Biome refers to the community of plants and animals that occur naturally in an area, often sharing common characteristics specific to that area. a community is a group or association of populations of two or more different species occupying the same geographical area at the same time Answer:(b)

Commensalism is the relationship where one organism is benefitted while the other is neither benefitted nor harmed. Orchid grows on mango tree to get proper light etc. and is benefitted but as it does not absorb nutrients from mango tree. Thus, the tree is neither harmed nor benefitted. Brood parasitism in birds is a fascinating example of parasitism in which the parasitic bird lays its eggs in the nest of its host and lets the host incubate them. Since small animals have a larger surface area relative to their volume, they tend to lose body heat very fast when it is cold outside; then they have to expend much energy to generate body heat through metabolism. This is the main reason why very small animals are rarely found in polar regions. Plants do not have such mechanisms to maintain internal temperatures. Option a is incorrect. Answer:(a)

Natality refers to the number of births during a given period in the population that are added to the initial density. Answer:(b)

A large variety of marine invertebrates and fish live at great depths in the ocean where the pressure could be >100 times the normal atmospheric pressure that we experience. Organisms living in such extreme environments show a fascinating array of biochemical adaptations. (i) is correct. Mammals from colder climates generally have shorter ears and limbs to minimise heat loss. (This is called the Allen’s Rule.) (ii) is correct. Altitude sickness is because in the low atmospheric pressure of high altitudes, the body does not get enough oxygen. But, gradually you get acclimatised and stop experiencing altitude sickness. The body compensates low oxygen availability by increasing red blood cell production, decreasing the binding affinity of hemoglobin and by increasing breathing rate. (iii) is correct. Desert lizards lack the physiological ability that mammals have to deal with the high temperatures of their habitat, but manage to keep their body temperature fairly constant by behavioural means. (iv) is incorrect. Answer:(a)

In the aquatic environment, the sediment-characteristics often determine the type of benthic animals that can thrive there. Answer:(b)

Species facing competition might evolve mechanisms that promote co-existence rather than exclusion. One such mechanism is ‘resource partitioning’. If two species compete for the same resource, they could avoid competition by choosing, for instance, different times for feeding or different foraging patterns. MacArthur showed that five closely related species of warblers living on the same tree were able to avoid competition and co-exist due to behavioural differences in their foraging activities. Answer:(a)

If bass disappears, then there is no predator for frogs and sunfishes. Hence their population will increase. Answer:(d)

Carrying capacity can be defined as a species' average population size in a particular habitat. The species population size is limited by environmental factors like adequate food, shelter, water, and mates. If these needs are not met, the population will decrease until the resource rebounds. Answer:(c)

The intrinsic rate of increase is inversely related to generation time t. Therefore, organisms with very high intrinsic growth rates have short generation time. Answer:(b)

birth rate is (number of births) x 1000 / estimated population at mid-year. Death rate is (number of death) x 1000 / estimated population at mid-year. The vital index is the ratio between natality or number of births and mortality or the number of deaths in a given time duration. Answer:(a)

Species A	Species B	Name of interaction
+	+	Mutualism
-	-	Competition
+	-	Predation
+	-	Parasitism
+	0	Commensalism
-	0	Amensalism

Interspecific interactions arise from the interaction of populations of two different species. They could be beneficial, detrimental or neutral (neither harm nor benefit) to one of the species or both. Assigning a ‘+’ sign for beneficial interaction, ‘-’ sign for detrimental and 0 for neutral interaction. Answer:(d)

Stationary population pyramids are those that show a somewhat equal proportion of the population in each age group. There is not a decrease or increase in population; it is stable. Answer:(c)

Top predators play an important role in maintaining the balance and biodiversity of an ecosystem. If the top predator is removed from the delicate balance of any particular ecosystem, there may be disastrous effects for the other plants and animals that inhabit the environment. Answer:(c)

R-selected species are those that produce a large number of offspring and contribute few resources to each individual offspring. They often offer little to no parental care, have high offspring mortality, short life spans, and small body sizes. Answer:(a)

Many animals, particularly birds, during winter undertake long-distance migrations to more hospitable areas. Every winter the famous Keolado National Park (Bharatpur) in Rajasthan host thousands of migratory birds coming from Siberia and other extremely cold northern regions Answer:(d)

