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7. [ Auto-Generated ] Structural Organization In Animals

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Part of NCERT 11 Biology

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Prerequisite Check: Animal Organization

Verify understanding of basic biological hierarchy: Cells, difference between unicellular and multicellular organisms, and the definition of a tissue.

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Prerequisite Check: Animal Organization
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From Cells to Systems

Explain the hierarchy of organization (Cell -> Tissue -> Organ -> Organ System) using the introduction on Page 79. Define 'Division of Labour' in multicellular animals.

From Cells to Systems

Ever wonder how complex animals are built? It’s all about teamwork! Unlike unicellular organisms where one cell does it all, multicellular animals organize their bodies to handle complex functions.

The Hierarchy of Organization

Just like bricks build a house, biological units build up step-by-step:

  • Cells: The starting point. In humans, billions of cells work together.
  • Tissues: A group of similar cells working together with intercellular substances to perform a specific function.
  • Organs: Tissues organized in specific proportions to form structures like the stomach, heart, or kidney.
  • Organ Systems: Two or more organs interacting physically or chemically to perform a common function (e.g., the digestive system).

Division of Labour

In complex animals, not every cell does every job. Instead, they split up the work.

Division of Labour means that specialized cells, tissues, organs, and systems handle specific tasks. This efficient organization allows the body to function better and ensures the survival of the organism as a whole!

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biology

Organization Hierarchy

Create a cloze test based on the definitions of Tissues, Organs, and Organ Systems from Page 79, Paragraph 1 & 2.

Fill each blank with the correct term.
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In multicellular animals, a group of similar cells along with intercellular substances performing a specific function is called a. These tissues are organized in specific patterns to form an, such as the stomach or heart. When two or more organs interact to perform a common function, they together form an.
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Meet the Frog: Rana tigrina

Introduce the Indian Bullfrog (Rana tigrina). Cover its classification (Chordata, Amphibia) and its cold-blooded nature (poikilotherms) from Page 80.

Meet the Frog: Rana tigrina

Did you know frogs can live on both land and in freshwater? The most common species found in India is the Rana tigrina (Indian Bullfrog).

Classification

Biologists classify these jumping creatures under:

  • Phylum: Chordata
  • Class: Amphibia

Cold-Blooded Nature

Frogs are cold-blooded animals, or poikilotherms. This means they do not have a constant body temperature; instead, it changes with the environment.

To survive extreme weather, they take shelter in deep burrows:

  • Aestivation: Summer sleep to protect against heat.
  • Hibernation: Winter sleep to protect against cold.

Did you know? Frogs can change color to hide from enemies! This protective camouflage is called mimicry.

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flashcard

Frog Survival Vocabulary

Create flashcards for key survival terms found on Page 80: Poikilotherms, Camouflage, Mimicry, Aestivation (Summer Sleep), and Hibernation (Winter Sleep).

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IMAGE

External Morphology of the Frog

Display 'Figure 7.1 External features of frog' from Page 80. Highlight the Head, Trunk, Fore limb, and Hind limb.

Diagram of a frog (Rana tigrina) showing its external features. The frog has olive-green skin with dark irregular spots. Labels point to the Head, Trunk, Fore limb, and Hind limb. The diagram highlights the absence of a neck and tail, and shows bulging eyes.
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Figure 7.1: The frog's body is divided into a head and trunk. Note the absence of a neck and tail, and the presence of fore and hind limbs.

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Morphology

Skin and Senses

Describe the frog's skin (mucus, moist, colors) and sensory organs (eyes, nictitating membrane, tympanum) based on Page 80, Section 7.2.1.

Skin and Senses

Let's explore the frog's unique body covering and specialized sensory organs found on the head!

🐸 The Skin

A frog's skin is vital for its survival:

  • Texture: It feels smooth and slippery due to the presence of mucus.
  • Moisture: The skin is always maintained in a moist condition.
  • Color: Generally olive green with dark spots on the back (dorsal side) and uniformly pale yellow on the belly (ventral side).
  • Hydration: Frogs never drink water! Instead, they absorb water directly through their skin.

👀 Sensory Organs

Frogs have specialized features to help them sense their environment:

  • Eyes: These are bulged and covered by a nictitating membrane. This membrane acts like built-in goggles, protecting the eyes while the frog is underwater.
  • Tympanum: Located on either side of the eyes, this membranous structure acts as the ear and receives sound signals.