A habitat is the place where an organism lives while a niche is that organism's role within that environment. Biome refers to the community of plants and animals that occur naturally in an area, often sharing common characteristics specific to that area. Answer : (d)

In most of the hydrophytes the stem is long, slender, spongy and flexible. The mechanical support system is underdeveloped. Answer : (b)

If in a population of size N, the birth rates (not total number but per capita births) are represented as b and death rates (again, per capita death rates) as d, then the increase or decrease in N during a unit time period t (dN/dt) will be dN/dt = (b – d) × N Let (b–d) = r, then dN/dt = rN The r in this equation is called the ‘intrinsic rate of natural increase’ Answer : (a)

Soil genesis or pedogenesis is the study of the origin and formation of soil. Pedology is “the study of soils that integrates their distribution, formation, morphology, and classification as natural landscape bodies”. Pedogenesis is studied as a branch of pedology. Answer:(a)

Biome refers to the community of plants and animals that occur naturally in an area, often sharing common characteristics specific to that area. Biome, also known as a major life zone, is an area that includes communities of plants and animals that have a common adaptation to that particular environment. Answer : (d)

The xerophytes commonly have a large proportion of sclerenchyma in their leaf structure than is observed normally in mesophytes. The sclerenchyma is either found in groups or in continuous sheets. It serves the function of providing structural support in plants. In stem the mechanical tissue is well developed and also bark is well developed to retain water Answer : (c)

dN/dt = rN(K-N /K)     = rN(1-N/K) Where N = Population density at time t r = Intrinsic rate of natural increase K = Carrying capacity Answer : (a)

The hydro-halophytes develop special type of negatively geotropic roots, called as pneumatophores or breathing roots. The pneumatophores usually develop from the underground roots and project in the air well above the surface of mud and water. Answer : (c)

diurnal temperature variation is the variation between a high air temperature and a low temperature that occurs during the same day. Maximum diurnal temperature variation is seen in desert, because desert areas receive a large amount of sunlight, the temperatures can get very high, but during the night the dry air cools quickly. Answer : (d)

Hydrophtes are supported by water. Thus, mechanical and vascular tissue of many hydrophytes is reduced. They often have large intercellular air spaces in their stems, roots, and leaves to overcome the difficulty of obtaining gases from the water. Answer : (d)

Pneumatophores, commonly found in mangrove species that grow in saline mud flats. Answer : (a)

Aerenchyma or aeriferous parenchyma is a modification of the parenchyma to form a spongy tissue that creates spaces or air channels in the leaves, stems and roots of some plants, which allows exchange of gases between the shoot and the root. The channels of air-filled cavities provide a low-resistance internal pathway for the exchange of gases between the plant above the water and the submerged tissues. Aerenchyma is also widespread in aquatic and wetland plants which must grow in hypoxic soils Answer : (c)

Myrmecophily is the term applied to positive interspecies associations between ants and a variety of other organisms, such as plants, other arthropods, and fungi. Answer : (a)

A good soil is one which has a high water holding capacity, but drains freely leaving air space. Water and nutrients in such a soil, will be easily available to plants. A good soil will be slightly acid (pH 6 – 6.8) at which level the nutrients required by plants are most freely available. Answer : (a)

Mortality is the number of deaths in the population during a given period. Answer : (d)

An ecological community consists of all the populations of all the different species that live together in a particular area. Interactions between different species in a community are called interspecific interactions—inter- means "between." Different types of interspecific interactions have different effects on the two participants, which may be positive (+), negative (-), or neutral (0). The main types of interspecific interactions include competition (-/-), predation (+/-), mutualism, (+/+), commensalism (+/0), and parasitism (+/-). Answer : (d)

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