Question 1

In mammals and birds, why it is necessary to separate oxygenated and deoxygenated blood?

Accepted Answer

The circulatory system in birds and mammals consists of oygenated and deoxydenated blood. However, they have a double circulation system where the oxygenated as well as deoxygenated blood remain separate. This is essential to maintain the body temperature efficiently over a wide range. As mammals and birds require to keep their body warm, they require a higher supply of oxygen. Thus, it is beneficial if the oxygenated blood remains separate as its mixing with deoxygenated blood can make the entire blood impure.

Question 2

All vertebrates are chordates but all chordates are not vertebrates. Justify the statement.

Accepted Answer

All chordates have a notochord. Chordates include Urochordates, Cephalochordates (both are called protochordates) and vertebrates. In vertebrates notochord is replaced by vertebral column (backbone), however vertebral column is not present in protochordates. Therefore, all vertebrates are chordates but all chordates are not vertebrates.

Question 3

List out the differences between class-Chondrichthyes and class Osteichthyes.

Accepted Answer

Class- Chondrichthyes Class- Osteichthyes 1. The mouth is positioned ventrally and the body is covered with placoid scales. 1. The mouth is positioned apically and body is covered with cycloid or ctenoid or ganoid scales 2. Gill slits, usually five pairs, open sepa&#173;rately and directly to the exterior. 2. Gill slits, usually four pairs, open in a gill chamber. 3. The endoskeleton is cartilaginous. 3. The endoskeleton is bony with amphicoelous vertebrae. 4. Operculum always absent.Examples- Sharks and chimaeras. 4. Operculum with branchiostegal mem&#173;brane always present.Examples- Lungfish and coelacanth

Question 4

"All vertebrates are chordates but all chordates are not vertebrates". Justify the statement.

Accepted Answer

The characteristic features of the phylum Chordata include the presence of a notochord and paired pharyngeal gill slits. In sub-phylum Vertebrata, the notochord present in embryos gets replaced by a cartilaginous or bony vertebral column in adults. But in cephelochordates, notochord persists throughout life as such and in urochordates, the notochord is present only in larval stages and absent in adults. Thus, it can be said that all vertebrates are chordates but all chordates are not vertebrates.

Question 5

Which of the following are correct?(i) Sponges : Cellular level of organisation(ii) Cnidaria : Tissue level of organisation(iii) Platyhelminthes : Organ level of organisation(iv) Annelids, Arthropods, Molluscs, Echinoderms and Chordates : Organ system level of organisation.

Accepted Answer

Animals show four different grades of organization:(i) Protoplasmic grade found in protozoans.(ii)&#10; Cellular grade is the characteristic of sponges and mesozoans because &#10;in a sponge, cells exhibit division of labour for performing specialized&#10; functions.(iii) Tissue grade is of two types : Cell-tissue grade is&#10; seen in coelenterates as there are cells not only specialised for &#10;different functions but also certain similar cells gather together to &#10;form tissue as well. Tissue - organ grade appears in flatworms &#10;(Platyhelminthes) with arrangement of tissues to form organs.(iv) In&#10; organ system level of organisation, organs are joined in a system to &#10;perform basic functions. It is found in higher invertebrates and all &#10;vertebrates.Hence the correct option is D.

Question 6

What are the characteristics features of mammals?

Accepted Answer

Characteristics features of mammals:(1) Body is covered with hair.(2) Skin is provided with sweat and sebaceous glands.(3) Heart is four chambered.(4) Fertilization is internal.(5) Females have mammary glands to produce milk to nourish their young ones.(6) External ear-pinna present.(7) Eyes have eye lids.(8) Warm-blooded.(9) Respiration through lungs.(10) Body cavity dividedinto thorax and abdomen by muscular diaphragm.

Question 7

Which of the following is not a character of the phylum Chordata?

Accepted Answer

Animals that belong to phylum Chordata are characterized by the presence of a notochord, a dorsal hollow nerve cord, and paired pharyngeal gill slits. These characters are known as three fundamental chordate characters. In some chordates notochord is replaced by the vertebral column in the adult stage. Protochordates i.e., Urochordata and Cephalochordata don't have a well-developed spinal cord. Thus, the correct answer is option D

Question 8

Tissue level of organization is found in:

Accepted Answer

Comb jelly belongs to the phylum Ctenophora and shows tissue level of organization. It does not show the presence of organs and organ systems. They are marine, radially symmetrical, and diploblastic organisms.Thus, the correct answer is option D.

Question 9

Differentiate between cartilaginous fishes and bony fishes.

Accepted Answer

CARTILAGINOUS FISHES BONY FISHES 1) Their endoskeleton is primarily made of cartilage.1) Their endoskeleton is entirely made of bone.  2) Their exoskeleton is made of placoids.2) Their exoskeleton is made up of cycloids or thin bony plates.  3) The position of their tail is heterocercal.3) Their tail fin is homocercal. 4) They have 5 gills that are overly exposed (no operculum).4) They have an operculum on either side of their gills.5) In them the fertilization is through internal mechanisms.5) They fertilize their eggs externally.  6) Eg- dog fish, electric ray torpedo and sharks.6) Eg-  fying fish, globe fish and sea horses.

Question 10

Justify the statement Mammals are the most successful and dominant animals today.

Accepted Answer

Mammals are the most successful and dominant animals today. They thrive very well in most of the environment of the world. Unique mammalian characteristics are: (a) Body covered with hair.(b) Presence of sebaceous and sweat glands in the skin.(c) Presence of mammary glands in females.(d) The heart is four chambered.(e) The red blood corpuscles (erythrocytes) are biconcave and enucleated.(f) Corpus callosum unites two cerebral hemispheres.(g) Testes are extra-abdominal in scrotal sacs.(h) Presence of penis for copulation in males.(i) Mostly viviparous and embryo attached to the uterine wall by the placenta.