Soil salinity is measured by

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To measure the mineral content (the total mineralisation) and salt concentration or the salinity of the soil, a instrument called the Conductivity meter is used. The conductivity meter measures the salt concentration of the soil by estimating the electrical conductivity of the soil and the water solution.

Salt on the soil and the water solution increase the ability of a solution to conduct an electrical current, so a high EC value indicates a high salinity level.

Which law of evolution states that “warm-blooded” mammals of hot and humid areas have abundant melanin pigment?

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Gloger’s Law states that warm-blooded animals (birds and mammals) have more melanin (black color pigments) in a hot humid environments such as the equator. The law was named after German zoologist Constantin Wilhelm Lambert Gloge (1803-1863). The darker skin color in animals better protects the intense solar UV radiation.

The rule can be applicable at the species level where different populations of the same species living in different latitudes possess different pigmentation. Humans living in high humid or equatorial regions possess darker skin color than their counterparts living away from the equatorial regions.

A species inhabiting different geographical area is known as

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Allopatric species inhabit different geographical areas. The allopatric speciation arises as a result of two populations of the same species becoming isolated from each other due to geographical barriers. It is a very slow and gradual process due to which one species evolve into two different species. The geographical barrier may be due to the formation of a new mountain range or river or canyons that hinders the physical interaction between two populations of the same species.

All others are occupying same geographical area but are reproductively isolated. Sympatric species occupy the same geographical area and speciation arises due to mutation or polyploidy. Biospecies are sexually interbreeding individuals that are isolated reproductively from other species. Sibling species are morphologically similar but reproductively isolated species.

The term ‘ecosystem’ was coined by :

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Ecosystem, the complex interrelationships among living organisms with their physical environment. Ecosystems comprise of living or biotic factors, such as plants, animals, and other organisms as well as nonliving or abiotic factors weather, landscape, temperature, and humidity.

The term “ecosystem” was first used by British ecologist Sir Arthur George Tansley in “The use and abuse of vegetational terms and concepts” in 1935.

Obligate parasites live:

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Obligate parasites are organisms that are unable to complete their life cycle without a suitable living host. Without a living host, the obligate parasite will fail to reproduce. Obligate parasitism is seen in a wide range of organisms, such as bacteria, viruses, animals, plants, and fungi. Examples of obligate parasitism are

(i) Plasmodium sp.: The genus Plasmodium contains unicellular eukaryotes such as P vivax and P falciparum. The parasite causes malaria in humans. Plasmodium sps. are obligate parasites of mosquitoes and humans. 

(ii) Viruses: All the viruses are obligate parasites. Viruses usually lack metabolic machinery to synthesize proteins or energy production. Due to which viruses always depend on host cells to carry out their growth and reproduction.

Which important greenhouse gas, other than carbon dioxide, is being produced from the agricultural fields?

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Greenhouse gases absorb and emit solar radiant energy and cause the greenhouse effect. The primary greenhouse gases are carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4), and ozone (O3).

The agricultural sector contributes about 10%–14% of global greenhouse gas emissions. The greenhouse gases that emit from agricultural activities are carbon dioxide, methane, and nitrous oxide. Methane gas is released into the atmosphere as a result of enteric fermentation from the castles. Further, the preparation of soil and land, as well as the burning of agricultural waste, contributes to the emission of carbon dioxide into the atmosphere.

The application of nitrogen-containing synthetic fertilizers and animal waste contributes to the emission of nitrous oxide. Nitrous oxide is produced by the Denitrifying soil microbes (Pseudomonas sp., Alcaligenes sp., and Bacillus sp.) using nitrogen-containing fertilizers.

The 10% energy transfer law in a food chain was proposed by:

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The ten percent law of energy transfer in a food chain from one trophic level to the next was proposed by American Ecologist Raymond Laurel Lindeman (1942). The law described the ecological efficiency  of energy transferred from one trophic level to the next.

