Diversity in Living Organisms Test - 69

A normal gut is one which has two openings, a mouth, and an anus. In an incomplete gut, the mouth is present but organisms have no anus. As soon as food enters the gut, the mouth closes and the cells of the gastrodermis begin to work. Digestive enzymes are secreted in the gastrovascular cavity. This is seen most commonly in platyhelminths group of invertebrates.

Birds are oviparous animals, not viviparous animals. This means that birds lay eggs and young ones develop from these eggs. Options A and B are correct statements.

$$\textbf{Correct option: (B)}$$

• The incomplete digestive system is the system in which entry of food and exit of waste material is done from a single opening. It is found in Cnidaria, Ctenophora or Platyhelminthes.
• Ascehelminthes and chordates have a complete digestive system i.e., they have separate openings for entering of food (mouth) and removal of waste (anus).
• Porifera has water canal system so they can trap the food present in the water.
• So the correct option is 'Platyhelminthes'.

The thorny devil (Moloch horridus) is an Australian lizard, also known as the mountain devil, the thorny lizard, or the moloch. This is the sole species of genus Moloch. The thorny dragon grows up to 20 cm (7.9 in) in length, and can live for 15 to 20 years. The females are larger than the males. Most of these lizards are coloured in camouflaging shades of desert browns and tans. These colours change from pale colours during warm weather and to darker colours during cold weather. These animals are covered entirely with conical spines that are mostly unclassified.

An arthropod is an invertebrate animal having an exoskeleton (external skeleton), a segmented body, and paired jointed appendages. Arthropods form the phylum Euarthropoda, which includes insects, arachnids, myriapods, and crustaceans. Arthropods are characterized by their jointed limbs and cuticle made of chitin, often mineralised with calcium carbonate. The arthropod body plan consists of segments, each with a pair of appendages. The rigid cuticle inhibits growth, so arthropods replace it periodically by moulting. Arthopods are bilaterally symmetrical and their body possesses an external skeleton. Some species have wings. Examples - Cockroach, scorpion, prawn.

Being a legless lizard, the slow worm (Anguis fragilis) is often mistaken for a snake. However, there are certain features that separate the slow worm from snakes, including the presence of eyelids and ear openings. The male and female differ in appearance; the female is usually brown, copper-coloured or red on the back, with brown or black sides, often with lighter iridescent. Depending on the local climate, the female slow worm will mate annually or once every two years. The slow worm is ovoviviparous, and instead of laying eggs, the female gives birth to an average of eight live young between mid-August and mid-September.

Bats are mammals with their forelimbs adapted as wings, they are the only mammals naturally capable of true and sustained flight. Bats are more manoeuvrable than birds, flying with their very long spread-out digits covered with a thin membrane or patagium. Most bats are nocturnal, and many roost in caves or other refuges; it is uncertain whether bats have these behaviours to escape predators. Bats are present throughout the world, with the exception of extremely cold regions. They are important in their ecosystems for pollinating flowers and dispersing seeds; many tropical plants depend entirely on bats for these services.

Polyspermy is the entry of several sperms into the egg during fertilisation although only one sperm nucleus actually fuses with the egg nucleus. It occurs in animals with yolky eggs (e.g., birds).

The turtle shell is a highly complicated shield for the ventral and dorsal parts of turtles, tortoises and terrapins (all classified as "turtles" by zoologists), completely enclosing all the vital organs of the turtle and in some cases even the head. It is constructed of modified bony elements such as the ribs, parts of the pelvis and other bones found in most reptiles. The bone of the shell consists of both skeletal and dermal bone, showing that the complete enclosure of the shell probably evolved by including dermal armor into the rib cage. The plastron is the nearly flat part of the shell structure of a turtle, what one would call the belly or ventral surface of the shell. It also includes within its structure the anterior and posterior bridge struts and the bridge of the shell. The plastron is made up of nine bones and the two epiplastra at the anterior border of the plastron are homologous to the clavicles of other tetrapods. The rest of the plastral bones are homologous to the abdominal ribs of other tetrapods.