Introduction to Life Processes

The video introduces Chapter 5, “Life Processes,” in Biology, noting it’s an easy chapter with basic concepts like digestion and respiration that students might have learned in earlier classes, now to be explored in more depth.

Life processes are defined as **basic functions performed by living organisms for their survival and body maintenance**. These processes help maintain life and allow living organisms to survive.

All living things perform certain life processes, including:

• Growth
• Excretion
• Respiration
• Circulation

The chapter will discuss specific life processes in depth, such as:

• Nutrition (broader than just digestion)
• Respiration (focusing on cellular respiration beyond just breathing)
• Transportation (earlier known as circulatory system)
• Excretion (removal of body waste)

Nutrition

Nutrition is the process of **taking food by an organism and its utilization by the body for life processes**. It involves consuming food for growth, maintenance, and survival. The video will cover nutrition in human body, plants, and animals.

Modes of Nutrition

There are two main modes of nutrition:

1. Autotrophic Nutrition
2. Heterotrophic Nutrition

Autotrophic Nutrition

In autotrophic nutrition, organisms **prepare their own food** from simple inorganic substances like carbon dioxide and water, in the presence of sunlight and chlorophyll. This process is known as **photosynthesis**.

Examples of autotrophs include **all green plants** (because they perform photosynthesis due to chlorophyll) and **some bacteria**.

Photosynthesis

Photosynthesis is the process by which **plants prepare food by using carbon dioxide and water in the presence of sunlight and chlorophyll**. Both sunlight and chlorophyll are essential for this process. The food prepared is **carbohydrates**, which are stored in the form of **starch**. **Oxygen is released as a byproduct** in this process; it is not the main food.

The chemical equation for photosynthesis is (simplified, balancing not detailed in source):
Solar Energy + Carbon Dioxide (CO2) + Water (H2O) + Chlorophyll → Glucose (C6H12O6) + Oxygen (O2)

Raw materials for photosynthesis are:

• Sunlight: Directly taken from the sun.
• Chlorophyll: Absorbs sunlight.
• Carbon Dioxide (CO2): Enters through **stomata**.
• Water (H2O): Along with dissolved minerals (like nitrogen, phosphorus), taken up by the **roots** from the soil.

The **site of photosynthesis** is the **chloroplasts in the leaves**, which contain the green pigment chlorophyll.

Main events of photosynthesis include:

• Absorption of light energy by chlorophyll.
• Conversion of light energy into chemical energy and splitting of water into hydrogen and oxygen.
• Reduction of CO2 to carbohydrates.

Stomata are tiny pores present in the leaves through which **exchange of gases** (CO2 in, O2 out) takes place. Each stoma has a pair of **guard cells** that control its opening and closing. When water enters guard cells, they swell and open the pores; when they lose water, they shrink and close the pores.

Functions of stomata include:

• Exchange of gases (O2 and CO2).
• Loss of large amount of water vapors during **transpiration**.

Heterotrophic Nutrition

In heterotrophic nutrition, organisms **get their food directly or indirectly from plants**. This mode of nutrition applies to all animals (including humans), fungi, and some bacteria.

There are three main types of heterotrophic nutrition:

1. Saprotrophic Nutrition
2. Parasitic Nutrition
3. Holozoic Nutrition

Saprotrophic Nutrition

Organisms obtain food from **dead and decaying organisms**. Examples include mushrooms, bread mold, yeast, and some bacteria.

Parasitic Nutrition

Organisms obtain food from **living organisms (hosts) without killing them**. Examples are lice, ticks, leeches, roundworms, tapeworms, and Cuscuta (Amarbel).

Holozoic Nutrition

Organisms **take food directly and then digest and absorb it**. Humans fall into this category. Examples include amoeba, paramecium, birds, fishes, and humans.

Amoeba, a unicellular animal living in water, takes food by forming **finger-like projections called pseudopodia** and forms a food vacuole. Food is digested and absorbed inside the food vacuole, and undigested food is sent out through the cell surface.

