NEET Biology Organisms and Populations MCQs Set 17

Answer: (b) Ecotone

Explanation:
1. Transition zone between two community is called ecotone. Ecoline – The intermediate form between two ecotypes Buffer zone – Zone of biosphere reserve where limited human activities are allowed like education, research etc Thermocline – It is equatic zone where temperature falls rapidly.
2. Hence option (b) is correct: Ecotone

Teacher's Note:
1. An ecotone is the transition zone between two communities and often has edge species.
2. An ecocline is a gradient, so check which term the question defines.

Answer: (c) a, b & c

Explanation:
1. Tropical rain forests - Buttress roots, vines, lianas and epiphytes with highly leached soil.
2. Hence option (c) is correct: a, b & c

Teacher's Note:
1. Tropical rain forests have buttress roots, lianas, epiphytes and strongly leached soils.
2. Their soils are poor in bases, since nutrients are locked in the vegetation.

Answer: (c) a(ii), b(i), c(iii)

Explanation:
1. Shallowest depth – Green algae Intermediate depth – Brown algae Greatest depth – Red algae
2. Hence option (c) is correct: a(ii), b(i), c(iii)

Teacher's Note:
1. Algae are zoned by depth according to the pigments that absorb the available light.
2. Green algae are shallow, brown intermediate and red the deepest.

Answer: (b) Conformers – They cannot maintain a constant internal environment

Explanation:
1. Nearly all plants and an overwhelming majority 99% of animals are conformers. They connot maintain a constant internal environment.
2. Hence option (b) is correct: Conformers – They cannot maintain a constant internal environment

Teacher's Note:
1. Most organisms are conformers because they cannot hold the internal environment constant.
2. Only a few animals are true regulators.

Answer: (c) Bharatpur (Rajasthan), Siberian cranes

Explanation:
1. Keolado national park is situated at Bharatpur (Rajasthan) and is famous for Siberian Cranes.
2. Hence option (c) is correct: Bharatpur (Rajasthan), Siberian cranes

Teacher's Note:
1. Keoladeo (Bharatpur) in Rajasthan is famous for migratory birds such as Siberian cranes.
2. Pair each national park with its main species.

Answer: (a) Desert lizards bask in the sun and absorb heat when their body temperature drops below comfort zone

Explanation:
1. Desert lizards bask in the sun and absorb heat when their body temperature drops below comfort zone.
2. Hence option (a) is correct: Desert lizards bask in the sun and absorb heat when their body temperature drops below comfort zone

Teacher's Note:
1. Desert lizards regulate behaviourally, basking when cold and burrowing when hot.
2. Behavioural adaptation is a common NEET theme.

Answer: (c) They are genetically similar

Explanation:
1. Ecotypes are genetically dissimilar.
2. Hence option (c) is correct: They are genetically similar

Teacher's Note:
1. Ecotypes are genetically distinct local variants of a species adapted to their habitat.
2. They are interfertile because they belong to one species.

Answer: (a) Organisms living in oceans, lakes and rivers do not face any water related problems

Explanation:
1. Organism living in water bodies also facing some problems like salinity, so animals are either euryhaline or stenohaline
2. Hence option (a) is correct: Organisms living in oceans, lakes and rivers do not face any water related problems

Teacher's Note:
1. Aquatic organisms also face water problems such as salinity, so they are euryhaline or stenohaline.
2. Statements with 'never' or 'do not' are usually wrong.

Answer: (b) Population never grows beyond carrying capacity

Explanation:
1. Population never grows beyond carrying capacity for logistic growth.
2. Hence option (b) is correct: Population never grows beyond carrying capacity

Teacher's Note:
1. A J-shaped curve is exponential growth that can crash when resources run out.
2. Only the logistic curve levels off at the carrying capacity.

Answer: (d) Closely related species growing in the same area

Explanation:
1. Competition for food, space and light is most severe between two closely related species growing in the same area.
2. Hence option (d) is correct: Closely related species growing in the same area

Teacher's Note:
1. Closely related species in the same area use nearly identical resources, so competition is fiercest.
2. This is why the competitive exclusion principle matters.

Answer: (b) Intrinsic rate of natural increase under environmental unlimited condition

Explanation:
1. Biotic potential is intrinsic rate of natural increase under environmental unlimited condition.
2. Hence option (b) is correct: Intrinsic rate of natural increase under environmental unlimited condition

Teacher's Note:
1. Biotic potential is the maximum rate of increase (r) under unlimited conditions.
2. Environmental resistance is what limits it.

Answer: (a) Poisonous glycosides

Explanation:
1. Hence option (a) is correct: Poisonous glycosides

Teacher's Note:
1. Calotropis produces poisonous cardiac glycosides, a chemical defence against herbivores.
2. Link plant chemicals with their defensive role.

Answer: (c) Insect through pseudocopulation mechanism

Explanation:
1. Pollination in Ophrys (orchid) occurs by insect (bee) through pseudocopulation mechanism. Here Ophrys employs "sexual deceit".
2. Hence option (c) is correct: Insect through pseudocopulation mechanism

Teacher's Note:
1. The Mediterranean orchid Ophrys mimics a female bee, and male bees pollinate it by pseudocopulation.
2. This is a co-evolution example.

Answer: (d) b&d

Explanation:
1. Tiger census is often based on pug marks and fecal pellets; size of population for any species is not a static parameter.
2. Hence option (d) is correct: b&d

Teacher's Note:
1. Population size is not static, and tiger census uses pug marks and faecal pellets.
2. Density can be measured in biomass or percent cover as well as numbers.

Answer: (b) Interacting species live closely together

Explanation:
1. In predation, parasitism and commensalism common characteristic is interacting species live closely together.
2. Hence option (b) is correct: Interacting species live closely together

Teacher's Note:
1. Predation, parasitism and commensalism all involve closely living species.
2. Mutualism and competition are the other common interactions.

Answer: (b) Negative interaction

Explanation:
1. Competition is a rivalry between two or more organisms for obtaining the same resources. It is a negative interaction.
2. Hence option (b) is correct: Negative interaction

Teacher's Note:
1. Competition is a (-,-) interaction, because both species lose fitness.
2. It is a negative interaction even though it is not parasitism.

Answer: (d) Only closely related species can show competition

Explanation:
1. Competition can occur either between closely related species or between unrelated species.
2. Hence option (d) is correct: Only closely related species can show competition

Teacher's Note:
1. Competition can occur between unrelated species also, e.g. flamingoes and fish feeding on zooplankton.
2. Connell's barnacle experiment shows competitive release.

Answer: (b) Yucca

Explanation:
1. Yucca have an obligate mutualism with a species of moth i.e. Pronuba.
2. Hence option (b) is correct: Yucca

Teacher's Note:
1. Yucca and its pollinator moth (Pronuba) show obligate mutualism.
2. Neither can complete its life cycle without the other.

Answer: (b) K=N

Explanation:
1. A population growing in a habitat with limited resources shows logistic growth curve. dN ⎛K – N⎞ For logistic growth  rN ⎜ ⎟ dt ⎝ K ⎠ K –N If K = N then =0 K dN  the = 0, the population reaches asymptote. dt
2. Hence option (b) is correct: K=N

Teacher's Note:
1. In the logistic equation growth stops when N equals K.
2. The curve then reaches its asymptote.

Answer: (c) Zero

Explanation:
1. Emigration – 30 + Population – 250 Natality 240 Mortality Density + 20 Immigration + 270 – 270 = 0
2. Hence option (c) is correct: Zero

Teacher's Note:
1. Net change = natality - mortality + immigration - emigration.
2. Here 250 - 240 + 20 - 30 = 0.