Characteristics of Living Things

Defining Life

• Highly Ordered Structure: Living organisms exhibit complex and organized structures at multiple levels.

• Reproduction: Ability to produce offspring of their own kind.

• Growth and Development: Controlled by inherited genetic material (DNA).

• Energy Processing: Use chemical energy to power activities.

• Response to Environment: React to stimuli in their surroundings.

• Regulation: Maintain internal environment to sustain life (homeostasis).

• Evolutionary Adaptation: Populations evolve over generations; individuals with useful traits reproduce more and pass on those traits.

Are These Things Alive?

Examples and Borderline Cases

• Crystals: Non-living, lack biological processes.

• Viruses: Borderline; require host cells to reproduce, lack independent metabolism.

• Bryozoans: Living colonial animals.

Biological Organization

Levels of Organization

• Biosphere: All environments that support life.

• Ecosystem: Organisms living in a particular area and the physical components they interact with.

• Community: Entire array of organisms living in an ecosystem; focuses on living things only.

• Population: Individuals of a species in a specific area (e.g., pack of wolves, guanacos).

• Organism: An individual living entity (e.g., a single wolf).

• Organ: Structure composed of tissues performing a specific function (e.g., heart).

• Tissues: Groups of cells performing similar functions (e.g., muscle tissue).

• Cells: Fundamental unit of life (e.g., muscle cell).

• Organelle: Membrane-bound structure with a specific function within a cell (e.g., sarcoplasmic reticulum).

• Molecule: Cluster of small chemical units held together by chemical bonds (e.g., ATP).

Cell Structure and Types

Basic Properties

• All cells are enclosed by a membrane.

• Two major types:

  • Eukaryotic: Large, with nucleus and membrane-bound organelles.

  • Prokaryotic: Small, no nucleus (DNA is loose), no membrane-bound organelles.

Transmission of Genetic Material

DNA and Genes

• Deoxyribonucleic acid (DNA): Molecule with instructions to make proteins; hereditary molecule.

• Double helix: Two chains that connect; each link is an 'alphabet' for hereditary code.

• Genes: Units of inheritance; long strips of DNA coding for specific proteins.

• Chromosome: Collection of many genes.

Transfer of Energy

Energy in Biological Systems

• Doing work requires energy.

• Energy is neither created nor destroyed; it is transferred or transformed.

• Energy Flow: Organisms interact with each other and the environment, transferring energy.

Diversity of Life and Classification

Three Domains of Life

• Bacteria: Prokaryotic.

• Archaea: Prokaryotic.

• Eukarya: Eukaryotic; includes kingdoms Plantae, Fungi, and Animalia.

Taxonomic Hierarchy (Example: Wolf)

• Domain: Eukarya

• Kingdom: Animalia

• Phylum: Chordata

• Class: Mammalia

• Order: Carnivora

• Family: Canidae

• Genus: Canis

• Species: Lupus

Evolution and Natural Selection

Key Concepts

• Evolution: Change over time; diversity is a product of evolution.

• Descent with Modification: Offspring are different from ancestors due to changes over time.

• Natural Selection: Individuals with traits that enable success leave more offspring; mechanism for evolution.

• Traits must be heritable (coded by DNA) for evolution to occur.

Darwin's Observations

• Individuals vary; not all are exact copies.

• Variation is heritable.

• More offspring are produced than can survive.

Scientific Method and Hypothesis Testing

Forming and Testing Hypotheses

• Hypothesis: Tentative answer to a well-framed question; must be testable and falsifiable.

• Theory: Broad explanation supported by evidence; can generate new hypotheses.

• Steps:

  • Testing ideas

  • Forming hypotheses

  • Predicting results

  • Doing experiments and making observations

  • Gathering data

  • Analyzing results

  • Interpreting results

  • Supporting or contradicting hypothesis

  • Inspire revised or new hypothesis

What Science Does and Does Not Do

• Provides objective framework for understanding the natural world.

• Does not address supernatural phenomena or make moral judgments.

Deductive Reasoning

• Type of logic where specific results are predicted from a general statement or hypothesis.

Experimental Design and Variables

Types of Data

• Qualitative: Descriptions rather than measurements.

