Biology Reviewer
1. Introduction to Biology
Definition: Biology is the scientific study of life and living organisms.
Branches of Biology: Botany (study of plants), Zoology (study of animals),
Microbiology (study of microorganisms), Genetics (study of heredity), Ecology (study of
ecosystems), etc.
Characteristics of Life: Organization, metabolism, homeostasis, growth, reproduction,
response to stimuli, and evolution.
2. Cell Biology
Cell Theory:
1. All living organisms are composed of cells.
2. The cell is the basic unit of life.
3. All cells arise from pre-existing cells.
Types of Cells:
o Prokaryotic: No nucleus, simpler structure (e.g., bacteria).
o Eukaryotic: Contains a nucleus and organelles (e.g., plant and animal cells).
Cell Organelles:
o Nucleus: Contains genetic material (DNA).
o Mitochondria: Powerhouse of the cell, site of ATP (energy) production.
o Ribosomes: Protein synthesis.
o Endoplasmic Reticulum (ER): Smooth ER (lipid synthesis), Rough ER (protein
synthesis).
o Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.
o Lysosomes: Digests cellular waste.
o Chloroplasts (in plant cells): Site of photosynthesis.
3. Genetics
DNA Structure: Double helix, composed of nucleotides (adenine, thymine, cytosine,
guanine).
Central Dogma: DNA -> RNA -> Protein.
Mendelian Genetics:
o Law of Segregation: Each organism carries two alleles for each trait, which
segregate during gamete formation.
o Law of Independent Assortment: Genes for different traits can segregate
independently during the formation of gametes.
Genotype vs. Phenotype:
o Genotype: Genetic makeup of an organism.
o Phenotype: Observable characteristics.
4. Evolution
Natural Selection: Process where organisms better adapted to their environment tend to
survive and produce more offspring.
Evolutionary Evidence: Fossils, comparative anatomy, molecular biology,
biogeography.
Speciation: Formation of new and distinct species in the course of evolution.
5. Ecology
Levels of Organization: Individual, population, community, ecosystem, biome,
biosphere.
Ecosystems: Biotic (living) and abiotic (non-living) components.
Energy Flow: Food chains and food webs, trophic levels.
Biogeochemical Cycles: Water, carbon, nitrogen, and phosphorus cycles.
Population Ecology: Study of population dynamics, growth models (exponential and
logistic).
6. Human Anatomy and Physiology
Major Systems:
o Circulatory System: Heart, blood vessels, blood.
o Respiratory System: Lungs, trachea, bronchi.
o Digestive System: Mouth, esophagus, stomach, intestines, liver, pancreas.
o Nervous System: Brain, spinal cord, nerves.
o Musculoskeletal System: Bones, muscles, joints.
o Reproductive System: Male and female reproductive organs.
o Endocrine System: Glands producing hormones.
7. Photosynthesis and Cellular Respiration
Photosynthesis:
o Occurs in chloroplasts.
o Equation: 6CO₂ + 6H₂O + light energy -> C₆H₁₂O₆ + 6O₂.
o Two stages: Light-dependent reactions and Calvin cycle.
Cellular Respiration:
o Occurs in mitochondria.
o Equation: C₆H₁₂O₆ + 6O₂ -> 6CO₂ + 6H₂O + ATP.
o Three stages: Glycolysis, Krebs cycle, Electron transport chain.
8. Microbiology
Types of Microorganisms: Bacteria, viruses, fungi, protozoa, algae.
Bacterial Classification: Shape (coccus, bacillus, spirillum), gram staining (Gram-
positive, Gram-negative).
Viral Structure: DNA or RNA core, protein coat (capsid), some with lipid envelope.
Antibiotics and Vaccines: Antibiotics target bacteria, vaccines stimulate immune
response to pathogens.
9. Biotechnology
Genetic Engineering: Manipulation of an organism's genes using biotechnology.
Cloning: Producing genetically identical organisms.
CRISPR: Gene-editing technology.
Applications: Medicine (gene therapy), agriculture (GMOs), industry (biofuels).
10. Important Biological Molecules
Carbohydrates: Sugars and starches, energy source.
Proteins: Amino acids, enzymes, structural components.
Lipids: Fats and oils, energy storage, membrane structure.
Nucleic Acids: DNA and RNA, genetic information.
Study Tips
Understand Key Concepts: Focus on understanding rather than memorizing.
Use Diagrams: Visual aids can help in grasping complex processes.
Practice Questions: Solve past papers and practice problems.
Group Study: Discussing with peers can enhance understanding.
