Principles of Biology

• Biology is the scientific study of life
• Explores structure, function, growth, origin, evolution, and distribution of living organisms
• Recognizes the cell as the basic unit of life and genes as the basic unit of heredity
• Evolution is the engine that propels the creation and extinction of species.
• Living organisms consume and transform energy and maintain homeostasis to survive
• Sub-disciplines are defined by organism scale, organism type, and study methods
• Molecular biology studies the fundamental chemistry of life
• Cell biology examines the cell as the basic building block of all life
• Physiology examines the physical and chemical functions of tissues, organs, and organ systems
• Ecology examines how organisms interact in their environment

Core Principles of Biology

• Based on unifying principles to explain and predict natural phenomena

Cell Theory

• All living organisms are composed of one or more cells
• The cell is the basic unit of structure and function in organisms
• All cells arise from pre-existing cells through cell division

Gene Theory

• Traits are inherited through genes
• Genes are specific regions of DNA that code for particular traits
• Genes are passed from parents to offspring and determine offspring characteristics

Evolution

• Change in the characteristics of a species over several generations
• Relies on the process of natural selection
• Natural selection is the differential survival and reproduction of individuals due to differences in phenotype.
• Evolutionary biology studies evolutionary relationships between organisms and mechanisms driving evolutionary change.

Homeostasis

• Maintenance of a stable internal environment despite external changes
• Essential for the proper functioning of cells and organisms
• Homeostatic mechanisms include temperature regulation, pH balance, and osmoregulation

Energy

• All living organisms require energy to carry out life processes
• Obtained from the sun (photosynthesis) or chemical compounds (cellular respiration or fermentation)
• Stored as ATP (adenosine triphosphate) and used to power cellular activities

Hierarchical Organization of Life

• Life is organized hierarchically, each level building upon the previous one
• Molecules are groups of atoms held together by chemical bonds
• Cells are the basic units of life, composed of molecules and capable of carrying out life processes
• Tissues are groups of similar cells that perform a specific function
• Organs are structures composed of different tissues working together to perform a specific function
• Organ systems are groups of organs working together to perform a complex function
• Organisms are individual living beings composed of organ systems
• Populations are groups of individuals of the same species in a particular area
• Communities are groups of interacting populations of different species in a particular area
• Ecosystems are communities of organisms interacting with their physical environment
• The biosphere is the sum of all ecosystems on Earth

The Tree of Life

• Illustrates the evolutionary relationships between all living organisms
• Based on molecular biology, paleontology, and comparative anatomy evidence
• Divided into three domains
  • Bacteria: single-celled prokaryotic organisms
  • Archaea: single-celled prokaryotic organisms more closely related to eukaryotes than bacteria
  • Eukarya: eukaryotic organisms, including protists, fungi, plants, and animals

Branches of Biology

Anatomy

• Study of the structure of organisms and their parts
• Includes gross anatomy (structures visible to the naked eye)
• Includes microscopic anatomy (structures visible only with a microscope)

Physiology

• Study of the function of organisms and their parts
• Examines the physical and chemical processes that occur in living organisms

Genetics

• Study of heredity and variation in organisms
• Explores how traits are passed from parents to offspring
• Includes the study of genes, DNA, and the mechanisms of inheritance

Ecology

• Study of the interactions between organisms and their environment
• Examines the distribution and abundance of organisms
• Studies the flow of energy and matter through ecosystems

Botany

• The scientific study of plants
• Encompasses plant physiology, structure, genetics, ecology, distribution, classification, and economic importance

Zoology

• The scientific study of animals
• Includes animal physiology, anatomy, behavior, ecology, evolution, and classification

Microbiology

• Study of microorganisms (bacteria, viruses, fungi, and protozoa)
• Explores their structure, function, genetics, and their roles in disease, industry, and the environment

Molecular Biology

• Studies the molecular basis of biological activity
• Focuses on the structure, function, and interactions of biological macromolecules
• Macromolecules include proteins, nucleic acids, carbohydrates, and lipids

Evolutionary Biology

• Studies the evolutionary processes that have shaped the diversity of life on Earth
• Examines the mechanisms of evolution, such as natural selection, genetic drift, and mutation
• Studies the evolutionary history of organisms and their relationships to one another

Scientific Method in Biology

• Biologists use the scientific method to investigate the natural world
• Involves
  • Observation: observing a phenomenon or identifying a problem
  • Hypothesis: formulating a testable explanation for the observation
  • Experimentation: designing and conducting experiments to test the hypothesis
  • Data analysis: analyzing the results of the experiments
  • Conclusion: drawing conclusions based on the data and determining whether the hypothesis is supported or rejected
  • Communication: sharing the findings with the scientific community through publications and presentations

Importance of Biology

• Essential for addressing many of the challenges facing humanity
• These challenges include
  • Human health: understanding disease, developing new treatments, and preventing the spread of infectious diseases
  • Environmental conservation: understanding ecosystems, protecting biodiversity, and mitigating the effects of climate change
  • Food security: developing new crops, improving agricultural practices, and ensuring a sustainable food supply
  • Biotechnology: developing new technologies based on biological principles, such as gene therapy, biofuels, and bioremediation