Natural Selection and Evolution

Principles of Natural Selection

Natural selection is a fundamental mechanism of evolution, describing how traits become more or less common in a population due to differential reproductive success.

• DNA Evolution: Animal DNA evolves without human interference.

• Overproduction of Offspring: More offspring are produced than can survive.

• Variation: Offspring have variable genetic makeup.

• Hereditary Traits: Genes are passed on to offspring.

• Limited Resources: Competition for resources leads to selection.

• Survival and Reproduction: Individuals with advantageous traits survive and reproduce more.

• Trait Favorability: Favorable traits are passed on to future generations.

• Energy Use: Animals with more volume use energy faster.

Secondary Metabolic Compounds

Secondary metabolic compounds are chemicals produced by organisms that are not essential for basic metabolism but serve other functions.

• Not Essential: Not required for plant metabolism.

• Metabolically Expensive: Require significant energy to produce.

• Camouflage: May help organisms avoid or confuse predators.

Classification of Life Domains

Life is classified into three major domains based on cellular characteristics.

Scientific Method

Steps of the Scientific Method

The scientific method is a systematic approach to inquiry in biology.

• Observation: Make observations and ask questions.

• Hypothesis Formation: Develop a testable hypothesis.

Chemistry in Biology

Atoms, Molecules, and Chemical Bonds

Atoms are the basic units of matter, and chemical bonds hold atoms together in molecules.

• Ionic Bonds: Formed when two elements bond, resulting in one positive and one negative ion.

• Planetary Model of the Atom: Electrons orbit the nucleus, which contains protons and neutrons.

Water and Life

Water is essential for life due to its unique chemical properties.

• Hydrolysis Reaction: Water breaks apart chemical bonds.

• Dehydration Synthesis: Water is removed to form bonds.

• Water Bonding: Water molecules form hydrogen bonds, contributing to its properties.

Water, pH, Acids, and Bases

pH measures the concentration of hydrogen ions in a solution, affecting biological processes.

• Neutral pH: Substances that dissolve easily are considered to have a neutral pH.

• Acidity: Lower pH means more acidic; higher pH means more basic.

• pH Scale: Each unit change represents a tenfold change in hydrogen ion concentration.

Example: pH 1 is 10x more acidic than pH 2, 100x more than pH 3, etc.

Energy and Organic Molecules

Endothermic and Exothermic Reactions

Chemical reactions in biology can absorb or release energy.

• Endothermic: Heat is absorbed (e.g., photosynthesis).

• Exothermic: Heat is released.

Photosynthesis Equation:

ATP and Hydrolysis

ATP (adenosine triphosphate) stores and releases energy for cellular processes.

• ATP Hydrolysis: Uses water to break down ATP, releasing energy.

Organic Molecules and Hydrocarbons

Organic molecules contain carbon and are the basis of life.

• Hydrocarbons: Molecules with only hydrogen and carbon; nonpolar and hydrophobic.

• Structure: Can form rings or branches.

Cellular Respiration

Autotrophs vs. Heterotrophs

Organisms obtain energy in different ways.

• Autotroph: Self-feeding, produces its own food (e.g., plants).

• Heterotroph: Consumes other organisms for energy.

Substrate and Phosphorylation

Substrate-level phosphorylation is a process that generates ATP by transferring a phosphate group to ADP.

• Substrate: The surface or material on which an organism lives or a reaction occurs.

• Phosphorylation: Addition of a phosphate group to a molecule (e.g., glucose or ATP).

Citric Acid Cycle and Oxidation

The citric acid cycle (Krebs cycle) is a series of chemical reactions used by all aerobic organisms to generate energy.

• Oxidation: Loss of electrons from an atom, molecule, or ion, increasing its oxidation state.

• Substrate-Level Phosphorylation: Direct formation of ATP from ADP and a substrate.

• Negative Feedback: Output of a process inhibits its own production.

• Glucose Breakdown: Glucose is split into ATP and NADH.

• Cristae: Folds in the inner mitochondrial membrane, increasing surface area for electron transport.

• Mitochondrial Matrix: The space inside the inner membrane where the citric acid cycle occurs.

Electron Transport Chain (ETC)

The ETC is a series of protein complexes that transfer electrons and produce ATP.

• Final Electron Receptor: Oxygen accepts electrons at the end of the chain.

• Proton Motive Force: Electrochemical gradient of protons (H+) across a membrane, storing potential energy.

• ATP Synthase: Enzyme that uses the proton gradient to produce ATP.

Photosynthesis

Structure and Function

Photosynthesis occurs in plant cells, primarily in the chloroplasts, and converts light energy into chemical energy.

• Pigments: Reflect different wavelengths of light; chlorophyll reflects green.

• Leaf Structure: Includes cuticle, epidermis, mesophyll, stoma, vascular bundle, and bundle sheath.

Light Reactions and Electron Transport

Light energy excites electrons in pigments, initiating a chain of reactions.

• Reaction Center: Site where light energy is converted to chemical energy.

• Z Scheme: Pathway of electron flow through photosystems I and II.

• NADPH: Electron carrier produced in the light reactions.

• Calvin Cycle: Begins with fixation of carbon dioxide by RuBP.

Example: The Calvin cycle uses ATP and NADPH to convert CO2 into glucose.

Additional info:

• Photosynthesis and cellular respiration are complementary processes: photosynthesis stores energy in glucose, while respiration releases it.

• pH scale ranges from 0 (most acidic) to 14 (most basic), with 7 being neutral.