11BIO7

Structural Organisation in Animals

Explore the structural organization in animals, from tissues to organ systems, with a detailed study of frog anatomy and morphology.

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Chapter Overview

Brief Introduction

This chapter explores how cells organize into tissues, tissues into organs, and organs into organ systems in multicellular animals. It focuses on the four basic types of tissues and their organization, with a detailed study of frog morphology and anatomy as a representative vertebrate.

Learning Objectives

• Understand the four basic types of animal tissues
• Learn about organ and organ system formation
• Study the morphology and anatomy of frogs
• Comprehend the digestive, circulatory, respiratory, and other systems in frogs
• Recognize the ecological importance of frogs

Key Topics Covered

• Animal Tissues: Types and Functions
• Organ and Organ Systems
• Frog: Classification and Characteristics
• External Morphology of Frog
• Internal Anatomy of Frog
• Digestive System
• Respiratory System
• Circulatory System
• Excretory System
• Nervous System
• Reproductive System

Interactive Chapter Index

Animal Tissues

Explore the four basic types of tissues that make up all complex animals.

Organ and Organ Systems

Understand how tissues organize into organs and systems for efficient functioning.

Frog Morphology

Study the external features and adaptations of frogs as amphibians.

Frog Anatomy

Explore the internal organ systems of frogs including digestive, respiratory, and circulatory systems.

Digestive System

Learn about the complete alimentary canal and digestive glands in frogs.

Chapter Summary

Review the key concepts and takeaways from this chapter.

Full Chapter Notes

7.1 Organ and Organ System

In multicellular animals, groups of similar cells along with intercellular substances perform specific functions, forming tissues. All complex animals consist of only four basic types of tissues:

Four Basic Types of Tissues:

1. Epithelial tissue: Forms coverings and linings of organs
2. Connective tissue: Provides support and connects different tissues
3. Muscular tissue: Responsible for movement
4. Neural tissue: Conducts impulses and coordinates activities

Tissue: A group of similar cells along with intercellular substances that perform a specific function in the body.

These tissues are organized in specific proportions and patterns to form organs like stomach, lung, heart, and kidney. When two or more organs perform a common function through physical and/or chemical interaction, they form an organ system (e.g., digestive system, respiratory system).

Q: Why is tissue organization important in multicellular animals?

A: Tissue organization is important because:

1. It allows division of labor among cells
2. It enables more efficient and coordinated activities
3. It facilitates specialization of cells for specific functions
4. It helps in the survival of the body as a whole
5. It allows complex functions to be performed by specialized groups of cells

Structural Organization - Mind Map

Organ and Organ System

Each organ in our body is made of one or more types of tissues. For example, our heart consists of all four types of tissues:

Tissues in the Heart:

• Epithelial tissue: Lines the heart chambers
• Connective tissue: Forms the heart valves and blood vessels
• Muscular tissue: Cardiac muscle for pumping action
• Neural tissue: Controls heart rate and rhythm

Evolutionary Trend: The complexity in organ and organ systems displays certain discernible patterns called evolutionary trends, showing how structures have become more specialized over time.

7.2 Frogs

Frogs can live both on land and in freshwater and belong to class Amphibia of phylum Chordata. The most common species of frog found in India is Rana tigrina.

Key Characteristics of Frogs:

• Poikilotherms (cold-blooded): Body temperature varies with environment
• Camouflage: Can change color to hide from enemies (protective coloration called mimicry)
• Aestivation: Summer sleep in deep burrows to avoid extreme heat
• Hibernation: Winter sleep to protect from extreme cold

Q: What are the advantages of being poikilothermic for frogs?

A: Advantages of being poikilothermic (cold-blooded):

1. Lower energy requirements as they don't need to maintain constant body temperature
2. Can survive on less food compared to warm-blooded animals
3. Adaptable to varying environmental temperatures
4. Can become inactive (aestivation/hibernation) during extreme conditions

7.2.1 Morphology

The skin of a frog is smooth and slippery due to mucus, always maintained in a moist condition. The dorsal side is generally olive green with dark irregular spots, while the ventral side is uniformly pale yellow.

