Biology Notes
1. Cell Biology
Cells are the basic units of life. There are two major types of cells: prokaryotic cells, which lack a
nucleus, and eukaryotic cells, which contain a nucleus and other membrane-bound organelles. Key
organelles in eukaryotic cells include:
- Nucleus: Stores genetic material (DNA) and controls cellular activities.
- Mitochondria: The powerhouse of the cell, producing ATP through respiration.
- Ribosomes: Sites of protein synthesis.
- Endoplasmic Reticulum: Rough ER is involved in protein synthesis; Smooth ER in lipid synthesis.
- Golgi Apparatus: Modifies, packages, and transports proteins.
- Lysosomes: Contain enzymes for digestion of macromolecules.
- Chloroplasts (in plants): Site of photosynthesis.
2. Genetics
Genetics is the study of heredity and variation. DNA (deoxyribonucleic acid) is the molecule that carries
genetic information. DNA is made up of nucleotides containing a sugar, phosphate, and nitrogenous
base (Adenine, Thymine, Cytosine, Guanine). Genes are sequences of DNA that code for proteins, and
chromosomes are long strands of DNA tightly coiled around histone proteins.
Key concepts include:
- Mendelian Genetics: Traits are inherited according to principles of dominance, segregation, and
independent assortment.
- Genotype vs. Phenotype: Genotype refers to genetic makeup; phenotype is the observable trait.
- Punnett Squares: Used to predict the probability of inheritance.
- DNA Replication: Semi-conservative process ensuring genetic continuity.
- Protein Synthesis: Involves transcription (DNA to RNA) and translation (RNA to protein).
3. Ecology
Ecology is the study of interactions between organisms and their environment. Ecosystems are
communities of organisms interacting with abiotic (non-living) and biotic (living) components. Energy
flows through ecosystems via food chains and food webs, beginning with producers (plants, algae) and
moving through consumers and decomposers.
Key ecological concepts:
- Trophic Levels: Levels in a food chain (producers, primary consumers, secondary consumers, etc.).
- Biogeochemical Cycles: Movement of elements like carbon, nitrogen, and water through ecosystems.
- Population Dynamics: Study of population size, growth, and regulation.
- Biodiversity: The variety of life in ecosystems, important for stability and resilience.
- Human Impact: Deforestation, pollution, climate change, and conservation efforts.