Monish Malla - [Template] 28 Population Distribution-S PDF

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Population Distribution How does population distribution affect the environment?

Why? Alaska contains over 127 million acres of untouched forest land. It is the largest state in the United States, yet with a population of nearly 700,000 people it has the same total population as Austin, Texas. New Jersey is one of the smallest states and home to a population of nearly 9 million, but almost 1.8 million of its 4.4 million total land acres are untouched natural woodland. What are the reasons for the ways populations organize themselves, and what effect does this organization have on the environment?

Model 1 – Population Density and Distribution 2 km Habitat 1

Habitat 4 2 km

Habitat 3

Habitat 2

Habitat 5 = individual organism

1. Refer to Model 1. a. What do the dots in the diagrams represent? Individual organisms

b. What do the boxes in the diagrams represent? Area of the habitat

2. Calculate the area of a single habitat. 4 km squared

3. Consider the arrangements of the dots in Model 1. a. Describe the arrangements of the dots in habitat 3. uniform, evenly distributed

Population Distribution

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b. Describe the arrangement of the dots in habitat 4. grouped together in clusters

4. Fill in the table below by counting the number of individuals in each habitat in Model 1 and then calculate the area available per individual. Habitat No.

Area (km2)

1

No. of Individuals

4

2

4

3

4

4

7.75/km

31 4

1/km 3/km

12

4

5

No. of Individuals/Unit area (Density)

3.75/km

15

7

4

1.75/km

5. Refer to the completed table above. a. Which habitat shows a high population density? Habitat 1

b. Which habitat shows the lowest population density? Habitat 2

6. Draw a vertical line through the middle of each of the boxes in model 1. Label the left side “a” and the right side “b” on each box. Complete the table below for each half of each habitat. Habitat No. 1

2 3

4 5

Area (km2)

a 2

a

2

b a b

3

7.5/km

1.5/km 0.5/km

1

2

3/km

6

2

6 2

a

8/km 15

2

a b

No. of Individuals/Unit area (Density)

16

2

b

b

No. of Individuals

11

2 2

5.5/km 4

2

3/km

2/km 2.5/km

5 2

1/km

7. For which of the habitats in Model 1 is population density very similar between sides a and b? Habitat 1 and 3

8. For which of the habitats in Model 1 is the population density quite different between sides a and b? Habitat 2,4 and 5

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POGIL™ Activities for High School Biology

9. Label each of the diagrams on Model 1 using the terms clumped (clustered), random, and uniform (even) to describe the population distribution within the boxes. 1,3 = uniform; 2, 5 = random; 4=clumped

10. Compare and contrast the terms population density and population distribution. Density is the number of individuals per unit area; distribution is the arrangement of individuals in a given area.

11. Assuming the population size stays constant, propose at least two factors that might cause a population to shift from a low density habitat to a high density habitat? Loss of food source, change in environment

12. Animals such as lions or wolves often show clumped distribution. Give a reason why this would be advantageous for these animals. Lions and wolves are social animals living and hunting in groups. Each group is territorial so their territories d not overlap

13. Other than social reasons, list any other factors that may lead to clumped distribution patterns in populations. The patterns of available resources in their environment, such as clustering around watering site, m be a factor. Other factors may include protection from predators, and the inability to move from on site to another, such as juveniles who depend on their mothers

14. For each of the organisms listed below state the type of population distribution and population density of their habitat. Give a reason for each answer. Organism

Distribution

Tigers

Uniform

Bison

Clumped

Ants

clumped

Density Low

High

High

Reason Territorial and lone hunters

Herding animals

Live in organized colonies seeds dispersed by wind so individuals land

Dandelions

Apple trees in an orchard

Random

Uniform

Population Distribution

High

High

and grow at random.

Evenly spaced to avoid competition

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Model 2 – Factors Affecting Density Factor

Density Dependent

Food supply

Density Independent

X

Rainfall

X

Flood Parasites

X X

Acidity

X

Disease

X

Drought

X

Competition Predation

X X

15. Refer to Model 2. a. Which factors are dependent on the population density? Food supply, parasitism, disease, competition, and predation

b. Describe how the food supply would be affected by the population density. Dense population are all competing for the same food source within a given area

c. Describe how the levels or spread of disease would be affected by population density. The more crowded the population, the higher the chance that disease will spread.

16. What do all the density-independent factors have in common? They are all environmental factors such as rainfall

17. In your own words, define density dependent and density independent by completing the sentences below. Density-dependent factors are Directly affected by the density of individuals in a given area

Density-independent factors are unaffected by the number of individuals in a given area,

18. Density-independent factors and density-dependent factors may be interrelated. For example, a lack of rainfall that causes a drought will impact the food supply in a habitat. Propose another pairing of a density-independent factor and density-dependent factor that might occur. Heavy rainfall or flooding can cause an increase in parasite species. Drought can cause an increase in competition for food sources among species

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POGIL™ Activities for High School Biology

Extension Questions Read This! Allelopathy (allelon – “of each other” and pathos – “to suffer”) is the chemical inhibition of one species by another. This phenomena is frequently found in plants where one species of plant releases a chemical into the environment that inhibits the growth of another species of plant. An example is the Creosote bush, which releases terpenes into the surrounding soil to inhibit the growth of other plants. 19. Describe what might be observed in a habitat that would indicate a plant species is allelopathic? A single species, clear zone; weak or sickly plants surrounding it.

20. Considering what you know about population distribution, what type of distribution is likely to arise as a result of allelopathy? Justify your answer using complete sentences. Uniform or clumped distribution of a single species would result since the growth of the other species would be inhibited.

21. What would be some advantages of allelopathy to a plant? No competition from other species; allows the plants to maximize the resources in the environment

22. What would be some disadvantages to the ecosystem where allelopathic plants grow? Lack of competition leads to the growth of single species, which would upset the balance of other life forms in the area. The interaction of living things in the ecosystem define the overall environment.

23. Is it likely that a species that exhibits allelopathy would evolve over time? Explain your answer using what you know about the mechanisms of evolution. Evolution arises from competition for scarce resources. If the competition between species in removed due to allelopathy, then new species may not rise through evolution.

24. The sorghum plant releases the allelotoxin sorgolene that disrupts mitochondrial functions and inhibits photosynthesis. Brainstorm with your group some positive applications for this allelotoxin. Weed suppressant.

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