In the absence of an external source of water, the kangaroo rat in North American deserts is capable of meeting all its water requirements through its internal fat oxidation (in which water is a by product). It also has the ability to concentrate its urine so that minimal volume of water is used to remove excretory products. The kangaroo rat is almost perfectly adapted to life in the desert. They can survive without ever drinking any water, getting needed moisture from their seed diet. Answer:(a)

The size of a population for any species is not a static parameter. It keeps changing with time, depending on various factors including food availability, predation pressure and adverse weather Answer:(d)

The desert locust (Schistocerca gregaria) are found primarily in the deserts and dry areas of northern and eastern Africa, Arabia, and southwest Asia. Aphids can be found on bushes, shrubs, trees, the leaves of vegetables, and the leaves of ornamental plants. Vulture inhabits relatively open areas which provide scattered forests or shrublands. Option (d) is correct answer. Answer:(d)

Circadian rhythms are physical, mental, and behavioral changes that follow a 24-hour cycle. zooplankton migrate to deep waters during the day to avoid predation and come up to the surface at night to feed. Answer:(b)

Predators also help in maintaining species diversity in a community, by reducing the intensity of competition among competing prey species. In the rocky intertidal communities of the American Pacific Coast the starfish Pisaster is an important predator. In a field experiment, when all the starfish were removed from an enclosed intertidal area, more than 10 species of invertebrates became extinct within a year, because of interspecific competition. Answer:(c)

Gause’s ‘Competitive Exclusion Principle’ may be true if resources are limiting, but not otherwise. Since both species are exisiting it meand resources might not be limited. Species facing competition might evolve mechanisms that promote co-existence rather than exclusion. One such mechanism is ‘resource partitioning. Distribution is wide beacuse there is no predator or competition release. Answer:(b)

The inherent maximum capacity of an organism to reproduce or increase in number is termed biotic potential. Nature keeps a check on the expression of biotic potential. With increase in population size, the environmental resistance tends to increase. Answer:(a)

chloride secretory cell: Any of the cells in the gills of marine bony fish that remove chloride from the blood and secrete it into the sea, thereby maintaining the osmotic composition of the body. In marine teleost fish, by expending energy to power the enzyme Na+/K+-ATPase and in coordination with other protein transporters, ionocytes pump excessive sodium and chloride ions against the concentration gradient into the ocean. Conversely, freshwater teleost ionocytes use this low intracellular environment to attain sodium and chloride ions into the organism, and also against the concentration gradient. Answer:(a)

Hermit crabs and sea anemones share an unusual and intimate underwater relationship. Young hermit crabs will often pick up a young sea anemone to attach to their shell and they become partners for life. They even grow at roughly the same rate. Commensalism means one organism benefits and the other organism isn't harmed by the partnership. Neither the hermit crab nor the sea anemone is negatively affected by their symbiotic and commensalistic relationship. The hermit crab gains protection from predators by its relationship with the sea anemone.. . Answer:(b)

Desert lizards lack the physiological ability that mammals have to deal with the high temperatures of their habitat, but manage to keep their body temperature fairly constant by behavioural means. Statement (iv) is incorrect. Rest of the statements are correct. Answer:(c)

In ecology, a niche is the match of a species to a specific environmental condition. It describes how an organism or population responds to the distribution of resources and competitors (for example, by growing when resources are abundant, and when predators, parasites and pathogens are scarce) and how it in turn alters those same factors (for example, limiting access to resources by other organisms, acting as a food source for predators and a consumer of prey). Answer:(b)

Under unfavourable conditions many zooplankton species in lakes and ponds are known to enter diapause, a stage of suspended development Answer:(b)

Population density is a measurement of population per unit area, or exceptionally unit volume; it is a quantity of type number density. Answer:(b)

Potenetial natality is mere estimation of birth. There are lot of factors which decreases the actual birth rate. In this case, they are: 1) Incubation period of egg in snakes is 45 to 60 days. It is possible that all egg are not completely incubated. or incubated egg did not reach adult stage. 2) Another reason can be Enviromental boomerang or ecological backlash. The unexpected and detrimental consequences of an environmental modification is known as ecologial backlash. Answer:(d)

Each year mature salmon make the long journey back to their natal river to reproduce, just once. Each female salmon can have between 1,500 and 10,000 eggs. Only a few (0 to 10) of these eggs will survive to be adult salmon. X= true and Y= false. Answer:(c)