Biological Processes

Biological processes are the various activities that support the functioning, growth, and maintenance of life. These processes control essential functions such as nutrition, respiration, transport, and excretion within the body.

 

Nutrition

Nutrition : refers to the process of ingesting food, absorbing the digested food, and utilizing it for the body's needs. Based on nutrition, organisms are classified into two main categories:

Autotrophic Nutrition :

Autotrophic organisms produce their own food from simple substances like sunlight, water, and carbon dioxide. This process is carried out mainly by green plants and certain bacteria.

Example: Green plants, some bacteria.

Heterotrophic Nutrition :

Heterotrophic organisms cannot produce their own food and depend on other organisms for nourishment. This type of nutrition is found in humans and other animals.

Example: Humans, lions, other animals.

Types of Heterotrophic Nutrition:

 

Type	Description	Example
Holozoic Nutrition	Organisms ingest complete food and digest it internally.	Humans, lions, elephants, other animals
Saprophytic Nutrition	Organisms live on decaying organic matter and absorb nutrients.	Fungi, bacteria, mold
Parasitic Nutrition	Organisms live on or inside a host, extracting nutrients without harming it.	Mistletoe, lice, tapeworms

 

Photosynthesis

Photosynthesis is the process by which autotrophic organisms, like green plants, make their food (glucose) using carbon dioxide and water in the presence of sunlight.

Required raw materials for photosynthesis:

• Sunlight
• Chlorophyll
• Carbon dioxide (absorbed from the atmosphere)
• Water (absorbed by the roots from the soil)

Stages of Photosynthesis:

• Chlorophyll absorbs sunlight.
• Solar energy is converted into chemical energy, splitting water molecules into hydrogen and oxygen.
• Carbon dioxide is used to produce carbohydrates (glucose).

Stomata

Stomata are microscopic pores on the surface of leaves that play a crucial role in gas exchange and transpiration.

Functions of Stomata:

• Gas exchange (e.g., carbon dioxide and oxygen).
• Evaporation of water vapor.

Nutrition in Amoeba

Amoeba is a protozoan that ingests food externally:

• It engulfs food particles using pseudopodia.
• The food is stored in a food vacuole, where complex substances are broken down into simpler ones.
• Undigested material is expelled from the cell surface.

Human Nutrition

Human nutrition takes place in the alimentary canal, a long tube that extends from the mouth to the anus. It involves ingestion, digestion, absorption, and excretion of food.

The Alimentary Canal:

Mouth:

• Ingestion of food and chewing.
• Tongue helps in mixing food with saliva.
• Teeth break food into smaller pieces.
• Salivary glands secrete saliva containing amylase to digest starch.

Esophagus

• The esophagus carries food from the mouth to the stomach. It undergoes peristaltic movement, which involves the contraction and relaxation of the muscles in the esophagus, pushing the food forward.

Stomach

• Gastric glands (जठर ग्रंथियाँ) secrete digestive enzymes (like pepsin (पेप्सिन)) and hydrochloric acid (HCl).
• Pepsin digests proteins.
• Hydrochloric acid creates an acidic environment for digestion and protects the inner lining of the stomach.

Small Intestine

• Final digestion of food takes place here.
• Digestive juices from the liver (यकृत) and pancreas (अग्नाशय) are secreted.
• Bile emulsifies fats.
• Pancreatic juice contains amylase (ऐमिलेज), trypsin (ट्रिप्सिन), and lipase (लाइपेज), which digest starch, proteins, and fats respectively.

Large Intestine

• The large intestine absorbs water and expels undigested waste from the body through the anus.
• Villi – These are tiny finger-like projections located on the inner walls of the small intestine, which increase the surface area for absorption.

Respiration

The food material consumed during the process of nutrition is utilized in the cells to produce energy. This process is known as cellular respiration, through which cells obtain energy.

1. Breakdown of Glucose

• Glucose (C₆H₁₂O₆) is broken down into pyruvate, resulting in energy production.

This process occurs in two ways:

i. Aerobic Respiration

• Occurs in the presence of oxygen.
• Glucose is completely oxidized.
• Products: Carbon dioxide (CO₂) + Water (H₂O) + Energy (36 ATP)
• Takes place in the mitochondria.
• Example: Humans.

ii. Anaerobic Respiration

• Occurs in the absence of oxygen.
• Glucose is partially oxidized.
• Products:
  Ethanol + Carbon dioxide (CO₂) + Energy (2 ATP) – Occurs in yeast.
  Lactic acid + Energy – Occurs in human muscle cells during oxygen deficiency.
• Takes place in the cytoplasm.
• Examples: Yeast, human muscle cells.

