This chapter explores the fundamental processes that sustain life in all living organisms. We will delve into the mechanisms by which organisms acquire nutrients, convert them into usable energy, eliminate waste products, and maintain their internal environment.
I. Introduction
- Life processes are the essential functions that organisms carry out to stay alive and function properly. These processes include nutrition, respiration, transport, excretion, control and coordination. They work together to maintain an organism’s internal balance (homeostasis).
- Major life processes covered in this chapter:
- Nutrition: Obtaining nutrients for energy and growth.
- Respiration: Breaking down food molecules to release energy.
- Transport: Moving nutrients, gases, and waste products throughout the organism.
- Excretion: Removing waste products from the body.
- Control and coordination: Regulating and responding to internal and external stimuli.
II. Nutrition
A. Modes of Nutrition: How Organisms Acquire Nutrients
There are two main modes of nutrition:
1. Autotrophic Nutrition: Manufacturing Food from Scratch
- Autotrophs (e.g., plants, some bacteria) can produce their own food using a process called photosynthesis.
- Photosynthesis occurs in chloroplasts within plant cells. Sunlight energy is captured by chlorophyll pigments and used to convert water and carbon dioxide into glucose (sugar) and oxygen.
The equation for photosynthesis:
* Sunlight + 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
* Photosynthesis is essential for life on Earth as it produces the organic compounds that most organisms rely on for energy and as building blocks for growth and repair.
2. Heterotrophic Nutrition: Obtaining Nutrients from Other Organisms
Heterotrophs (e.g., animals, fungi) cannot produce their own food and must obtain it from other organisms.
There are two main types of heterotrophic nutrition:
a. Holozoic Nutrition (Animal-like Nutrition):
- Organisms ingest (eat) whole food particles.
- Food is digested (broken down) into smaller molecules that can be absorbed by the body.
- Absorbed nutrients are used for cellular processes, and undigested waste is eliminated (egestion).
- Example: Amoeba engulfs food particles with its pseudopodia, digests them in its food vacuole, and eliminates waste.
b. Saprophytic Nutrition (Decomposer Nutrition):
- Organisms obtain nutrients from dead and decaying organic matter.
- Saprophytes (decomposers) secrete digestive enzymes that break down dead organic matter into simpler molecules they can absorb.
- This process is essential for nutrient cycling in ecosystems, as it returns nutrients to the environment for reuse by other organisms.
III. Transport
Importance of Transport Systems:
- Transport systems are vital for moving essential materials (nutrients, gases, waste products) within an organism.
- They ensure that cells receive the materials they need and can eliminate waste products.
A. Different Transport Mechanisms
- 1. Diffusion: Passive movement of molecules from an area of high concentration to an area of low concentration until equilibrium is reached.
- Requires no energy input.
- Example: Oxygen diffuses from the lungs into the bloodstream.
- 2. Osmosis: Movement of water molecules across a selectively permeable membrane (allows some molecules to pass through but not others) from an area of low solute concentration (high water concentration) to an area of high solute concentration (low water concentration) until equilibrium is reached.
- Driven by the difference in solute concentration across the membrane.
- Example: Water enters plant cells through osmosis.
- 3. Active Transport: Movement of molecules against a concentration gradient (from low concentration to high concentration) using energy (ATP) from cellular respiration.
- Requires energy input to move molecules against the natural flow.
- Example: Absorption of nutrients in the small intestine of animals.
B. Transport Systems in Multicellular Organisms
- 1. The Circulatory System: Network of blood vessels that transport nutrients, gases, and waste products throughout the body.
- Blood: Composed of plasma (liquid portion) and blood cells (red blood cells for oxygen transport, white blood cells for immune function, platelets for clotting).
- 2. The Xylem and Phloem in Plants: Vascular tissues responsible for transporting water, minerals, and dissolved sugars.
- Xylem: Transports water and dissolved minerals from the roots to the leaves.
