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The correct answer is Asterias.

Concept:

• Filter feeders are feeding animals that extract suspended matter and food particles from water by passing it through a specialized filtering structure (gills).
• Filter feeding is the characteristic feature of certain animals known as filter feeders.
• Some animals like Unio, sponges, Amphioxus, Herdmania and many fishes use this feature.

Explanation:

• Unio-
• Unio belongs to the phylum Mollusca.
• Molluscs are filter feeders, and their gill plates trap phytoplanktons.
• Water enters the mantle cavity through an opening and rises through the gills to the suprabranchial chamber.
• Amphioxus-
• Amphioxus belongs to the phylum Chordata and subphylum Cephalochordata.
• In Amphioxus slits are modified to form gills, that extracts food particles from the water in which the animals live.
• Herdmania-
• Herdmania belongs to the phylum Chordata and subphylum Urochordata.
• Herdmania is a filter-feeding tunicate that lives in marine environments.
• Asterias-
• Asterias belongs to the phylum Echinodermata.
• In Asterias specialized filtering structures (gills) are absent.
• So, Asterias is not a filter-feeder.

The correct answer is Axon.

• Nodes of Ranvier are found in (Axon) myelinated nerve fibre.
• A neuron is a microscopic structure composed of three major parts i.e., Cell body, dendrites and axon.
• Axon- 
• Axon is a single, usually very long process of uniform thickness.
• The part of cyton from where the axon arises are called axon hillock (most sensitive part of neuron).
• Axon does not have Nissl's granules, cell organelles and granular bodies.
• The axon transmits nerve impulses away from the cell body to a synapse or to a neuromuscular junction.

Axon are of two types:

1. Myelinated nerve-fibre

• In Myelinated nerve-fibres, Schwann cells form myelin sheath around the axon.
• The gaps between two adjacent myelin sheaths are called nodes of Ranvier.
• Myelinated nerve-fibres are found in cranial, spinal nerves and white matter of brain.

2. Non-myelinated nerve-fibre

• ​In Non-myelinated nerve-fibres, Schwann cells do not form myelin sheath around the axon and are without nodes of Ranvier.
• They are commonly found in autonomic and somatic neural systems.

Thus, Node of Ranvier are found on Axon.

Concept-

• Soil is the uppermost layer of the earth's crust.
• It is a mixture of living or nonliving materials.
• The formation of soils is done by weathering of material (which includes sediments, rocks, etc.) that are deposited by the water bodies near their shore.
• Soils are mainly classified into:
• ​Zonal - These are matured soil types that have developed over a long period of time under good drainage conditions.
• Azonal - They do not have well-developed soil horizons but have uniformity of soil from top to bottom.
• Intrazonal - These are formed in waterlogged areas and may have high content of soluble salts.

Important Points

• Alluvial soils are very fertile because it contains silt and sand carried by the water of rivers.
• It is usually most extensive in the lower part of a river's course, forming floodplains and deltas, but they may form at any point where the river overflows.
• One of the major characteristic of alluvial soil is that it is made by the deposition of the river load as it flows from its upper to its lower.
• On the basis of its ages alluvial soil is divided into Bhangar (Old alluvium) and Khadar (New alluvium).
• It is porous as well as light, so it is easily tillable.
• Alluvial soils are formed mainly due to silt deposited by Indo-Gangetic-Brahmaputra rivers (transported or azonal soils).
• Hence, alluvial soil is a recently formed soil.

Therefore alluvial soil is a type of azonal soil.

Additional InformationZonal soil

• Zonal soil is a major soil group often classified as a category of the highest rank and generally covering a wide geographic region or zone and embracing soils that are well-developed from the parent material by the normal soil-forming action of climate and living organisms.

Intrazonal soil

• These types of soils are intrazonal soils that develop from parent material and are highly rich in lime.
• The soil develops in sub-humid tropics and is very fertile.

Concept-

• Coffea arabica, also known as the Arabian coffee, is a species of flowering plant in the madder family Rubiaceae.
• Coffea arabica is itself the result of a hybridization between the Coffea canephora and Coffea eugenioides.

Key Points

• Rubiaceae, the madder family (order Gentianales) of flowering plants consists of 611 genera with more than 13,150 species of herbs, shrubs, and trees.
• It is distributed primarily in tropical areas of the world.
• Members of the family have leaves opposite each other with stipules or in whorls, unbroken leaf margins, and leaflike appendages at the base of the leafstalks.
• Plants may bear a single flower or many small flowers clustered together.
• Much branched tap root system.
• Inflorescence found is dichasial cymes, sometimes aggregated into heads.