In the 10% law of energy transfer, Lindeman quantifies the efficiency of energy transfer between trophic levels from the incident radiation (from the sun as light energy) received by an ecological community through its producer (green plants) during photosynthesis to its subsequent use by other trophic levels such as herbivores, carnivores, and decomposers.

Ecological efficiency measures the amount of energy that enters from one trophic level to the next. Energy transfer between one trophic level to the next is energy inefficient. The efficiency is about 5–15%. This inefficiency of energy transfer between two trophic levels limits the length of food chains as little energy remains present after four or five trophic levels.

For example, the Sun releases about 10,000 J of energy. Plants receive only 1% of the energy (100 J) from the sunlight. A herbivore gets only 10% of energy (10 J) from the plant. A carnivore gets again 10% of energy (1 J) from the herbivore. An apex carnivore gets 10% of energy (0.1 J) from the carnivore. The energy lost from one trophic level is in the form of respiration, defecation, and non-predatory death.


Which of the following groups of organisms are ecologically similar?

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Producer protists:

Producer protists are unicellular. Many of them produce their foods using sunlight and CO2. Like green plants, producer protists contain chlorophyll a, chlorophyll c pigments, peridinin, and diadinoxanthin pigments. Zooxanthellae (dinoflagellates) are mostly photosynthetic protists. Some protozoa synthesized their food using chlorophyll pigments in presence of sunlight, and CO2. Example: Euglena (Euglena gracilis) an Dinobryon (Dinobryon divergens)

Consumer protist:

On the other hand, consumer protists are heterotrophs in nature. Consumer protists obtained their nutrition and energy from organic materials. They consume other organisms. Protozoa such as Amoebas ingest solid particles through phagocytosis. During phagocytosis, the plasma membrane invaginates inward to engulfs a food particle. Then the food particle surrounded by a membrane is pinching off intracellularly to form a food vacuole.

Fungi:

Fungi are eukaryotic heterotrophic organisms. They are nonmotile organisms, and the cell walls contain chitin. They are multicellular organisms (few are unicellular: yeasts). Most of the fungi are saprophytes in nature. They obtain nutrition and energy from wastes and dead/decaying organic matter. Saprophytic fungi act as decomposers. Example: Mushrooms.

Monera:

Organisms in the Kingdom of Monera are Prokaryotic in nature. They are unicellular, and the true cell nucleus is absent. Examples: Archaeobacteria, Eubacteria, and Cyanobacteria. Many bacteria are saprophytic in nature. They obtained their nutrition and energy from the dead/decaying organic matter.

A coprolite is fossilized

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A coprolite is a fossilized faeces. It is also known as coprolith. Coprolites are categorized as trace fossils and give evidence about the diet of extinct animals. The term coprolite is derived from the Greek words “kopros” and “lithos” which means dung stone. Coprolites are very rare as the faecal matter decay very rapidly. The indigestible part, bones, scales, teeth, or shells are preserved very well in the coprolites.

In coprolites, the original organic composition is replaced by silicates and calcium carbonates. Sometimes the shape of the coprolites indicates the respective organism. The spiral-shaped coprolites indicate the shark species. The spiral-shaped is due to the presence of the spiral valve in the shark’s intestine.

Coprolites were first identified as “bezoar stones” by British fossil hunter Mary Anning in 1924. Scientists from Australia, New Zealand, and the United States of America reported traces of DNA in the coprolites. They found the coprolites of extinct birds contain ectomycorrhizal fungi (Boast et al., 2018, PNAS).

Qvarnström et al (2021) recently reported an extinct species of beetle Triamyxa coprolithica in a Triassic period coprolite. The age of the fossils is about 230-million-year-old. The beetle belongs to a member of the extinct family Triamyxidae. The coprolite was expected to excrete by Silesaurus opolensis.

References: Boast et al., 2018, PNAS and Qvarnström et al., 2021, Current Biology