• Tissue- A group of similar cells which perform same functions.
  • In complex animal, have only 4 type of basis tissues. The tissue are combine in specific proportion and similar pattern to form an organ like lung, heart, kidney etc. When 2 or more organ perform particular function to make system like digestive system, respiratory system etc.
  • Cells, Tissue, Organ and Organ system split up the work in a way that shows division of labour (or worker) and contribute to the survival of the body as a whole.

Organ And Organ System-

  • Organ system present in multicellular organisms.
  • Many similar or different type of tissue combine to form an organ.
  • Organ system display certain discernable trend which referred to the evolutionary trend.
  • Organ- It is a part of body that performs a specific function. ex- heart, lungs, etc.
  • Organ system- It is a group of organs working together to perform related functions. ex-digestive system, circulatory system, etc.

Frog-

Classification and Habitat

  • Frogs belong to the class Amphibia of the phylum Chordata.
  • The common frog species in India is Rana tigrina (Indian bullfrog).
  • Frogs are cold-blooded (poikilothermic), meaning their body temperature changes with the environment.

Adaptations

  1. Camouflage: Frogs can change color to blend in and hide from predators, a phenomenon called mimicry.
  2. Aestivation and Hibernation:
    • Summer sleep (aestivation) protects from extreme heat.
    • Winter sleep (hibernation) helps survive cold conditions.

Morphology (External Features)

  • Skin: Smooth, slippery, moist (contains mucus).
    • Dorsal side: Olive green with dark spots.
    • Ventral side: Pale yellow.
    • Frogs absorb water through their skin; they don’t drink water.
  • Body Structure: Divided into head and trunk. No neck or tail.
  • Eyes: Bulging with a protective nictitating membrane for underwater vision.
  • Ears: A tympanum (membranous ear) helps detect sounds.
  • Limbs:
    • Hind limbs: Larger, muscular, end in 5 webbed digits (help in swimming).
    • Forelimbs: Smaller, end in 4 digits.
  • Sexual Dimorphism:
    • Male frogs have vocal sacs for sound and a copulatory pad on the first digit of forelimbs (absent in females).

Anatomy (Internal Features)

  1. Digestive System:
    • Components: Mouth → Buccal cavity → Pharynx → Esophagus → Stomach → Intestine → Rectum → Cloaca.
    • Digestive Glands:
      • Liver: Produces bile (stored in gall bladder).
      • Pancreas: Secretes digestive enzymes.
    • Food Digestion:
      • Starts in the stomach with gastric juices and HCl.
      • Bile emulsifies fats; pancreatic enzymes digest proteins and carbohydrates.
      • Nutrient absorption occurs in the intestine via villi.
      • Undigested food exits through the cloaca.
  2. Respiratory System:
    • In Water: Respiration occurs through the skin (cutaneous respiration).
    • On Land:
      • Lungs (pulmonary respiration) and buccal cavity.
      • Lungs are sac-like and pink.
  3. Circulatory System:
    • Heart: Three chambers (two atria, one ventricle) enclosed by a pericardium.
    • Blood Composition:
      • RBCs (nucleated, contain hemoglobin), WBCs, and platelets.
      • Blood transports nutrients, gases, and wastes.
    • Portal Systems:
      • Hepatic Portal: Connects liver and intestine.
      • Renal Portal: Connects kidneys and lower body.
  4. Excretory System:
    • Organs:
      • Kidneys (bean-shaped, dark red).
      • Ureters: Transport urine.
      • Cloaca: Common exit for urine, feces, and gametes.
    • Excretory Product: Urea (ureotelic animal).
  5. Nervous System:
    • Divisions:
      • Central: Brain (protected by the cranium) and spinal cord.
      • Peripheral: Cranial and spinal nerves.
      • Autonomic: Sympathetic and parasympathetic systems.
    • Brain Regions:
      • Forebrain (olfactory lobes, cerebral hemispheres).
      • Midbrain (optic lobes).
      • Hindbrain (cerebellum, medulla oblongata).
  6. Sense Organs:
    • Well-developed: Eyes (vision) and tympanum (hearing, balance).
    • Basic: Organs for touch, taste, and smell.

Reproductive System

  • Male:
    • Testes are yellow and connected to kidneys via vasa efferentia.
    • Sperms are expelled through the cloaca.
  • Female:
    • Ovaries release 2500–3000 eggs at a time.
    • Eggs are fertilized externally in water.
  • Development:
    • Tadpoles undergo metamorphosis to become adult frogs.

Ecological Role

  • Frogs control insect populations, protecting crops.
  • They serve as an important link in the food chain.
  • In some countries, frog legs are used as food.

Key Points for Competitive Exams

  • Frogs exhibit dual respiration (skin and lungs).
  • Unique features include nucleated RBCs, external fertilization, and poikilothermy.
  • They have both hepatic and renal portal systems.
  • Understand differences between aestivation, hibernation, and mimicry.

