General Biology: Foundations, Chemistry, and Biological Organization

Characteristics of Living Things

Shared Features of All Living Organisms

All living things possess certain fundamental characteristics that distinguish them from non-living matter.

• Cellular Structure: Composed of basic units called cells.

• Genetic Code: Use a universal genetic code (DNA).

• Metabolism: Obtain and use materials and energy.

• Growth and Development: Grow and develop over time.

• Reproduction: Ability to reproduce and pass on traits.

• Response to Environment: Respond to environmental stimuli.

• Homeostasis: Maintain stable internal conditions.

• Evolution: Change over generations through adaptation.

Unifying Themes in Biology

Five Unifying Themes

Biology is organized around several major themes that help explain the unity and diversity of life.

• Organization: Biological systems are structured from atoms up to the biosphere.

• Information: Genetic information is essential for life processes.

• Energy and Matter: Life requires energy transfer and matter cycling.

• Interactions: Organisms interact with each other and their environment.

• Evolution: Explains the unity and diversity of life.

Biological Organization

Hierarchy of Biological Organization

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

• Atoms

• Molecules

• Organelles

• Cells

• Tissues

• Organs

• Organisms

• Populations

• Communities

• Ecosystems

• Biosphere

Emergent Properties

Emergent properties arise from the arrangement and interaction of parts as complexity increases.

• These properties are not present in individual components but emerge when components interact.

• Example: Life is an emergent property of complex molecular interactions within cells.

Structure and Function

Structure and function are closely related in biology; the shape and arrangement of biological molecules and cells determine their roles and effectiveness.

• Example: The structure of enzymes allows them to catalyze specific biochemical reactions.

Cell Types and Genetic Information

Prokaryotic vs. Eukaryotic Cells

Cells are classified into two major types based on their structure.

• Similarities: Both have DNA, cytoplasm, a membrane, and ribosomes.

• Differences: Eukaryotic cells are larger, have membrane-bound organelles, and a nucleus; prokaryotic cells do not.

DNA and Gene Expression

DNA is the hereditary material that dictates cellular structure and function.

• Gene Expression: The process of converting genetic information from DNA into functional products (proteins).

• Example: DNA is transcribed into RNA, which is then translated into protein.

Tree of Life and Biological Classification

Biologists organize living things using the concept of the "Tree of Life," which illustrates evolutionary relationships.

• Three domains: Bacteria, Archaea, Eukarya.

• Each domain branches into kingdoms and further subdivisions.

Evolution as a Unifying Principle

Evolution explains how all living organisms are related and have diversified from common ancestors.

• All living organisms are modified descendants of common ancestors.

Scientific Method and Experimental Design

Variables in Experiments

Experiments are designed to test hypotheses using variables:

• Control: Group not receiving experimental treatment.

• Dependent Variable: The measured outcome affected by changes.

• Independent Variable: The factor changed by the researcher.

Chemistry of Life

Atoms, Elements, Compounds, and Molecules

All matter is composed of atoms, which combine to form elements, compounds, and molecules.

• Atom: Smallest unit of matter retaining properties of an element.

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

• Compound: Substance consisting of two or more elements in fixed ratio.

• Molecule: Two or more atoms held together by covalent bonds.

Essential vs. Trace Elements

Elements required for life are classified as essential or trace elements.

• Essential Elements: Make up most of living matter (e.g., carbon, hydrogen, oxygen, nitrogen).

• Trace Elements: Required in minute quantities (e.g., iron, zinc).

Elements Essential for Life

• Main: Carbon, hydrogen, oxygen, nitrogen, calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium.

• Trace: Boron, chromium, cobalt, copper, fluorine, iodine, iron, manganese, molybdenum, selenium, tin, vanadium, zinc.

Subatomic Particles

Atoms are composed of subatomic particles:

• Neutrons: No charge, found in nucleus.

• Protons: Positive charge, found in nucleus.

• Electrons: Negative charge, found in electron cloud around nucleus.

Atomic Number, Mass, and Isotopes

• Atomic Number: Number of protons in nucleus.

• Atomic Mass: Sum of protons and neutrons.

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

Radioisotopes in Biology

Radioisotopes are used as tracers in biological research and medicine.

• Radioactive Tracers: Used in metabolic diagnostics and imaging.

Application	Description
Radiometric Dating	Uses decay of radioisotopes to date fossils and rocks.
Medical Imaging	Imaging techniques like PET scans to monitor cancer growth and metabolism.

Electron Energy Levels, Orbitals, and Valence Shells

• Energy Level: Capacity to cause change.

• Orbitals: Regions where electrons are found 90% of the time.

• Valence Shell: Outermost shell, determines chemical behavior.

Chemical Bonds

Atoms form chemical bonds to achieve stability.

• Covalent Bonds: Atoms share electrons (usually non-metals).

• Ionic Bonds: Atoms transfer electrons, forming charged ions (metals and non-metals).

Polarity of Covalent Bonds

• Nonpolar: Atoms share electrons equally (similar electronegativity).

• Polar: Atoms share electrons unequally (different electronegativity).

Hydrogen Bonds

Hydrogen bonds are weak interactions important for biological molecules.

• Occur when hydrogen covalently bonded to an electronegative atom is attracted to another electronegative atom.

• Stabilize structures like DNA and proteins.

• Contribute to water's unique properties (high specific heat, cohesion).

Van der Waals Interactions

Weak attractions between molecules due to transient charge differences.

• Important for molecular recognition and structure.

Reactants and Products

• Reactant: Starting molecules of a chemical reaction.

• Product: Resulting molecules after the reaction.

Additional info:

• Equations for atomic mass: $\text{Atomic mass} = \text{Number of protons} + \text{Number of neutrons}$

• General formula for chemical reactions: $\text{Reactants} \rightarrow \text{Products}$