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Practice each question, then open the answer or worked solution.
Give three major differences between chordates and non-chordates and
draw a schematic sketch of a chordate showing those features.
| Chordates | Non-Chordates |
| Have notochord
The tail is present at some stage Heart is ventral CNS is dorsal Gill slits are present in the pharynx |
Don’t have a notochord
Tail is absent Heart is dorsal CNS is central, solid and double Gill slits are absent |
What is the relationship between germinal layers and the formation of the body cavity in case of coelomate, acoelomates and pseudocoelomates?
Germinal layers are those which formed during the process of gastrulation. The outer layer of germ is called ectoderm, the middle one is endoderm and the innermost is the endoderm. Coelomates are the organisms possessing coeloms. The coelom is the body cavity lined by the mesoderm. Examples of coelomates are phylum Annelida, Mollusca, arthropods, etc. The organisms with absent body cavities are called coelomates. E.g. Platyhelminthes. Some of the organisms do not have a lining by mesoderm. Instead of that, it will be in the form of a scattered pouch in between ectoderm and endoderm. Such a body cavity is called pseudocolour and animals possessing pseudocoelom are referred to as pseudocoelomates e.g., Ascaris.
Comment upon the habitats and external features of animals belonging to class, amphibia and reptilia.
Amphibia
They are thin and have smooth skin, which can live on both land and water. Their eyes have eyelids, and have a pair of limbs. A tympanum represents the ears. Examples are Rana(frog) and cobra
Reptiles
They are covered with dry and confined skin and scales. They mostly live on land. Tympanum represents ear. They have a pair of limbs. They will creep and crawl. These category organisms are oviparous, fertilization is internal and development is direct or indirect.
Examples are crocodile, turtle etc
Mammals are most adapted among the vertebrates. Elaborate.
Mammals are found in a variety of habitats like deserts, plains and mountains. They differ in the type of jaws and sexes are separate and fertilization is internal. They have pairs of limbs which are used for walking, burrowing, climbing etc. Their mammary glands produce milk to nourish their young ones. They are warm-blooded which helps them maintain their body temperature in different weather conditions. They have hair-like structures which act as insulation against cold. The 4-chambered heart is present in mammals. The brains are more developed. Examples of Mammals: Humans, Whales, Dogs, Camels, etc.