Life Processes

Determining Life: Characteristics used to define living organisms include visible movement, ability to breathe, and growth.
Molecular Movement: Invisible movements at the molecular level are crucial for life, indicating the necessity of molecular activity in defining life.

Maintenance Processes: Continuous biological processes essential for sustaining life, even during inactivity (e.g., sleeping).
Energy Requirement: Life processes require energy, which organisms obtain through nutrition.
- Nutrition Purpose: To transfer energy and raw materials needed for growth and cellular functions.

Sources of Nutrition:
- Autotrophs: Organisms (like green plants) that create their own food from simple substances (e.g., CO2, water) using sunlight (photosynthesis).
- Heterotrophs: Organisms (like animals, fungi) that consume complex food materials produced by autotrophs.

Photosynthesis: The process where autotrophs convert light energy, CO2, and water into carbohydrates, which serve as stored energy (e.g., starch).
Key Steps in Photosynthesis:
1. Absorption of light energy.
2. Conversion of light energy to chemical energy; splitting of water molecules.
3. Reduction of carbon dioxide to carbohydrates.

Methods of Food Acquisition:
- External Digestion: Fungi secrete enzymes to digest food outside their bodies.
- Internal Digestion: Organisms ingest whole food and digest internally, such as humans.
- Parasitic Nutrition: Some organisms derive nutrients from host organisms without killing them.

Alimentary Canal: A long tube where food is processed from mouth to anus.
Digestion Process:
1. Food is mechanically broken down and mixed with saliva (contains amylase enzyme).
2. Travels down the esophagus to the stomach, where it is mixed with gastric juices (HCl and pepsin).
3. Complete digestion occurs in the small intestine, aided by bile and pancreatic juices from other organs.
Absorption: Through villi in the small intestine, nutrients enter the bloodstream.

Energy Use: Energy from glucose is released through respiration.
Types of Respiration:
- Aerobic Respiration: Requires oxygen, produces more energy (CO2 and water as by-products).
- Anaerobic Respiration: Occurs in absence of oxygen; less energy produced (by-products can include lactic acid or ethanol).
Cellular Respiration Role: Produces ATP, which fuels cellular activities.

Circulatory System Functionality:
- Components: Heart, blood, and blood vessels facilitate the transport of nutrients, gases, and wastes.
- Double Circulation: Blood goes through the heart twice in mammals; separates oxygenated and deoxygenated blood for efficiency.
Transport in Plants:
- Xylem: Transports water and minerals from roots to leaves.
- Phloem: Distributes products of photosynthesis from leaves to other parts of the plant.

Purpose: Removal of harmful metabolic wastes from the body.
Methods of Excretion:
- Unicellular Organisms: Simple diffusion through cell membranes.
- Multicellular Organisms: Specialized organs (e.g., kidneys in humans) facilitate waste removal.

Kidneys: Main organs for filtering blood and producing urine. Each nephron filters waste products and reabsorbs necessary substances.

Plants can excrete waste products in various ways including storage in vacuoles, leaf dropping, or into the soil.

Life processes encompass nutrition, respiration, transport, and excretion, crucial for maintaining homeostasis and supporting life functions. Autotrophs and heterotrophs exhibit different strategies for nutrition, while the circulatory system ensures efficient material transport in complex organisms. Excretion methods vary significantly between unicellular and multicellular organisms, highlighting the diversity of life forms.