Diversity in Living Organisms

Skin: People kill snakes and sell their skin at high prices as it is highly lustrous and shiny.

Both (1) and (2): People kill snakes because they are poisonous and some people sell their skin at high price.

Snakes do not have external ears like human beings. But they have internal ears located near the lower jaw.

Both (1) and (2): Cobra and Duboiyo are poisonous snakes and brown - water snake is a non-poisonous snake.

Brown water snake: It is a non-poisonous snake found in Southeast United State. It is found in swamps and streams.

Hydra uses its tentacles to move, and it shows both looping and somersault movement. 

Unicellular organisms respire and reproduce.

Bacteria are called prokaryotes as they do not have a well-defined nuclear membrane around the nucleus of their cell.

Prokaryotes are unicellular organisms with an undefined nucleus.

They have a well-organised nucleus.

Protozoan euglena is an animal cell having plastids.

There are many kinds of fish, some with skeletons made entirely of cartilage, such as sharks, and some with a skeleton made of both bone and cartilage, such as tuna or rohu.

Notochord (chord – string) is a long, flexible rod-like structure that provides support to the body. Animals that possess notochord are called chordates and animals without notochord are called non-chordates, e.g. platyhelminthes, porifera, coelenterata, nematoda, annelida, arthropoda, mollusca, echinodermata, etc. are all non-chordates.  Vertebrata - The members of vertebrata possess notochord during the embryonic period. The notochord is later replaced by a cartilaginous or bony vertebral column in the adult. Thus, all vertebrates are chordates, but not all chordates are vertebrates.

Echinodermata includes free-living and marine animals. It is also known as group of marine animals. Free-living means the ability to move and live independently. Marine – Living in sea. In Greek, ‘echino’ means hedgehog and ‘derma’ means skin. Therefore, they are spiny-skinned organisms. They are found at the bottom of the ocean and in the deep sea. They often make up the bulk of living material. Examples are starfish and sea urchins. Protochordata includes marine animals that are not free-living, e.g. Balanoglossus, Amphioxus, etc. Mollusca - It is the second largest animal group (first largest group is Arthropoda). Molluscs are terrestrial (living on land) or aquatic (marine or freshwater) having an organ-system level of organisation. Examples are snails and mussels.

Platyhelminthes - The body of the animals in this group is dorsoventrally flattened (top to bottom), which is why these animals are called flatworms. They are either free-living or parasitic. Examples of free-living animals are planarians and parasitic animals like liver flukes. 

Snakes, lizards and turtles belong to class Reptilia. Animals of this class are cold-blooded, bear scales and breathe through lungs. Most of them have a three-chambered heart except crocodiles, which have four-chambered heart. They lay eggs with tough coverings. Notochord (chord – string) is a long flexible rod that provides support to the body. Animals with notochord are called chordates and without notochord are called non-chordates. Reptiles are chordates with a true vertebral column and internal skeleton.