1. Population Dynamics
Chapter 15

2. Learning Objectives Characterising Species distribution
Abundance and Population
Age Structure
Rate of Growth
Distribution
Birth and Death Rate
Characterising Species distribution
Factors that determine the size of a population
Carrying capacity
population rate of growth
Mortality
Biotic/abiotic factors
predation & competition

3. Population: Abundance and Sampling
Abundance: The number of individuals of a species per unit area (Density)
Sampling Techniques:
Mark-recapture technique
Total number= (# marked x total caught)/ # marked ones caught
Sampling through quadrats.
Transects (changes in environment)
DynamicScience – Population sampling information
Distribution: Uniform, Random, Clumped
Sampling allows us to map distribution and density of organisms

4. Population distribution
Abundance assists us with determining distribution.
What factors affect Distribution?
Food source
Predation/ hunting/ habitat destruction
Climate, temp, environment
Reproductive factors
What factors Abiotic/Biotic might be affecting the distribution of the elephant population  (Questions from internet)

5. Population: Age Structure
Pre-reproductive age
Reproductive age
Post-reproductive age

6. Population Growth Curves
Usually there are 3 phases:
Slow growth as numbers are built up
Rapid growth
Population growth decreases, population is approximately stable.
Stable, no growth
Rapid growth
Slow growth

7. Population Growth Patterns
J Shaped Curves: Exponential growth
Lag phase
Acceleration phase
Population (next generation)= Rate of increase x Population (previous gen.)

8. Population Growth Patterns
S Shaped Curves: Logistic Growth
Deceleration phase: growth slows due to environmental resistance, competition, organism death
Growth rate is stopped by the Carrying Capacity of the environment
Carrying Capacity: maximum population that can be sustained by the environment
- Affected by Biotic and abiotic factors
Birth rate Vs. Death Rate
Population explosions
• Reproduction (many new offspring) & lower death rate
• Abiotic environment (lots of food)
• Predator control (lack of predators)
• Dispersal (spreading into new areas)

9. Factors affecting growth rates
Density- dependent factors (Intraspecific): (food/ resources) Increased influence in higher populations
Density- Independent factors: floods, drought.
Interspecific Factors: (Competition with other species)
Predation & Habitat Destruction
Growth Rate (intrinsic)- K-selected/ R-selected strategy (pg 493)
Feature
R-selected Strategy
K-selected strategy
Life span
Shorter-lived
Longer-lived
No. offspring
Many
few
Energy req. for reproduction
Small energy
Large energy
Survival Rate
Low
High
Sexual maturity
Earlier in life
Later in life
Incubation period
Short/ none
Extensive (mths)
Parental care
Little/none
Extensive

10. Population Interactions
Competition: Food, resources (nests, sunlight)
Predator + Prey relationships
Which population peaks first?
In the absence of adequate predators what happens?
Without predators, how is prey population regulated?
How many ‘boom-bust’ cycles can we see?
What other factors not visible on this graph could be influencing populations

11. Application Questions
Complete questions online at

12. Population Evaluations & Changes in Ecosystems
Chapter 15 & 16

13. Population Evaluations
Population growth = (births + immigration) – (deaths + emigration)
Percentage population growth rate in a given period = (pop. change during the period/ pop. At start of the period) x 100
Example
100 dolphins in years later they found 143 dolpins. What is the population growth per year?
Pop. Change= = 43.
% Growth Rate = (43/100) x 100 (remember this is over 3 yr period)
Per year = 43/3 (gives us the % per year) = 14.3% growth per year

14. Population Elements
Birth Rate
Birth rate = (number of births per year/ tot. pop in the same year) x 1000
Death Rate
Death rate= (no. of deaths per year/ total. Pop. In the same year) x 1000
Factors affecting Birth rate in Humans
Factors affecting Death Rate In humans
Political policies & economic conditions
War and natural disasters
Cultural & Religious background
Food supply
Birth control
Safe Drinking water & sanitation
Education level
Life expectancy and Age profile (more oldies = higher death rate)
Social elements and pressures
Disease and access to medical care

15. Population Analysis Relate the changes to population: Death rate
Birth rate
Overall growth

16. Changes in Ecosystems Is the change environmental
Regular (tides, seasons)
Sporadically / Irregular (floods in tropical areas)
One-off events (100 year flood or fire, volcanic eruption)
Disease or a flow on from population change in another interacting organism.
Is the change the result of humans
Oil spill
De-forestation
Habitat Destruction
Global Warming
Introduction of new species (deliberate, accidental or ‘classical biocontrol’)
Examples and effects.
Management: Biocontrol (biopesticides- bacteria, fungi), Immunocontraception.

17. Human Impact on Ecosystems