profound changes (e.g. enrollments in schools and
colleges) have occurred — and continue to occur — in
U.S. society as this bulge passes into ever-older age
brackets.
Do you know which
countries have the
highest population?

Can you name the top 5?
to
list
A Few more…
Who’s the LEAST populous?

Let’s keep going down the list…
Human Population:
What Does Bill Nye
It……

Let’s take a look at some
human population
demographics…
Human Impact

How are humans affecting
ecosystems all over the Earth?
Biodiversity
   Refers to the
variety of life
in an area
Why is Biodiversity
important? It’s not just
Life depends on life…
*brings stability to an ecosystem
*living things create niches for other
living things
*symbiotic relationships can be
established or maintained
*effective food webs can be
established          or maintained
Human Impact
   Importance to
nature –
biodiversity
Importance to humans?
 Production of oxygen and carbon
dioxide
 Diet

 Prevention of starvation

 Cross-breeding to make stronger,
hardier organisms
 Materials for clothes, furniture,
buildings
 medicines
Loss of Diversity
   Extinction of Species
   Endangered Species
   Threatened Species
– Believe it or
not….99.9% of all once
living species are now
extinct!
– How big is the problem?
Loss of Biodiversity
   Extinct: entire species has died out and can
never return

Dodo Bird
Last confirmed
sighting in
1662.
Thought to be
extinct by
1690.
Loss of Biodiversity
   Endangered: species in immediate
danger of becoming extinct

Grizzly Bear
Loss of Biodiversity
   Threatened species: species are likely
to become endangered in the future

endangered
if conditions
surrounding
them begin
to or
continue to
Source: http://ecos.fws.gov/tess_public/StateListing.do?state=all = updated daily
Source: http://ecos.fws.gov/tess_public/StateListing.do?state=all = updated daily
Monday, Sept. 14, 2009
Threats to
Biodiversity
Threats to Biodiversity

 1.Invasive Species
 2.Habitat Destruction

 3.Habitat Fragmentation
– Biotic Issues
– Abiotic Issues
– Air Pollution
– Water Pollution
– Land Pollution
1. Invasive Species
   Non-native
organisms that
“move-in” to a
particular area
   There can be a
lack of competitors
= exponential
growth
   Out-compete
natives for
resources
   Can take over the
niches of native
species
Kudzu
Invasive Species
The Nutria…
Other Threats to
Biodiversity
   2. Habitat loss
*deforestation
*clear-cutting grasslands
*draining wetlands
   3. Habitat fragmentation
*makes it difficult for species to re-
establish themselves
*can change climate
(damage to habitat by
pollution)
*3 types of pollution: water, land, air
Chemical Pollution
Cycle
   Pollution added to the environment will
cycle & ultimately reach humans:
– EX: Chemicals are:
1. Dumped – land/water  river/lake/ocean

2. Enter the food chain

3. Harm the aquatic & terrestrial life

4. Threaten humans
Water Pollution
   Additions of solid or liquid waste that is not
naturally occurring

Ex. Excess fertilizer and
animal waste wash into
streams, rivers, lakes,
ponds, and oceans cause
ALGAL BLOOMS
Land Pollution
   Trash, garbage, and litter
*average American produces ~1.8
kg of solid waste daily
HUGE human impact
global problems…
 Biomagnification
 Ozone layer

