Introduction to Biology and Cell Structure

• Biology is the study of life and living organisms, exploring physical structure, physiological mechanisms, molecular interactions, growth, evolution, and distribution.

Branches of Biology

• Botany entails studying plants.
• Zoology entails studying animals.
• Microbiology entails studying microorganisms.

Cell Biology

• Cells serve as the basic structural and functional units of life.
• Organisms are either unicellular (single-celled) or multicellular (many-celled).

Cell Structure

• The cell membrane is the cell's outer boundary, protecting it and controlling the movement of substances.
• Cytoplasm is a gel-like substance containing organelles within the cell.
• The nucleus acts as the control center, housing DNA or genetic material.

Cell Organelles

• Mitochondria function as the cell's powerhouse, generating energy through cellular respiration.
• The endoplasmic reticulum (ER) is a network of membranes for protein and lipid synthesis.
  • Rough ER contains ribosomes and is involved in protein synthesis.
  • Smooth ER handles lipid synthesis and detoxification.
• The Golgi apparatus modifies, sorts, and packages proteins and lipids for transport.
• Ribosomes are the sites of protein synthesis.
• Lysosomes have enzymes for intracellular digestion and waste removal.
• Vacuoles store water, nutrients, and waste.
• Chloroplasts, found in plant cells, facilitate photosynthesis, which converts light energy into chemical energy.
• The cell wall is a rigid outer layer in plant cells that offers support and protection.

Cell Types

• Prokaryotic cells are simple, lacking a nucleus and membrane-bound organelles; bacteria are an example.
• Eukaryotic cells are complex, containing a nucleus and membrane-bound organelles; examples include animal, plant, fungi, and protist cells.

Cell Division

• Mitosis is cell division yielding two identical daughter cells for growth and repair.
  • Prophase involves chromosomes condensing and becoming visible.
  • Metaphase involves chromosomes aligning centrally.
  • Anaphase involves sister chromatids separating and moving to opposite poles.
  • Telophase involves the nuclear membrane reforming around separated chromosomes.
• Meiosis is cell division producing four genetically different daughter cells (gametes) for sexual reproduction.

Tissues

• Tissues consist of similar cells performing specific functions
• Epithelial tissue covers body surfaces and lines cavities, providing protection, absorption, and secretion.
• Connective tissue supports, connects, and separates tissues and organs. It includes bone, cartilage, blood, and adipose tissue.
• Muscular tissue facilitates movement.
  • Skeletal muscle, attached to bones, allows voluntary movements.
  • Smooth muscle, in internal organ walls, enables involuntary movements.
  • Cardiac muscle, in the heart, pumps blood.
• Nervous tissue transmits electrical signals for communication and coordination.

Plant Tissues

• Meristematic tissue, in growth areas, handles cell division and differentiation.
• Permanent tissue comes from meristematic tissue and performs specific functions.
  • Simple tissues comprise one cell type (e.g., parenchyma, collenchyma, and sclerenchyma).
  • Complex tissues comprise different cell types (e.g., xylem and phloem).

Diversity in Living Organisms

• Classification organizes organisms by characteristics and evolutionary relationships.
• Kingdoms represent the broadest classification level: Monera, Protista, Fungi, Plantae, and Animalia.

Kingdom Monera

• Includes prokaryotic organisms (bacteria and archaea).
• Lack a true nucleus and membrane-bound organelles.

Kingdom Protista

• Includes unicellular eukaryotic organisms (protozoa, algae).
• Exhibit diverse modes of nutrition (autotrophic and heterotrophic).

Kingdom Fungi

• Includes multicellular eukaryotic organisms (mushrooms, molds, yeasts).
• Heterotrophic organisms that obtain nutrients by absorption.

Kingdom Plantae

• Includes multicellular eukaryotic organisms (plants).
• Autotrophic organisms that produce their own food through photosynthesis.
• Divided into divisions such as algae, bryophytes, pteridophytes, gymnosperms, and angiosperms.

Kingdom Animalia

• Includes multicellular eukaryotic organisms (animals).
• Heterotrophic organisms that obtain nutrients by ingestion.
• Divided into phyla such as Porifera, Coelenterata, Platyhelminthes, Nematoda, Annelida, Arthropoda, Mollusca, Echinodermata, and Chordata.

Health and Diseases

• Health is a state of complete physical, mental, and social well-being.
• Disease is a condition impairing normal body function.

Types of Diseases

• Infectious diseases are caused by pathogens (bacteria, viruses, fungi, protozoa) and are transmittable.
• Non-infectious diseases are not caused by pathogens and are non-transmittable (e.g., diabetes, cancer).

Infectious Diseases

• Pathogens like bacteria, viruses, fungi, or protozoa cause infectious diseases.
• Spread occurs via air, water, physical contact, or vectors.
• Examples of infectious diseases include:
  • Bacterial: Tuberculosis, typhoid fever, cholera.
  • Viral: Common cold, influenza, AIDS (HIV).
  • Fungal: Ringworm, athlete's foot.
  • Protozoan: Malaria, amoebic dysentery.

Modes of Transmission

• Air: Droplets from coughing or sneezing spread diseases like the common cold and tuberculosis.
• Water: Contaminated water transmits diseases like cholera and typhoid.
• Physical contact: Direct contact spreads skin infections and sexually transmitted infections.
• Vectors: Insects or animals carry pathogens, spreading diseases like malaria and dengue fever.

Prevention of Diseases

• Maintain personal hygiene through hand washing and regular bathing
• Ensure proper sanitation and waste disposal.
• Consume safe drinking water and food.
• Get vaccinated against infectious diseases.
• Avoid contact with infected individuals or contaminated environments.
• Control vectors.

Natural Resources

• Natural resources are materials or substances occurring in nature used for economic gain.
• Examples include air, water, soil, minerals, and forests.

Air

• Air is essential for respiration and other life processes.
• Air pollution comes from pollutants like smoke, dust, and gases from industries and vehicles.
• Air pollution results in respiratory problems and other health issues.

Water

• Water is essential for all living organisms.
• Water pollution is caused by pollutants like sewage, industrial waste, and agricultural runoff.
• Water pollution leads to waterborne diseases and harm aquatic life.

Soil

• Soil provides support and nutrients for plant growth.
• Soil erosion results from deforestation, overgrazing, and improper agricultural practices.
• Soil erosion leads to loss of soil fertility and desertification.

Biogeochemical Cycles

• Water Cycle: Continuous movement of water between the earth's surface, atmosphere, and oceans.
• Carbon Cycle: Circulation of carbon atoms through various components of the ecosystem.
• Nitrogen Cycle: Conversion of nitrogen gas into usable forms by microorganisms and plants.
• Oxygen Cycle: Circulation of oxygen atoms through various components of the ecosystem.

This material covers the basics of biology, including its branches such as botany, zoology, and microbiology. It provides an overview of cell biology, focusing on cell structure and key organelles like the cell membrane, cytoplasm, the nucleus, mitochondria, and endoplasmic reticulum.