These all are the notes of chapter 7. And important questions are below HERE. *#THANKS FOR VISITING, VISIT AGAIN #* 😊

1. What is a tissue?

Answer:
A tissue is a group of similar cells that work together to perform a specific function.

2. How are tissues organized in the body?

Answer:
Tissues combine in specific proportions and patterns to form organs (like the heart or lungs).
Several organs work together to form an organ system (like the digestive or respiratory system).

3. What is the role of tissues, organs, and organ systems in the body?

Answer:
Tissues, organs, and organ systems divide the body’s work. Each performs specific tasks, contributing to the survival and proper functioning of the body as a whole. This is called division of labor.

4. What is an organ?

Answer:
An organ is a part of the body made up of tissues that work together to perform a specific function.
Example: The heart pumps blood, and the lungs help in breathing.

5. What is an organ system?

Answer:
An organ system is a group of organs that work together to perform related functions.
Example:

  • The digestive system breaks down food.
  • The respiratory system helps in breathing.

6. What are the main characteristics of frogs?

Answer:

  • Frogs belong to the class Amphibia and are cold-blooded (poikilothermic).
  • The common frog species in India is Rana tigrina (Indian bullfrog).
  • Frogs can live on land and in water.
  • They adapt to survive through aestivation (summer sleep) and hibernation (winter sleep).

7. What are the external features of a frog?

Answer:

  • Skin: Smooth, slippery, and moist (helps absorb water).
  • Body: Divided into head and trunk, no neck or tail.
  • Eyes: Bulging with a protective membrane for underwater vision.
  • Limbs:
    • Hind limbs: Larger with 5 webbed toes (for swimming).
    • Forelimbs: Smaller with 4 toes.

8. How can you differentiate male and female frogs?

Answer:

  • Male frogs have vocal sacs for producing sound and a copulatory pad on the first digit of their forelimbs.
  • Females lack these features.

9. What are the main adaptations of frogs?

Answer:

  • Camouflage: Frogs change their skin color to blend with the environment (mimicry).
  • Aestivation: Frogs sleep during summer to avoid heat.
  • Hibernation: Frogs sleep during winter to survive cold.

10. How does the digestive system of a frog work?

Answer:

  • Food path: Mouth → Buccal cavity → Pharynx → Esophagus → Stomach → Intestine → Cloaca.
  • Liver produces bile (stored in the gall bladder) to digest fats.
  • Pancreas produces enzymes to digest proteins and carbohydrates.
  • Nutrient absorption happens in the intestine.
  • Undigested food exits through the cloaca.

11. How do frogs respire?

Answer:

  • In water: Frogs use their skin (cutaneous respiration).
  • On land: Frogs use their lungs (pulmonary respiration) and buccal cavity.
  • Lungs are sac-like and pink in color.

12. Describe the circulatory system of a frog.

Answer:

  • Frogs have a three-chambered heart (two atria and one ventricle).
  • Blood contains nucleated RBCs, WBCs, and platelets.
  • Portal systems:
    • Hepatic Portal: Connects the liver and intestine.
    • Renal Portal: Connects kidneys and the lower body.

13. How do frogs excrete waste?

Answer:

  • Main organs: Kidneys, ureters, and cloaca.
  • Frogs excrete urea (they are ureotelic).
  • The cloaca is a common exit for urine, feces, and reproductive cells.

14. Describe the nervous system of a frog.

Answer:
The frog’s nervous system has three parts:

  • Central Nervous System (CNS): Brain and spinal cord.
  • Peripheral Nervous System (PNS): Cranial and spinal nerves.
  • Autonomic Nervous System: Controls involuntary actions.
    Brain regions:
  • Forebrain: For smell and thinking.
  • Midbrain: For vision.
  • Hindbrain: For balance and coordination.

15. How do frogs reproduce?

Answer:

  • Male frogs have testes, and female frogs have ovaries.
  • Eggs and sperms are released into water, where fertilization occurs externally.
  • Tadpoles hatch from eggs and undergo metamorphosis to become adult frogs.

16. What is the ecological role of frogs?

Answer:

  • Frogs control insect populations, protecting crops.
  • They are an important link in the food chain.
  • In some countries, frog legs are used as food.

17. What are the key differences between aestivation, hibernation, and mimicry?

Answer:

  • Aestivation: Summer sleep to avoid heat.
  • Hibernation: Winter sleep to survive cold.
  • Mimicry: Changing appearance to blend with surroundings and hide from predators.

18. What makes the circulatory system of frogs unique?

Answer:

  • Frogs have nucleated RBCs (unlike mammals).
  • They have both hepatic and renal portal systems.

19. What is the significance of the frog’s skin?

Answer:

  • Frog skin is moist and slippery due to mucus.
  • It helps in cutaneous respiration (breathing through the skin).
  • Frogs absorb water through their skin and do not drink water.

20. Why is the study of frogs important?

Answer:

  • Frogs are indicators of environmental health because they are sensitive to changes in their habitat.
  • Understanding their anatomy helps in comparative studies of other vertebrates.