Figure 7.1: External features of frog

External Features:

• Body divisible into head and trunk (neck and tail absent)
• Pair of nostrils above the mouth
• Bulged eyes covered by nictitating membrane for protection in water
• Membranous tympanum (ear) on either side of eyes
• Forelimbs and hind limbs for swimming, walking, leaping and burrowing
• Hind limbs larger and more muscular than forelimbs
• Hind limbs end in five digits, forelimbs in four
• Feet have webbed digits for swimming

Sexual Dimorphism: Frogs exhibit differences between males and females. Male frogs can be distinguished by:

• Sound producing vocal sacs
• Copulatory pad on the first digit of fore limbs (absent in females)

7.2.2 Anatomy

The body cavity of frogs accommodates different organ systems with well-developed structures and functions:

Figure 7.2: Diagrammatic representation of internal organs of frog showing complete digestive system

Digestive System

The digestive system consists of alimentary canal and digestive glands:

Alimentary Canal:

1. Mouth opens into buccal cavity
2. Leads to oesophagus through pharynx
3. Oesophagus opens into stomach
4. Stomach continues as intestine, rectum
5. Finally opens outside by the cloaca

Digestive Glands:

• Liver: Secretes bile stored in gall bladder
• Pancreas: Produces pancreatic juice containing digestive enzymes

Digestion Process:

1. Food captured by bilobed tongue
2. Digestion starts by HCl and gastric juices in stomach
3. Partially digested food (chyme) passes to duodenum
4. Duodenum receives bile and pancreatic juices through common bile duct
5. Final digestion occurs in intestine
6. Absorption by villi and microvilli in intestinal wall
7. Undigested waste moves to rectum and passes out through cloaca

Q: Why is the alimentary canal of frogs relatively short compared to herbivores?

A: The alimentary canal of frogs is relatively short because:

1. Frogs are carnivores and meat is easier to digest than plant material
2. Plant material requires more time and longer digestive tracts for cellulose breakdown
3. Carnivores typically have shorter intestines as protein digestion is more efficient
4. The reduced length is sufficient for their dietary needs

Respiratory System

Frogs respire on land and in water by different methods:

Respiratory Organs:

• In water: Skin acts as aquatic respiratory organ (cutaneous respiration)
• On land: Buccal cavity, skin and lungs act as respiratory organs

Pulmonary Respiration: Respiration by lungs. Frogs have a pair of elongated, pink-colored sac-like lungs in the upper trunk region. Air enters through nostrils into buccal cavity, then to lungs.

During aestivation and hibernation, gaseous exchange occurs only through the skin.

Circulatory System

The vascular system of frog is well-developed closed type with both blood vascular and lymphatic systems:

Components:

• Heart: Muscular, three-chambered (2 atria, 1 ventricle)
• Blood vessels: Arteries carry blood from heart, veins return blood
• Blood: Composed of plasma and cells (RBCs, WBCs, platelets)
• Lymphatic system: Lymph, lymph channels and lymph nodes

Special Features:

• Hepatic portal system: Venous connection between liver and intestine
• Renal portal system: Venous connection between kidney and lower body
• RBCs are nucleated and contain hemoglobin

Excretory System

The excretory system eliminates nitrogenous wastes and consists of:

Components:

• Kidneys: Compact, dark red, bean-like structures on both sides of vertebral column
• Ureters: Emerge from kidneys (urinogenital duct in males)
• Cloaca: Common chamber for excretory and reproductive systems
• Urinary bladder: Thin-walled, ventral to rectum, opens into cloaca

Excretion: Frogs excrete urea (ureotelic). Wastes are carried by blood to kidneys where they are separated and excreted.

Nervous System

The system for control and coordination includes both neural system and endocrine glands:

Neural System:

• Central nervous system: Brain and spinal cord
• Peripheral nervous system: Cranial and spinal nerves (10 pairs)
• Autonomic nervous system: Sympathetic and parasympathetic

Brain Structure:

1. Fore-brain: Olfactory lobes, cerebral hemispheres, diencephalon
2. Mid-brain: Pair of optic lobes
3. Hind-brain: Cerebellum and medulla oblongata

Sense Organs:

• Touch: Sensory papillae
• Taste: Taste buds
• Smell: Nasal epithelium
• Vision: Eyes (spherical, simple eyes)
• Hearing: Tympanum with internal ears (also for balance)

Reproductive System

Frogs have well-organized male and female reproductive systems:

Figure 7.3: Male and female reproductive systems of frog

Male Reproductive System:

• Testes: Pair of yellowish ovoid structures adhered to upper kidneys by mesorchium
• Vasa efferentia: 10-12 ducts from testes entering kidneys
• Urinogenital duct: Comes out of kidneys, opens into cloaca

Female Reproductive System:

• Ovaries: Pair near kidneys (no functional connection)
• Oviducts: Pair arising from ovaries, opening into cloaca separately
• A mature female can lay 2500-3000 ova at a time

Reproduction:

• Fertilization is external (in water)
• Development involves larval stage called tadpole
• Tadpole undergoes metamorphosis to form adult

Ecological Importance:

• Eat insects and protect crops
• Maintain ecological balance as important link in food chain
• In some countries, muscular legs are used as food

Chapter Summary

Key Takeaways:

• Cells organize into tissues, organs and organ systems for efficient functioning
• There are four basic types of animal tissues: epithelial, connective, muscular and neural
• The Indian bullfrog (Rana tigrina) is covered by highly vascularized skin with mucous glands
• Frogs respire through skin in water and through lungs on land
• They have a closed circulatory system with three-chambered heart
• Excretory system includes kidneys, ureters and urinary bladder
• Male reproductive system has testes, female has ovaries (can lay 2500-3000 ova)
• Fertilization is external with tadpole stage undergoing metamorphosis
• Frogs are ecologically important as insect controllers and food source

NCERT Solutions

Question 1: Draw a neat diagram of digestive system of frog.

