Foundations of General Biology: Themes, Chemistry, and the Nature of Science

Evolution and Themes in Biology

Opening Questions and the Study of Life

Biology is the scientific study of life, aiming to understand living organisms and their interactions. The field is unified by several major themes that help organize biological knowledge.

• Key Questions:

  • What is the study of life?

  • What is science?

  • How is science done?

• Five Unifying Themes of Biology:

  • Organization

  • Information

  • Evolution

  • Energy and Matter

  • Interactions

Theme 1: New Properties Emerge at Successive Levels of Biological Organization

Biological complexity arises from the arrangement and interactions of parts as complexity increases.

• Emergent Properties: Result from the arrangement and interaction of parts within a system (e.g., hydrogen and oxygen combine to make water; parts of a bicycle work together to allow movement).

• Biosphere: All life on Earth.

• Reductionism: Approach that studies the simpler components of living systems, while systems biology studies interactions among parts of a system.

• Structure and Function: The structure of a biological component gives clues about its function.

• Cell: The cell is the smallest unit of organization that can perform all activities required for life.

Theme 2: Life Processes Involve the Expression and Transmission of Genetic Information

• DNA: The molecule that contains genetic material in the form of deoxyribonucleic acid.

• Genes: Units of inheritance, transmitted from parents to offspring.

• Gene Expression: The process by which information in a gene directs the production of a cellular product (e.g., crystallin protein in the eye lens).

Theme 3: Transfer and Transformation of Energy and Matter

• Energy flows through ecosystems, entering as light and exiting as heat.

• Producers: Organisms that make their own energy (e.g., plants).

• Consumers: Organisms that obtain energy by consuming other organisms.

Theme 4: Interactions Are Important in Biological Systems

• Interactions occur at all levels, from molecules to ecosystems.

• Feedback regulation is a process in which the output of a system regulates that system (e.g., regulation of blood sugar).

Theme 5: Evolution Accounts for the Unity and Diversity of Life

• All living organisms are modified descendants of common ancestors.

• Diversity of Life: Over 1.8 million species identified, classified into three domains:

  • Bacteria

  • Archaea

  • Eukarya

• Charles Darwin: Developed the theory of natural selection to explain evolution.

The Nature of Science

How Science Works

Science is a way of knowing about the natural world through observation, experimentation, and reasoning.

• Scientific Inquiry: Involves asking questions, forming hypotheses, and testing them.

• Types of Data:

  • Quantitative (numerical measurements)

  • Qualitative (descriptions)

• Inductive Reasoning: Derives generalizations from specific observations.

• Deductive Reasoning: Uses general premises to make specific predictions.

Forming and Testing Hypotheses

• Hypothesis: A testable explanation based on observations and assumptions.

• Controlled Experiment: Compares an experimental group with a control group.

• Variables:

  • Independent Variable: The factor manipulated by the researcher.

  • Dependent Variable: The factor measured in response to the independent variable.

Scientific Theory

• A scientific theory is broader in scope than a hypothesis and is supported by a large body of evidence.

• Theories are not just guesses; they are well-substantiated explanations.

Diverse Viewpoints in Science

• Science benefits from a diversity of backgrounds and viewpoints among its practitioners.

• Many important inventions have occurred where different cultures interacted (e.g., the printing press).

Chemistry of Life

Elements, Compounds, and Matter

All living organisms are composed of matter, which consists of elements and compounds.

• Element: A substance that cannot be broken down to other substances by chemical reactions.

• Compound: A substance consisting of two or more elements in a fixed ratio.

Atomic Structure and Isotopes

• Atoms are composed of protons, neutrons, and electrons.

• Atomic Number: Number of protons in the nucleus.

• Mass Number: Number of protons plus neutrons.

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

Chemical Bonds

• Atoms interact to complete their valence shells, forming chemical bonds.

• Covalent Bonds: Form when pairs of electrons are shared between atoms.

  • Single Bond: One pair of shared electrons (e.g., H2).

  • Double Bond: Two pairs of shared electrons (e.g., O2).

  • Nonpolar Covalent Bond: Electrons are shared equally (e.g., H2, CH4).

  • Polar Covalent Bond: Electrons are shared unequally due to differences in electronegativity (e.g., H2O).

• Ionic Bonds: Form between a positively charged cation and a negatively charged anion (e.g., NaCl).

• Hydrogen Bonds: Attraction between a hydrogen atom carrying a partial positive charge and an electronegative atom (e.g., oxygen or nitrogen).

Water: Properties and Importance

• Polarity: Water is a polar molecule, allowing it to form hydrogen bonds.

• Cohesion: Water molecules stick together due to hydrogen bonding.

• Adhesion: Water molecules stick to other substances.

• Moderation of Temperature: Water absorbs and releases heat with little temperature change.

• Expansion upon Freezing: Ice is less dense than liquid water, allowing it to float.

• Solvent of Life: Water dissolves many substances, making it an excellent solvent.

Acids, Bases, and pH

• Acids donate protons (H+), bases accept protons.

• pH measures the concentration of hydrogen ions in a solution.

Carbon: The Backbone of Life

• Carbon can form four covalent bonds, allowing for a diversity of stable organic molecules.

• Can bond with many different elements (e.g., hydrogen, oxygen, nitrogen).

• Can form single, double, and triple bonds.

• Carbon's versatility allows for the formation of large, complex molecules essential for life.

Table: Valence and Bonding of Key Elements

Element	Valence Electrons	Number of Bonds Needed to Fill Valence Shell
Hydrogen (H)	1	1
Oxygen (O)	6	2
Nitrogen (N)	5	3
Carbon (C)	4	4

Example: Urea Molecule

• Urea is an organic compound with the formula CO(NH2)2.

• Each atom forms the required number of bonds to satisfy its valence.

Additional info:

• Some explanations and examples have been expanded for clarity and completeness.

• Table entries and chemical examples are standard for introductory biology and chemistry courses.