Nutrition in Human Beings

Human nutrition involves five steps:

1. Ingestion: Intaking food.
2. Digestion: Breakdown of complex food into simpler ones.
3. Absorption: Movement of digested food.
4. Assimilation: Utilization of absorbed food (energy production).
5. Egestion: Removal of waste products.

Human Digestive System

The main organs of the human digestive system are:

• Mouth
• Oesophagus (Food Pipe)
• Stomach
• Small Intestine
• Large Intestine
• Anus

Glands that secrete juices and enzymes to aid digestion include:

• Salivary Glands
• Gastric Glands
• Liver
• Pancreas
• Intestinal Glands

Process of Digestion

• In the Mouth: Food is broken down by teeth and mixed with **saliva** from **salivary glands**. Saliva contains the enzyme **salivary amylase**, which converts **starch into sugar**.
• In the Stomach: Food passes through the oesophagus into the stomach. **Gastric glands** in the stomach produce **gastric juice**, containing:
  • Pepsin: Breaks down **protein**.
  • Hydrochloric Acid (HCl): Makes the medium acidic, aiding pepsin’s action.
  • Mucus: Protects the stomach walls from the acid.
• In the Small Intestine: The food then passes into the small intestine. This is the **site of complete digestion** of carbohydrates, proteins, and fats.
  • The **Liver** secretes **bile juice**, which breaks down fats into smaller globules (emulsification).
  • The **Pancreas** secretes **pancreatic juice**, containing enzymes like:
    • Trypsin: Further breaks down **proteins**.
    • Lipase: Breaks down **fats**.
  • The walls of the small intestine produce **intestinal juice**. Its enzymes convert:
    • Carbohydrates into glucose.
    • Fats into fatty acids and glycerol.
    • Proteins into amino acids.
  • The small intestine has **finger-like projections called villi**, which increase the surface area for the absorption of digested food. The absorbed food is then transported by blood to all body cells.
• In the Large Intestine: The undigested food passes into the large intestine. Here, **water is absorbed**, and the waste material is removed from the body through the **anus**.

Respiration

Respiration involves two main aspects:

• Gaseous Exchange (Breathing): Intake of oxygen from the atmosphere and release of carbon dioxide.
• Breakdown of Simple Food to Release Energy (Cellular Respiration): This is the primary focus, where digested food is broken down to release energy in the form of **ATP** molecules.

Types of Respiration

Based on oxygen requirement, respiration is of two types:

• Aerobic Respiration: Occurs in the **presence of oxygen**.
• Anaerobic Respiration: Occurs in the **absence of oxygen**.

Breakdown of Glucose (Cellular Respiration Pathways)

Glucose (a 6-carbon molecule) is broken down via various pathways:

1. First Step (Common to all): In the **cytoplasm** (semi-liquid, jelly-like material in the cell), glucose is broken down into **pyruvic acid** (a 3-carbon molecule). This step also produces some energy.
2. Subsequent Steps (Depend on Oxygen Availability):
   • In Absence of Oxygen (Anaerobic): Occurs in organisms like **yeast**. Products are **ethanol**, **carbon dioxide**, and **energy**.
   • In Lack of Oxygen (Anaerobic): Occurs in **muscle cells** (e.g., during intense exercise leading to cramps). Product is **lactic acid** (a 3-carbon molecule) and **energy**.
   • In Presence of Oxygen (Aerobic): Occurs in **mitochondria** (powerhouse of the cell). Products are **carbon dioxide**, **water**, and a **larger amount of energy**.

The energy released during respiration is used to make and store **ATP molecules** (Adenosine Triphosphate). When cells need energy, ATP molecules mix with water to release it.

Difference between Aerobic and Anaerobic Respiration

• Presence/Absence of Oxygen: Aerobic occurs with O2, Anaerobic occurs without O2.
• Site of Occurrence: Aerobic in Mitochondria (and cytoplasm for first step), Anaerobic in Cytoplasm.
• End Products: Aerobic produces CO2 and H2O; Anaerobic produces Alcohol (ethanol) and Lactic Acid.
• Energy Production: Aerobic produces **more amount of energy**; Anaerobic produces **less amount of energy**.

