What is the ecological principle behind the biological control method of managing with pest insects?
Solution and Explanation
The basis of various biological control methods is on the concept of predation. Predation is a biological interaction between the predator and the prey whereby the predator feeds on the prey. Hence, the predators regulate the population of preys in a habitat thereby helping in the management of pest insects.
Top Questions on Organisms and Populations
- Read the following passage and answer the questions that follow:
In nature, we rarely find isolated, single individuals of any species; majority of them live in groups in a well-defined geographical area, share or compete for similar resources, potentially interbreed and thus constitute a population. The population has certain attributes whereas, an individual organism does not. A population at a given time is composed of individuals of different ages. The size of the population tells us a lot about its status in the habitat. Whatever ecological processes we wish to investigate in a population, be it the outcome of competition with another species, the impact of the predator or the effect of pesticide application, we always evaluate in terms of any change in the population size. The size, in nature, could be low or go into millions. Population size, technically called population density (N) need not necessarily be measured in numbers only. The size of a population for any species is not a static parameter. It keeps on changing with time depending on various factors including food availability, predation pressure and adverse weather. (a) The Monarch butterfly is highly distasteful to its predator because of a special chemical present in its body. How does the butterfly acquire this chemical?
(b) If population density at a time t + 1 is 800, Emigration = 100, Immigration = 200, Natality = 200 and Mortality = 150, calculate the population density at time t and comment upon the type of age pyramid that will be formed in this case.
Student to attempt either sub-part (c) or (d):
(c) What is the difference in a method of measuring population density in an area if there are 200 carrot grass plants to only single huge banyan tree?
\begin{center} OR \end{center} (d) Name two methods to measure the population density of tigers.- CBSE CLASS XII - 2025
- Biology
- Organisms and Populations
- Who proposed the competitive exclusion principle?
- CBSE Compartment XII - 2025
- Biology
- Organisms and Populations
- The population interaction where one species is harmed and the other is unaffected is:
- CBSE Compartment XII - 2025
- Biology
- Organisms and Populations
- (a) Draw a graph for a population whose population density has reached the carrying capacity.
(b) Out of the two population growth curves, which one is considered a more realistic for most populations? Why?
(c) Draw a growth curve where resources are not limiting for the growth of a population and give its equation.
- CBSE CLASS XII - 2025
- Biology
- Organisms and Populations
Student to attempt either option (A) or (B):
(A) How is the interaction between Ophrys and its specific bee pollinator one of the best examples of co-evolution? Explain.
OR
(B) Arrange the given important steps of decomposition in their correct order of occurrence in the breakdown of complex organic matter and explain the fourth step in the process.- CBSE CLASS XII - 2025
- Biology
- Organisms and Populations
Questions Asked in CBSE CLASS XII exam
- Nita, Vidur and Mita were partners in a firm sharing profits and losses in the ratio of 3 : 4 : 1. On 1st April 2024, they decided to admit Samir as a new partner. The new profit sharing ratio between Nita, Vidur, Mita and Samir will now be 1 : 1 : 1 : 1. The balance sheet of Nita, Vidur and Mita before Samir’s admission showed machinery at ₹ 6,00,000. On the date of admission, it was found that the machinery is overvalued by 20%. The value of machinery shown in the new Balance Sheet after Samir’s admission will be :
- CBSE CLASS XII - 2025
- Admission of a Partner
- Altima Ltd. invited applications for 2,00,000 equity shares of ₹ 10 at a premium of ₹ 4 per share. Amount payable:
On application and allotment – ₹ 7 (incl. ₹ 1 premium)
On first and final call – Balance.
Applications received for 2,40,000 shares. 30,000 rejected. Manvi allotted 4,000 shares failed to pay first and final call. Her shares were forfeited. These were reissued at ₹ 4 per share fully paid-up.
Pass journal entries in the books of Altima Ltd.- CBSE CLASS XII - 2025
- Accounting for Share Capital
- If \( \vec{\alpha} = \hat{i} - 4 \hat{j} + 9 \hat{k} \) and \( \vec{\beta} = 2\hat{i} - \hat{j} + \lambda \hat{k} \) are two mutually parallel vectors, then \( \lambda \) is equal to:
"There is widely spatial variation in different sectors of work participation in India." Evaluate the statement with suitable examples.
- CBSE CLASS XII - 2025
- Population
Alexia Limited invited applications for issuing 1,00,000 equity shares of ₹ 10 each at premium of ₹ 10 per share.
The amount was payable as follows:- On application ₹ 9 per share (Including premium ₹ 6 per share)
- On allotment ₹ 8 per share (Including premium ₹ 4 per share)
- On first and final call ₹ 3 per share.
Applications were received for 1,50,000 equity shares and allotment was made to the applicants as follows:
Category A: Applicants for 90,000 shares were allotted 70,000 shares.
Category B: Applicants for 60,000 shares were allotted 30,000 shares.
Excess money received on application was adjusted towards allotment and first and final call.
Shekhar, who had applied for 1200 shares failed to pay the first and final call. Shekhar belonged to category B.
Pass necessary journal entries for the above transactions in the books of Alexia Limited. Open calls in arrears and calls in advance account, wherever necessary.
Concepts Used:
Population Interactions
Population interaction is generally between two different species populations.“Population interaction is the interaction between different populations. It refers to the effects that the organisms in a community have on one another.”
An ecosystem is a geographic area wherein plants, animals, and many other organisms, alongwith weather and landscape, work together to form a bubble of life.
Types of Population Interactions:
Interactions can be beneficial or neutral or detrimental. Accordingly, there are six types of population interaction.
The different ways populations interact with each other can be summarized under the following headings.
- Competition
- Predation
- Herbivory
- Mutualism
- Commensalism
- Parasitism
- Competition