Write short notes

Question 13 Marks

Write the distinguishing features of class Reptilia.

Answer

Diagnostic characters of Reptilia:

Habitat: They are crawling animals. They are the first true terrestrial vertebrates. Few may be aquatic or semi- aquatic and are also found in marshy areas.
Locomotion: Locomotion occurs by limbs in most animals. The limbs are pentadactyl with clawed digits, which help the animal to walk, creep or crawl. Snakes are limbless and crawl on their belly.
Body temperature: They are poikilotherms.
Exoskeleton: Skin is dry, non-glandular and covered by an exoskeleton of epidermal scales or scutes, shields or plates. Lizards and snake shed their skin periodically.
Ear: Tympanum is present
Circulatory system: It has two complete auricles but the ventricles are incompletely partitioned. Therefore, the heart of reptiles is not perfectly four chambered (except in crocodile the heart is four chambered).
Nervous system: The brain is well developed. The olfactory lobes and cerebellum are better developed as compared to amphibians.
Reproduction: Sexes are separate and exhibit prominent sexual dimorphism. Fertilization is internal and the animals are oviparous (exception – viper, it is viviparous). They show little parental care.
e.g. Naja naja (Cobra), Hemidactylus (Wall lizard), Chelonia (Turtle), Crocodilus (Crocodile), Testudo (Tortoise), Chameleon (Tree lizard), Bangarus (Krait), Vipera (Viper).

Question 23 Marks

Write a short note on Superclass Pisces. Give one example.

Answer

Important features of superclass Pisces:

Habitat: These are aquatic animals and are present in fresh, marine and brackish waters.
Body temperature: Pisces are poikilothermic animals i.e., cold blooded animals, in which body temperature changes according to the change in the surrounding temperature.
Sensory orgAnswer:They have lateral line system which shows the presence of rheoreceptors for the detection of water current.
Locomotion: Locomotion is by body muscles and fins. Caudal fin helps in steering wheel.
Skeleton: Exoskeleton is made up of dermal scales. It is either bony or cartilaginous.
Body shape: Body is streamlined and boat-shaped and helps to overcome resistance during swimming.
Respiration: Respiration is by gills.
Circulation: It shows single and closed circulation. Heart is two-chambered and ventral in position. Heart of fishes is described as venous heart (presence of deoxygenated blood).
Nervous system: They have a well-developed brain with large olfactory lobes.
Reproduction: Sexes are separate. Most of the fishes are oviparous, however some are viviparous.

Question 33 Marks

Write a short note on Urochordates.

Answer

Distinguishing features of Tunicata or Urochordata:

Habitat: They are exclusively marine.
Body covering: Soft body is covered by ‘test’ or ‘tunic’ which is made up of tunicine.
Notochord: Notochord is present only in the tail of the larva and is lost during metamorphosis. Hence, the name Urochordata.
Respiration: Pharynx with many gill slits for respiration.
Circulation: Closed circulatory system is present.
Reproduction: Development is indirect, e. g. Herdmania, Salpa, Doliolum, Ascidia.

Question 43 Marks

Write a short note on amphibians.

Answer

These animals live on land as well as in water (freshwater only).
Amphibians are poikilothermic animals.
Body is differentiated into head, and trunk. Neck and tail are absent in many adults with few exceptions.
Two pairs of limbs arise from the pectoral and pelvic girdles respectively, which help in locomotion.
Skin is moist and glandular with mucous glands.
Exoskeleton is absent.
Eyelids are present. Tympanum represents the ear.
Excretory products, digestive products and gametes are released through the common chamber cloaca.
Circulatory system is of closed type. Heart is three-chambered and ventral. RBCs are biconvex and nucleated.
Respiration is by skin, lungs and bucco-pharynx.
Nervous system is well developed.
Sexes are separate. Amphibians are oviparous. Fertilization is external and development is indirect through aquatic larval stage.
They exhibit metamorphosis. e.g. Rana (Frog), Bufo (Toad), Salamandra (Salamander), Ichthyophis, Hyla (Tree frog), etc.

Question 53 Marks

Write a short note on lancelets.

Answer

Cephalochordates are also known as lancelets and are small fish-like animals that rarely exceed 5 cm in length.
Lancelets are exclusively marine and live partly buried in soft marine sediments.
Notochord extends throughout entire length of the body and persists throughout life.
Myotomes (muscle blocks) are present.
Post anal tail is present.
Circulatory system is closed type. Blood lacks pigment, e.g. Branchiostoma

Biology Write short notes