Important Points

• C. arabica is mostly cultivated in Latin America.
• Arabica coffee is considered a mild, aromatic brew that is more flavourful than the other varieties.
• Arabica and Robusta are two major coffee varieties, which are obtained from C. arabica and C. canephora respectively.

Additional Information

• Apocynaceae-
• Apocynaceae is a family of trees, shrubs or sometimes herbs usually with milky sap, that comprises about 200 genera and 2,000 species.
• The leaves are simple, usually opposite and decussate, or whorled, while stipules are usually absent.
• The flowers are bisexual and actinomorphic or sometimes weakly zygomorphic.
• Acanthaceae-
• These have simple leaves arranged in opposite pairs, with cystoliths (enlarged cells containing crystals of calcium carbonate) in streaks or protuberances in the vegetative parts.
• The bisexual flowers are frequently bilaterally symmetrical and are usually enclosed by leaflike bracts, often coloured and large.
• Solanaceae-
• They have taproot system.
• The stem is either erect or climber.
• It includes herbs, shrubs, small trees, and climbers.
• The leaves are alternate, simple or pinnately compound (rarely); exstipulate with reticulate venation.

The correct answer is A. R. Wallace.

Key Points

• Zoogeography is the "study of the geographic distribution of animals".
• It is the science whose primary aim is to identify, describe, and explain the distribution of both land and aquatic species of animals in the different regions and localities of the earth.
• The concept was originated by naturalists like A. R. Wallace in the 19^th century.
• The faunal regions are mostly described on the basis of vertebrate fauna, including invertebrates only at times.
• It was also shown as evidence of continental drift and how migration of species took place from their centers of origin.
• Each region more or less coincides with a major continental land mass separated by oceans, deserts or mountain ranges.

Important Points

• There are 7 zoogeographic regions:
• Palearctic - comprises Europe and Asia from north of the tropics.
• Ethiopian - comprises of Africa south of the Sahara desert and parts of southern Arabia.
• Oriental - includes tropical Asia and associated continental islands.
• Nearctic - consists of North America except for tropical Mexico.
• Neotropical - comprises South and Central America including Mexico.
• Australian - covers Australia and New Guinea.
• Antarctic - essentially covers the Antarctica continent.

Additional Information

Table : Scientist & their discoveries

The correct answer is DPD.

Concept:

• Diffusion is a movement of substances from the region of their high concentration to the region of their lower concentration.
• The diffusion process is an important phenomenon in plants as it is the only means of the transport of the gases and materials in them.

Explanation:

Diffusion pressure deficit (DPD)

• Diffusion pressure deficit (DPD) is the force that determines the flow of water from one cell to the another.
• It is the difference in diffusion pressure between two solutions.
• It is the amount by which the diffusion pressure of water or solvent in a solution is less than the diffusion pressure of pure water or solvent.
• Because of the diffusion pressure gradient, it allows for easy water absorption. Water flows from low to high Diffusion pressure deficit.
• DPD = Osmotic Pressure - Turgor Pressure

Important Points

• DPD in a plant is an important parameter as it defines how much water a cell can take up.
• For a turgid cell, DPD is zero.
• Whereas, it will be highest for a plasmolyzed cell.

Additional Information

• Osmotic pressure (OP)
• It is defined as the amount of pressure which must be applied in order to prevent the passage of solvent due to osmosis.
• Water potential (WP)
• The difference between the free energy of water molecules in pure water and the energy of water in any other system is known as water potential.
• Turgor pressure (TP)
• When water enters a plant cell through diffusion, it becomes turgid due to building up of pressure against the cell wall in a plant system, this pressure is known as turgor pressure.

The correct answer is Theobroma cacao.

Key Points

Theobroma cacao, also called the Cacao tree and the cocoa tree, is a small evergreen tree in the Family Malvaceae (Family of Hibiscus i.e. Shoe Flower),

• Native: It is native to the Amazon basin, Central and South America.
• Seeds: About 20-60 seeds are contained in the pod of a single cacao fruit.
• Commercial use: Cocoa are seeds obtained which are then processed to make chocolate, chocolate liquor, cocoa solids, cocoa butter and other such variants.

