Properties of Life

Key Characteristics of Living Things

Living organisms share several fundamental characteristics that distinguish them from non-living matter. These properties are essential for the study of biology.

• Order: Living things exhibit complex organization, from molecules up to entire biospheres.

• Energy Processing: Organisms obtain and use energy to power life processes (metabolism).

• Growth and Development: Organisms grow and develop according to specific instructions coded in their DNA.

• Reproduction: Living things can reproduce, passing genetic material to offspring.

• Response to Environment: Organisms detect and respond to environmental stimuli.

• Evolutionary Adaptation: Populations evolve over generations through adaptations that enhance survival and reproduction.

• Regulation: Organisms maintain internal stability (homeostasis) despite external changes.

Levels of Biological Organization

Biological systems are organized in a hierarchy from smallest to largest:

• Organelles → Cells → Tissues → Organs → Organ Systems → Organisms → Populations → Communities → Ecosystems → Biosphere

Metabolism

Metabolism encompasses all chemical reactions in an organism, divided into two main types:

• Anabolic Metabolism: Building up molecules (e.g., photosynthesis); requires energy.

• Catabolic Metabolism: Breaking down molecules (e.g., cellular respiration); releases energy.

• Autotrophs: Use inorganic sources of carbon (e.g., algae, plants, some bacteria).

• Heterotrophs: Require organic sources of carbon (e.g., animals, fungi, most bacteria).

• Trophs: Refers to feeding strategies (e.g., autotroph, heterotroph).

• Some plants (e.g., Venus flytrap) can be both autotrophic and heterotrophic.

Growth, Reproduction, and Response to Stimuli

• Growth: Increase in size and number of cells.

• Reproduction: Inheritance of genetic material. Can be asexual (binary fission, mitosis) or sexual (meiosis, fertilization).

• Response to Stimuli: Organisms detect and respond to changes in their environment (e.g., plants bending toward light, animals using nervous systems).

Regulation and Homeostasis

• Homeostasis: Maintenance of stable internal conditions (e.g., temperature, pH, hormone levels).

Classification of Organisms

Hierarchy of Life

Biological classification organizes living things into a hierarchy:

• Atoms (e.g., Carbon)

• Molecules (e.g., Lipids)

• Organelles (e.g., Golgi apparatus)

• Cells (e.g., Hepatocytes)

• Tissues (e.g., Liver parenchyma)

• Organs/Organ Systems (e.g., gastrointestinal tract)

• Organisms (e.g., humans)

• Population (same species living together)

• Community (different species living together)

• Ecosystem (all living and nonliving things in an area)

• Biosphere (all life on Earth)

Taxonomy: Classifying the Diversity of Life

• Taxonomy: The science of classifying organisms.

• Domains: Most encompassing level (Bacteria, Archaea, Eukarya).

• Species: Most specific designation.

• Hierarchy: Species, Genus, Family, Order, Class, Phylum, Kingdom, Domain.

• Mnemonic: "Dear King Philip Came Over For Good Soup"

Binomial Nomenclature

• Each species is given a two-part scientific name: Genus species.

• Genus name is capitalized and italicized/underlined; species name is lowercase and italicized/underlined.

• Example: Homo sapiens

Three Domains of Life

• Archaea: Unicellular, prokaryotic, distinct metabolism, often extremophiles.

• Bacteria (Eubacteria): Unicellular, prokaryotic, found everywhere, lack nucleus.

• Eukarya: Unicellular or multicellular, have a nucleus, includes Protists, Fungi, Plantae, Animalia.

Table: Comparison of the Three Domains

Scientific Inquiry and the Scientific Method

Nature of Scientific Inquiry

Science is a systematic way of knowing and understanding the natural world, based on evidence and testable explanations.

Stages of the Scientific Method

1. Exploration and Observation: Ask questions about the natural world.

2. Gathering Data: Collect quantitative or qualitative data.

3. Reasoning/Logic: Formulate hypotheses based on observations.

4. Data Analysis: Test hypotheses and draw conclusions.

Types of Reasoning

• Inductive Reasoning: Uses specific observations to make generalizations or predictions.

• Deductive Reasoning: Uses general premises to reach specific conclusions.

Hypothesis Testing

• Hypothesis: A testable, educated guess about how things work.

