S8 - Q4 - Unit 1 Review
Biological Evolution + Critical Thinking
Learning Objectives
Explain how scientists use the rock record, fossils, and dating methods to determine Earth's history
Describe Darwin's four principles of natural selection and explain how they drive evolution
Compare types of adaptations and patterns of natural selection, and explain how speciation occurs
Classify organisms using the 8-level taxonomic hierarchy, 3 domains, and 4 kingdoms of Eukarya
Identify the 8 logical fallacies by name and definition
Detect logical fallacies in real-world scenarios
Apply the 3-question defense strategy to evaluate claims
Rock Record Review
~5 minutesReading 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.Start: 100%. After 1 half-life: 50%. After 2: 25%. After 3: 12.5%. After 4: 6.25%. Each half-life cuts the remaining amount in half.
Rock Record Practice
According to the Law of Superposition, where are the OLDEST rock layers found?
Relative dating tells you the exact age of a rock in years.
A radioactive element has a half-life of 1,000 years. If you start with 200 grams, how much will remain after 3,000 years (3 half-lives)?
What makes a fossil an 'index fossil'?
Arrange the divisions of the geologic time scale from LARGEST to SMALLEST.
The dating method that gives the actual age of a rock in years is called ______ dating, also known as radiometric dating.
A scientist finds the same index fossil in rock layers at two locations 500 miles apart. What can the scientist conclude?
An unconformity in a rock sequence indicates:
Natural Selection Review
~5 minutesNatural 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.
Overproduction: producing more offspring than can survive. Variation: differences in traits among individuals. Selection: better-suited traits lead to higher survival. Inheritance: favorable traits passed to the next generation. Fitness: how well an organism survives and reproduces in its environment. Mutation: random DNA change. Gene flow: movement of genes between populations. Phenotype: visible traits. Genotype: DNA sequence.
Natural Selection Practice
Match each principle of natural selection to its description.
Natural selection acts on an organism's genotype (DNA) directly.
Which of the following is a source of genetic variation?
In a population of rabbits, those with thicker fur survive cold winters better and produce more offspring. Over many generations, the average fur thickness in the population increases. Which principle is MOST directly responsible for this change?
A bodybuilder's children will be born with larger muscles because the parent developed them through exercise.
In evolutionary biology, 'fitness' refers to:
Which of the following are sources of genetic variation? (Select all that apply)
Select all that apply.
A population of beetles has brown and green individuals. Birds eat the brown beetles more easily against green leaves. After many generations, the population is mostly green. This is an example of:
Adaptation and Speciation Review
~5 minutesAdaptation 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 speciesReproductive Isolation
When two populations can no longer produce fertile offspring together, they have achieved reproductive isolation.Structural adaptation: a physical body feature. Behavioral adaptation: an action or behavior. Physiological adaptation: an internal body process. Directional selection: one extreme is favored. Stabilizing selection: the average is favored. Disruptive selection: both extremes are favored. Geographic isolation: a physical barrier separates a population. Reproductive isolation: populations can no longer interbreed. Speciation: the formation of new, separate species.
Adaptation and Speciation Practice
Match each adaptation to its type.
In a population of snails, the average shell thickness provides the best protection. Snails with very thin or very thick shells are less likely to survive. Which pattern of selection is this?
A mountain range divides a population of squirrels. After thousands of years, the two groups can no longer interbreed. This is an example of:
Which pattern of natural selection favors ONE extreme trait over the average?
Behavioral adaptations are changes in an organism's DNA structure.
In a population of moths, light-colored and dark-colored moths both survive well, but medium-colored moths are easily spotted by predators. Which selection pattern is occurring?
When two populations can no longer produce fertile offspring together, they have achieved ______ isolation and are considered separate species.
A cactus has spines instead of broad leaves. This is an example of which type of adaptation?
Taxonomy Review
~5 minutesTaxonomy 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 > SpeciesMnemonic: 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.Dear King Philip Came Over For Good Spaghetti = Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species. Broadest to most specific.
Taxonomy Practice
Arrange the levels of classification from BROADEST to MOST SPECIFIC.
Who is known as the 'father of modern taxonomy' and created the binomial nomenclature system?
Match each domain to its description.
Which kingdom of Eukarya is MOST closely related to animals?
In the scientific name Homo sapiens, 'Homo' represents the:
Which of the following are characteristics of Kingdom Plantae? (Select all that apply)
Select all that apply.
Critical Thinking Review
~3 minutesLogical 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" |
When you hear a claim, ask: (1) What is the actual claim? (2) What evidence supports it? (3) Is the reasoning valid, or does it contain a fallacy?
Critical Thinking Practice
Which logical fallacy distorts someone's argument into an extreme version and then attacks that distorted version?
Match each statement to the logical fallacy it demonstrates.
'A famous actor says this vitamin supplement changed his life, so it must really work.' Which fallacy is this?
'This new policy is the best decision because it is the right thing to do.' Which fallacy is this?
'Why are we discussing homework policies when the gym needs new equipment?' Which fallacy is this?
A classmate argues: 'You want to add a recycling program? That's just the first step. Next they'll make us give up our cars, then our electricity, and soon we'll be living like cave people.' Which TWO fallacies are present?
Select all that apply.
What is the THIRD and final question in the 3-question defense strategy?
'Everyone knows that studying with music helps you learn better.' Which fallacy is this?