Organisms and Populations
Each subtopic includes About section, revision page link, 10 preview questions, and practice CTAs.
Organisms and Environment
SubtopicOrganisms and Environment under Organisms and Populations for Grade 12 CBSE.
Preview questions (no answers)
- 1.
In many lakes and ponds, various species of zooplankton respond to unfavorable environmental conditions by entering a specific stage of suspended development. Identify the term for this stage as represented by 'X' in the process below.
A.Aestivation
B.Hibernation
C.Diapause
D.Migration
- 2.
In addition to temperature and light, which abiotic factor is most critical for the survival of organisms?
A.Soil
B.Water
C.Air
D.Pressure
- 3.
What is the primary source of energy for almost all ecosystems on Earth?
A.Soil
B.Water
C.Sun
D.Wind
- 4.
Bears going into caves during winter is an example of:
A.Aestivation
B.Hibernation
C.Diapause
D.Migration
- 5.
Evolutionary, the 'costs and benefits' of maintaining a constant internal environment are significant. This explains why:
A.All organisms are regulators
B.Regulators are more common than conformers
C.Many species have not evolved to be regulators
D.Conformers have no survival advantage
- 6.
The productivity and distribution of plants are heavily dependent on which abiotic factor after temperature?
A.Soil type
B.Water
C.Light
D.Wind speed
- 7.
Which pigment allows certain red algae to live at great depths in the ocean where only specific wavelengths of light penetrate?
A.Chlorophyll a only
B.Phycoerythrin
C.Carotenoids only
D.Xanthophylls
- 8.
A scientist finds a plant that has high leaf succulence, a thick cuticle, and sunken stomata. However, its most unique feature is 'Salt Glands' on the leaves. This plant is most likely a:
A.Mesophyte
B.Hydrophyte
C.Halophyte
D.Sciophyte
- 9.
What is the primary role of 'Chaperonins' in organisms subjected to sudden thermal stress?
A.To increase the rate of glycolysis for more ATP
B.To prevent the misfolding and aggregation of cellular proteins
C.To act as antifreeze agents in the cytoplasm
D.To signal the cell to undergo apoptosis immediately
- 10.
Which of the following best defines an 'Ecotype'?
A.A group of individuals of different species living in the same habitat
B.A genetically distinct geographic variety or population within a species, adapted to local environmental conditions
C.The total range of environmental conditions a species can tolerate
D.The physical appearance of an organism as determined by its environment
Download the worksheet for Organisms and Populations - Organisms and Environment to practice offline. It includes additional chapter-level practice questions.
Populations: Growth, Attributes and Age Pyramids
SubtopicPopulations: Growth, Attributes and Age Pyramids under Organisms and Populations for Grade 12 CBSE.
Preview questions (no answers)
- 1.
Which of the following is true for a population with an expanding age pyramid?
A.Birth rate is higher than death rate
B.Death rate is higher than birth rate
C.Birth rate and death rate are equal
D.The population is decreasing
- 2.
The total number of individuals of a species per unit area or volume at a given time is called:
A.Population size
B.Population density
C.Population distribution
D.Vital index
- 3.
Which phase is NOT part of the logistic growth curve?
A.Lag phase
B.Phase of acceleration
C.Phase of deceleration
D.Infinite growth phase
- 4.
Relative density is often used when:
A.The population is very small
B.The population is very large and counting is impossible
C.The species is extinct
D.Individual organisms are very large
- 5.
In the study of population ecology, evolutionary biologists maintain that organisms evolve towards the most efficient reproductive strategy to maximize their 'Darwinian fitness' under given selection pressures. Which of the following parameters is used as a quantitative measure of this fitness?
A.Intrinsic rate of natural increase ()
B.Carrying capacity ()
C.Environmental resistance
D.Population density at time ()
- 6.
What does 'K' stand for in the equation ?
A.Kill rate
B.Carrying capacity
C.Kinship coefficient
D.Constant of proportionality
- 7.
In a population, if there are more individuals in the post-reproductive age group than in the pre-reproductive age group, the population is likely to:
A.Increase in size
B.Remain stable
C.Decrease in size
D.Reach carrying capacity
- 8.
In a population of 1000 individuals, the sex ratio is and the per capita birth rate is . If the sex ratio of the population shifts to (males:females) while the average number of offspring produced per female remains constant, what will be the new per capita birth rate () for this population?
A.0.096
B.0.192
C.0.240
D.0.150
- 9.
In a population of flour beetles, if and the current population is 100, what is the instantaneous rate of increase ?
A.1.2
B.12
C.120
D.0.12
- 10.
For a population with a stable size, the age pyramid is typically:
A.Triangular
B.Bell-shaped
C.Urn-shaped
D.Spindle-shaped
Download the worksheet for Organisms and Populations - Populations: Growth, Attributes and Age Pyramids to practice offline. It includes additional chapter-level practice questions.
