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Practice each question, then open the answer or worked solution.
Identify the phylum in which adults exhibit radial symmetry and larva
exhibit bilateral symmetry.
In the phylum Echinodermata, the radial symmetry is exhibited by the adult while the bilateral symmetry is exhibited by the larva.
What is the importance of pneumatic bones and air sacs in Aves?
Pneumatic bones make their body lightweight and facilitate the flying and air sacs are helpful in respiration and buoyancy.
What is metagenesis? Mention an example which exhibits this phenomenon.
The phenomenon of alternation of generations between sexual and asexual mode of reproduction is called metagenesis.
What is the role of feathers?
In aves, besides pneumatic bones, feathers are also helpful in making the body weigh lighter and help in flight.
Which group of chordates possess sucking and circular mouth without jaws?
Cyclostomes possess sucking and circular mouth without jaws. Since their mouth is circular and lacks jaws, they are also called agnathans.
Give one example each for an animal possessing placoid scales and that with cycloid scales.
Placoid scales are the tiny tough scales that cover the skin. Examples are Trygon, Pritis
Cycloid scales are characterized by having a smooth outer margin. Examples are Catla, Clarias
Mention two modifications in reptiles required for terrestrial mode of life.
Internal fertilization (makes the chances of the survival of young ones better). The body is covered with dry and cornified skin and epidermal scales.
Mention one example each for animals with a chitinous exoskeleton and those covered by a calcareous shell.
Chitinous exoskeleton covers the body of cockroach (Arthropods) and calcareous shell covers the body of Pila (Molluscs).
What is the role of the radula in molluscs?
The radula is a special structure in molluscs which is used to scrape and scratch the food and to create a depression in rocks which molluscs use as their habitat.
Name the animal, which exhibits the phenomenon of bioluminescence. Mention the phylum to which it belongs.
The phenomenon of production and emission of light by an organism as a result of a chemical reaction during which chemical energy is converted to light energy is called bioluminescence. Members of the phylum ctenophores like Ctenoplana, Velamen, Beroe, etc.