General Biology 1
Introduction to Biology
What is Biology?
• Etymologically, it came from “bios” which means life, and “logos” which can be
translated as the study of. Hence, it simply means “thestudy of life”.
• It is the scientific study of life and life processes of organisms.
• The individual who is an expert in biology is called a biologist.
Major Branches of Biology
• Botany – The study of plants, including their structure, properties, life processes,
classification, and interactions with the environment.
• Ecology – The study of how organisms interact with each other and their
environments, including ecosystems, population dynamics, and environmental
factors.
• Zoology – The scientific study of animals, including their biology, behavior,
physiology, classification, and distribution.
• Biochemistry – The branch of biology that explores the chemical processes within
and related to living organisms, often bridging biology and chemistry.
• Genetics – The study of heredity, genes, and variation in living organisms,
including how traits are passed from one generation to the next.
• Microbiology – The study of microscopic organisms, such as bacteria, viruses,
fungi, and protozoa.
• Biophysics – The application of physics principles and techniques to understand
biological systems at molecular and cellular levels.
• Comparative Anatomy – The study of similarities and differences in the anatomy
of different species, often used to understand evolutionary relationships.
• Taxonomy – The science of classifying organisms into groups based on shared
characteristics and giving them scientific names.
• Systematics – The broader field that includes taxonomy and focuses on the
evolutionary relationships and classification of organisms.
• Cytology – The study of cells, their structure, function, and chemistry, often
referred to as cell biology.
• Biotechnology – The use of living organisms or biological systems in the
development of products or technologies, especially in medicine, agriculture, and
industry.
• Aerobiology – The study of airborne biological particles, such as pollen, spores,
and microorganisms, and their impact on health and the environment.
• Astrobiology – The study of the origin, evolution, distribution, and possibility of
life beyond Earth.
• Biogeology – The study of the interactions between the Earth's biosphere (living
organisms) and its geological components (rocks, minerals, etc.).
• Bioengineering – The application of engineering principles to biological systems
for the development of technologies in healthcare, agriculture, and other fields.
Hierachy of Life
• Atom – The smallest unit of matter (e.g., carbon, oxygen).
• Molecule – A group of atoms bonded together (e.g., DNA, water).
• Organelle – Structures within a cell that perform specific functions (e.g., nucleus,
mitochondria).
• Cell – The basic unit of life; can be unicellular or part of a multicellular organism.
• Tissue – A group of similar cells working together to perform a specific function
(e.g., muscle tissue).
• Organ – A structure made up of different tissues working together (e.g., heart,
lungs).
• Organ System – A group of organs that work together to perform complex body
functions (e.g., circulatory system).
• Organism – A single, complete living thing (e.g., a human, a plant).
• Population – A group of individuals of the same species living in the same area.
• Community – All the different populations living and interacting in an area.
• Ecosystem – A community of living organisms and their physical environment
interacting together.
• Biome – A large region characterized by specific climate and organisms (e.g.,
desert, rainforest).
• Biosphere – The global sum of all ecosystems; the part of Earth where life exists.
Properties of Life
• Order – Living organisms exhibit a highly organized structure, from molecules to
cells to complex body systems, showing a specific arrangement that supports life.
• Evolutionary Adaptation – Over generations, living organisms undergo changes
that improve their survival and reproduction in their environment. These
adaptations are driven by natural selection.
• Regulation – The ability of an organism to maintain stable internal conditions
(homeostasis), such as body temperature, pH, or water balance, even when the
external environment changes.
• Energy Processing – All organisms take in energy (e.g., from food or sunlight)
and convert it into a form they can use to carry out life processes like movement,
growth, and repair.
• Growth and Development – Organisms grow by increasing in size and cell
number. Development involves changes in structure and function as the organism
matures.
• Response to Stimuli – Living things can detect and respond to environmental
changes or stimuli (e.g., plants bending toward light, humans reacting to loud
sounds).
• Reproduction – The biological process by which living organisms produce new
individuals (offspring), ensuring the continuation of their species. This can be
sexual or asexual.
3 Domains of Life
Bacteria
• Unicellular prokaryotes (cells without a nucleus)
• Have simple cell structures
• Cell walls usually contain peptidoglycan
• Found in many environments, including soil, water, and inside living organisms
• Example: Escherichia coli (E. coli)
Archaea
• Also unicellular prokaryotes, but genetically and biochemically different from
bacteria
• Cell walls do not contain peptidoglycan
• Often live in extreme environments (e.g., hot springs, salt lakes)
• Example: Halobacterium
Eukarya
• Organisms with eukaryotic cells (cells that have a nucleus and membrane-bound
organelles)
• Includes both unicellular and multicellular organisms
• This domain includes four kingdoms: Protista, Fungi, Plantae, and Animalia
• Example: humans, mushrooms, trees, amoebas
Summary:
• Prokaryotes are simpler, smaller, and lack a nucleus.
• Eukaryotes are more complex, with a nucleus and many internal structures.
Careers in Biology