Population Interactions (Mutualism, Competition, Predation, Parasitism)
SubtopicPopulation Interactions (Mutualism, Competition, Predation, Parasitism) under Organisms and Populations for Grade 12 CBSE.
Preview questions (no answers)
- 1.
The association where one species is harmed and the other is unaffected is known as:
A.Commensalism
B.Amensalism
C.Mutualism
D.Competition
- 2.
Many insects and frogs are cryptically colored to:
A.Attract a mate
B.Avoid being detected by predators
C.Absorb more sunlight
D.Thermoregulate
- 3.
Which of the following interactions results in the death of the host organism eventually (though not always immediately)?
A.Mutualism
B.Commensalism
C.Parasitism
D.Competition
- 4.
What does the plant provide to the fungus in a mycorrhizal relationship?
A.Minerals
B.Water
C.Energy-yielding carbohydrates
D.Soil nutrients
- 5.
Two different species cannot occupy the same niche for a long time if resources are limiting. This observation relates to:
A.Competitive exclusion
B.Co-existence through partitioning
C.Mutualistic co-dependence
D.Amensalism
- 6.
Which of the following statements about predation is FALSE?
A.Predators help in maintaining species diversity in a community
B.If a predator is too efficient, it might cause the extinction of its prey
C.Predators act as conduits for energy transfer across trophic levels
D.Herbivores are ecologically very different from predators
- 7.
The 'sexual deceit' strategy in the Mediterranean orchid is an example of:
A.Parasitism because the bee is harmed
B.Mutualism because the bee gets nectar
C.Mutualism, even though the bee doesn't get a typical reward
D.Commensalism because only the orchid benefits
- 8.
In the interaction between the 'Silverfish' and 'Army Ants', the silverfish follows the ants to scavenge on the remains of the prey caught by the ants. The ants are neither helped nor harmed. This is:
A.Mutualism
B.Parasitism
C.Commensalism
D.Amensalism
- 9.
Which of the following is a 'Cheater' in a mutualistic system?
A.A wasp that pollinates the fig and lays eggs.
B.A bee that consumes nectar from a flower without transferring pollen.
C.A mycorrhizal fungus that provides phosphorus and receives sugar.
D.A lichen where the fungus provides minerals and the alga provides food.
- 10.
The process of 'Competitive Exclusion' is more likely to occur in environments that are:
A.Highly variable and unpredictable.
B.Stable and constant over time.
C.Frequently disturbed by natural disasters.
D.Resource-abundant with no limiting factors.
Download the worksheet for Organisms and Populations - Population Interactions (Mutualism, Competition, Predation, Parasitism) to practice offline. It includes additional chapter-level practice questions.
Life History Variation
SubtopicLife History Variation under Organisms and Populations for Grade 12 CBSE.
Preview questions (no answers)
- 1.
Under a particular set of selection pressures, organisms evolve towards the most efficient:
A.Hunting strategy
B.Reproductive strategy
C.Camouflage
D.Digestive system
- 2.
Producing many small offspring is a strategy often seen in:
A.Stable environments
B.Unstable or unpredictable environments
C.Environments with no predators
D.Very cold environments only
- 3.
Which is an example of an organism breeding many times?
A.Bamboo
B.Pacific salmon
C.Elephant
D.Century plant
- 4.
Ecologists study life history variation to understand:
A.How species survive and propagate in habitats
B.The chemical composition of cells
C.The movement of planets
D.Atomic structures
- 5.
Which of the following is a result of selection pressures in the habitat?
A.Development of vestigial organs only
B.Evolution of specific life history traits
C.Spontaneous generation of new species
D.Decrease in all values
- 6.
Life history variation explains why:
A.All animals look different
B.Different species have different reproductive strategies
C.Photosynthesis is important
D.DNA is the genetic material
- 7.
Which of the following combinations is commonly seen in mammals?
A.Low parental care, many offspring
B.High parental care, few offspring
C.No parental care, one-time breeding
D.Low survival rate, many small offspring
- 8.
The concept of 'r-selection' and 'K-selection' was originally proposed to explain:
A.The movement of nutrients through an ecosystem.
B.The different life history strategies evolved under different population densities and environmental stabilities.
C.The chemical composition of different species.
D.The rate of mutation in different climates.
- 9.
If an organism has a high 'Reproductive Effort' (RE), it means it is:
A.Spending a small fraction of its energy on reproduction.
B.Allocating a large proportion of its available resources to the production of offspring.
C.Taking a long time to find a mate.
D.Exhibiting very little parental care.
- 10.
Which of the following describes a species with a 'Type III' survivorship curve, typical of many -selected species?
A.Constant mortality rate throughout life.
B.High mortality early in life, with low mortality for the few who reach adulthood.
C.Low mortality early in life, with most individuals dying at an old age.
D.Mortality that only occurs during the reproductive phase.
Download the worksheet for Organisms and Populations - Life History Variation to practice offline. It includes additional chapter-level practice questions.