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Study Guidance for College Biology: Evolution, Diversity, and Physiology

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Q1. Draw a phylogeny representing the three domains of life. Which two are prokaryotes?

Background

Topic: Phylogenetics and Domains of Life

This question tests your understanding of evolutionary relationships among Bacteria, Archaea, and Eukarya, and your ability to represent these relationships visually.

Key Terms:

  • Phylogeny: A diagram showing evolutionary relationships.

  • Prokaryote: Organisms without a nucleus (Bacteria and Archaea).

  • Eukaryote: Organisms with a nucleus (Eukarya).

Step-by-Step Guidance

  1. Start by drawing a root representing the last universal common ancestor (LUCA).

  2. Branch the tree into three main domains: Bacteria, Archaea, and Eukarya.

  3. Label Bacteria and Archaea as prokaryotes, and Eukarya as eukaryotes.

  4. Indicate any major traits or synapomorphies that distinguish these domains (e.g., presence/absence of nucleus, cell wall composition).

Try solving on your own before revealing the answer!

Q2. What do members of all three domains have in common? What traits are different?

Background

Topic: Comparative Biology

This question asks you to compare and contrast the fundamental characteristics of Bacteria, Archaea, and Eukarya.

Key Terms:

  • Universal traits: Features shared by all life (e.g., DNA, cell membrane).

  • Distinct traits: Features unique to each domain (e.g., cell wall composition, presence of organelles).

Step-by-Step Guidance

  1. List traits common to all domains (e.g., genetic material, ribosomes, cell membrane).

  2. Identify traits that differ, such as cell wall structure (peptidoglycan in Bacteria, pseudopeptidoglycan in Archaea, cellulose in some Eukarya).

  3. Note differences in cellular organization (prokaryotic vs. eukaryotic).

  4. Consider metabolic pathways and environmental adaptations unique to each domain.

Try solving on your own before revealing the answer!

Q3. How old are the earliest prokaryotic fossils?

Background

Topic: Fossil Record and Early Life

This question tests your knowledge of the timeline of life on Earth, specifically the age of the oldest prokaryotic fossils.

Key Terms:

  • Prokaryote: Bacteria and Archaea.

  • Fossil: Preserved remains or traces of ancient organisms.

Step-by-Step Guidance

  1. Recall the geologic time scale and major events in Earth's history.

  2. Identify the approximate age range when prokaryotes first appeared (e.g., billions of years ago).

  3. Consider evidence from stromatolites and microfossils.

Try solving on your own before revealing the answer!

Q4. What themes occur in the evolution of prokaryotes?

Background

Topic: Evolutionary Biology

This question asks you to identify recurring patterns or processes in prokaryote evolution.

Key Terms:

  • Adaptation: Changes that increase fitness.

  • Diversity: Variety of forms and functions.

  • Lateral gene transfer: Exchange of genes between organisms.

Step-by-Step Guidance

  1. List major evolutionary themes such as adaptation to diverse environments, metabolic diversity, and gene transfer mechanisms.

  2. Consider the role of mutation and selection in prokaryote evolution.

  3. Think about how prokaryotes have influenced Earth's atmosphere and ecosystems.

Try solving on your own before revealing the answer!

Q5. What is a biofilm and why are biofilms adaptive for the prokaryotes that make them? Can you describe an example?

Background

Topic: Microbial Ecology

This question tests your understanding of biofilms, their structure, and their ecological significance.

Key Terms:

  • Biofilm: A community of microorganisms attached to a surface.

  • Adaptation: Traits that enhance survival.

Step-by-Step Guidance

  1. Define biofilm and describe its basic structure (e.g., extracellular matrix).

  2. Explain how biofilms protect prokaryotes from environmental stressors.

  3. Provide an example, such as dental plaque or biofilms in water pipes.

Try solving on your own before revealing the answer!

Q6. What is the Gram stain and how does it separate bacteria into two distinct groups?

Background

Topic: Microbiology Techniques

This question tests your knowledge of the Gram stain procedure and its significance in classifying bacteria.

Key Terms:

  • Gram stain: A method to differentiate bacteria based on cell wall structure.

  • Gram-positive: Bacteria with thick peptidoglycan walls.

  • Gram-negative: Bacteria with thin peptidoglycan and outer membrane.

Step-by-Step Guidance

  1. Describe the steps of the Gram stain (crystal violet, iodine, alcohol, safranin).

  2. Explain how cell wall structure affects staining outcome.

  3. Discuss the implications for bacterial classification and antibiotic susceptibility.

Try solving on your own before revealing the answer!

Q7. How do Prokaryotes reproduce? What are several ways that they exchange genes?

Background

Topic: Microbial Genetics

This question tests your understanding of prokaryotic reproduction and genetic exchange mechanisms.

Key Terms:

  • Binary fission: Asexual reproduction in prokaryotes.

  • Gene transfer: Transformation, transduction, conjugation.

Step-by-Step Guidance

  1. Describe binary fission as the main reproductive method.

  2. List and briefly explain gene exchange methods: transformation (uptake of DNA), transduction (virus-mediated), conjugation (direct transfer).

  3. Discuss the significance of gene exchange for genetic diversity.

Try solving on your own before revealing the answer!

Q8. What is lateral gene transfer and why does it affect phylogenies?

Background

Topic: Evolutionary Genetics

This question tests your understanding of lateral gene transfer and its impact on evolutionary trees.

Key Terms:

  • Lateral gene transfer: Movement of genes between unrelated organisms.

  • Phylogeny: Evolutionary tree.

Step-by-Step Guidance

  1. Define lateral gene transfer and give examples (e.g., antibiotic resistance genes).

  2. Explain how gene transfer can blur evolutionary relationships.

  3. Discuss challenges in constructing accurate phylogenies due to gene transfer.

Try solving on your own before revealing the answer!

Q9. What is quorum sensing? How does it work? Give an example.

Background

Topic: Microbial Communication

This question tests your understanding of how prokaryotes coordinate behavior through chemical signaling.

Key Terms:

  • Quorum sensing: Cell-to-cell communication based on population density.

  • Autoinducers: Signaling molecules.

Step-by-Step Guidance

  1. Describe the process of quorum sensing (production and detection of signaling molecules).

  2. Explain how gene expression changes when a threshold concentration is reached.

  3. Provide an example, such as bioluminescence in Vibrio fischeri.

Try solving on your own before revealing the answer!

Q10. What are some of the diverse metabolic pathways that prokaryotes have? Describe each.

Background

Topic: Metabolic Diversity

This question tests your knowledge of the various ways prokaryotes obtain energy and carbon.

Key Terms:

  • Photoautotroph: Uses light and CO2.

  • Chemoautotroph: Uses chemicals and CO2.

  • Chemoheterotroph: Uses chemicals and organic carbon.

  • Photoheterotroph: Uses light and organic carbon.

Step-by-Step Guidance

  1. List the main metabolic categories and define each.

  2. Describe examples of organisms for each pathway.

  3. Explain the ecological significance of metabolic diversity.

Try solving on your own before revealing the answer!

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