## Reading the Rock Record

Earth's history is recorded in layers of rock. Understanding how scientists read these layers is essential.

### Law of Superposition In undisturbed rock layers, the OLDEST layers are at the BOTTOM and the YOUNGEST are at the TOP.

### Dating Methods - Relative dating: determines which rock or fossil is OLDER or YOUNGER without giving an exact age. Uses position in rock layers. - Absolute (radiometric) dating: gives the ACTUAL AGE in years using radioactive decay. Measures how much of a radioactive element has decayed into a stable element.

### Half-Life The time it takes for HALF of a radioactive sample to decay. - After 1 half-life: 50% remains - After 2 half-lives: 25% remains - After 3 half-lives: 12.5% remains

### Common Dating Methods | Method | Range | Used On | |--------|-------|---------| | Carbon-14 | Up to ~50,000 years | Organic material | | Potassium-Argon | Millions to billions of years | Volcanic rock | | Uranium-Lead | Oldest rocks | Ancient minerals |

### Index Fossils Fossils of organisms that lived for a SHORT time over a WIDE area. Used to match rock layers across different locations.

### Geologic Time Scale Eons > Eras > Periods > Epochs (largest to smallest). Major divisions are based on mass extinctions and major changes in life.

### Unconformities Gaps in the rock record where layers are missing due to erosion or non-deposition. They represent "missing time" in the geological record.

## Natural Selection

Darwin identified four key principles that drive evolution:

1. Overproduction: organisms produce MORE offspring than can survive 2. Variation: individuals in a population have DIFFERENT traits (due to genetic variation) 3. Selection (differential survival): individuals with traits better suited to the environment are more likely to SURVIVE and REPRODUCE 4. Inheritance: favorable traits are passed to the NEXT GENERATION through genes

### Sources of Genetic Variation - Mutations: random DNA changes, the only source of entirely NEW genetic material - Sexual reproduction: mixing of genes from two parents creates new combinations - Gene flow: movement of genes between populations through migration

### Key Concepts - Fitness: how well an organism can survive and reproduce in its specific environment. Fitness is about adaptation to environment, NOT physical strength. - Natural selection acts on PHENOTYPE (visible traits), but evolution occurs through changes in GENOTYPE (DNA). - Acquired traits (like a scar or learned behavior) are NOT inherited and do NOT drive evolution.

## Adaptation and Speciation

### Three Types of Adaptations 1. Structural: physical body parts (giraffe's long neck, cactus spines, polar bear's thick fur) 2. Behavioral: actions an organism takes (migration, hibernation, playing dead, nocturnal activity) 3. Physiological: internal body processes (venom production, antibiotic resistance, ability to digest certain foods)

### Three Patterns of Natural Selection 1. Directional: one EXTREME trait is favored (example: longer beaks in birds to reach deeper flowers) 2. Stabilizing: the AVERAGE trait is favored (example: medium-weight babies have highest survival) 3. Disruptive: BOTH EXTREMES are favored over the average (example: very light and very dark moths survive, but medium ones are eaten)

### Speciation Process 1. Geographic isolation separates a population 2. Each group faces different environments 3. Natural selection favors different traits in each group 4. Over many generations, groups become so different they can no longer interbreed 5. They are now separate species

### Reproductive Isolation When two populations can no longer produce fertile offspring together, they have achieved reproductive isolation.

## Taxonomy and Classification

### What Is Taxonomy? The science of identifying, classifying, and naming organisms.

### Carl Linnaeus Father of modern taxonomy. Created binomial nomenclature (two-part Latin name: Genus species). Example: Homo sapiens.

### 8-Level Hierarchy (broadest to most specific) Domain > Kingdom > Phylum > Class > Order > Family > Genus > Species

Mnemonic: Dear King Philip Came Over For Good Spaghetti

### Three-Domain System | Domain | Cell Type | Description | |--------|-----------|-------------| | Bacteria | Prokaryotic | Single-celled, found everywhere | | Archaea | Prokaryotic | Single-celled, extreme environments | | Eukarya | Eukaryotic | Cells contain a nucleus |

### Four Kingdoms of Eukarya | Kingdom | Cells | Cell Walls | Nutrition | Notes | |---------|-------|------------|-----------|-------| | Animalia | Multicellular | No cell walls | Heterotrophs | Most are mobile | | Plantae | Multicellular | Cellulose | Autotrophs (photosynthesis) | Produce their own food | | Fungi | Mostly multicellular | Chitin | Heterotrophs (decomposers) | Break down dead matter | | Protista | Mostly single-celled | Varies | Varies | Diverse "catch-all" group |

### Surprising Fact Fungi are more closely related to ANIMALS than to plants. Both are heterotrophs, both store glycogen, and DNA evidence confirms the relationship.

### Modern Classification Modern classification uses DNA evidence and evolutionary relationships, not just physical appearance.

## Logical Fallacies Quick Reference

| Fallacy | What It Does | Example | |---------|-------------|---------| | Ad Hominem | Attacks the person, not the argument | "You failed math, so your opinion on the budget is worthless" | | Straw Man | Distorts the argument into an extreme version | "You want less homework? So you want students to never learn anything?" | | Red Herring | Changes the subject to distract | "Why worry about pollution when there are potholes on the roads?" | | Bandwagon | Claims it's true because everyone does it | "Everyone is buying this phone, so it must be the best" | | False Dilemma | Presents only two options when more exist | "Either you agree with me, or you don't care about the environment" | | Slippery Slope | Claims one step leads to disaster without evidence | "If we allow phones in class, students will never read books again" | | Appeal to Authority | Uses a famous person without relevant expertise | "This celebrity says the product works, so it must" | | Circular Reasoning | Uses the conclusion as its own evidence | "This is the best school because no school is better" |