Life processes are the fundamental activities performed by living organisms to maintain and sustain life. These processes are essential for survival and include all the basic functions that keep an organism alive and healthy.

The major life processes include:

• Nutrition
• Respiration
• Transportation / Circulation
• Excretion
• Control and Coordination
• Reproduction (though not always covered under basic 'maintenance' processes for an individual's survival)

Photosynthesis is the process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll, carbon dioxide, and water. It is the primary way energy enters most ecosystems.

Balanced Chemical Equation:

$6CO_2 (Carbon\ Dioxide) + 6H_2O (Water) \xrightarrow{\text{Sunlight, Chlorophyll}} C_6H_{12}O_6 (Glucose) + 6O_2 (Oxygen)$

Raw materials required:

• Carbon dioxide ($CO_2$)
• Water ($H_2O$)
• Sunlight (energy source)
• Chlorophyll (pigment that absorbs light energy)

The human digestive system is a long tube called the alimentary canal, along with associated glands. The pathway of food is:

1. Mouth: Food is ingested, chewed (mechanical digestion), and mixed with saliva. Salivary amylase in saliva begins starch digestion.
2. Pharynx: Common passage for food and air.
3. Esophagus (Food Pipe): Food moves down to the stomach by peristaltic movements (rhythmic contractions and relaxations of muscles).
4. Stomach: Muscular bag. Gastric glands secrete:
   • Hydrochloric acid (HCl): Kills germs, provides acidic medium for enzyme action.
   • Pepsin: Digests proteins.
   • Mucus: Protects stomach lining from acid.
5. Small Intestine: The longest part of the alimentary canal. Site of complete digestion and absorption.
   • Receives bile from the liver (emulsifies fats).
   • Receives pancreatic juice from the pancreas (contains amylase for carbohydrates, trypsin for proteins, lipase for fats).
   • Intestinal walls secrete intestinal juice.
   • Inner lining has finger-like projections called villi, which increase surface area for absorption of digested food.
6. Large Intestine: Absorbs excess water from the undigested food.
7. Anus: Undigested waste is egested from the body.

Plants respire by exchanging gases (oxygen and carbon dioxide) with the atmosphere. Unlike animals, plants do not have specialized respiratory organs like lungs. Gaseous exchange in plants occurs through diffusion across various surfaces.

The structures involved in gaseous exchange in plants are:

• Stomata: Tiny pores present on the surface of leaves, primarily on the lower epidermis. They open and close to regulate the exchange of gases ($CO_2$ intake for photosynthesis, $O_2$ release, and $O_2$ intake for respiration, $CO_2$ release).
• Lenticels: Small, raised pores found on the bark of woody stems and roots. They allow for gaseous exchange between the atmosphere and the internal tissues of the stem.
• General surface of roots: Root hairs absorb oxygen from the air spaces present between soil particles.

Transportation in plants involves specialized vascular tissues:

• Transportation of Water and Minerals (by Xylem):
  • Xylem is the vascular tissue responsible for transporting water and dissolved minerals from the roots upwards to the stem, leaves, and other aerial parts of the plant.
  • This movement is primarily unidirectional, driven by transpiration pull (the suction force created by the loss of water vapor from leaves).
  • Water enters the root hairs by osmosis and then moves through the xylem vessels.
• Transportation of Food (by Phloem):
  • Phloem is the vascular tissue that transports prepared food (sugars) from the leaves (where photosynthesis occurs) to all other parts of the plant, including roots, fruits, and storage organs.
  • This movement is bidirectional, meaning food can be transported both upwards and downwards, depending on the plant's needs.
  • The process is called translocation and involves active transport of sugars into the phloem, followed by movement due to osmotic pressure.

Transpiration is the process by which plants lose water in the form of water vapor from the aerial parts, primarily through tiny pores called stomata on the surface of leaves. It also occurs to a lesser extent through lenticels on stems and the cuticle.

Importance of Transpiration:

• Transpiration Pull: It creates a suction force (transpiration pull) that helps in the upward movement of water and dissolved minerals from the roots to the leaves against gravity. This is crucial for water absorption.
• Cooling Effect: The evaporation of water from the leaf surface helps to cool the plant, preventing overheating, especially in direct sunlight.
• Distribution of Minerals: It helps in the distribution of mineral salts throughout the plant body, as minerals are transported along with water.

Human blood is a vital connective tissue composed of a fluid matrix called plasma and three types of formed elements (blood cells):

• Plasma:
  • The yellowish liquid component of blood, making up about 55% of blood volume.
  • Function: Transports water, digested food (glucose, amino acids), carbon dioxide, nitrogenous wastes, hormones, and proteins throughout the body.
• Red Blood Cells (RBCs) / Erythrocytes:
  • Biconcave, disc-shaped cells, lack a nucleus in mammals.
  • Contain hemoglobin, a red pigment that binds to oxygen.
  • Function: Primarily responsible for the transport of oxygen from the lungs to all body cells. Also transports a small amount of carbon dioxide.
• White Blood Cells (WBCs) / Leukocytes:
  • Larger than RBCs, nucleated, and colorless.
  • Function: Form the body's defense system. They fight infections by engulfing pathogens (phagocytosis) or producing antibodies.
• Platelets / Thrombocytes:
  • Small, irregular-shaped cell fragments.
  • Function: Play a crucial role in blood clotting (coagulation) at the site of injury, preventing excessive blood loss.

The nephron is the structural and functional unit of the kidney. Each human kidney contains about one million nephrons, which are responsible for filtering blood and forming urine.

