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What factors affect population growth and decline?Passage IThe size of populations fluctuate over time due to four major factors: birth of new organisms, death of organisms, immigration (organisms enter into a community) and emigration (organisms exit a community and move to another community). The combination of these factors can lead to different growth patterns in populations, shown in Figure 1. In the lag phase, a population begins to colonize an area. If there are no limiting factors in the environment, the birth/emigration rate can far exceed the death rate, leading to exponential growth. However, a population can only grow so much before it is limited by environmental pressures called density dependent and density independent factors. This leads to logistic growth. Density dependent factors operate when a population reaches a very large size that can no longer be sustained by the environment, while density-independent factors affect all populations in similar ways, regardless of the size. As the death rate/emigration rate approaches the birth/immigration rate, the growth a population slows until it ultimately levels out or becomes stable at its carrying capacity.Figure 1Using the letters B (birth), D (death), E (emigration), and I (immigration) to represent these factors, write mathematical expressions to show the types of population described below. (Note: The use of > and < will be needed.)A stable population (total number of organisms is not changing).A declining population (total number of organisms is decreasing).A growing population (total number of organisms is increasing).For each of the following scenarios, determine if the population is limited by a density dependent or density independent factor. Explain your reasoning.The population of Giant Pandas in China is maintained due to competition among the animals for bamboo, their major food source.A hurricane in the Atlantic Ocean off of the Florida coast leads to a drastic decrease in the fish population that lives in the shallow waters in this region.Propose an explanation for why density dependent and density independent factors are named as they are.THE MOOSE OF ISLE ROYALEPassage IIIsle Royale is a forested island in the middle of Lake Superior in Michigan. The island is about 50 miles long and about 8 miles wide and is a protected forest reserve. A herd of moose lives on the island, but there were no moose-predators, like wolves, living on the island with them. In 1970 the moose population of the island was about 2000 animals. Although the island had excellent vegetation for feeding, the food supply obviously had limits. Thus the forest management personnel feared that overgrazing might lead to mass starvation. Since the area was too remote for hunters, the wildlife service decided to bring in natural predators to control the moose population. It was hoped that natural predation would keep the moose population from becoming too large and also increase the moose quality (or health), as predators often eliminate the weaker members of the herd. In 1971, ten wolves were flown into the island.The results of this program are shown in the following table. The Population Change is the number of moose born minus the number of moose that died during that year. Fill out the last column for each year (the first has been calculated for you).Calculate the population change for each year and enter it into the last column in Table 2. The population change is equal to the number of moose that were born minus the number of moose that dies during the year.Graph the moose and wolf populations on the graph on the next page. Use the left axis for the moose population and the right axis for the wolf population. Plot each line using a different color.According to the figure drawn in question 2 and the information in passage I:Describe how the moose population changed between 1971 and 1980.Describe how the wolf population changed between 1971 and 1980.What type of population growth did the wolf population experience from 1971-1975? Explain your reasoning.Propose an explanation for why the wolf population was able to experience the type of growth identified in part c.Was the change in the wolf population from 1971-1980 due to density dependent or independent factors? Explain your reasoning.What is the carrying capacity for the moose and wolf population on Isle Royale?What must be true of the death/emigration rate and the birth/immigration rate within a population if it has reached its carrying capacity?Willow and birch trees are staples in a moose’s diet. If more willow and birch trees were planted on Isle Royale, how would the carrying capacities of wolves and moose change? Explain your reasoning.39865301687195B00B44240452141220C00CCladocerans are a class of small crustaceans commonly referred to as water flea. They can live up to 100 days, but lifespans are usually shorter. The figure below displays the change in two populations of cladocerans when introduced to a marine environment that is suitable for their growth and development. The labels A, B, and C indicate three different phases of population growth and decline. Describe how the population changes in each phase and propose an explanation for why it changes in this way.1355090127050040030020010002001030504060Time (days)Number of cladocerans(per 200 ml)50040030020010002001030504060Time (days)Number of cladocerans(per 200 ml)3218180189230A00APassage IIIFigure 1 below show the age and sex of the human populations in Country I and Country II. The ages are grouped by 5-year classes, and the sexes are represented separately. The percentages in the different age classes are shown by the relative widths of successive horizontal bars. Among humans, pre-reproductive age is considered to be 19 and younger; reproductive age is considered to be 20-44 years old; and post-reproductive age is considered to be 45 and older.The list below indicates types of population growth that can occur based on the average frequencies (f) of pre-reproductive (p) individuals in an age group and reproductive (r) individuals in an age group.If fp > fr, then the population will experience exponential growthIf fp < fr, then the population will experience negative growthIf fp = fr, then the population will experience zero growth (maintain size)Figure 1In Country 1, approximately what percentage of individuals is younger than 15 years of age?In Country 2, what is the approximate ratio of males to females for individuals between the ages of 5 and 14?If, in country I, infant mortality (death) declined and the birth rate remained the same, how would you expect the fp and fr to change?Determine whether each of the following scenarios would cause growth, decline, or leveling of the population in country 2 over the next 15 years and explain your answer.Infant mortality is reduced to half of its current level.Each couple has fewer children than the number required to replace themselves.The average number of children a couple has is 3.Based on the passage and the information provided in Figure 1, what types of population growth will County I and Country II experience over the next several years? Explain your reasoning. ................
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