Download What is a population pyramid?


Bell-Ringer
◦ What is population Density and name
two types of dispersion
◦ Grab New Ecology Part 2 Packet
Population Ecology
Population Ecology is the science of
understanding the change in populations over
time.
◦ 2 levels of study
 Whole Population
 Cohort- who you live
with
Each species has a
unique pattern of
development,
reproductive rate,
migration, and
survivorship


All species occur in groups called
populations
Limiting factors = factors that are
biotic or abiotic that keep a population
from continuing to increase indefinitely
What Affects Population Size?
Some Limiting Factors
BIRTHS
DEATHS
Immigration
Emigration
“Reproduction
rate”
“Mortality rate”
- predation
- disease
- birth issues
Definition: Moving
Definition:
• Density
• Parental ability
and status
Others?
INTO a new EXITing a
area
area
Reasons:
• Resources
• Mates
• Food
• etc
Reasons:
• Competition
• Resources
• Population
density

2 types of Population-Limiting Factors:
• density-independent factors
• density-dependent factors
A.
BRAINSTORM IN GROUPS

Density-independent factors = Any factor in the
environment that does not depend on the number
of members in a population per unit area

Usually abiotic (natural phenomena)

Ex:

Weather events (tornadoes, floods, hurricanes)

Fire

Human alterations of the landscape

Air, land, and water pollution

Density-dependent factor = Any factor in the
environment that depends on the number of
members in a population per unit area

Usually biotic

Ex:
◦ Predation
◦ Disease- (high population density--> disease
quickly spreads)
◦ Parasites
◦ Competition – food, space limitations


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Target: I know the difference between
exponential growth and logistic growth
Bell-Ringer: 20 acre farm has 20 deer,
10 acre farm has 2 deer- which has
bigger density?
Get out Bio notes packet

The population growth rate (PGR)
explains how fast a given population
grows.


Lag Phase – Period of no growth
Exponential Growth Phase- Tons of
growth

Deceleration Phase- slows down

Stable Equilibrium Phase - stabilizes


Exponential growth
(J curve) Growth
Curve is smooth and
becomes infinitely
steep
All populations grow
exponentially until
some limiting factor
slows the population’s
growth.

The population’s growth slows or stops
following exponential growth, at the
population’s carrying capacity. – DUE
TO LIMITING FACTORS

A population stops increasing when the
number of births is less than the
number of deaths or when emigration
exceeds immigration.

Carrying capacity = The maximum
number of individuals in a species that
an environment can support for the long
term.
◦ Where Births start to relatively
equal deaths in the population –
write down in margin of notes
◦ limited by the energy, water, oxygen, resources,
and nutrients available.
◦ Population can also exceed carrying capacity
(Overshoot)- deaths outnumber births because
resources are not available to support all
individuals

Pages 11-14 in Ecology part 2 packet

Due Monday!

Bell-ringer
◦ Which period in time correlates with the
start of human exponential growth?
 A) the plague
 B) “the baby boom”
 C) the industrial revolution
POPULATION
PYRAMIDS
Human Population
• Human Population Growth Rate – influenced
heavily by the industrial revolution
• The study of human population size, density,
distribution, movement, and birth and death
rates is demography.
Zero Population Growth
• Zero population growth (ZPG) occurs when
the birthrate equals the death rate.
What is a population pyramid?
• It is a diagram that gives information about
the proportion of males and females in
each age group.
• Also shows:
- proportion of young people (0 -14 )
- proportion of working people (15 – 59)
- proportion of elderly people (60+)
What is a population pyramid?
Vertical Axis - Age Groups
Elderly dependents
Working population
Young dependents
Horizontal Axis – Percentage / number
How to read a population pyramid?
• Read the title e.g. country or city or
racial group
• Comment on general shape of the
pyramid
• Note the proportion of people in various
age groups
• Note the sex ratio
• Interpret the data
Types of Population Pyramid
1. Triangular shaped
2. Beehive-shaped Pyramid
3. Rectangular-shaped Pyramid
Shape of pyramids is controlled by
–births,
–deaths, &
–migrations.
You can also determine Growth Patterns by looking at these graphs
Population Pyramids in Transition
Each pyramid tells a story
about the
past, present & future
of a country & its people.
Importance of Population Pyramids
• Policy Planning
~ future housing estates
~ future schools
~ future jobs
• Comparison with other countries
~ developed (US) vs developing (India)
What is biodiversity?
• Biodiversity is the variety of life in an area that
is determined by the number of different
species in that area.
• Biodiversity increases the stability of an
ecosystem and contributes to the health of
the biosphere.
Types of Biodiversity
• The variety of genes or inheritable
characteristics that are present in a population
comprises its genetic diversity.
• Genetic diversity increases the chances that
some species will survive during changing
environmental conditions or during the
outbreak of disease.
Types of Biodiversity
• The number of different
species and the relative
abundance of each
species in a biological
community is called
species diversity.
With your neighbor….
• What environmental
factors might be
involved in the
increasing diversity of
species as one moves
from northern latitudes
to the tropics?
How do the two compare in regards to
species diversity?
The Importance of Biodiversity
• Most of the world’s food crops come from just
a few species.
• Wild species serve as reservoirs
of desirable genetic traits that
might be needed to improve
domestic crop species.
• A disease comes through that only effects people
with blue eyes – Brainstorm in your groups why
genetic diversity is important for this issue? Would
species diversity be helpful here?
Extinction Rates
• The gradual process of species becoming
extinct is known as background extinction.
• Mass extinction is an event in which a large
percentage of all living species become extinct
in a relatively short period of time.
• What things do you think have greatly
impacted changes on Earth?
Overexploitation
• Overexploitation, or excessive use, of species
that have economic value is a factor increasing
the current rate of extinction.
– Examples
•
•
•
•
Bison
Passenger pigeons
Rhinoceros
Ocelot
Habitat Fragmentation
• The separation of an ecosystem into small
pieces of land is called habitat fragmentation.
• Carving the large ecosystem into small parcels
increases the number of edges—creating edge
effects.
Biological magnification
• Biological magnification
is the increasing
concentration of toxic
substances in organisms
as trophic levels
increase in a food chain
or food web.
Eutrophication
• Eutrophication occurs
when substances rich in
nitrogen and
phosphorus flow into
waterways, causing
extensive algae growth.
Introduced Species
• Nonnative species that are either
intentionally or unintentionally
transported to a new habitat are
known as introduced species.
Other threats
•
•
•
•
•
Habitat Loss
Destruction of Habitat
Disruption of Habitat
Pollution
Acid Precipitation