• Quantitative: Numerical measurements; often organized into tables or graphs.

Controlled Experiments

• Manipulate variables to cause differences between groups (e.g., gene knockout mice).

• Comparative experiments look for differences between samples/groups (e.g., sample group of male seals vs. female seals).

Variables

• Independent Variable: Variable being manipulated (e.g., genes in mice).

• Dependent Variable: Variable being measured (e.g., mass in both groups).

Chemistry of Life

Matter and Elements

• Matter: Anything that takes up space and has mass; can be solid, liquid, or gas.

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

• Atom: Smallest unit retaining properties of an element.

Subatomic Particles

• Electron: Negatively charged, found in cloud around nucleus.

• Proton: Positively charged, found in nucleus.

• Neutron: Neutral charge, found in nucleus.

Isotopes and Radioisotopes

• Isotope: Different forms of the same element; same number of protons, different number of neutrons.

• Radioisotope: Unstable isotope; decays and releases energy.

• Uses: Ecology, medicine, paleontology, archaeology, geology.

• Tracer: Labeled compounds (e.g., glucose with radioactive carbon) used to track biological processes.

Electron Shells and Chemical Bonds

Electron Shells

• First shell: Maximum 2 electrons.

• Second shell: Maximum 8 electrons.

• Third shell: Maximum 8 electrons.

• Valence shell: Outermost shell; determines chemical reactivity.

Types of Chemical Bonds

• Covalent: Atoms share electrons; can be polar (unequal sharing) or nonpolar (equal sharing).

• Ionic: Formed by electrical attraction between oppositely charged ions (cation and anion).

• Hydrogen bond: Noncovalent attraction between hydrogen and electronegative atom; important in water and biological molecules.

Water and Its Properties

Importance of Water

• Organisms are made mostly of water; life depends on water's properties.

• Polarity: Water is polar; oxygen has a more negative charge than hydrogen.

• Cohesion: Water molecules stick together via hydrogen bonds.

• Adhesion: Water molecules stick to other substances.

• Surface tension: Responsible for water's high surface tension.

Thermal Properties

• Temperature: Average kinetic energy of molecules.

• Specific heat: Amount of heat needed to raise temperature; water has high specific heat.

• Evaporative cooling: High heat of vaporization; water absorbs heat when evaporating.

• Freezing: Ice is less dense than liquid water; floats.

Solutions and Solubility

• Solution: Homogeneous mixture of two or more substances.

• Solvent: Dissolving agent (water is a common solvent).

• Solute: Substance that dissolves.

• Hydrophilic: Polar substances that dissolve easily in water.

• Hydrophobic: Nonpolar substances that do not dissolve in water.

Acids, Bases, and pH

• Acid: Substance that increases H+ concentration.

• Base: Substance that reduces H+ concentration (releases OH-).

• At 20°C, the product of H+ and OH- concentrations is:

• pH is defined as:

• Buffers minimize changes in pH by accepting or donating H+ ions.

Carbon Chemistry and Biological Molecules

Carbon and Its Importance

• All organic materials contain carbon; carbon's valence determines chemical characteristics.

Hydrocarbons

• Molecules made of only carbon and hydrogen.

• Major component of fossil fuels.

• Hydrocarbons are nonpolar; soluble in nonpolar solvents.

Variation in Carbon-Containing Molecules

• Length, branching, double bond position, presence of rings.

Functional Groups

• Components of organic molecules; most commonly involved in chemical reactions.

• Presence and arrangement of functional groups give molecules unique properties.

• Example: ATP (Adenosine Triphosphate) is a functional group important for energy transfer.

Monomer vs. Polymer

• Monomer: Individual molecular unit.

• Polymer: Many monomers linked together; can be very large.

• Polymers are formed by linking monomers via chemical reactions.

Ocean Acidification

• CO2 dissolves in ocean water, forming carbonic acid:

• Carbonic acid dissociates into hydrogen ions and bicarbonate ions:

• Additional H+ combines with carbonate ions () to form more bicarbonate ().

Summary Table: Levels of Biological Organization

Additional info:

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

• Equations and chemical reactions are provided in LaTeX format for academic accuracy.