Introduction to Biology

• Biology is the scientific study of life.
• It explores the structure, function, growth, origin, evolution, and distribution of living organisms.
• Biology recognizes the cell as the basic unit of life, genes as the basic unit of heredity, and evolution as the engine that propels the creation and extinction of species.
• Living organisms are open systems that survive by transforming energy and decreasing their local entropy.

Core Principles

• Cell theory states all living organisms are composed of cells.
• Gene theory states hereditary information is encoded in DNA, and genes are the basic units of inheritance.
• Evolution refers to life evolving over time through natural selection.
• Homeostasis refers to living organisms maintaining a stable internal environment.
• Thermodynamics states life depends on energy transformations.

Branches of Biology

• Biochemistry studies the chemical processes within and relating to living organisms.
• Molecular Biology studies biological activity at the molecular level.
• Cell Biology studies cell structure and function.
• Genetics studies heredity and variation in organisms.
• Microbiology studies microorganisms.
• Botany studies plants.
• Zoology studies animals.
• Ecology studies the interactions between organisms and their environment.
• Evolution studies the history of life and the processes that shaped it.
• Physiology studies the functions and mechanisms in a living system.

Chemical Basis of Life

• Organisms consist of organic and inorganic molecules.
• Carbon is the main element in organic molecules due to its ability to form stable bonds with other atoms.
• Water is essential for life because of its properties as a solvent, its high heat capacity, and its role in many biochemical reactions.
• Biomolecules include carbohydrates, lipids, proteins, and nucleic acids.
  • Carbohydrates provide energy and structural support.
  • Lipids store energy, form cell membranes, and act as hormones.
  • Proteins perform various functions, including catalyzing reactions, transporting molecules, and providing structural support.
  • Nucleic acids store and transmit genetic information.

Cell Structure and Function

• Cells are the basic units of life and are enclosed by a plasma membrane.
• Two main types of cells exist: prokaryotic and eukaryotic.
  • Prokaryotic cells lack a nucleus and other membrane-bound organelles.
  • Eukaryotic cells have a nucleus and other membrane-bound organelles.
• Organelles found in eukaryotic cells include:
  • The nucleus contains the cell's DNA.
  • Mitochondria produce ATP through cellular respiration.
  • Ribosomes synthesize proteins.
  • The endoplasmic reticulum is involved in protein and lipid synthesis.
  • The Golgi apparatus processes and packages proteins.
  • Lysosomes digest cellular waste.
• The cell membrane controls the movement of substances in and out of the cell through processes like diffusion, osmosis, and active transport.

Energy and Metabolism

• Metabolism is the sum of all chemical reactions occurring in an organism.
• Catabolism breaks down complex molecules to release energy.
• Anabolism uses energy to build complex molecules from simpler ones.
• Photosynthesis uses light energy to convert carbon dioxide and water into glucose and oxygen.
• Cellular respiration breaks down glucose to produce ATP, the cell's main energy currency.
• Enzymes are biological catalysts speeding up chemical reactions by lowering activation energy.

Genetics

• Genes are segments of DNA that code for proteins.
• DNA consists of two nucleotide strands arranged in a double helix structure.
• DNA replication is the process of copying DNA.
• Transcription synthesizes RNA from a DNA template.
• Translation synthesizes proteins from an RNA template.
• Mutations are changes in the DNA sequence that can lead to genetic variation.
• Mendelian genetics describes the basic principles of inheritance.

Evolution

• Evolution is the change in the heritable characteristics of biological populations over successive generations.
• Natural selection refers to the process by which organisms with traits that better enable them to adapt to their environment tend to survive and reproduce in greater numbers.
• Evidence supporting evolution includes:
  • Fossil record.
  • Comparative anatomy.
  • Embryology.
  • Molecular biology.
• Speciation defines the process by which new species arise.
• Phylogenetic trees illustrate the evolutionary relationships between different species.