1. Population Dynamics Chapter 6 pp. 194-201

2. Populations
Population – members of one species living and reproducing in the same region at the same time.
Species Richness – number of different species in a community.
Factors that affect species richness include:
Physical size of area
Latitude (or distance from the equator)

3. Population Dynamics Three Key Features of Populations Size
Distribution
(clumped, even/uniform, random)
Density
Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

4. Three Key Features of Populations
1. Size: number of individuals in an area
Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

5. Population size Population growth rate:
= (birth rate + immigration rate) – (death rate + emigration rate)
= (br + ir) – (dr + er)

6. POST-REPRODUCTIVE
REPRODUCTIVE
PRE-REPRODUCTIVE

7. Population of a Stable Country

9. You decide!
Calculating change in population size practice

10. Distribution of populations
Distribution – spread of members of a population over space.
Uniform – may indicate high levels of intra-specific competition, so each individual stays at an equidistance from another individual e.g. penguin colony
Random – occurs when environmental conditions are equivalent throughout an area and when the presence of one member or a population has no effect on the location of another member. Both of these conditions are rare.
Clumped – This is the most common and is often because mammals form herds or schools as a strategy for reducing predation and in plants it may be because the particular pH of the soil is only suitable in certain areas. e.g. elephants, fish

11. How could knowing the distribution of species be helpful?
Keeping track of pest and plague species
Fishing industry: so they know about fish stocks
Forestry industry: so they know where valuable tree species are
Population density and distribution practice

12. Population Abundance (or density)
Abundance (or density) – number of individuals of a given species per unit area. Can be expressed qualitatively (rare, infrequent, frequent, abundant or very abundant) or quantitatively.
Measuring abundance:
Total count/True census (counting all members of a population in a given area. E.g. large animals/plants or slow moving animals)
Sampling (one or more random samples of a population taken and assumed to be representative of the entire population E.g. small, shy, very mobile animals).
Formula: Dp= N
Population Density = # of individuals ÷ unit of space S

13. Population Abundance Cannot be based on one count.
Must be repeated several times. Why?
Changes in abundance can occur over time due to:
Migration
Breeding patterns

14. Factors influencing population density
This works in a similar way to homeostasis. If a population rises above equilibrium, competition for resources such as food and space begin to take effect. Alternatively if a population falls below the set point then there is less competition and the population rises again.
Figure 6.19 page 200

15. Density dependant and Density independent factors
Density-dependant factors:
Biotic factors that have an increasing effect as population increases:
Disease
Competition
Parasites
Predation
Density – independent factors
Abiotic factors in the environment that effect
populations no matter what the size is:
Rainfall
Habitat Destruction
Salinity
Temperature
Natural disasters

16. Why measure population abundance?
Conservation concerns – endangered species need to be counted to determine if they are stable, increasing or decreasing and if they are at risk of extinction.
Control or elimination of exotic pests – monitor changes in their abundance and range.
Interested in diversity – need to count the numbers of various populations in a community.
Interested in why populations ‘explode’ – detect patterns and identify causes of these explosions in population numbers.
Predation and Population Cycles
Sampling a Rocky Shore Community