As competition increases and resources become increasingly scarce, populations reach the carrying capacity (K) of their environment, causing their growth rate to slow nearly to zero. This produces an S-shaped curve of population growth known as the logistic curve (right). Answer : (d)

The topsoil is usually darker than lower layers (or horizons) because this is where organic matter accumulates. Soil colour is usually due to 3 main pigments: black—from organic matter. Answer : (c)

Nekton or necton refers to the actively swimming aquatic organisms in a body of water. The term was proposed by German biologist Ernst Haeckel to differentiate between the active swimmers in a body of water, and the passive organisms that were carried along by the current, the plankton. Answer : (d)

Halophytes are salt-tolerant plants that grow in waters with high salinity, such as in mangrove swamps, marshes, seashores and saline semi-deserts Answer : (b)

An obligate parasite or holoparasite is a parasitic organism that cannot complete its life-cycle without exploiting a suitable host. Rafflesia is an example of the obligate root parasites. It depends on the host for water and sugars. It is done with the help of an absorptive organ, the haustorium. Answer : (d)

Answer : (a)

The biosphere is the global ecological system integrating all living beings and their relationships, including their interaction with the elements of the lithosphere, hydrosphere, and atmosphere. Answer : (b)

A biotic factor is a living organism that shapes its environment. Answer : (c)

saprophytes: a plant, fungus, or microorganism that lives on dead or decaying organic matter. Microalgae or microphytes are microscopic algae invisible to the naked eye. Macrophytes are aquatic plants growing in or near water. They may be either emergent (i.e., with upright portions above the water surface), submerged or floating. Answer : (a)

Deep black soil is considered a productive soil due to the presence of a high proportion of clay and humus. Deep black soil are high retentivity of moisture and comprises a lot of organic matter. Answer : (c)

Semantic differential is a type of a rating scale designed to measure the connotative meaning of objects, events, and concepts. Differential scanning calorimetry is a thermoanalytical technique in which the difference in the amount of heat required to increase the temperature of a sample and reference is measured as a function of temperature. A real-time polymerase chain reaction, also known as quantitative polymerase chain reaction, is a laboratory technique of molecular biology based on the polymerase chain reaction. It monitors the amplification of a targeted DNA molecule during the PCR MALDI-TOF (matrix-assisted laser desorption/ionization) is an ionization technique that uses a laser energy absorbing matrix to create ions from large molecules with minimal fragmentation. Answer : (b)

The genus Agave is primarily known for its succulent and xerophytic species that typically form large rosettes of strong, fleshy leaves. Answer : (d)

The littoral zone is the near shore area where sunlight penetrates. The limnetic zone is the open water area where light does not penetrate to the bottom. Answer : (a)

Population index- It is used to summarise population dynamics. This can be calculated by subtracting the death rate from the birth rate. Answer : (b)

Each organism has an invariably defined range of conditions that it can tolerate, diversity in the resources it utilises and a distinct functional role in the ecological system, all these together comprise its niche. Answer : (d)

Ecology is a subject which studies the interactions among organisms and between the organism and its physical (abiotic) environment. Ecology at the organismic level is essentially physiological ecology which tries to understand how different organisms are adapted to their environments in terms of not only survival but also reproduction Answer:(d)

Due to the availability of water in plenty, roots, the principal organs of water absorption, in such plants become of less significance. In aquatic plants or hydrophytes, roots caps are absent and root pockets are present. Answer : (c)

Red mangroves have prop roots descending from the trunk and branches, providing a stable support system. Pneumatophores, commonly found in mangrove species that grow in saline mud flats, are lateral roots that grow upward out of the mud and water to function as the site of oxygen intake for the submerged primary root system. mangrove species have unique way of reproduction, which is generally known as vivipary. In this method of reproduction, seeds germinate and develop into seedlings while the seeds are still attached to the parent tree. Answer : (d)

Mutualism: This interaction confers benefits on both the interacting species. (a) is false. The interaction where one species is benefitted and the other is neither benefitted nor harmed is called commensalism. (b) is false. Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. (c) is true. Symbiosis is any type of a close and long-term biological interaction between two different biological organisms. Mutualism is a symbiotic relationship in which both species benefit. (d) is true. Answer : (d)

The amount of humus in clay soil can help improve aeration, reduce water holding capacity, and increase nutrient content. Answer : (c)

Biota: It comprises the animals and plants living in a particular place, time, or habitat. Answer : (a)

Eutrophication is the process by which an entire body of water, or parts of it, becomes progressively enriched with minerals and nutrients, particularly nitrogen and phosphorus. Answer : (a)

In primary succession in water, the pioneers are the small phytoplanktons(Volvox),which are replaced with time by rooted-submerged plants(Hydrilla), rooted-floating angiosperms followed by free-floating plants(Pistia), then reedswamp (Scirpus), marsh-meadow (Lantana), scrub and finally the trees (Oak). The climax again would be a forest. With time the water body is converted into land. Answer : (d)

synecology (or community ecology) refers to the study of groups of organisms in relation to their environment. Answer : (d)

Answer : (a)

Answer : (d)

Answer : (d)

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 : (c)

Rhizophora is a genus of tropical mangrove trees, sometimes collectively called true mangroves. The most notable species is the red mangrove Answer : (b)

A population is a distinct group of individuals, whether that group comprises a nation or a group of people with a common characteristic. Answer : (c)