1. Chapter 8 Characteristics of Populations
Population Dynamics
Chapter 8
Characteristics of Populations

2. Key Questions
Heinemann Biology 1 Relationships in an Ecosystem 7.2 Review Questions 1-6

3. Revisual

4. Revisual

5. Revisual

6. Keystone Species
Keystone species maintain the structure of its ecosystem.
e.g. top predators

7. Keystone Species
Loss or removal of a keystone species results in less stable ecosystems and structural changes.

8. Sea Star Population - Keystone
Predator: Sea Star
Ecosystem: Rock pool
Experimental group
Increased mussel population
Decreased algal population

9. Great White is a Keystone sp. too!

10. 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

11. What do you think?
Can you estimate the current world population?

12. Population Characteristics
Population Size

13. Population Size Population size is determined by four primary events:
Birth
Death
Immigration
Emigration

14. 30 – 15 = + 15 (population increase of 15)
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)

15. Pause and Think
Which of the following describes a population that is increasing in size?
(B= birth, D= death, I= immigration, E= emigration)
(B + D) > (I + E)
(B + E) > (D + I)
(D + E) < (B + I)
(B + E) < (D + I)

17. Population Characteristics
Population Density

18. Word Work!
Density

19. Word Work!
The density of bone tissue decreases in osteoporosis sufferers.

21. 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.

22. 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 = = ~ 0.7 animals/km2

23. Population Characteristics
Population Distribution
Occupation of a population with respect to one another.
Random
Uniform
Clumped

24. Pause and Think
Identify the type of distribution (random, uniform or clumped) observed in each population below.
Clumped
Uniform
Random

25. Pause and Think
CLUMPED

26. Pause and Think
UNIFORM

27. Pause and Think
RANDOM

28. Pause and Think
If some cattle wandered off, would they still be considered part of the population?
If a new herd came by, would they be part of the existing population?

29. 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

30. Key Questions
1. Label the blanks in the diagram with the four processes that affect population size.
Population Size
Increase
Decrease

31. Key Questions
2. State whether each factor is a biotic or abiotic factor.
Water
Trees
Algae
Animals pH
Salinity
Soil
Hawk

32. 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.

33. Biozone
139 – The Role of Keystone Species 140 – Population Density and Distribution 141 – Measuring Distribution and Abundance