Download Population Dynamics

Population
Dynamics
Chapter 8
Characteristics of Populations
Key Questions
Heinemann Biology 1
Relationships in an Ecosystem
7.2 Review
Questions 1-6
Revisual
Revisual
Revisual
Keystone Species
Keystone species maintain the structure of its
ecosystem.
e.g. top predators
Keystone Species
Loss or removal of a keystone species results
in less stable ecosystems and structural
changes.
Sea Star Population - Keystone
Predator: Sea Star
Ecosystem: Rock pool
Experimental group
Increased mussel
population
Decreased algal population
Great White is a Keystone sp.
too!
Word Work!
Population dynamics: The study of change in
population size over time.
Population: A number of organisms of the
same species that live in a defined geographic
area.
Abundance: The size of the population.
Density: The number of individuals per unit
area or volume.
Distribution: Where a species lives: it’s
geographic range and its preferred habitat
What do you think?
Can you estimate the
current world population?
http://www.worldometers.info
Population Characteristics
1. Population Size
Population Size
Population size is determined by four primary
events:
1. Birth
2. Death
3. Immigration
4. Emigration
Mathematically…
Change in population size =
(births + immigration) − (deaths + emigration)
ENTRIES – EXITS
e.g. (20 B + 10 I) – (5 D + 10 E) =
30 – 15 = + 15 (population increase of 15)
Pause and Think
Which of the following describes a population that is
increasing in size?
(B= birth, D= death, I= immigration, E= emigration)
A.
B.
C.
D.
(B + D) > (I + E)
(B + E) > (D + I)
(D + E) < (B + I)
(B + E) < (D + I)
Population Characteristics
2. Population Density
Word Work!
Density
Word Work!
The density of bone tissue decreases in
osteoporosis sufferers.
Abundance (or density)
Can be expressed:
• qualitatively, e.g. scarce or rare,
infrequent, frequent, abundant, very
abundant
• quantitatively, e.g. the number of ants
per square metre.
Pause and Think
One study identified 54 Tasmanian devils
living in an area of 80 square kilometres in
Tasmania.
What will be the abundance of this
population, in quantitative terms
(abundance/km2)?
54/80 = 0.675 = ~ 0.7 animals/km2
Population Characteristics
3. Population Distribution
Occupation of a population
with respect to one another.
• Random
• Uniform
• Clumped
Pause and Think
Identify the type of distribution (random, uniform
or clumped) observed in each population below.
Clumped
Uniform
Random
Pause and Think
CLUMPED
Pause and Think
UNIFORM
Pause and Think
RANDOM
Pause and Think
1. If some cattle wandered off, would they still be
considered part of the population?
2. If a new herd came by, would they be part of the
existing population?
Factors that determine
Distribution and Abundance
1. Characteristics of environment – Abiotic
factors
2. Characteristics of the organism
(adaptations) – particular features allow
an organism to survive and reproduce
3. Interactions between organisms – including
availability of prey, parasites, competition
Key Questions
1. Label the blanks in the diagram with the four
processes that affect population size.
Population Size
Increase
Decrease
Key Questions
2. State whether each factor is a biotic or abiotic
factor.
A.
B.
C.
D.
Water
Algae
pH
Soil
E.
F.
G.
H.
Trees
Animals
Salinity
Hawk
Key Questions
3. Use a specific example to explain how one abiotic
factor can affect population growth.
4. a) Compare interspecific and intraspecific
competition and give an example of each.
b) Name three limiting factors that affect population
growth.
Biozone
139 – The Role of Keystone Species
140 – Population Density and Distribution
141 – Measuring Distribution and Abundance