Ecology

Geology/Geography/Oceanography/Atmospheric Sciences

Quiz 11 :

Population Growth

Quiz 11 :

Population Growth

Question Type
search
arrow
Population biologists may refer to abiotic factors, such as temperature and moisture, as density-independent because such factors can affect population processes independently of local population density. At the same time, biotic factors, such as disease and competition, are called density-dependent factors because their effects may be related to local population density. Explain how abiotic factors can influence populations in a way that is independent of local population density. Explain why the influence of a biotic factor is often affected by local population density. Now, explain how the impact of an abiotic factor may also be affected by the local population density, that is, may behave at least partly as a densitydependent factor.
Free
Essay
Answer:

Answer:

Populations are affected by the environmental factors such as abiotic factors and biotic factors.
The abiotic factors are also called density-independent factors as their action is usually not dependent on population density. These factors include temperature, rainfall, light intensity, gases, and natural phenomena such as floods and droughts.
The biotic factors are affected by population density. Hence, they are also called density-dependent factors. They include food, predation, competition, parasitism, and disease.
The action of density-independent factors can be explained through the following examples.
1. Temperature exerts similar effect on population irrespective of population density.
2. Rainfall varies with the geographical location and not with the population density.
3. Natural disasters are not predictable and can occur at any region of the world irrespective of the population density.
The action of density dependent biotic factors can be explained as follows:
1. An infectious disease can affect more individuals in a dense population compared to a sparse population.
2. Competition for food is more in dense population.
3. Depletion of resources is rapid in dense populations.
Abiotic factors can be sometimes influenced by population density in following ways:
1. The mortality caused due to natural calamities in an area is more if the population is dense.
2. Light intensity reaching the forest ground depends on the density and canopy structure of the trees in the forest.
3. Algal blooms affect the availability of light to the animals beneath them in the oceans.

Tags
Choose question tag
close menu
arrow
Where on earth is human population density highest? Where is it lowest? Where on earth do no people live? Where are human populations growing the fastest? Where are they approximately stable?
Free
Essay
Answer:

Answer:

The human population shows a clumped distribution on a large scale. The density of human population is highly variable.
The human population shows the highest density in the coastal regions of all the continents and in valleys of major rivers. The highest density has been recorded in eastern and southern parts of Asia.
Human population shows the lowest density in the Arctic region and the Antarctica. Mongolia is a country that also shows a very low population density.
Human population exists on most of the regions of the earth. Some of the regions where humans do not inhabit are the oceans (except the islands), high mountain peaks, volcanic regions, regions of dense forests, and deserts. Most of the Polar Regions show absence of human population.
Human populations grow fast in the developing countries, especially in Africa. The birth rate greatly exceeds the death rate in these countries.
Human populations approximately stay stable and in some cases decline in the developed countries.

Tags
Choose question tag
close menu
arrow
While populations of gray and blue whales have grown rapidly, the North Atlantic right whale population remains dangerously small despite many decades of complete protection. Assuming that differences in population growth rates are determined by whale life histories and not by external factors such as pollution, what information would you need to explain the slower growth by the right whale populations? (Hint: While female gray and blue whales give birth every 2 years, right whales give birth only every 4 to 7 years.)
Free
Essay
Answer:

Answer:

The growth of a population can be assessed by studying the parameters of the population such as the net reproductive rate, the generation time, the geometric rate of increase, and per capita rate of increase.
Despite many efforts of protection, the population size of the right whale has remained small. This shows a slower growth rate when compared to the other species of the whale.
If the external factors such as the environmental factors are excluded from the study, the slow growth rate of the right whale population can be explained by estimation of the population parameters.
The right whale populations are found to reproduce once in a span of 4 to 7 years. This indicates a pulsed reproduction and geometric pattern of growth.
The other information needed for explaining the slow growth of the right whale population can be due to their birth rate and the death rate of the population.
The estimation of various population parameters needs information about the survivorship and number of individuals of each age class. This information can help to determine the net reproductive rate, the generation time, the geometric rate of increase, and the per capita rate of increase.
The values of population parameter such as per capita rate of increase can explain the population growth.
A positive value of per capita rate of increase indicates a growing population whereas a negative value indicates a declining population.

Tags
Choose question tag
close menu
arrow
For what types of organisms is the geometric model of population growth appropriate? For what types of organisms is the exponential model of population growth appropriate? In what circumstances would a population grow exponentially? In what circumstances would a population not grow exponentially?
Essay
Answer:
Tags
Choose question tag
close menu
arrow
What is the relationship between per capita rate of increase, r, and the intrinsic rate of increase, r max ? In chapter 10, we estimated r from the life tables and fecundity schedules of two species. How would you estimate r max ?
Essay
Answer:
Tags
Choose question tag
close menu
arrow
Both abiotic and biotic factors influence birth and death rates in populations. Make a list of abiotic and biotic factors that are potentially important regulators of natural populations.
Essay
Answer:
Tags
Choose question tag
close menu
arrow
In question 3, you thought about how the logistic growth equation produces a sigmoidal growth curve. Now, let's think about nature. What is it about the natural environment that produces sigmoidal growth? Pick a real organism living in an environment with which you are familiar and list the things that might limit the growth of its population.
Essay
Answer:
Tags
Choose question tag
close menu
arrow
Would the results of the goodness of fit analysis described here have been significant if we had chosen a significance level of P = 0.01?
Essay
Answer:
Tags
Choose question tag
close menu
arrow
What factors will determine the earth's carrying capacity for Homo sapiens? Explain why the earth's long-term (thousands of years) carrying capacity for the human population may be much lower than the projected population size for the year 2050. Now argue the other side. Explain how the numbers projected for 2050 might be sustained over the long term.
Essay
Answer:
Tags
Choose question tag
close menu
arrow
How do you build the logistic model for population growth from the exponential model? What part of the logistic growth equation produces the sigmoidal growth curve?
Essay
Answer:
Tags
Choose question tag
close menu
arrow
Suppose Sinervo and Lively study another population of side-blotched lizards in which there are five male pheno- types. If they did a "goodness of fit" analysis to test for an equal distribution of males among phenotypes in this population, what would be the degrees of freedom for their test and what would be the critical value of ? 2 for P = 0.05?
Essay
Answer:
Tags
Choose question tag
close menu