Human Respiratory System

Pathway:

Nostrils → Pharynx → Larynx → Trachea → Bronchi → Lungs → Alveoli → Blood Vessels

The human respiratory system is responsible for supplying oxygen to the body and expelling carbon dioxide. It consists of various organs and structures involved in breathing:

1. Nostrils

• The first stage of respiration begins at the nostrils, which are the openings of the nose. Air enters the respiratory system through the nostrils. The air is filtered, warmed, and moistened here to ensure that the air reaching the lungs is clean and of suitable temperature and humidity.

2. Pharynx

• From the nostrils, air passes into the pharynx. This is a shared passage for both the respiratory and digestive systems, located at the back of the throat. It connects the nasal cavity to the larynx and esophagus.
  

3. Larynx (Voice Box)

• The air moves from the pharynx into the larynx, also known as the voice box. The larynx helps in the production of sound and directs air into the trachea. The epiglottis, a flap-like structure in the larynx, prevents food from entering the trachea by closing during swallowing.

4. Trachea (Windpipe)

• The larynx leads to the trachea, a long, rigid tube made up of cartilage rings. These rings keep the airway open and allow air to pass smoothly to the lungs.

5. Bronchi

• The trachea divides into two major bronchi before entering the lungs. Each bronchus leads into one lung, allowing air to flow into the lungs.

6. Lungs

• The bronchi branch into smaller tubes called bronchioles within the lungs. The bronchioles further divide and end in small air sacs known as alveoli, where gas exchange takes place.

7. Alveoli

• Alveoli are small, balloon-like structures at the end of bronchioles. These tiny air sacs are where the exchange of oxygen and carbon dioxide occurs. Oxygen from the air diffuses into the blood, while carbon dioxide from the blood diffuses into the alveoli to be exhaled.

8. Blood Vessels

 

• Capillaries surround the alveoli, allowing the exchange of gases. Oxygen enters the bloodstream, and carbon dioxide is removed, facilitating efficient respiration and maintaining oxygen supply to body tissues.
• Respiratory Process

 

Process	Description
Inhalation	1. The lungs expand. 2. The volume of the thoracic cavity increases. 3. Air pressure decreases. 4. Air from the environment enters the lungs. 5. Muscles around the ribs contract and the chest moves outward.
Exhalation	1. The lungs return to their normal size. 2. The muscles around the ribs relax. 3. The chest wall is pulled inward. 4. The pressure in the cavity increases. 5. CO₂-rich air exits the lungs.

 

Gas Exchange

Oxygen (O₂) Entry:

• Alveolus → Blood (Oxygen enters the blood)
• Hemoglobin in the blood + O₂ → Oxyhemoglobin (HbO₂) is formed.

Carbon Dioxide (CO₂) Removal:

• Blood → Alveolus (CO₂ moves from the blood to the alveoli)
• Alveolus → Outside (CO₂ exits through the lungs)

Human Circulatory System

The circulatory system supplies nutrients, oxygen, and other essential substances to all body parts and tissues, and removes waste products (like CO₂, urea). This system consists of the heart, blood vessels, and blood.

 

1. Heart

Function of the Heart: The heart works like a pump, sending blood to different parts of the body. The function of the heart occurs in a cyclical process, called the cardiac cycle, which can be understood in four main stages:

1. Blood Arrival:

• Right Atrium: Oxygen-poor blood (rich in CO₂) enters the right atrium through veins and vena cava.
• Left Atrium: Oxygen-rich blood (enriched with O₂) enters the left atrium through the pulmonary veins from the lungs.

2. Blood Flow from Atria to Ventricles:

• Right Atrium → Right Ventricle: Blood flows from the right atrium to the right ventricle.
• Left Atrium → Left Ventricle: Blood flows from the left atrium to the left ventricle.
• Valves (such as tricuspid and mitral valves) ensure that the blood flows in one direction and does not flow backward.

3. Pumping of Blood:

• Right Ventricle → Lungs: The right ventricle pumps oxygen-poor blood to the lungs for oxygenation.
• Left Ventricle → Rest of the Body: The left ventricle pumps oxygen-rich blood to the rest of the body to supply oxygen to the organs.

4. Blood Return:

• Oxygenated blood from the lungs returns to the left atrium through veins.
• Oxygen-poor blood from the body returns to the right atrium through veins.
• This cyclical process continues, ensuring a constant supply of oxygen and nutrients to the body.

2. Blood Vessels

 

1. Artery:

• Carries blood from the heart to the organs.
• The walls of arteries are thick.
• They can withstand high pressure of blood.
• Arteries do not have valves, as blood flows in one direction.

2. Vein:

• Carries blood back to the heart from the organs.
• Veins have valves.
• Valves help in the one-way flow of blood.
• Veins have thinner walls and lower blood pressure.

