NEET Biology Ecology Environment and Human Health MCQs Set 03

Answer: (a) amoebiasis

Explanation:
1. House flies carry the cysts of Entamoeba histolytica on their legs and mouthparts from faeces to food.
2. Malaria is carried by female Anopheles and plague by rat fleas.

Teacher's Note:
1. A mechanical carrier does not host the parasite's life cycle.
2. Flies also spread typhoid, cholera and dysentery.

Answer: (c) histamine

Explanation:
1. Histamine released from mast cells causes the symptoms of an allergy.
2. Adrenaline, steroids such as cortisol, and antihistamines such as cetirizine are used to relieve the symptoms.

Teacher's Note:
1. Allergens trigger IgE-mediated release of histamine and serotonin.
2. Antihistamines block histamine receptors.

Answer: (b) malignant tumour

Explanation:
1. Malignant tumours invade neighbouring tissue and spread through blood or lymph to distant sites, which is metastasis.
2. Benign tumours remain localised.

Teacher's Note:
1. Metastasis is the hallmark of malignancy.
2. Osteoma is a benign bone tumour.

Answer: (a) alcoholism

Explanation:
1. Excessive alcohol consumption causes fat to accumulate in liver cells, resulting in fatty liver.
2. Alcohol damages the liver and can progress to cirrhosis.

Teacher's Note:
1. Alcohol is metabolised mainly in the liver.
2. Long-term abuse may lead to cirrhosis and liver failure.

Answer: (a) Ranikhet disease

Explanation:
1. Ranikhet disease (Newcastle disease) is caused by a virus.
2. Fowl cholera (bacterial, Pasteurella), pullorum (bacterial, Salmonella) and brooder pneumonia (fungal, Aspergillus) are not viral.

Teacher's Note:
1. Ranikhet disease spreads rapidly and can be controlled by vaccination.
2. Pullorum is also called bacillary white diarrhoea.

Answer: (b) Anabaena

Explanation:
1. Azolla is a water fern that has the cyanobacterium Anabaena azollae in its leaf cavities.
2. Anabaena fixes atmospheric nitrogen, so Azolla is used as a biofertiliser in rice fields.
3. Frankia forms nodules in non-leguminous trees such as Alnus.

Teacher's Note:
1. Anabaena, Nostoc and Oscillatoria are free living nitrogen fixing cyanobacteria.
2. Spirulina is a cyanobacterium used as single cell protein.

Answer: (d) long life span

Explanation:
1. r-selected species reproduce rapidly with many small offspring and little parental care, and they have a short life span.
2. A long life span is a feature of K-selected species.

Teacher's Note:
1. r-selection is typical of unstable environments, K-selection of stable ones.
2. Insects and weeds are r-selected; elephants and humans are K-selected.

Answer: (d) All of these

Explanation:
1. (a) True: phytoplankton are small and have a short life, so the standing crop of biomass is lower than that of zooplankton.
2. (b) True: energy is lost at every trophic level, so the pyramid is always upright.
3. (c) True: the detritus food chain is the main channel in land ecosystems.
4. (d) True: humus is a dark amorphous substance that decomposes extremely slowly. All four statements are correct.

Teacher's Note:
1. In the sea the grazing food chain is the main channel.
2. Pyramids of number and biomass may be inverted, but never the pyramid of energy.

Answer: (a) orthophosphate

Explanation:
1. Phosphorus occurs in rocks as phosphates.
2. Plants absorb it from the soil solution as phosphate ions, mainly the orthophosphates \(\mathrm{H_2PO_4^-}\) and \(\mathrm{HPO_4^{2-}}\).

Teacher's Note:
1. The phosphorus cycle has no gaseous phase except traces in dust.
2. Phosphorus is returned by decomposers.

Answer: (c) solar energy

Explanation:
1. Conventional sources are coal, petroleum, natural gas, hydro and nuclear power, which have been used for a long time.
2. Solar energy is a non-conventional (renewable, alternative) source.

Teacher's Note:
1. Other non-conventional sources are wind, tidal, geothermal and biogas.
2. They are generally renewable and non-polluting.

Answer: (d) over-production

Explanation:
1. The Evil Quartet comprises habitat loss and fragmentation, over-exploitation, alien species invasions, and co-extinctions.
2. Over-production is not part of it.

Teacher's Note:
1. Habitat loss is the most important cause of extinction.
2. Co-extinction occurs when a species dependent on another goes extinct with it.

Answer: (c) both mean annual precipitation and temperature

Explanation:
1. Biomes are characterised by climate, mainly the mean annual temperature and precipitation, which give rise to many habitats within them.
2. Soil and other factors play a secondary role.

Teacher's Note:
1. Temperature and rainfall determine the vegetation of a biome.
2. Examples are the tundra, taiga and tropical rain forest.

Answer: (d) man: primary consumer, autotrophs

Explanation:
1. Phytoplankton are producers and the pioneer community in aquatic ecosystems.
2. Zooplankton are herbivores and primary consumers, and humans can be top carnivores.
3. Humans are heterotrophs and are not autotrophs, so the pair 'man: primary consumer, autotrophs' is not correct.

Teacher's Note:
1. Primary consumers are herbivores.
2. Autotrophs are producers at the first trophic level.

Answer: (a) smaller

Explanation:
1. Phosphorus has no gaseous form, so its input from the atmosphere is very small.
2. The atmospheric input of phosphorus through rainfall is much smaller than that of carbon.

Teacher's Note:
1. Carbon dioxide is an abundant gas in the atmosphere.
2. Phosphorus is mainly cycled from rocks and soil.