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Population Dynamics
Unit 1: Ecology
What would be some potential
problems if a population became too
big?
Population Dynamics
• Population:
• All the individuals of a species that live
together in an area
Population Dynamics
• Three Key Features of Populations
•Size
•Density
• Dispersion
Three Key Features of Populations
Size: number of individuals in an area
Three Key Features of Populations
• Growth Rate:
• Birth Rate (natality) - Death Rate (mortality)
• How many individuals are born vs. how many
die
• Birth rate (b) − death rate (d) = rate of natural
increase (r)
Three Key Features of Populations
Density: measurement of population per unit
area or unit volume
Pop. Density = # of individuals ÷ unit of space
How Do You Affect Density?
1. Density-dependent factors: Biotic factors in the
environment that have an increasing effect as
population size increases (disease, competition,
parasites)
2. Density-independent factors: Abiotic factors in
the environment that affect populations
regardless of their density (temperature,
weather)
How Do Populations Grow?
•
Idealized models describe two kinds of
population growth:
1. Exponential Growth
2. Logistic Growth
How is Population Growth Predicted?
Exponential Growth
(aka “J-shaped” curve)
occurs when population growth
starts slow then increases
rapidly.
Logistic Growth
(aka “S-shaped” curve)
occurs when
population growth
reaches its carrying
capacity
due to limiting factors
and levels off.
Carrying Capacity
• Carrying Capacity (k):
• The maximum
population size that can
be supported by the
available resources
• There can only be as
many organisms as the
environmental resources
can support
How does an ecosystem work?
•
An ecosystem changes over time. Species replacement
is characterized by an ecological succession in which
one community slowly replaces another as the
environment changes.
•
There are two types of succession:
1. Primary which is the colonization of new land which
was never inhabited
2. Secondary, colonization of land that takes place after
a natural disasters (hurricanes, earthquakes, etc) or
human actions.
Reintroduction of Organisms
• The first organisms to inhabit an area are
called pioneer species (lichen).
• The 2nd group of organisms to inhabit the
area are bacteria, protists, mosses, and fungi
• The 3rd group include insects & arthropods
• The 4th group include grasses, herbs, shrubs,
& trees
• http://www.youtube.com/watch?v=E0qdWoLdk1c
Checkpoint #1
• Q: What are the 2 types of succession?
• A :Primary and secondary
• Q: The first group of species to inhabit an
area are _________ example_____.
• A: Pioneer species example lichen
• Q: What are the last group of species to
inhabit an area?
• A: trees and grass
Checkpoint #2
1. An active volcano under the ocean erupts, and the build-up
of cooled lava eventually forms a new island. What type of
succession will immediately occur on the newly formed
island?
A. primary succession
C. both primary & secondary
B. secondary succession
D. no succession
2. A lack of food prevents further growth in a deer population.
This is an example of a
A. range of tolerance
C. phonic zone
B. limiting factor
D. biome
3. When populations increase, resource depletion may result in
A. exponential growth
C. competition
B. straight-line growth
D. increase in predators
Continued…
4. Type of population growth that reaches carrying
capacity is called________.
A. demography
C. logistic
B. exponential
D. j- shaped
5. An example of a density dependent factor is
__________.
A. disease
C. weather
B. natural disaster
D. seasonal cycles
6. An example of a pioneer specie would be_______.
A. pine trees
C. maple trees
B. lichen
D. shrub