- Phloem: Transports dissolved sugars (products of photosynthesis) from the leaves to other parts of the plant.
IV. Respiration
Cellular Respiration: The process by which cells release energy stored in organic molecules (usually glucose) for cellular functions. This energy is captured in a molecule called adenosine triphosphate (ATP).
A. Aerobic Respiration (Requires Oxygen)
- Occurs in the presence of oxygen.
- Breaks down glucose into carbon dioxide, water, and ATP.
- Stages of Aerobic Respiration:
- Overall Equation for Aerobic Respiration:
C₆H₁₂O₆ (glucose) + 6O₂ → 6CO₂ + 6H₂O + 36 ATP (approximately) - Glycolysis: Occurs in the cytoplasm. Glucose is broken down into a simpler molecule called pyruvate with a small amount of ATP produced.
- Krebs Cycle (Citric Acid Cycle): Occurs in the mitochondria. Pyruvate enters the mitochondria and is further broken down into simpler molecules, releasing energy captured by carrier molecules (NADH and FADH2).
- Electron Transport Chain: Occurs in the inner membrane of the mitochondria. Energy from NADH and FADH2 is used to pump protons across the membrane. This creates a gradient that drives the production of ATP through a process called chemiosmosis.
B. Anaerobic Respiration (Without Oxygen)
- Occurs in the absence of oxygen.
- Less efficient than aerobic respiration and produces less ATP.
- Fermentation: A type of anaerobic respiration where glucose is partially broken down into organic molecules like lactic acid (in muscles) or ethanol (in yeast).
V. Excretion
Importance of Excretion:
- Removing waste products produced during cellular metabolism is essential to maintain homeostasis.
- Waste products can be toxic if allowed to accumulate in the body.
A. Types of Excretory Organs in Different Organisms
- 1. Excretory System in Animals:
- Kidneys: Filter waste products (urea) from the blood and eliminate them in urine.
- Lungs: Remove carbon dioxide, a waste product of cellular respiration, from the bloodstream through exhalation.
- Skin and Sweat Glands: Eliminate excess water, salts, and some waste products through sweat.
- 2. Excretion in Plants:
- Stomata and Lenticels: Tiny openings in leaves and stems that allow for gas exchange (oxygen in, carbon dioxide out) and some waste removal.
B. Importance of Maintaining Internal Balance (Homeostasis)
- Homeostasis: The ability of an organism to maintain a stable internal environment despite changes in the external environment.
- Excretion plays a crucial role in homeostasis by removing waste products that can disrupt the body’s internal balance.
VI. Control and Coordination
Importance of Control and Coordination:
- Organisms need to be able to respond to internal and external stimuli (changes in the environment) to maintain homeostasis and ensure survival.
A. Nervous System in Animals
- The complex network of nerves and specialized cells (neurons) that transmit signals throughout the body for rapid responses.
- Neurons carry electrical impulses ( nerve impulses) that coordinate actions between different parts of the body.
B. Endocrine System in Animals
- A network of glands that produce hormones, chemical messengers that regulate various body functions.
- Hormones travel through the bloodstream and target specific organs to influence their activities.
- Examples: Insulin (regulates blood sugar), thyroid hormone (regulates metabolism).
C. Plant Hormones (Plant Growth Regulators)
- Chemical messengers that regulate growth, development, and responses to stimuli in plants.
- They are produced in various parts of the plant and can travel throughout the plant to influence other tissues.
- Examples: Auxin (promotes stem growth), ethylene (promotes fruit ripening).
VII. Conclusion
- Life processes are essential for the survival, growth, and reproduction of all living organisms.
- These processes work together to maintain an organism’s internal balance (homeostasis).
- Metabolism: The sum of all chemical reactions occurring within living cells. These reactions include processes like cellular respiration, photosynthesis, and the breakdown and synthesis of molecules for growth and repair.
Remember: This chapter provides a foundational understanding of life processes. As you progress in your studies, you’ll delve deeper into the complexities of each process.