Figure. Process of Chocolate Making from Cocoa Beans

Additional Information

Concept:

• Jean-Baptiste Lamarck was a French biologist who was one of the first to propose biological evolution.
• His theory is called Lamarckism and is based on two basic principles:
• Inheritance of acquired characters
• Use and disuse of organs during the lifetime of an organism.
• He proposed that changes in environment necessitates new needs in organism.
• This leads to new uses of pre-existing features or disuse of pre-existing features, causing a physical change in the features.
• He also stated that these changes were then acquired by the offspring in the next generation.
• The theory was explained with the example of giraffe.
• It was stated the giraffe ancestors stretched their necks to reach out to the leaves on higher branches of a tree.
• The ones with longer neck were more successful in getting food and produced offspring with longer necks.

Key Points

• Lamarck's "acquired trait theory" was challenged by August Weismann.
• Weismann conducted rat tail clipping and dissemination experiments for several generations.
• He cut off the tails of mice over several generations without creating tailless types.
• He believed that this was evidence against the inheritance theory of acquired traits.
• Weismann was able to show the inadequacy of much of the evidence generally accepted by Lamarckism.
• He also pointed out that germplasm continuity is sufficient to explain the inheritance of majority of the traits common to all **individuals. **​

Additional Information

• Charles Darwin -
• Charles Darwin was an English naturalist and biologist who went on the famous voyage of H.M.S Beagle.
• ​He is known for writing the book 'On the Origin of Species' in which he explained the theory of evolution by natural selection as 'descent with modification'.
• He gave the 'theory of natural selection' and the concept of 'survival of the fittest' as mechanisms of evolution.
• Hugo de Vries -
• ​Hugo de Vries was a botanist and geneticist, known for his mutation theory of evolution.
• He suggested that speciation (evolution of species) occurs due to sudden large changes in traits rather than small gradual changes, as was previously suggested by Darwin.
• H. Spencer -
• ​Herbert Spencer was a philosopher, anthropologist, biologist who is known for his hypothesis on social Darwinism.
• He stated that social evolution takes place much like biological evolution where the same principles of natural selection and ‘survival of the fittest’ can be applied.

The correct answer is Lophotrichous.

Concept:

• Flagella : It is a slender threadlike structure, especially a microscopic part that enables many protozoa, bacteria, spermatozoa, etc. to swim.
• Parts of flagella : Bacterial flagellum is composed of three parts – filament, hook and the basal body.

Explanation:

Based on the number and placement of flagella on the cell, there are four types of flagellar arrangements. They are -  

Additional Information

• Based on the shape, Bacterias are categorized into - 
• Cocci (Round shaped bacteria)
• Bacilli (Rod-shaped bacteria),
• Cocco-bacilli (combination of Round-Rod shaped bacteria),
• Spirilla (Spiral-shaped bacteria).
• Vibrio (Comma-shaped bacteria),
• Spirochete (Slender spiral-shaped bacteria).

The correct answer is Archaebacteria.

Key Points

• Methanogenic bacteria belong to the Kingdom Archaebacteria, which is now known as the domain Archaea.
• Methanogens bacteria are a single-celled organism.
• Methanogenic bacteria are primitive prokaryotes as they lack well-defined cell nuclei.
• These bacteria are anaerobic.
• They live anaerobically in swamps, marshes and in the guts of several ruminants such as cows, buffaloes, goats, etc.
• They live as symbionts in the rumen (first part of stomach) of herbivorous animals that chew their cud (example cow, buffalo, goat, etc.).
• These bacteria also help in the digestion of cellulose in ruminants.
• These bacteria have been exploited for the production of methane-rich gobar gas or biogas from the dung of these animals.
• The fermentation of cattle dung by methanogens is done in specially designed gobar gas plants.
• It not only provide cooking gas (fuel gas), but also leaves behind a slurry which can be used as an organic matter for growing crops.
• They produce almost 65% of atmospheric methane.

Additional Information

• Mycoplasma -
• It is genus of bacteria that lack cell wall.
• It is placed under the domain Bacteria.
• Eubacteria -
• They refer to the "true bacteria" which have a rigid cell wall.
• They are single-celled prokaryotic organisms.
• Cyanobacteria -
• They refer to a phylum of bacteria that can perform photosynthesis.
• They were previously placed under Cyanophyta as an algal group.
• Hence, they are also sometimes referred as blue-green algae.