Biology: The Study of Life

Introduction to Biology

Biology is the scientific study of life and living organisms. It encompasses the structure, function, growth, origin, evolution, and distribution of living things.

• Definition: Biology is the knowledge about the natural world, specifically life and living organisms.

• Key Questions in Biology:

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

  • How do various living things function?

  • How do we organize the diversity of life to better understand it?

  • How did this diversity arise and how is it continuing?

Properties of Life

Key Characteristics of Living Organisms

All living organisms share several key characteristics or functions. These properties distinguish living things from non-living matter.

• 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 stimuli (e.g., plants grow toward light).

• Reproduction: Organisms reproduce, passing genetic material (DNA) to offspring. In humans, sex is determined by X and Y chromosomes.

• Adaptation: Organisms evolve traits that help them survive and reproduce in their environment.

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

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

• Energy Processing: Organisms use energy for metabolic activities (e.g., birds eat food and convert it to energy).

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

Levels of Organization of Living Things

Biological Hierarchy

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

Hierarchy (Highest to Lowest): Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

Phylogenetic Tree: Diagram showing evolutionary relationships among species based on similarities and differences in genetic or physical traits.

Branches of Biological Study

• Molecular Biology: Studies biological processes at the molecular level (DNA, RNA, proteins).

• Microbiology: Study of microorganisms.

• Paleontology: Study of fossils and evolutionary history.

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

Scientific Ethics

• Ethical considerations are important in scientific research, especially regarding human subjects.

• Example: Testing medical treatments in different populations requires informed consent and ethical oversight.

The Process of Science

Scientific Method

The scientific method is a systematic approach to understanding the natural world through observation, hypothesis formation, experimentation, and analysis.

• What is Science? Knowledge about the natural world.

• Hypothesis: A testable statement, often in "if...then" format.

• Scientific Method Steps:

  1. Ask a question

  2. Form a hypothesis

  3. Conduct experiments

  4. Analyze data

  5. Draw conclusions

• Scientific Laws: Expressed in mathematical formulas, describe how elements of nature behave under certain conditions.

• Physical Sciences: Study nonliving matter (e.g., chemistry, physics).

Scientific Inquiry

Scientific inquiry involves asking questions, making observations, and conducting experiments to answer those questions.

Essential Chemistry for Biology

Elements and Compounds

• Matter: Anything that occupies space and has mass.

• Mass: Measure of the amount of material in an object.

• Element: Substance that cannot be broken down by chemical reactions.

• All matter is composed of chemical elements.

• Of 92 naturally occurring elements, 25 are essential for life. Four elements (oxygen, carbon, hydrogen, nitrogen) make up about 96% of the human body.

• Trace Elements: Required in very small amounts but essential for life (e.g., iron, iodine).

Atoms and Subatomic Particles

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

• Composed of subatomic particles:

  • Proton: Positive charge

  • Neutron: No charge

  • Electron: Negative charge

• Atomic Number: Number of protons in an atom.

• Mass Number: Sum of protons and neutrons in the nucleus.

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

• Radioactive Isotope: Nucleus decays spontaneously, emitting radiation.

Chemical Bonding and Molecules

• Atoms bond to form molecules, which are essential for life.

• Chemical Bonds: Attractions that hold atoms together.

  • 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 (e.g., between water molecules).

• Polar Molecule: Molecule with unequal distribution of charge (e.g., H2O).

Table: Types of Chemical Bonds

Water and Life

• Life on Earth began in water; cells are 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 of Life: Water dissolves many substances, forming aqueous solutions.

• Solution: Homogeneous mixture of two or more substances.

• Solvent: Dissolving agent (e.g., water).

• Solute: Substance dissolved in solvent.

Acids, Bases, and pH

• Acid: Substance that increases hydrogen ion (H+) concentration in solution.

• Base: Substance that reduces hydrogen ion concentration.

• pH Scale: Measures acidity or basicity of a solution.

Additional info:

• Scientific laws in biology are often expressed mathematically, such as the Hardy-Weinberg equilibrium in population genetics.

• Examples of trace elements include zinc and copper, which are vital for enzyme function.