Answer: Option D. -> limiting resources
:
D
The carrying capacity of a habitat, represented by K is the maxmimum number of individuals from a population that a habitat can hold. Or in other words its the amount of resources that a habitat contains for a given population. Therefore the carrying capacity of a population is determined by the limiting resources in the habitat.

Answer: Option C. -> Intraspecific competition
:
C
Intraspecific competitionis an interaction in population ecology, whereby members of the same speciescompetefor limited resources. This leads to a reduction in fitness for both individuals.By contrast, interspecificcompetitionoccurs when members of different speciescompetefor a shared resource.
Protocooperation - It is a positive interaction in which both the species will benefit but they can live equally well without this association.
Predation - is a biological interaction where an organism that is hunting (predator) feeds on another organism (prey).

Answer: Option B. -> Status of the population
:
B
Age structure pyramids can graphically represent the state of the population. In most populations individuals are of different ages. The proportion of individuals in each age group is depicted in theage structure pyramid of that population. It also represents the growth status, that is whether the population is growing, declining or is stable.

Answer: Option D. -> All of these
:
D
Some organisms reduce their metabolic activity and enter a suspended state to tide over unfavorable conditions. This form of inactivity is called hibernation, in endothermal animals that suspend many of their metabolic activity and resort to sleep during winter. When animals suspend their metabolic activity during summer it is called aestivation. Anda period of suspended development in an insect, other invertebrate, or mammal embryo, during unfavourable environmental condition is called diapause.

Answer: Option B. -> Tropical rainforest
:
B
The tropical rainforest biome gets the highest precipitation or rainfall annually. Most regions get at least 200 cm to about 430 cm rain annually. Deserts and tundra get the least amount of precipitation. Taiga gets a higher amount of precipitation, of about 30-75 cm. Temperate forests recieve a high level of precipitation of about 75-150 cm annually.

Answer: Option D. -> Assertion is false and reason is true
:
D
Open systems are material systems in whichmass or energy can be lost to or gained from the environment. Living organismsbasically gain energy from the sun or other organisms, that is from a source outside the organism, and theylose energy in the form of heat. Similarly they gain mass through food, from an outside source. Therefore matter and energy enters the system from an external source and is lost from the system eventually. Therefore living organisms are open systems.

Answer: Option D. -> Head louse living on the human scalp as well as laying eggs on human hair
:
D
Head louse living on the human scalp as well as laying eggs on human hair is a parasite in true sense. Female mosquito is not considered a parasite, as it needs human blood only for reproduction. Cuckoo that lays eggs in crow's nest is a brood parasite not a parasite in true sense.

Answer: Option B. -> Adaptation by the prey, which warns predators not to eat them
:
B
Aposematism can be best described as antipredator adaptation. Certain organisms display warning signals to the potential prey that consuming them could be a serious mistake. This warning signs helps the organism to avoid predation from other organisms.

Answer: Option A. -> (i) Mutualistic (ii) leguminous plant and rhizobium 
:
A
Root nodules are mutualistic association, that is an interaction where both partners benefit, between a leguminous plant and a rod shaped bacteria present in soil called rhizobium. The rhizobium assists the plant in nitrogen fixation and in return the plant serves as a host for the bacteria providing shelter and nourishment.

Answer: Option C. -> Plants resistant to salt 
:
C
A halophyte is a plant that grows in waters of high salinity, coming into contact with saline water through its roots or by salt spray, such as in saline semi-deserts, mangrove swamps, marshes and sloughs and seashores.Plants dividedon the basis of soil in which they are found into the following groups.
(i) Halophytes are plants growing in saline soil i.e., these plants are salt resistant
(ii) Oxalophytes are plants growing in acidic soil
(iii) Lithophytes are plants growing on the surface of rocks
(iv) Xerophytes plants resistant to dry conditions.