NEET Biology Ecology Environment and Human Health MCQs Set 02

Answer: (a) bacteria, virus and prions

Explanation:
1. Typhoid is caused by the bacterium \(\textit{Salmonella typhi}\). Mumps is caused by a virus (paramyxovirus).
2. Creutzfeldt-Jakob disease is a prion disease, caused by abnormally folded proteins.

Teacher's Note:
1. Prions also cause mad cow disease (BSE) and scrapie.
2. Antibiotics are effective against bacteria but not against viruses or prions.

Answer: (d) a bean-shaped cell

Explanation:
1. The spleen is a large, bean-shaped organ, not a cell. It is a secondary lymphoid organ that filters the blood, traps blood-borne microbes and contains lymphocytes and phagocytes.
2. It also acts as a reservoir of erythrocytes.

Teacher's Note:
1. Lymph nodes are also secondary lymphoid organs.
2. The thymus and bone marrow are primary lymphoid organs.

Answer: (d) IgE

Explanation:
1. Allergens trigger the production of IgE antibodies, which bind to mast cells.
2. On re-exposure, mast cells release histamine and serotonin, which cause the allergic symptoms.

Teacher's Note:
1. Antihistamines and steroids reduce the symptoms.
2. IgA is found in secretions such as milk (colostrum).

Answer: (b) malignant, metastasis

Explanation:
1. Only malignant tumours spread to other parts of the body. This spread to distant sites is called metastasis.
2. Benign tumours remain confined to the site of origin. Normal cells show contact inhibition, which cancer cells lack.

Teacher's Note:
1. Metastasis is the main reason why malignant tumours are so dangerous.
2. Loss of contact inhibition causes uncontrolled growth.

Answer: (b) taiga

Explanation:
1. The taiga (boreal coniferous forest) covers a vast belt across northern Eurasia and North America and is the largest terrestrial biome.
2. Tundra, savannah and chaparral cover smaller areas.

Teacher's Note:
1. Taiga is dominated by conifers such as spruce, pine and fir.
2. Tropical rain forests are the richest in biodiversity.

Answer: (c) prey

Explanation:
1. Prey species have evolved defences against predators, such as camouflage, poisonous chemicals and warning colours.
2. So species A is the prey and species B is the predator.

Teacher's Note:
1. Monarch butterflies are protected from predators by cardiac glycosides taken from milkweed.
2. Defences such as thorns protect plants against herbivores.

Answer: (c) 20%

Explanation:
1. According to the NCERT text, the Amazon rain forest, with its huge biodiversity, is estimated to produce about 20 percent of the total oxygen in the earth's atmosphere.

Teacher's Note:
1. This is why the forest is called the lungs of the planet.
2. Deforestation reduces both the biodiversity and the oxygen output.

Answer: (a) Protection of hotspots can induce an ongoing mass extinction by almost 30%.

Explanation:
1. Conservation of hotspots could reduce the ongoing mass extinction by almost 30 percent, not induce it, so (a) is incorrect.
2. The other three statements are correct.

Teacher's Note:
1. Hotspots are regions with very high species richness and endemism that are threatened.
2. The Johannesburg summit of 2002 pledged to reduce the rate of biodiversity loss.

Answer: (a) in situ conservation of biodiversity

Explanation:
1. In situ conservation protects species in their natural habitats. National parks, sanctuaries, biosphere reserves and sacred groves are in situ methods.
2. Zoos, botanical gardens and seed banks are ex situ methods.

Teacher's Note:
1. Sacred groves are patches of forest protected by local communities on religious grounds.
2. The evil quartet means habitat loss, overexploitation, alien species invasions and co-extinctions.

Answer: (c) 16th September

Explanation:
1. The Montreal Protocol was signed on 16 September 1987, so World Ozone Day is celebrated on 16 September.
2. 5 June is World Environment Day and 22 April is Earth Day.

Teacher's Note:
1. The Montreal Protocol controls the emission of ozone-depleting substances.
2. The ozone layer absorbs harmful UV-B radiation.

Answer: (a) Doha, Qatar (2012), CoP-18

Explanation:
1. The Kyoto Protocol was extended to 2020 by the Doha Amendment at the 18th Conference of the Parties (CoP-18) in Doha, Qatar, in 2012.
2. The Paris Agreement was adopted at CoP-21 in 2015.

Teacher's Note:
1. The Kyoto Protocol is concerned with the reduction of greenhouse gas emissions.
2. It was originally adopted in 1997.

Answer: (d) net community productivity

Explanation:
1. Gross primary productivity is the total organic matter made by photosynthesis, and net primary productivity is GPP minus respiration losses.
2. The organic matter that remains per unit area after the heterotrophs have consumed their share is the net community productivity.

Teacher's Note:
1. Net primary productivity is the biomass available to heterotrophs before they consume it.
2. Secondary productivity is the rate at which consumers form new organic matter.

Answer: (b) oviposition

Explanation:
1. The \(\textit{Ophrys}\) flower mimics a female bee in colour, scent and shape. The male bee tries to copulate with it (pseudocopulation, a sexual deceit), and in doing so it pollinates the flower.
2. The bee does not lay eggs on the flower, so oviposition is not observed.

Teacher's Note:
1. This is an example of mutualism with deceit, and the orchid benefits at no cost.
2. Floral resemblance to a female bee is called sexual mimicry.

Answer: (b) decomposers

Explanation:
1. Decomposers break down dead organic matter and convert it into inorganic substances and nutrients that are returned to the soil for use by producers. They transform organic matter into inorganic matter, so they are called transformers of nature.

Teacher's Note:
1. Fungi and bacteria are the main decomposers.
2. Detritus is the raw material for decomposition.

Answer: (d) quality of the breed

Explanation:
1. The milk yield mainly depends on the genetic quality of the breed. Good feeding and hygiene are needed, but they cannot raise the yield beyond what the breed can give.
2. Selection and crossing of breeds such as Jersey and Brown Swiss with local cattle improve the yield.

Teacher's Note:
1. The main aim in dairy farming is to select good breeds with high yielding potential and resistance to diseases.
2. Regular visits by a veterinary doctor are also important.

Answer: (c) coacervates

Explanation:
1. Coacervates are aggregates of organic molecules, such as proteins and nucleic acids, surrounded by a membrane-like boundary. They are non-cellular, can show some properties of life, and were proposed by Oparin as precursors of cells.
2. Microbes and protists are cellular organisms.

Teacher's Note:
1. Oparin and Haldane proposed the chemical origin of life.
2. Microspheres, described by Fox, are similar structures.