Organisms and Population
Investigate how individual organisms interact with their physical environment and each other. This chapter covers population dynamics, growth models, and the various ecological adaptations that ensure survival in extreme conditions.
1. Autecology is the:
a. Relation of heterogenous populations to its environment
b. Relation of an individual to its environment
c. Relation of a community to its environment
d. Relation of a biome to its environment
Key Answer: b. Relation of an individual to its environment
Explanation: Autecology studies individual organisms and their interactions with the environment. It focuses on adaptations and responses.
2. Ecotone is:
a. A polluted area
b. The bottom of a lake
c. A zone of transition between two communities
d. A zone of developing community
Key Answer: c. A zone of transition between two communities
Explanation: Ecotones connect two ecosystems or communities. They often show high biodiversity and edge effects.
3. Biosphere is:
a. a component in the ecosystem
b. composed of the plants present in the soil
c. life in the outer space
d. composed of all living organisms present on earth which interact with the physical environment
Key Answer: d. composed of all living organisms present on earth which interact with the physical environment
Explanation: Biosphere includes all ecosystems on Earth. It consists of living organisms and their surroundings.
4. Ecological niche is:
a. the surface area of the ocean
b. an ecologically adapted zone
c. the physical position and functional role of a species within the community
d. formed of all plants and animals living at the bottom of a lake
Key Answer: c. the physical position and functional role of a species within the community
Explanation: Ecological niche describes how an organism lives and functions. It includes habitat, food and interactions.
5. According to Allen’s Rule, the mammals from colder climates have:
a. shorter ears and longer limbs
b. longer ears and shorter limbs
c. longer ears and longer limbs
d. shorter ears and shorter limbs
Key Answer: d. shorter ears and shorter limbs
Explanation: Shorter body appendages reduce heat loss in cold climates. This helps conserve body temperature.
6. Salt concentration (Salinity) of the sea measured in parts per thousand is:
a. 10 – 15
b. 30 – 70
c. 0 – 5
d. 30 – 35
Key Answer: d. 30 – 35
Explanation: Average ocean salinity is about 35 parts per thousand. It mainly consists of dissolved salts like sodium chloride.
7. Formation of tropical forests needs mean annual temperature and mean annual precipitation as:
a. 18 – 25°C and 150 – 400 cm
b. 5 – 15°C and 50 – 100 cm
c. 30 – 50°C and 100 – 150 cm
d. 5 – 15°C and 100 – 200 cm
Key Answer: a. 18 – 25°C and 150 – 400 cm
Explanation: Tropical forests require warm temperatures and heavy rainfall. These conditions support dense vegetation.
8. Which of the following forest plants controls the light conditions at the ground?
a. Lianas and climbers
b. Shrubs
c. Tall trees
d. Herbs
Key Answer: c. Tall trees
Explanation: Tall trees form the canopy layer in forests. They regulate the amount of sunlight reaching the ground.
9. What will happen to a well growing herbaceous plant in the forest if it is transplanted outside the forest in a park?
a. It will grow normally
b. It will grow well because it is planted in the same locality
c. It may not survive because of change in its micro climate
d. It grows very well because the plant gets more sunlight
Key Answer: c. It may not survive because of change in its micro climate
Explanation: Forest plants are adapted to specific humidity and shade conditions. Sudden environmental change may affect survival.
10. If a population of 50 Paramoecium present in a pool increases to 150 after an hour, what would be the growth rate of population?
a. 50 per hour
b. 200 per hour
c. 5 per hour
d. 100 per hour
Key Answer: d. 100 per hour
Explanation: Growth rate = Final population − Initial population. Here, 150 − 50 = 100 per hour.
11. What would be the per cent growth or birth rate per individual per hour for the same population mentioned in the previous question (Question 10)?
a. 100
b. 200
c. 50
d. 150
Key Answer: b. 200
Explanation: Percentage growth rate = (100 ÷ 50) × 100. Therefore, the growth rate is 200%.
12. A population has more young individuals compared to the older individuals. What would be the status of the population after some years?
a. It will decline
b. It will stabilise
c. It will increase
d. It will first decline and then stabilise
Key Answer: c. It will increase
Explanation: More young individuals indicate higher reproductive potential. Such populations usually expand rapidly.
13. What parameters are used for tiger census in our country’s national parks and sanctuaries?
a. Pug marks only
b. Pug marks and faecal pellets
c. Faecal pellets only
d. Actual head counts
Key Answer: b. Pug marks and faecal pellets
Explanation: Tiger census commonly uses footprints and faecal samples. These help estimate population size accurately.
14. Which of the following would necessarily decrease the density of a population in a given habitat?
a. Natality > mortality
b. Immigration > emigration
c. Mortality and emigration
d. Natality and immigration
Key Answer: c. Mortality and emigration
Explanation: Mortality reduces population size and emigration removes individuals. Both decrease population density.
15. A protozoan reproduces by binary fission. What will be the number of protozoans in its population after six generations?
a. 128
b. 24
c. 64
d. 32
Key Answer: c. 64
Explanation: Binary fission doubles population every generation. After 6 generations: 2⁶ = 64.
16. In 2005, for each of the 14 million people present in a country, 0.028 were born and 0.008 died during the year. Using exponential equation, the number of people present in 2015 is predicted as:
a. 25 millions
b. 17 millions
c. 20 millions
d. 18 millions
Key Answer: c. 20 millions
Explanation: Net growth rate = 0.028 − 0.008 = 0.02. Applying exponential growth predicts approximately 20 million people.
17. Amensalism is an association between two species where:
a. one species is harmed and other is benefitted
b. one species is harmed and other is unaffected
c. one species is benefitted and other is unaffected
d. both the species are harmed.
Key Answer: b. one species is harmed and other is unaffected
Explanation: In amensalism, one organism suffers while the other is unaffected. Antibiotic production by fungi is an example.
18. Lichens are association of:
a. bacteria and fungus
b. alga and bacterium
c. fungus and alga
d. fungus and virus
Key Answer: c. fungus and alga
Explanation: Lichens are symbiotic associations of fungi and algae. Algae provide food while fungi offer protection.
19. Which of the following is a partial root parasite?
a. Sandal wood
b. Mistletoe
c. Orobanche
d. Ganoderma
Key Answer: a. Sandal wood
Explanation: Sandalwood performs photosynthesis but depends partly on host roots. Hence it is a partial root parasite.
20. Which one of the following organisms reproduces sexually only once in its life time?
a. Banana
b. Mango
c. Tomato
d. Eucalyptus
Key Answer: a. Banana
Explanation: Banana is monocarpic and flowers only once before dying. Such plants reproduce sexually once in their lifetime.