Module 8 Lesson 4 - 4

Distribution Patterns

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Three types of distribution patterns occur in wild populations: uniform, random, and clumped. The distribution patterns are affected by the resources in the habitat, the environmental conditions, the interaction with members of a community, and the interaction within the population.


Uniform distribution
In uniform distribution, organisms are equally spaced. This pattern occurs in artificial environments such as agriculture for crop fields or tree plantations. Uniform distribution may occur in organisms that set up territories. King penguins and golden eagles exhibit a uniform pattern of distribution, for example.

Random distribution

The rarest type of pattern is random distribution, which has no identifiable pattern. This occurs in environments with minimal competition.

Clumped distribution
The most common type of pattern is clumped distribution. Organisms are grouped in areas with favourable living conditions. Humans exhibit a clumped pattern of distribution. We tend to live together in towns and cities where water, food, and shelter are abundant.  

Self-Check

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Try the following questions and check your work.

1. A Case Study of Swans in Grande Prairie: A breeding flock of trumpeter swans near Grande Prairie has 50 pairs. This year saw 165 live hatchlings, no new birds joined the flock, 5 animals were shot, and 8 did not return this spring from their migration.
   
   How has the population of trumpeter swans changed?


2. 1. The Canadian human population is growing significantly, yet birth rates are dropping. Use the ΔN formula to suggest three  explanations.
   
   
   2. Population numbers have much to do with the lifespan of the organism. Why do women of Japanese ethnicity have a longer life expectancy when they live in Japan than when they live in North America? Suggest three possible reasons and explain your answers. 


3. How might a drought that decreased grass populations affect herbivore population numbers? Referring to the formula for ΔN, suggest four ways.


4. The population size of microscopic Paramecia in a 1 L hay infusion needed to be determined. By using a depression slide (a microscope slide with a well in the centre) at medium power and averaging the results of three 1 mL samples, a technician found on average 4 Paramecia/mL of hay infusion. What was the population (N) in the entire 1 L infusion?


5. Will the lack of competition and natural selection in white-tailed deer populations increase or decrease the genetic diversity of the gene pool? Explain your answer.  


6. A lovely white daisy with fern-like leaves adds brightness and cheer to the roadside ditches of rural Alberta. Unfortunately, it is an inadvertently introduced species and is very invasive, competing vigorously with Indigenous wild species. Your job is to provide data on the spread of the species, beginning with a population count in a 1 km² parcel of land.
   
   
   1. How would you count them?
      
   
   
   2. Would you do one sampling or several? Why?
   
   
   3. Would it be more informative to express the count as N (population size) or as density (D_p = number/area)? Explain.



7. Your job is to determine N for black spruce in a 100 km² parcel of land. In the chart below are the numbers of black spruce in 5 randomly chosen quadrants of 1 km² each.
   
   

   Sample (1 km2)	N  black spruce
   1	14
   2	0
   3	8
   4	6
   5	2