AP Biology – Chapter 23: Broad Patterns of Evolution – Guided Study

Study Guide - Smart Notes

Tailored notes based on your materials, expanded with key definitions, examples, and context.

Q1. What is macroevolution? List the order of classification from kingdom to species.

Background

Topic: Macroevolution and Biological Classification

This question tests your understanding of large-scale evolutionary changes (macroevolution) and the hierarchical system of biological classification.

Key Terms:

Macroevolution: Large-scale evolutionary changes that occur over long time periods, resulting in the emergence of new species and higher taxonomic groups.
Taxonomic Hierarchy: The system used to classify living organisms into groups based on shared characteristics.

Step-by-Step Guidance

Start by defining macroevolution in your own words, focusing on how it differs from microevolution (which involves small-scale changes within a species).
Recall the main taxonomic ranks used in biological classification. Arrange them from the broadest (most inclusive) to the most specific (least inclusive).
Think about how each level groups organisms based on shared traits, with each subsequent level becoming more specific.

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Q2. What is a fossil and where are they usually found? What are the pros and cons of using fossils to record macroevolution?

Background

Topic: Fossils and the Fossil Record

This question examines your understanding of what fossils are, where they are typically located, and the strengths and limitations of using fossils to study evolutionary history.

Key Terms:

Fossil: Preserved remains or traces of ancient organisms, typically found in sedimentary rock layers.
Fossil Record: The collection of all known fossils and their placement in rock formations and sedimentary layers.

Step-by-Step Guidance

Define what a fossil is and describe the typical environments where fossils are most likely to be found.
List at least two advantages (pros) of using fossils to study macroevolution, such as providing direct evidence of past life forms.
List at least two disadvantages (cons), such as gaps in the fossil record or the rarity of fossilization.

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Q3. How is the fossil record like wallpaper in an old house?

Background

Topic: Interpreting the Fossil Record

This question uses an analogy to help you understand how layers in the fossil record can reveal information about Earth's history.

Key Concepts:

Stratification: The process by which sedimentary rocks are layered, similar to layers of wallpaper.
Analogy: Comparing the sequence of rock layers to layers of wallpaper to illustrate how older layers are buried beneath newer ones.

Step-by-Step Guidance

Think about how wallpaper is applied in layers over time, with the oldest layers at the bottom and the newest on top.
Relate this to how sedimentary rock layers form and how fossils are preserved within these layers.
Consider what information can be inferred by examining the sequence of layers in both wallpaper and rock strata.

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Q4. How is the age of a fossil determined? Explain radiometric dating and half-life. Define radioactive isotope.

Background

Topic: Dating Fossils

This question tests your understanding of methods used to determine the age of fossils, especially radiometric dating and the concept of half-life.

Key Terms and Formulas:

Radiometric Dating: A technique that uses the decay of radioactive isotopes to estimate the age of rocks and fossils.
Half-life: The time required for half of the radioactive atoms in a sample to decay.
Radioactive Isotope: An unstable form of an element that decays into a different element over time.

Key Formula:

= amount of radioactive isotope remaining after time
= original amount of isotope
= half-life of the isotope

Step-by-Step Guidance

Describe how radiometric dating works, focusing on the decay of radioactive isotopes.
Define half-life and explain its significance in determining the age of a sample.
Explain what a radioactive isotope is and why it is useful for dating fossils.
Set up the formula for calculating the age of a fossil using the proportion of remaining radioactive isotope.

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Q5. In fossils less than 75,000 years, what isotopes are used in radiometric dating? What isotopes do scientists use for fossils older than 75,000 years? Why are different isotopes needed for older fossils? What are the challenges to dating older fossils?

Background

Topic: Radiometric Dating – Isotope Selection

This question focuses on the selection of appropriate isotopes for dating fossils of different ages and the challenges involved in dating very old fossils.

Key Terms:

Carbon-14: Used for dating relatively recent fossils (up to about 75,000 years old).
Uranium-238, Potassium-40: Used for dating much older fossils.
Half-life: Determines how long an isotope can be used for dating.

Step-by-Step Guidance

Identify which isotope is commonly used for dating fossils less than 75,000 years old and explain why.
List the isotopes used for dating older fossils and discuss their longer half-lives.
Explain why different isotopes are needed for older fossils (consider the concept of half-life and detectability).
Discuss at least one challenge scientists face when dating very old fossils, such as contamination or the absence of suitable isotopes in the sample.

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Q6. How is earth’s geological record divided?

Background

Topic: Geological Time Scale

This question tests your knowledge of how Earth's history is organized into different time intervals based on major events in the fossil record.

Key Terms:

Eon, Era, Period, Epoch: The main divisions of the geological time scale, from largest to smallest.

Step-by-Step Guidance

Recall the largest divisions of geological time and their order from largest to smallest.
Think about how major events (such as mass extinctions) are used to define boundaries between these divisions.
List the main eons, eras, and periods relevant to the study of evolution.

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Q7. Use Figure 23.5 to answer the following questions: Which group of organisms have been around the longest? How long has this group been around? At what time point did atmospheric oxygen increase? When did single-celled eukaryotes arrive? Multicellular eukaryotes? Colonization of land? Humans?

Background

Topic: Timeline of Life on Earth

This question asks you to interpret a figure showing the history of life and major evolutionary events.

Key Concepts:

Prokaryotes, Eukaryotes, Multicellularity, Colonization of Land: Key milestones in the history of life.
Atmospheric Oxygen: The Great Oxygenation Event and its timing.