Human Respiratory System

Main organs of the respiratory system include:

• Nasal Cavity (Nostrils): Air intake and filtration by fine hairs and mucus.
• Pharynx: Common area for both air and food passage.
• Larynx (Voice Box): Responsible for voice production.
• Trachea (Windpipe): Air passage, supported by **rings of cartilage** to prevent collapse.
• Bronchi: Trachea divides into two bronchi leading to each lung.
• Bronchioles: Bronchi further divide into smaller tubes.
• Alveoli: Tiny **balloon-like structures** at the end of bronchioles in the lungs; **site of gas exchange**.

The **alveoli** are richly supplied with blood and are where the **exchange of oxygen and carbon dioxide occurs**. This exchange happens through **diffusion**, as gases move from an area of high concentration to low concentration. Blood brings CO2 to the alveoli for release, and oxygen from the alveolar air is taken up by the blood to be transported to all body cells.

The lungs always contain a residual volume of air during breathing to allow sufficient time for gas exchange.

The respiratory pigment **hemoglobin**, present in red blood cells, carries oxygen from the lungs to different body tissues. Low hemoglobin can affect breathing.

Mechanism of Breathing

• When we breathe in: Muscles of the **diaphragm contract and move downward**, and the **chest cavity expands**, allowing air to enter the lungs.
• When we breathe out: Muscles of the **diaphragm relax and move upward**, and the **chest cavity contracts**, pushing air out of the lungs.

Aquatic organisms use dissolved oxygen from water for respiration.

Respiration in Plants

Plant respiration is simpler than in animals. Gaseous exchange occurs through:

• Stomata in leaves.
• Lenticels in stems.
• General surface of **roots**.

Transportation

Human beings, like other multicellular organisms, need a regular supply of food, oxygen, etc. This function is performed by the **circulatory system** or **transport system**.

The circulatory system in humans consists of:

• Heart: The pumping organ.
• Blood Vessels: Arteries, Veins, and Capillaries.
• Circulatory Medium: Blood and Lymph.

Blood Vessels

• Arteries:
  • Carry **pure (oxygenated) blood** from the heart to all parts of the body.
  • Have **thick walls**.
  • **Do not have valves**.
• Veins:
  • Carry **impure (deoxygenated) blood** from all parts of the body back to the heart.
  • Have **thin walls**.
  • **Have valves** to prevent backward flow of blood.
• Capillaries:
  • Very **narrow blood vessels** that **connect arteries and veins**.
  • Site of exchange of food, water, oxygen, CO2, etc., between blood and cells.

Circulatory Medium

• Blood: Transports food, oxygen, and waste products. It consists of:
  • Plasma: Liquid component that transports food, water, CO2, nitrogenous waste.
  • Red Blood Cells (RBCs): Transport **oxygen** (due to hemoglobin).
  • White Blood Cells (WBCs): Kill harmful microbes and protect the body.
  • Platelets: Help in **blood clotting** to prevent blood loss during injury.
• Lymph: A **colorless liquid** formed from **plasma that leaks out from the pores of capillaries**. It is similar to plasma but contains less protein and **no red blood cells**.
  • Transports digested fat and drains excess fluid from intercellular spaces back into the blood.
  • Contains lymphocytes which kill germs and protect the body.

Heart

The heart is a **muscular organ that pumps blood to all parts of the body**.

• It has **four chambers**:
  • Upper chambers are called **Atria** (singular: Atrium).
  • Lower chambers are called **Ventricles**.
• The **right and left chambers are separated by a septum**, which prevents the mixing of oxygenated and deoxygenated blood.
• Valves are present between atria and ventricles to prevent backward flow of blood.
• The **right side of the heart** contains **deoxygenated (impure) blood**.
• The **left side of the heart** contains **oxygenated (pure) blood**. (Mnemonic: LORD – Left Oxygenated, Right Deoxygenated)

Working of the Heart (Blood Circulation)

The process of blood circulation involves:

1. Deoxygenated blood from the upper body enters the **right atrium** via the **superior vena cava**, and from the lower body via the **inferior vena cava**.
2. From the right atrium, blood flows through valves into the **right ventricle**.
3. The right ventricle pumps this deoxygenated blood into the **pulmonary artery**, which carries it to the **lungs** for oxygenation.
4. Oxygenated blood returns from the lungs to the **left atrium** via the **pulmonary vein**.
5. From the left atrium, blood, 48].

