مقدمة في علم الأحياء

Introduction to Biology

• Biology is the study of living organisms, encompassing their morphology, anatomy, behavior, origin, and distribution.
• It originates from Greek words: "Bios" (life) and "Logos" (study).

History of Biology

• Aristotle (384-322 BCE): A famous Greek philosopher who pioneered zoology and classified living things. He divided plants into herbs, shrubs, and trees, and animals into land, water, and air dwellers.
• Galen (AD 131-200): A Greek physician who described human anatomy through animal dissections (apes and pigs). He noted arteries carried blood, but his work contained inaccuracies, unchallenged for 1300 years.
• Versalius (1514-1564): The "Father of Modern Anatomy," conducted the first human dissections to study anatomy.
• William Harvey (1578-1657): An English physician who demonstrated the circulation of blood through the body, linking structure and function.
• Marcello Malpighi (1628-1694): An Italian physician who was a microscopist. He discovered capillaries in 1661. He also discovered red blood cells.

Cell Theory

• Microscopes revolutionized the study of cells.
• Robert Hooke (mid-1600s): Used a microscope to observe cork, remarking on the "cells" he saw, like compartments in a monastery.
• Antonie van Leeuwenhoek (1632-1694): Improved microscopy and observed microorganisms, sperm, and single-celled organisms.
• Schwann and Schleiden: Key scientists who proposed fundamental cell theory principles that cells were the basic units of structure and function in living things.

Cell Types: Prokaryotic and Eukaryotic

• Prokaryotic cells: Lack membrane-bound organelles (like bacteria).
• Eukaryotic cells: Contain membrane-bound organelles (like animal and plant cells).
• Both types share common features, such as a plasma membrane, cytosol, chromosomes, and ribosomes.

Similarities and Differences

• Similarities: Both cell types are surrounded by a plasma membrane, contain cytosol, chromosomes, and ribosomes.
• Differences: Eukaryotic cells have a nucleus and membrane-bound organelles while prokaryotes lack a nucleus and membrane bound organelles.

Cell Division

• Eukaryotic cells reproduce via mitosis (for somatic cells) and meiosis (for gamete production).
• Prokaryotic cells reproduce via binary fission, a simpler process.

Additional Properties of Life

• Adaptation: Adjusting to meet the environment's needs
• Metabolism: Set of chemical reactions converting food into energy.
• Specific organization: Different cell parts performing specific functions (e.g., heart, nucleus).
• Homeostasis: Maintaining a stable internal state (e.g., water balance).
• Responsiveness: Reacting to stimuli (e.g., light, temperature).

Animal vs. Plant Cells

• Similarities: Both have a nucleus, mitochondria, cytoplasm, and Golgi apparatus.
• Differences: Plant cells have a cell wall, chloroplasts (for photosynthesis), and a large central vacuole, animal cells mostly don't.

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