Introduction to Biology & Homeostasis

Characteristics of Living Organisms

Living organisms share several fundamental characteristics that distinguish them from non-living matter. Understanding these traits is essential for studying human biology.

• Organization: Biological systems are structured hierarchically, from cells to tissues, organs, organ systems, and ultimately complex organisms.

• Metabolism: The sum of all chemical reactions in an organism, enabling the acquisition and transformation of energy for growth, repair, and maintenance.

• Homeostasis: The process by which organisms maintain a stable internal environment (e.g., body temperature, blood glucose levels) despite external changes.

• Response to Stimuli: The ability to sense and react to environmental changes, ensuring survival and adaptation.

• Reproduction and Development: The transmission of genetic information to offspring and the progression through life stages.

The Scientific Method

The scientific method is a systematic approach used to investigate natural phenomena and answer biological questions.

1. Observation: Identifying a phenomenon or question based on empirical evidence.

2. Hypothesis: Formulating a testable and falsifiable explanation for the observation.

3. Experimentation: Testing the hypothesis using controlled variables:

   • Independent Variable: The factor manipulated by the researcher.

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

   • Control Group: The baseline group that does not receive the experimental treatment, used for comparison.

4. Conclusion: Analyzing data to accept or reject the hypothesis, leading to further investigation or theory development.

Chemistry of Life

Atomic Structure & Chemical Bonds

Atoms are the basic units of matter, and their interactions form the foundation of biological molecules.

• Atoms: Consist of protons (positive charge), neutrons (neutral), and electrons (negative charge).

• Ionic Bonds: Formed when electrons are completely transferred from one atom to another, resulting in charged ions.

• Covalent Bonds: Formed when atoms share electrons. Polar covalent bonds involve unequal sharing, while nonpolar covalent bonds involve equal sharing.

• Hydrogen Bonds: Weak attractions between a partially positive hydrogen atom and a partially negative atom (such as oxygen in water).

Water & pH Balance

Water is essential for life, and its unique properties support biological processes. Maintaining pH balance is critical for cellular function.

• Properties of Water: High specific heat (resists temperature changes), excellent solvent, cohesive (sticks to itself) and adhesive (sticks to other substances).

• pH Scale: Measures hydrogen ion concentration ():

  • Acidic: (High concentration)

  • Neutral:

  • Basic/Alkaline: (Low concentration)

• Buffers: Chemical systems that absorb excess or ions to maintain stable blood pH (normally around ).

Biological Macromolecules

Macromolecules are large, complex molecules essential for life. Each type has unique building blocks and functions.

Practice Quiz

Sample Questions & Answers

• Question: What is the primary difference between a polar covalent bond and a nonpolar covalent bond? Answer: Polar covalent bonds involve unequal sharing of electrons between atoms, whereas nonpolar covalent bonds involve equal sharing of electrons.

• Question: Which organelle or chemical system prevents drastic changes in human blood pH? Answer: Biological buffer systems (such as the bicarbonate buffering system).

• Question: What type of macromolecule forms the primary bilayer component of cell membranes? Answer: Lipids (specifically phospholipids).