 Acid Rain

 Earth’s temperature
BIOMAGNIFICATION
   A concentration INCREASE in a
chemical as it moves up the trophic
levels
   WHY?
   EX: DDT, Mercury
Biomagnification – Where less is more
•Put on your name tag – who are you?
•Populations? Community? Ecosystem?
•What is the relationships of these organisms?
•Food web: birds can eat fish & shrimp; fish can
eat shrimp and algae; shrimp can eat algae; what
Biomagnification – Where Less is More
•Problem: DDT has reached the ocean habitat of
your organisms and has entered the food chain in
low, non lethal levels
•Each organism has a different exposure –
•Algae – 1 beans (PP)
•Shrimp – 2 beans (PP)
•Fish – 3 beans (PP)
•Bird – 0 beans*
Biomagnification – Where Less is More
•Organisms “swim” around holding pesticide
particles in the left hand
•When you hear the sound, find the organism closest
to you, introduce yourself and determine any feeding
relationship
•To “eat” an organism, high five that organism with
•The organism preyed upon gives the predator
his/her beans and sits down. The predator keeps
“swimming”
At the end of the simulation, if you are still “alive”
count the number of DDT particles you have.
If you “survived” what are the effects of the
pesticide on you?
Data Table: Pesticide Effects by Concentration
Organism      3 PP           4 PP               5 PP             6 PP or greater
Algae         inability to   cell wall          organism death
reproduce      damage                                  --------
Shrimp        no effect      softening of the   offspring        organism death
exoskeleton        develop with
(shell)            fewer legs
Fish          no effect      mutations in       kidney damage    tumor
egg cells                           formation
Bird          no effect      no effect          softening of egg problems with
shells           migration
patterns and
mating
behaviors
OZONE DEPLETION
   Ozone (O3) Depletion
– O3 forms a “good layer”
around the Earth
– CFC release is breaking
down the protective ozone
layer                   ●
   CFC’s are used in refrigeration
equipment
– UV rays increase skin
cancers & other cell
mutations to plants &
animals!
Figure 54.27a Erosion of Earth’s ozone shield: The ozone hole over the
Antarctic
Ozone Depletion –
What’s Been Done?
 CFC’s banned in most 190 countries in
the 1970’s
 This is a success story!
ACID RAIN/PRECIPITATION
   Acid Precipitation
– rain, snow, dew or fog
– Created when gases
such as nitrogen oxide
(NO2) and sulfur oxide
(SO2), come from the
burning of fossil fuels
(coal and oil)
– They react in the
atmosphere with
sunlight to produce
acids…
   nitric and sulfuric acid
– These acids dissolve in
water to become acid
precipitation
How is Acidity Measured?
 Acidity is measured in
units called pH.
 The pH scale = 0 to 14
– pH 7 indicates neutral
– higher pH numbers =
alkalinity (base)
– smaller numbers = acid

 We’lldo more on pH in the
“Biochemistry” chapter
Natural Acid Precipitation
   CO2 combines with
water to form a weak
acid
– H2CO3 (carbonic acid)
   But we are adding to
the problem…
sulfuric acids
Look at the “clean
slightly acidic???
Effects of Acid Precipitation
• In Japan, rain which registers pH 5.6 or less is considered acid rain;
some 80-90% of the rain that falls in Japan in a year is acid rain.
• In Japan, acid rain with acidity equal to lemon juice has been
observed at Mount Tsukuba in 1984 (pH 2.5) and at Kagoshima in
1987 (pH 2.45). The problem is even more serious in North America
and Europe. In those regions, forests are withering and lakes
becoming uninhabitable to fish, and stone structures such as buildings
and bronze statues are being damaged by corrosion.

1970                   1985
Acid Rain – What’s
Been Done?
 Lower NOx and SOx emission fuels &
technologies for cars
with low NOx and SOx emissions
 Reduced reliance on coal electric
power
– Hydroelectric
– Nuclear
Climate Change
   “The Greenhouse Effect”
– Fossil fuels give off lots of CO2
 This   builds a blanket around the earth
 It is predicted that the Earth temp. will
increase ~50C before 2050 = Ice age???
 Greenhouse gases slow/stop the
escape of heat from Earth’s surface
Global Warming
   Long-term increase in the temperature
of Earth’s lower atmosphere
   CO2 – blue
   Temp – red
Carbon Dioxide
   Carbon dioxide levels fluctuate seasonally

   The average level is steadily increasing

   Burning of fossil fuels & deforestation are
contributing to the increase
Other “Natural”
Greenhouse Gases
   Methane - produced by bacteria,
termites, cows, locked in glaciers and
YOU!
   Nitrous oxide - released by bacteria,
fertilizers, and animal wastes
Global Warming –
What’s Been Done?
 Better fuels and technologies for
combustion in cars and industry
 Research into oceanic pumping of
CO2
 Algae “scrubbers” on smokestacks

 Legislation & conferences – Kyoto
Protocol
 Green initiatives in society
Conservation
Political Initiatives
 Lay Down The Law
–   National Parks Act - 1916
–   Clean Air Act - 1970
–   Clean Water Act - 1972
–   1973 = US Endangered
Species Act
   Made it illegal to harm any
species on the endangered
OR threatened list
– Including changing an
ecosystem where the
species lived
Conservation
   Nature preserves
– Protects entire communities/ecosystems
Conservation
 Reintroduction Programs
 Captivity Breeding

Example:
The Ginkgo Tree
would probably
be extinct if it
were not for
Chinese monks
keeping it in
captivity around
temples
Conservation
   Sustainable use:
– Use what you need, but don’t damage the
ecosystem

Is this a
good
example of
sustainable
use?

```
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