Answer:

The digestive system of frog includes:

1. Mouth and buccal cavity with bilobed tongue
2. Oesophagus leading to stomach
3. Stomach continuing as intestine
4. Rectum opening into cloaca
5. Associated glands: liver with gall bladder and pancreas

Refer to Figure 7.2 in the chapter for detailed diagram.

Question 2: Mention the function of the Ureters in frog.

Answer:

Functions of ureters in frog:

1. In male frogs, ureters act as urinogenital ducts carrying both urine and sperm
2. Transport urine from kidneys to cloaca
3. In females, ureters and oviducts open separately into cloaca

Practice Questions

1. Which of the following is NOT a basic type of animal tissue?

a) Epithelial tissue b) Connective tissue c) Muscular tissue d) Vascular tissue

Correct Answer: d) Vascular tissue

Explanation: The four basic types of animal tissues are epithelial, connective, muscular and neural. Vascular tissue is found in plants, not animals.

2. Frogs respire through all EXCEPT:

a) Skin in water b) Lungs on land c) Gills throughout life d) Buccal cavity on land

Correct Answer: c) Gills throughout life

Explanation: Frogs have gills only in their tadpole stage, not as adults. Adult frogs respire through skin (in water), and lungs, buccal cavity and skin on land.

3. The number of chambers in a frog's heart is:

a) Two b) Three c) Four d) One

Correct Answer: b) Three

Explanation: Frog's heart has three chambers - two atria and one ventricle. This is different from the four-chambered heart of mammals and birds.

1. What are the differences between male and female frogs?

Answer:

Differences between male and female frogs:

• Male frogs have sound producing vocal sacs, females don't
• Males have a copulatory pad on the first digit of fore limbs, absent in females
• Males are generally smaller in size than females
• During breeding season, males develop nuptial pads to grip females

2. Name the four basic types of animal tissues and give one function of each.

Answer:

1. Epithelial tissue: Forms protective coverings and linings of organs
2. Connective tissue: Provides support and connects different tissues/organs
3. Muscular tissue: Responsible for movement and locomotion
4. Neural tissue: Conducts nerve impulses for coordination and control

1. Describe the digestive system of a frog with a labeled diagram.

Answer:

The digestive system of frog consists of:

1. Alimentary Canal:
   • Mouth → Buccal cavity (with bilobed tongue) → Pharynx → Oesophagus → Stomach → Intestine → Rectum → Cloaca → Cloacal aperture
2. Digestive Glands:
   • Liver: Secretes bile which is stored in gall bladder
   • Pancreas: Produces pancreatic juice containing digestive enzymes

Digestive Process:

• Food captured by sticky bilobed tongue
• Digestion begins in stomach by HCl and gastric juices
• Partially digested food (chyme) passes to duodenum
• Bile and pancreatic juices enter duodenum through common bile duct
• Final digestion occurs in intestine
• Absorption by villi and microvilli in intestinal wall
• Undigested waste passes to rectum and out through cloaca

Refer to Figure 7.2 for labeled diagram.

2. Explain the structural organization in animals from cells to organ systems.

Answer:

The structural organization in animals follows this hierarchy:

1. Cells: Basic structural and functional units
   • Perform all basic life functions in unicellular organisms
   • Specialized for specific functions in multicellular organisms
2. Tissues: Groups of similar cells with intercellular substances
   • Four basic types: epithelial, connective, muscular, neural
   • Perform specific coordinated functions
3. Organs: Formed by combination of tissues
   • Example: Heart (all four tissue types)
   • Perform complex functions beyond tissue capabilities
4. Organ Systems: Groups of organs working together
   • Example: Digestive system (mouth, stomach, intestines, etc.)
   • Perform major physiological functions
5. Organism: All systems working in coordination
   • Represents the complete living animal

This organization allows division of labor, specialization, and efficient functioning of the whole organism.

Interactive Flashcards

What are the four basic types of animal tissues?

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The four basic types are:

1. Epithelial tissue
2. Connective tissue
3. Muscular tissue
4. Neural tissue

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Practice Questions

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NCERT Textbook Chapter

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