Step-by-Step Guidance

Examine the figure to identify which group of organisms appeared first and estimate how long ago they originated.
Locate the point on the timeline when atmospheric oxygen levels increased significantly.
Find when single-celled and multicellular eukaryotes first appeared.
Identify the approximate time of the colonization of land and the appearance of humans.

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Q8. Explain the theory of plate tectonics. What is continental drift? How many times in the Earth’s history has a supercontinent formed?

Background

Topic: Plate Tectonics and Continental Drift

This question tests your understanding of Earth's dynamic crust and the formation of supercontinents.

Key Terms:

Plate Tectonics: The theory that Earth's outer shell is divided into plates that move over the mantle.
Continental Drift: The gradual movement of continents across Earth's surface.
Supercontinent: A large landmass comprising multiple continents joined together.

Step-by-Step Guidance

Define the theory of plate tectonics and explain how it accounts for the movement of continents.
Describe what is meant by continental drift and how it relates to plate tectonics.
Research or recall how many times supercontinents have formed in Earth's history (e.g., Pangaea, Rodinia).

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Q9. How does continental drift impact evolution? How does it promote allopatric speciation?

Background

Topic: Evolutionary Consequences of Continental Drift

This question explores how the movement of continents can lead to the formation of new species through geographic isolation.

Key Terms:

Allopatric Speciation: The formation of new species due to geographic separation of populations.
Continental Drift: Movement of continents that can separate populations.

Step-by-Step Guidance

Explain how the movement of continents can physically separate populations of organisms.
Describe how geographic isolation can lead to genetic divergence and eventually speciation.
Provide an example of how continental drift might have led to allopatric speciation in the past.

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Q10. How many mass extinctions have occurred in Earth’s history and what caused them? Are we currently in the 6th mass extinction period? Why or why not? What might be causing this high level of extinctions?

Background

Topic: Mass Extinctions

This question asks you to recall the number of mass extinction events, their causes, and to consider current extinction rates.

Key Terms:

Mass Extinction: A rapid decrease in the diversity and abundance of life on Earth.
Anthropogenic: Caused by human activity.

Step-by-Step Guidance

List the generally accepted number of mass extinction events in Earth's history.
Identify at least two causes of past mass extinctions (e.g., asteroid impact, volcanic activity).
Discuss evidence for or against the idea that we are currently experiencing a sixth mass extinction.
List possible causes for current high extinction rates, focusing on human impacts.

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Q11. How long does it take for a diverse community of organisms to recover after a mass extinction event? How else does mass extinction alter ecological communities?

Background

Topic: Recovery from Mass Extinction

This question explores the aftermath of mass extinction events and their effects on ecosystems.

Key Concepts:

Ecological Recovery: The process by which ecosystems regain diversity and complexity after a disturbance.
Community Structure: The composition and organization of species within an ecosystem.

Step-by-Step Guidance

Research or recall the typical time frame for ecological recovery after a mass extinction (often millions of years).
Discuss how mass extinctions can change which groups of organisms dominate an ecosystem.
Consider how new ecological niches may open up, leading to adaptive radiations.

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Q12. What is adaptive radiation? What are the causes of adaptive radiation? What allowed for the adaptive radiation of mammals?

Background

Topic: Adaptive Radiation

This question tests your understanding of how new species rapidly evolve to fill available ecological niches.

Key Terms:

Adaptive Radiation: The rapid evolution of many diverse species from a common ancestor.
Ecological Niche: The role and position a species has in its environment.

Step-by-Step Guidance

Define adaptive radiation and give a general example.
List at least two causes of adaptive radiation, such as the availability of new habitats or the extinction of competitors.
Explain what event(s) allowed mammals to undergo adaptive radiation (e.g., extinction of dinosaurs).

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Q13. What is heterochrony? Give two examples of this phenomenon.

Background

Topic: Evolutionary Developmental Biology

This question focuses on changes in the timing or rate of developmental events and how they can lead to evolutionary changes.

Key Terms:

Heterochrony: Evolutionary change in the timing or rate of developmental events.

Step-by-Step Guidance

Define heterochrony and explain its significance in evolution.
Think of two examples where changes in developmental timing have led to differences between species (e.g., paedomorphosis in salamanders).

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Q14. What are homeotic genes? What are Hox genes? How can these genes lead to speciation?

Background

Topic: Genetic Control of Development

This question examines the role of specific genes in controlling body plans and their potential to drive evolutionary change.

Key Terms:

Homeotic Genes: Genes that control the identity of body parts during development.
Hox Genes: A subset of homeotic genes that determine the head-to-tail axis in animals.

Step-by-Step Guidance

Define homeotic genes and explain their general function.
Describe what Hox genes are and their specific role in animal development.
Discuss how changes in these genes can result in new body plans and potentially lead to speciation.

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Q15. What did geneticist Francois Jacob mean by 'evolution is like tinkering'?

Background

Topic: Evolutionary Mechanisms

This question asks you to interpret a metaphor about how evolution works through modification of existing structures rather than creating new ones from scratch.

Key Concepts:

Tinkering: Making small adjustments or modifications to existing structures or systems.

Step-by-Step Guidance

Consider what it means to 'tinker' versus to 'engineer' something from the ground up.
Relate this idea to how evolution modifies existing traits rather than inventing entirely new ones.
Think of an example where a biological structure evolved by modification of a pre-existing structure.