Class 12/Question Bank/Competency Based
Created by Titas Mallick
Biology Teacher • M.Sc. Botany • B.Ed. • CTET (CBSE) • CISCE Examiner
BioNotesBioNotesCreated by Titas Mallick
Biology Teacher • M.Sc. Botany • B.Ed. • CTET (CBSE) • CISCE Examiner
Competency Based Questions on Organisms and Population
1. Analyze the Age Pyramid: A population of rabbits in a forest has an age pyramid with a very broad base that tapers sharply towards the top. What does this indicate about the future of this rabbit population? a) It is declining rapidly. b) It is stable and will not change. c) It is expanding and the population size will increase. d) The post-reproductive individuals are dominating.
2. Evaluate the Interaction: In a dense forest, a large banyan tree provides support for an orchid to grow on its branches. The orchid gets better access to sunlight, but the banyan tree is neither harmed nor benefited. This interaction is an example of: a) Mutualism b) Parasitism c) Commensalism d) Amensalism
3. Predict the Growth: A bacteria culture is growing in a flask with unlimited nutrients. If the intrinsic rate of natural increase (r) remains constant, the growth curve obtained will be: a) S-shaped (Sigmoid) b) J-shaped (Exponential) c) Straight line d) Bell-shaped
4. Assertion (A): The prickly pear cactus introduced into Australia in the 1920s caused havoc by spreading rapidly. Reason (R): The cactus had no natural predators in the new environment to check its population growth. a) Both A and R are true and R is the correct explanation of A. b) Both A and R are true but R is not the correct explanation of A. c) A is true but R is false. d) A is false but R is true.
5. Calculate: In a pond, there were 20 lotus plants last year and through reproduction, 8 new plants were added. The birth rate (per lotus per year) is: a) 0.8 b) 0.2 c) 0.4 d) 0.04
6. Competitive Exclusion: Two species of birds feed on the same type of seeds. According to Gause's Competitive Exclusion Principle, what is the most likely long-term outcome if resources are limited? a) They will hybridize to form a new species. b) Both species will coexist indefinitely by sharing resources. c) One species will outcompete and eliminate the other. d) Both species will increase their population size.
7. Resource Partitioning: To avoid the outcome in Question 6, species often evolve mechanisms like "Resource Partitioning". Which of the following is an example of this? a) Fighting physically for the same territory. b) One species feeding at dawn and the other at dusk. c) One species eating the other. d) Both species migrating to a new area.
8. Adaptation Analysis: Kangaroo rats in North American deserts can survive without drinking water. How do they achieve this? a) They absorb water from the air through their skin. b) They rely entirely on metabolic water produced during fat oxidation. c) They store water in a hump like camels. d) They only come out when it rains.
9. Identify the Strategy: An organism invests all its energy into a single, massive reproductive effort (breeding once) and then dies. This strategy is called Semelparity. Which of the following is an example? a) Humans b) Birds c) Bamboo / Pacific Salmon d) Elephants
10. Logistic Growth: In the logistic growth equation , what does 'K' represent? a) The initial population size. b) The rate of reproduction. c) The carrying capacity of the environment. d) The mortality rate.
11. Ecological Niche: Which statement best describes an "ecological niche"? a) The physical place where an organism lives. b) The functional role and status of an organism in its community. c) The collection of all species in an area. d) The climate of a region.
12. Parasitism vs Predation: Why is a female mosquito not considered a parasite, even though it needs human blood? a) It kills the human. b) It lives permanently on the human body. c) It needs blood only for reproduction (egg development), not for its own survival/food. d) It is smaller than the host.
13. Population Attribute: Which of the following is an attribute of a population but not of an individual? a) Birth b) Death c) Sex Ratio d) Sex
14. Amensalism: The interaction between Penicillium mold and Staphylococcus bacteria is an example of Amensalism because: a) Both benefit. b) The mold kills the bacteria, but the mold is unaffected. c) The bacteria eat the mold. d) The mold lives inside the bacteria.
15. Verhulst-Pearl Logic: Why is the logistic growth model considered more realistic than the exponential model for most natural populations? a) Because resources are rarely unlimited in nature. b) Because predators do not exist in nature. c) Because 'r' is always zero in nature. d) Because diseases kill organisms before they reproduce.
In the rocky intertidal zone of Scotland, two species of barnacles, Balanus and Chthamalus, compete for space. Joseph Connell observed that Balanus dominates the deeper zone, while Chthamalus is restricted to the upper zone. When he removed Balanus experimentally, Chthamalus colonized the deeper zone successfully.
16. Analyze: What does this experiment demonstrate about the relationship between these two species? a) They are in a mutualistic relationship. b) Balanus is competitively superior to Chthamalus in the deeper zone. c) Chthamalus prefers the upper zone and cannot survive deep water. d) They do not compete at all.
17. Concept: The fact that Chthamalus could live in the deeper zone but doesn't because of Balanus illustrates the difference between: a) Predator and Prey. b) Fundamental Niche and Realized Niche. c) Immigration and Emigration. d) Parasitism and Commensalism.
18. Prediction: If Chthamalus evolves a stronger shell that Balanus cannot crush, what might happen to their distribution? a) Chthamalus might reclaim some of the deeper zone (Niche expansion). b) Balanus will go extinct immediately. c) Both will migrate to the open ocean. d) No change.
Fig trees and wasp species show a tight one-to-one relationship. A specific fig species can only be pollinated by its partner wasp species. The wasp lays eggs in the fig fruit, and the larvae feed on some of the seeds.
19. Identify: What type of interaction is this? a) Parasitism (Wasp eats seeds). b) Commensalism (Wasp gets home, fig unaffected). c) Mutualism (Both benefit: Pollination & Food/Shelter). d) Competition.
20. Cheating: Sometimes, a wasp lays eggs but does not pollinate the flower. What term is used for such an individual? a) Mutualist b) Commensal c) Cheater d) Predator
21. Evolutionary Consequence: If the fig species goes extinct, what will happen to its specific pollinator wasp? a) It will adapt to pollinate oak trees. b) It will become a predator. c) It will also go extinct (Co-extinction). d) It will survive on other fruits.
A lake has a carrying capacity (K) for 1000 fish. Currently, there are 500 fish. The intrinsic rate of increase (r) is 0.1.
22. Calculate: Using the logistic growth formula, what is the rate of population growth () at this moment? Formula: a) 50 b) 25 c) 100 d) 10
23. Analyze: When the population reaches 1000 fish (N=K), what will be the growth rate? a) Maximum (rN) b) Zero c) Negative d) 0.1
24. Reasoning: Which factor is likely a "Density-dependent" factor regulating this fish population as it approaches K? a) A sudden flood (Natural disaster). b) A drop in temperature. c) Competition for food and oxygen. d) Sunlight intensity.
25. Designing an Investigation: You suspect that allelopathy (Amensalism) is occurring in a field where Walnut trees are growing (no grass grows under them).
26. Scenario Analysis (Invasive Species): Scenario: The Water Hyacinth (Eichhornia) was introduced to India for its beautiful flowers. It has now clogged waterways and killed native fish.
27. Creating a Model: Draw a graph showing Population Growth over time.
28. Ethical/Practical Debate: Topic: "To save the Endangered Tiger, we should remove all other predators (like Leopards) from the sanctuary."
29. Formulating a Strategy: You are managing a fishery. You want to harvest fish for maximum profit without crashing the population.
30. Adaptation Design: Design a hypothetical organism adapted to live in a Deep Sea Hydrothermal Vent (High pressure, high temp, no light).