Aquatic and Marine Biology

Sea otters (Enhydra lutris) are commonly cited as an example of a keystone species because they limit the density of sea urchins.

 Yes, it is correct. There are some organisms in which the young ones resemble their adults and humans are one of them.

Reason: Oysters are cultivated for the pearls they make. Oysters have long been valued for the precious pearls that develop in them. Some oysters are also eaten as food. But shell and teeth are not useful in them. 

Reason: Mussels and oysters thrive in marine (in sea) water habitat. Inland fisheries include freshwater resources like canals, ponds, reservoirs and rivers. Brackish water resources are the ones where sea-water and fresh water mix together such as estuaries and lagoons.

Reason: The practice of culturing marine fish stock is known as mariculture. Apiculture is the practice of rearing and breeding bees. Aquaculture is the farming of freshwater and saltwater organisms such as fishes and aquatic plants. It is also called aqua farming. Hydroculture is growing of plants in a media that allows the distribution of water and nutrients through capillary action. Clay can be used to anchor plants. It generally involves growth of plants without the use of soil.

Reason: Peneaus monodon is a type of marine (in sea) prawn. Inland fisheries include freshwater resources like canals, ponds, reservoirs and rivers. Brackish water resources are the ones where sea-water and fresh water mix together such as estuaries and lagoons. 

Reason: Marine fisheries include deep seas and coastline. In India, it includes 7500 km coastline and the deep seas beyond it. Popular marine fish varieties include pomphret, tuna and sardine, while freshwater fishes inhabit rivers and lakes. For example, catla is a freshwater fish.

Reason: The practice of growing four to five fish species in a single fish pond is known as composite fish culture. In such systems, these species are selected so that there does not exist any competition for food among them having different types of food habits. E.g. catlas are surface feeders, rohus feed in the middle zone of the pond, mrigals and common carps are bottom feeders and grass carps feed on the weeds. These species when together, can use all the food in the pond without competing with one another. This increases the fish yield from the pond.

Reason: Catlas serve as surface feeders in a composite fish culture. The practice of growing four to five fish species in a single fish pond is known as composite fish culture. In such systems, these species are selected so that there does not exist any competition for food among them having different types of food habits, e.g. catlas are surface feeders, rohus feed in the middle zone of the pond, mrigals and common carps are bottom feeders, and grass carps feed on the weeds. These species, when together, can use all the food in the pond without competing with one another. This increases the fish yield from the pond. 

Plankton are microscopic organisms that float freely in water bodies and form the base of aquatic food chains. They include both phytoplankton (plant-like) and zooplankton (animal-like).

Chiton, Pila (apple snail), and Unio (freshwater mussel) are all molluscs - they belong to the phylum Mollusca. Prawn, however, is an arthropod (class Crustacea). Arthropods have jointed legs and an exoskeleton, while molluscs have a muscular foot and soft body. The prawn is the odd one out because it belongs to a completely different phylum.

Dogfish are small sharks, which belong to the class Pisces (fish). More specifically, they are cartilaginous fish (Chondrichthyes). They are not mammals (which have hair and mammary glands), reptiles (which have scales and lay eggs on land), or amphibians (which typically have metamorphic life cycles). As fish, they have gills, fins, and live entirely in water.

Pisces (fish) are oviparous, meaning they lay eggs that develop and hatch outside the body. Most fish species produce large numbers of eggs that are fertilized externally, with the embryos developing within the eggs in water. This is in contrast to viviparous animals that give birth to live young, or saprophytes/parasites which describe nutritional modes not reproductive strategies.

Amphibians are uniquely adapted to live both on land and in water during their life cycle. Most amphibians have aquatic larval stages (like tadpoles) and terrestrial adult stages, requiring moist skin and specialized respiratory methods for both environments. This dual lifestyle distinguishes them from purely aquatic fish, purely terrestrial birds and mammals, or animals confined to one habitat.

Pisces (fish) are cold-blooded animals with streamlined bodies and gills for aquatic respiration. Amphibians have both aquatic and terrestrial life stages, reptiles have lungs, and birds are warm-blooded.