Foundations of General Biology: Properties of Life, Organization, and Essential Chemistry

Biology: The Study of Life

Definition and Scope

Biology is the scientific study of life and living organisms, encompassing their structure, function, growth, evolution, distribution, and taxonomy. Biologists seek to understand what makes something "alive" and how living things function and interact.

• Key Questions:

  • What are the shared properties that make something "alive"?

  • How do various living things function?

  • How do we organize the diversity of life?

  • How does biological diversity arise and persist?

Properties of Life

Eight Key Characteristics of Living Organisms

All living organisms share several fundamental characteristics or functions that define life:

• Order: Living things are highly organized, with specialized cells forming tissues and organs (e.g., heart, lungs).

• Sensitivity or Response to Stimuli: Organisms respond to environmental changes (e.g., plants grow toward light).

• Reproduction: Living things produce offspring, passing on genetic material (DNA) to the next generation.

• Adaptation: Organisms evolve traits that enhance survival and reproduction in changing environments.

• Growth and Development: Organisms grow and develop according to genetic instructions.

• Regulation/Homeostasis: Organisms maintain stable internal conditions (e.g., body temperature, pH).

• Energy Processing: Living things obtain and use energy for metabolic activities (e.g., birds convert food to energy).

• Evolution: Populations of organisms change over time through mutations and natural selection.

Levels of Organization of Living Things

Hierarchical Structure

Living things are organized in a hierarchy from the smallest chemical units to the biosphere:

• Atom: The smallest unit of matter, composed of protons, neutrons, and electrons.

• Molecule: A chemical structure consisting of two or more atoms held together by chemical bonds.

• Macromolecule: Large molecules formed by combining smaller units (monomers), e.g., proteins, DNA.

• Organelle: Specialized structures within cells (e.g., mitochondria).

• Cell: The smallest unit of life; can be prokaryotic (no nucleus, e.g., bacteria) or eukaryotic (nucleus present, e.g., humans).

• Tissue: Groups of similar cells performing a common function.

• Organ: Collections of tissues grouped together based on a common function.

• Organ System: Groups of organs working together for a specific function.

• Organism: An individual living entity.

• Population: All individuals of a species in a given area.

• Community: All living organisms in a particular area.

• Ecosystem: All living things in an area plus the abiotic environment.

• Biosphere: The collection of all ecosystems on Earth.

Taxonomic Hierarchy (Highest to Lowest)

• Domain

• Kingdom

• Phylum

• Class

• Order

• Family

• Genus

• Species

Carl Linnaeus first proposed organizing species into this hierarchical taxonomy.

Branches of Biological Study

Major Fields

• Molecular Biology: Studies biological processes at the molecular level, including DNA, RNA, and protein interactions.

• Microbiology: Studies the structure and function of microorganisms.

• Paleontology: Studies fossils to understand life's history.

• Zoology and Botany: Study animals and plants, respectively.

Scientific Ethics

Ethics in science involves conducting research responsibly and considering the impact on society and individuals.

The Process of Science

Scientific Method

The scientific method is a systematic approach to research, involving defined steps:

• Observation

• Question

• Hypothesis ("If...then" statement)

• Experiment

• Analysis

• Conclusion

Scientific laws are expressed in mathematical formulas and describe how elements of nature behave under certain conditions.

Essential Chemistry for Biology

Elements and Compounds

All matter is composed of chemical elements. Elements cannot be broken down by chemical reactions. Compounds are substances formed by the chemical combination of two or more elements.

• Matter: Anything that occupies space and has mass.

• Mass: The amount of material in an object.

• Element: A substance that cannot be broken down into other substances by chemical reaction.

• Compound: Substance formed from two or more elements in fixed proportions.

Of the 92 naturally occurring elements, 25 are essential to life. Four elements (carbon, hydrogen, oxygen, nitrogen) make up about 96% of the human body. Trace elements are required in very small amounts but are essential for life.

Atoms and Subatomic Particles

• Atom: The smallest unit of matter that retains the properties of an element.

• Atoms are composed of:

  • Protons: Positive charge

  • Neutrons: No charge

  • Electrons: Negative charge

• Atomic number: Number of protons in an atom.

• Mass number: Sum of protons and neutrons in the nucleus. $\text{Mass number} = \text{Number of protons} + \text{Number of neutrons}$

• Isotopes: Atoms of the same element with different numbers of neutrons.

• Radioactive isotope: An isotope whose nucleus decays spontaneously.

Chemical Bonding and Molecules

• Chemical bonds hold atoms together in molecules and compounds.

• Covalent bonds: Atoms share electrons; strongest type of bond.

• Ionic bonds: Atoms transfer electrons, forming charged ions (e.g., NaCl).

• Hydrogen bonds: Weak attractions between polar molecules, such as water.

Table: Types of Chemical Bonds

Bond Type	Description	Strength	Example
Covalent	Atoms share electrons	Strongest	H2O, CH4
Ionic	Atoms transfer electrons, forming ions	Strong	NaCl
Hydrogen	Weak attraction between polar molecules	Weak	Between water molecules

Water and Life

• Life on Earth began in water; cells are composed of 70-95% water.

• Cohesion: Water molecules stick together due to hydrogen bonding, aiding transport in plants.

• Temperature moderation: Water resists temperature change due to hydrogen bonding.

• Solvent properties: Water dissolves many substances, forming aqueous solutions.

Table: Water's Unique Properties

Property	Description	Biological Importance
Cohesion	Water molecules stick together	Transport in plants
Temperature Moderation	Resists temperature change	Maintains stable environments
Solvent	Dissolves many substances	Facilitates chemical reactions

Acids, Bases, and pH

• Acid: Substance that increases hydrogen ion concentration in solution.

• Base: Substance that reduces hydrogen ion concentration.

• pH scale: Measures acidity or basicity; ranges from 0 (acidic) to 14 (basic), with 7 as neutral.

Example: Radiation and Cancer Treatment

• Radiation can kill cells by damaging DNA; used in cancer treatment.

• Studies compare effectiveness of surgery and radiation for prostate cancer.

• Scientific method is used to test hypotheses about treatment effectiveness.

Additional info:

• Some content inferred and expanded for clarity and completeness, such as the full list of properties of life and the taxonomic hierarchy.

• Tables reconstructed and expanded for academic context.