3. Blood

Blood consists of four main components:

1. Red Blood Cells (RBCs):

Function: RBCs primarily transport oxygen (O₂) and carbon dioxide (CO₂). They carry oxygen from the lungs to the organs and return CO₂ from the organs to the lungs for exhalation.

Characteristics:

• RBCs contain a red pigment called hemoglobin, which binds to oxygen to form oxyhemoglobin.
• They lack a nucleus, providing more space for oxygen transport.
• The lifespan of RBCs is approximately 120 days, after which they are destroyed in the liver and spleen.

2. White Blood Cells (WBCs):

Function: WBCs are part of the immune system and fight infections. They destroy foreign invaders like bacteria, viruses, and other pathogens.

Characteristics:

• WBCs have a nucleus and are larger than RBCs.
• There are different types of WBCs, such as neutrophils, lymphocytes, and monocytes, each with specific functions.
• Their lifespan can range from a few hours to several years, depending on the type.

3. Platelets:

Function: Platelets help in blood clotting. When a wound occurs, platelets gather at the site and form a clot to stop bleeding.

Characteristics:

• Platelets are very small and are not full cells but fragments of cells.
• Their lifespan is about 7 to 10 days.
• The process of clot formation is called "coagulation," and it involves platelets and other blood proteins like fibrin.

4. Plasma:

Function: Plasma is the liquid part of the blood, transporting nutrients, hormones, and waste products to various parts of the body.

Characteristics:

• Plasma is made up of about 90% water, keeping it fluid.
• It contains proteins like albumin, globulin, and fibrinogen.
• Plasma also carries minerals like sodium, potassium, calcium, and bicarbonate, aiding in biological functions.
• It transports hormones, antibodies, and waste products like urea, ammonia, and CO₂.

Function of Blood:

The primary function of blood is to transport nutrients, oxygen, and hormones to all body parts and to remove waste products (such as CO₂ and urea) from the body. This transport system plays a crucial role in maintaining homeostasis in the body.

 

Human Excretory System

The excretory system is responsible for eliminating waste products (such as urea) produced by the body. The main organs involved in this system are:

 

1. Kidneys:

• The kidneys filter nitrogenous waste products to produce urine. The structural and functional unit of the kidney is the nephron. This is a complex process involving filtration, reabsorption, and secretion.

2. Ureter:

• The ureters transport urine from the kidneys to the bladder.

 

3. Bladder:

• The bladder temporarily stores urine.

4. Urethra:

• The urethra is the tube through which urine is expelled from the bladder.

Nephron Functions:

The nephron is the structural and functional unit of the kidney. Each kidney contains approximately 1 million nephrons. Their primary function is to remove waste products from the body and filter toxins from the blood to form urine. The structure and function of the nephron can be divided into three main processes:

1. Filtration:

Location: This process takes place in the glomerulus and Bowman's capsule.

Function:

• When blood enters the nephron through the renal artery, it passes through the small blood vessels (capillaries) in the glomerulus.
• Due to high pressure, plasma from the blood (which contains water, minerals, glucose, amino acids, and waste products such as urea, creatinine, etc.) is filtered into the Bowman's capsule.
• This initial filtration is called Initial Filtrate, which amounts to around 180 liters per day.

2. Reabsorption:

Location: This process occurs in the proximal convoluted tubule, Loop of Henle, and distal convoluted tubule.

Function:

• Useful substances in the initial filtrate (such as water, glucose, amino acids, and some salts) are reabsorbed back into the blood.
• Most of the reabsorption occurs in the proximal convoluted tubule, where glucose, amino acids, and water are primarily reabsorbed.
• The Loop of Henle plays a crucial role in reabsorbing water and salts, helping maintain the balance of water and sodium in the body.
• The distal convoluted tubule reabsorbs some additional salts and water.

3. Tubular Secretion:

Location: This process occurs in the distal convoluted tubule and collecting duct.

Function:

• In this phase, additional substances like urea, excess water, and extra salts are actively secreted from the blood into the tubules.
• Urea, potassium, hydrogen ions, and substances like drugs that may be in excess in the blood are transported into the tubules.
• This completes the final stage of urine formation, ensuring that the balance of substances is maintained.

4. Urine Formation:

• After all these processes, the substances remaining in the nephron are termed as urine.
• The urine collects in the collecting duct and is then transported through the ureter to the bladder.

Excretion in Plants:

• Transpiration: Plants get rid of excess water through the process of transpiration.
• Many waste products in plants are stored in vacuoles.
• Other waste products, like resins and gums, are stored in the old xylem tissue.
• Plants also excrete some waste products into the surrounding soil.