   Different organisms have varying heart chambers based on their energy needs and body temperature regulation:

   • Mammals and Birds: **Four chambers**, separated septum to prevent mixing of oxygenated/deoxygenated blood. This is necessary to maintain their body temperature, requiring more energy.
   • Amphibians and Reptiles: **Three chambers**, allowing some mixing of blood, as they do not need to maintain a constant body temperature (their body temperature is same as surrounding).
   • Fishes: **Two chambers**. Blood is oxygenated in the **gills**.

Transportation in Plants

Transportation of materials like food, water, and minerals in plants occurs through **conducting tissues**:

• Xylem
• Phloem

Xylem

Xylem transports **water and minerals from the roots to all parts of the plant**. It consists of xylem vessels and tracheids.

Water and minerals enter the roots by **diffusion** (movement from high to low concentration). The upward movement of water and minerals (against gravity) is primarily aided by two forces:

• Transpiration (Suction Force): The loss of water in the form of vapors from the aerial parts of the plant (leaves, stem, flowers) creates a suction force that pulls water upwards. This happens mainly during the daytime.
• Root Pressure: At night, when transpiration is low, roots continue to absorb water, creating pressure that pushes water up the xylem.

Xylem cells are dead cells.

Phloem

Phloem transports **food from the leaves (where it’s produced) to other parts of the plant**. This process is called **translocation**.

Phloem consists of sieve tubes and companion cells. Phloem cells are living cells.

Food from leaves is transferred to phloem (sometimes involving xylem) with the energy of ATP molecules. Due to **osmotic pressure** (movement of solvent from low solute concentration to high solute concentration across a semi-permeable membrane), water enters the phloem, helping in the transport of food throughout the plant. This allows for both upward and downward movement of food.

Excretion

Excretion is the process by which **waste products produced during metabolic activities are removed from the body**.

• In Unicellular Organisms: Waste products are removed from cells into the surroundings by **diffusion**.
• In Multicellular Organisms: Waste products are removed through **specialized organs**.

Excretion in Human Beings

The human excretory or urinary system consists of:

• A pair of **Kidneys** (excretory organs, located in the abdomen on either side of the backbone).
• A pair of **Ureters** (tubes that drain urine from kidneys to bladder).
• A **Urinary Bladder** (where urine is stored).
• A **Urethra** (channel for urine to exit the body).

Nephron (Filtering Unit of Kidney)

Each kidney has a large number of basic filtration units called **nephrons**.

Structure of a Nephron:

• A **cup-like structure called Bowman’s Capsule**.
• Inside the Bowman’s Capsule, there is a **bundle of capillaries called Glomerulus**.
• The Bowman’s Capsule leads into a **tubular part** (including the Loop of Henle).
• The tubular part terminates into a **collecting duct**.

Process of Urine Formation:

1. The **renal artery** brings oxygenated blood (containing nitrogenous waste like urea, uric acid) to the kidney.
2. Blood gets **filtered through the glomerulus** in the Bowman’s Capsule.
3. This **filtrate enters the tubular part** of the nephron.
4. As the filtrate moves down the tubular part, **glucose, amino acids, salts, and excess water are selectively reabsorbed** by the blood vessels surrounding these tubules. This ensures useful substances are returned to the body.
5. The fluid remaining in the tubular part is now **urine**, which gets collected in the collecting ducts of the nephrons.
6. These collecting ducts combine to form the **ureter**, which drains the urine into the urinary bladder.
7. Urine is stored in the urinary bladder until it is passed out through the urethra.

Excretion in Plants

Plants do not have a specialized excretory system and remove waste in various ways:

• **Gaseous waste products** (like oxygen from respiration) are removed through **stomata** in leaves.
• **Excess water** is removed through stomata via **transpiration**.
• Some waste products are **stored in leaves** and removed when the leaves dry and fall off.
• Some waste products like **gums and resins are stored in old xylem cells**.
• Some waste products are removed through the **roots** into the soil.