• Null Hypothesis (H0): States that any observed difference is due to random chance.

• Alternative Hypothesis (HA): States that observed differences are due to a specific cause.

• P-value: Probability that the observed difference is due to chance. Common threshold: 0.05.

• If p < 0.05, reject the null hypothesis.

Experimentation

• Manipulate one factor (variable) to observe its effect.

• Experimental group: receives the variable being tested.

• Control group: does not receive the variable.

• Uncontrolled variables can weaken conclusions.

Evolution and the Limits of Science

Darwin's Points and Natural Selection

• Individuals with traits suited to their environment are more likely to survive and reproduce.

• Evolution occurs as unequal reproductive success adapts populations to their environment.

Science and Faith

• Creationism: All organisms were created by God at the beginning.

• Intelligent Design: Complexity of life suggests a designer.

• Evolution: Life changes over time through mutations and natural selection.

Limitations of Science

• Science is limited to observable phenomena.

• Cannot bring dead to life or restore extinct species.

• Cannot test supernatural/religious phenomena.

Basic Chemistry for Biology

Matter and Elements

• Matter: Anything that has mass and occupies space.

• Mass: Measured in grams (g).

• Elements: Pure substances consisting of one type of atom.

• Four elements make up 96% of living matter: Carbon (C), Oxygen (O), Hydrogen (H), Nitrogen (N).

• Trace elements are required in small amounts (e.g., iron, zinc).

• Compounds: Substances formed from two or more elements in a fixed ratio (e.g., NaCl).

Atomic Structure

• Atomic Number: Number of protons in the nucleus.

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

• Radioisotopes: Unstable isotopes that emit radiation (alpha, beta, gamma particles).

• Radioisotopes have applications in medicine (e.g., PET scans, cancer treatment).

Electrons and Chemical Bonds

• Electrons are involved in chemical reactions and determine chemical properties.

• Electrons occupy energy levels (shells) around the nucleus.

• Valence electrons are in the outermost shell and determine bonding behavior.

• Each orbital can hold a maximum of 2 electrons.

Types of Chemical Bonds

• Covalent Bonds: Sharing of electron pairs between atoms.

• Single covalent bond: sharing one pair of electrons.

• Double covalent bond: sharing two pairs of electrons.

• Ionic Bonds: Transfer of electrons from one atom to another, resulting in charged ions.

• Hydrogen Bonds: Weak attractions between a hydrogen atom covalently bonded to one electronegative atom and another electronegative atom.

• Van der Waals Interactions: Weak, temporary attractions due to asymmetrical electron distribution.

Electronegativity

• Electronegativity is the tendency of an atom to attract electrons in a bond.

• Differences in electronegativity determine bond type (nonpolar covalent, polar covalent, ionic).

Water and Its Properties

Importance of Water

• Water covers about 75% of Earth's surface; most is in liquid form.

• Most living tissues are at least 70% water.

• Water is the solvent for many compounds in living tissues.

States of Water

• Solid: Ice, forms a lattice due to hydrogen bonds, less dense than liquid water.

• Liquid: Hydrogen bonds break and reform, allowing fluidity.

• Gas: Water vapor, hydrogen bonds are broken.

Cohesion, Adhesion, and Surface Tension

• Cohesion: Water molecules stick together via hydrogen bonds (important for water transport in plants).

• Adhesion: Water molecules stick to other substances (e.g., cell walls).

• Surface Tension: Measure of how difficult it is to stretch or break the surface of a liquid.

Acids, Bases, and pH

• Acid: Substance that increases the concentration of H+ ions in solution.

• Base: Substance that decreases the concentration of H+ ions (often by accepting protons).

• pH: Measure of hydrogen ion concentration; calculated as .

Carbon and Molecular Diversity

Organic Compounds

• Organic compounds contain carbon and hydrogen.

• Carbon can form four covalent bonds, allowing for a variety of molecular structures.

• Functional groups (e.g., hydroxyl, carboxyl, amino, phosphate) determine chemical reactivity and properties.

ATP and Energy

• ATP (Adenosine Triphosphate): Main energy currency of the cell.

• Contains three phosphate groups; energy is released when a phosphate group is removed.

Additional info: Some explanations and examples were expanded for clarity and completeness, including the table comparing domains and the summary of functional groups.