Structure of a Nephron:

• Glomerulus: A tuft of capillaries where blood filtration begins.
• Bowman's Capsule: A cup-shaped structure that encloses the glomerulus.
• Renal Tubule: A long, convoluted tube extending from Bowman's capsule, divided into:
  • Proximal Convoluted Tubule (PCT)
  • Loop of Henle
  • Distal Convoluted Tubule (DCT)
• Collecting Duct: Receives urine from several nephrons and carries it towards the ureter.

Function of a Nephron (Urine Formation):

1. Glomerular Filtration: Blood enters the glomerulus under high pressure. Water, salts, glucose, amino acids, and urea are filtered from the blood into the Bowman's capsule, forming the glomerular filtrate. Large proteins and blood cells do not pass.
2. Tubular Reabsorption: As the filtrate passes through the renal tubule, essential substances like glucose, amino acids, most of the water, and some salts are selectively reabsorbed back into the blood capillaries surrounding the tubule.
3. Tubular Secretion: Certain waste products (like excess potassium ions, hydrogen ions, and some drugs) that were not filtered initially are actively secreted from the blood into the filtrate in the renal tubule.

The remaining fluid, now called urine, passes into the collecting ducts and then to the ureters.

Plant hormones (Phytohormones) are chemical substances produced naturally by plants that regulate their growth, development, and responses to environmental stimuli. They are active in very small concentrations.

Two plant hormones and their functions are:

• Auxins:
  • Function: Promote cell elongation in shoots, involved in phototropism (growth towards light) and geotropism (growth in response to gravity). They also promote root initiation and apical dominance.
• Gibberellins:
  • Function: Promote stem elongation, breaking of dormancy in seeds and buds, and flowering.
• (Other examples: Cytokinins - promote cell division; Abscisic Acid - inhibits growth, promotes dormancy; Ethylene - promotes fruit ripening).

Reflex Action: A sudden, involuntary, and almost instantaneous response to a stimulus, without conscious thought or control from the brain. Reflex actions are protective mechanisms that help organisms respond quickly to potentially harmful situations.

Reflex Arc: The pathway taken by nerve impulses during a reflex action. It involves the following components:

1. Receptor: Detects the stimulus (e.g., pain receptors in the skin).
2. Sensory Neuron (Afferent Neuron): Carries the nerve impulse from the receptor to the central nervous system (spinal cord).
3. Relay Neuron (Interneuron): Located in the spinal cord, it connects the sensory neuron to the motor neuron.
4. Motor Neuron (Efferent Neuron): Carries the nerve impulse from the spinal cord to the effector organ.
5. Effector: A muscle or gland that carries out the response (e.g., a muscle contracting).

Example: Withdrawing hand from a hot object.

When you accidentally touch a hot object:

• The heat (stimulus) is detected by receptors in your skin.
• A nerve impulse travels along a sensory neuron to the spinal cord.
• In the spinal cord, the sensory neuron synapses with a relay neuron, which then synapses with a motor neuron.
• The motor neuron carries the impulse to the muscles of your arm (effector).
• Your arm muscles contract, causing you to quickly withdraw your hand. This happens before your brain even registers the pain.

The three main parts of the human brain are:

• Cerebrum (Forebrain):
  • Function: Responsible for higher-level functions such as thought, memory, learning, reasoning, intelligence, voluntary actions, and processing sensory information (sight, hearing, touch, taste, smell).
• Cerebellum (Hindbrain):
  • Function: Coordinates voluntary movements like posture, balance, speech, and muscle coordination. It ensures smooth and precise movements.
• Medulla Oblongata (Hindbrain):
  • Function: Controls vital involuntary actions of the body, such as heartbeat, breathing, blood pressure, swallowing, coughing, and sneezing.

The endocrine system is a system of glands that secrete hormones directly into the bloodstream to regulate various body functions. It works alongside the nervous system to control and coordinate body activities, often over longer durations.

Two endocrine glands and the hormones they secrete are:

• Pituitary Gland: Often called the "master gland."
  • Hormone: Growth Hormone (GH), Thyroid-Stimulating Hormone (TSH), etc.
  • Function: Growth Hormone regulates growth and development. The pituitary gland also controls the function of many other endocrine glands.
• Thyroid Gland: Located in the neck.
  • Hormone: Thyroxine.
  • Function: Regulates the body's metabolism (rate at which the body uses energy), affecting growth and development.
• (Other examples: Pancreas - Insulin, Glucagon; Adrenal Gland - Adrenaline; Testes - Testosterone; Ovaries - Estrogen, Progesterone).

Insulin is a hormone secreted by the pancreas. Its primary role in the human body is to regulate blood sugar (glucose) levels.

• Role of Insulin:
  • After a meal, when blood glucose levels rise, the pancreas releases insulin.
  • Insulin helps body cells (especially muscle and fat cells) absorb glucose from the bloodstream, using it for energy or converting it into glycogen (for storage in the liver and muscles).
  • This effectively lowers high blood glucose levels back to a normal range.
• Deficiency of Insulin:
  • A deficiency or insufficient production of insulin, or the body's inability to use insulin effectively, leads to a condition called Diabetes Mellitus.
  • In diabetes, blood glucose levels remain high (hyperglycemia) because glucose cannot enter the cells efficiently.
  • Symptoms include frequent urination, increased thirst, increased hunger, fatigue, and weight loss. Long-term complications can affect the eyes, kidneys, nerves, and heart.