What went wrong when the king rode under the arch?

It was too low and knocked off his crown

How does the chain of blame unfold in the poem?

Each accused person blames another, ending with the king's own changes

To which class and phylum does the frog belong?

The frog belongs to class Amphibia of phylum Chordata; the common Indian species is Rana tigrina.

Why is the frog called a poikilotherm?

Because it is cold-blooded; its body temperature varies with the temperature of its surroundings.

What are aestivation and hibernation in frogs?

Aestivation is summer sleep and hibernation is winter sleep, both spent sheltering in burrows to avoid extreme heat or cold.

How does the frog respire on land and in water?

In water it respires through the skin (cutaneous respiration) and on land through the skin, buccal cavity and lungs (pulmonary respiration).

Describe the heart of a frog.

The frog has a three-chambered heart with two atria and one ventricle, covered by a pericardium, with a sinus venosus and conus arteriosus.

Why is the frog said to be ureotelic?

Because it excretes nitrogenous waste mainly in the form of urea, removed by a pair of kidneys through the ureters and cloaca.

What is the function of the ureters in a frog?

In males the ureters act as urinogenital ducts carrying both urine and sperms to the cloaca; in females they carry only urine, while the oviducts open separately.

How is sexual dimorphism shown in frogs?

Male frogs have vocal sacs for sound production and a copulatory pad on the first digit of the forelimb, both absent in females.

Into which parts is the frog brain divided?

The brain is divided into fore-brain (olfactory lobes, cerebral hemispheres, diencephalon), mid-brain (optic lobes) and hind-brain (cerebellum and medulla oblongata).

How are frogs useful to humans?

They eat insects and protect crops, maintain ecological balance as a link in food chains, and in some countries their legs are used as food.

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Chapter 7: Structural Organisation in Animals — Class 11 Biology

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Chapter 7: Structural Organisation in Animals

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The common Indian frog studied as a representative vertebrate is:

Summary

This chapter introduces the idea that in multicellular animals groups of similar cells form tissues, tissues form organs, and organs form organ systems, illustrating division of labour, and then studies the morphology and anatomy of the frog as a representative vertebrate. The common Indian frog, Rana tigrina, belongs to class Amphibia of phylum Chordata; it is a cold-blooded (poikilothermic) animal that can change colour for camouflage and undergoes aestivation and hibernation. Externally the body is divided into head and trunk, with moist slippery skin through which water is absorbed, bulged eyes with a nictitating membrane, a tympanum, and limbs with webbed digits; males show vocal sacs and a copulatory pad. Internally the frog has well-developed digestive, respiratory, circulatory, excretory, nervous and reproductive systems. It is carnivorous with a short alimentary canal, respires through skin, buccal cavity and lungs, has a three-chambered heart with a closed single circulation and nucleated red blood cells, excretes urea (it is ureotelic), and has a brain divided into fore-, mid- and hind-brain. Fertilisation is external and development passes through a tadpole stage that metamorphoses into the adult. Frogs are ecologically and agriculturally useful.

Organ and organ-system level of organisationFrog: habitat and external featuresDigestive and respiratory systems of frogCirculatory and excretory systemsNervous system and sense organsReproductive system, development and significance

Key terms

Tissue

A group of similar cells together with intercellular substances performing a specific function.

Poikilotherm

A cold-blooded animal whose body temperature varies with that of the environment, such as a frog.

Aestivation

Summer sleep, in which a frog takes shelter in burrows to avoid extreme heat.

Ureotelic

Excreting nitrogenous waste mainly as urea, as the frog does.

Cloaca

The common chamber that receives faecal matter, urine and gametes before they pass to the exterior.

Metamorphosis

The transformation of the larval tadpole into the adult frog.

Important questions

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A group of similar cells together with intercellular substances performing a specific function.

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Practice quiz · Structural Organisation in Animals

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