###### Advertisements

###### Advertisements

(a) Name the two growth models that represent population growth and draw the respective growth curves they represent.

(b) State the basics for the difference in the shape of these curves

(c) Which one of the curves represents the human population growth at present? Do you think such a curve is sustainable? Give reason in support of your answer.

###### Advertisements

#### Solution

(a) Two types of growth models:

1) Exponential growth: When resources are unlimited, the population tends to grow in an exponential pattern. If the population size is N and the birth and death rates are b and d, respectively, then the increase or decrease in N at t (time period) is

dN/dt=(b-d)*N

if (b-d)=r, then

dN/dt=rN

r is the intrinsic rate of natural increase.

Or

N_{t}=N_{ο}e^{rt}

^{}

N_{t}: Population density at time t

N_{0}: Population density at time 0

r: Intrinsic rate of natural increase

e: Base of natural logarithm (2.71828)

2) Logistic growth: When the resources are limited leading to competition between individuals and survival of the fittest, the population tends to grow logistically. In this kind of growth, there is an initial lag phase followed by acceleration or deceleration phases, and finally asymptote, when it reaches its carrying capacity (K). When N in relation to t is plotted, it results in a sigmoid curve which is

dN/dt=rN`((K-N)/K)`

N: Population density at time t

r: Intrinsic rate of natural increase

K: Carrying capacity

(b) The difference in the shape of these curves is the amount of resources available for the given population. For exponential growth, the amount of resources is considered infinite, while in logistic growth, there is limited amount of resources available.

(c) The present human population is following the logistic growth curve because the number of human beings is increasing rapidly but the available resources are not increasing at the same pace. Such a growth pattern is not sustainable because at one point the human population would reach a place where there would not be enough resources for everyone. For sustainable growth, we must find ways to develop and use already present resources more intelligently.

#### APPEARS IN

#### RELATED QUESTIONS

Construct an age pyramid which reflects a stable growth status of human population.

"Analysis of age-pyramids for human population can provide important inputs for long-term planning strategies." Explain.

What is an age-pyramid?

Define the Carrying capacity.

What is reproductive fitness? Explain it with the help of an example.

**Answer the following question.**

"The size of a population for any species is not a static parameter." Justify the statement with specific reference to fluctuations in the population density of a region in a given period of time.

Study the flow chart given below and complete the equation that follows by identifying 1, 2, 3 and 4.

N_{t + 1} = N_{t} + {(1+ 2) − (3 + 4)}

Animals that can move from fresh water to sea called as ________.

Give an account of population regulation.

Measures of ‘Central tendency’ refer to:

Nutrient enrichment of water body result.

The phenomenal and rapid increase of population in a short period is called ______.

Population having large number of postreproductive and small number of prereproductive age group is called

`"dN"/"dt" = "rN" (("K"- "N")/"K")` in logistic growth "K" represents:

Age distribution in a population can influence

Label the three tiers 1, 2, 3 given in the above age pyramid.

What type of population growth is represented by the above age pyramid?

List any four characters that are employed in human population census.

Given below is the Age Pyramid of the population in one of the states in India as per 2011 census. It depicts the male population on the left-hand side, female population on the right-hand side, newborns towards the base and gradually increasing age groups as we move from base to the top, with the oldest population at the top. Study this pyramid and comment upon the appropriateness of the Assertion and the Reason.

** Percentage to the total population**

**Assertion:** It is a stable population.

**Reason:** The pre-reproductive and reproductive individuals are almost in equal numbers and the post-reproductive individuals are relatively fewer.

Write the best method to measure the population density of a single Banyan tree in comparison to Partlzenium weeds in a forest by an ecologist. Explain and justify your answer.

**Important attributes belonging to a population but not to an individual are:**

- Birth rate and death rate
- Male and female
- Birth and death
- Sex-ratio

Select the correct option from the given options:

With the help of neatly labelled diagrams, explain the different types of age pyramids of human population.