Chapter 26 Study Guide – College Biology: Prokaryotes, Phylogeny, and Domains of Life

Q2. How do you read a phylogenetic tree? What do tips and nodes represent, and how can you infer relationships about relatedness of different taxa?

Background

Topic: Phylogenetic Trees & Evolutionary Relationships

This question tests your understanding of how to interpret phylogenetic trees, which are diagrams used to show evolutionary relationships among organisms.

Key Terms:

• Tip: Represents a taxon (species or group) at the end of a branch.

• Node: Represents a common ancestor where two lineages diverge.

• Taxa: Groups of organisms.

• Relatedness: How closely two taxa share a common ancestor.

Step-by-Step Guidance

1. Identify the tips of the tree; each tip corresponds to a specific taxon (species or group).

2. Locate the nodes; each node represents a hypothetical common ancestor shared by the taxa branching from that point.

3. To infer relatedness, look for the most recent common ancestor shared by two taxa. The closer the node is to the tips, the more recently those taxa diverged.

4. Compare the branching patterns: taxa that share a node are more closely related to each other than to taxa branching from a more distant node.

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Q3. What type of data are most phylogenetic trees based on? How are relationships determined?

Background

Topic: Data Sources for Phylogenetic Trees

This question is about the types of evidence used to construct phylogenetic trees and how scientists infer evolutionary relationships.

Key Terms:

• Molecular data: DNA, RNA, or protein sequences.

• Morphological data: Physical traits and structures.

• Homology: Similarity due to shared ancestry.

• Cladistics: Method for determining relationships based on shared derived characteristics.

Step-by-Step Guidance

1. Recognize that most modern phylogenetic trees are constructed using molecular data, such as DNA or protein sequences.

2. Understand that relationships are determined by comparing similarities and differences in these sequences among taxa.

3. Scientists look for homologous traits (shared due to common ancestry) to group organisms together.

4. Cladistic analysis is used to build trees based on shared derived characteristics (synapomorphies).

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Q4. Name the three domains of life and list shared features that provide evidence that all organisms share a single common ancestor.

Background

Topic: Domains of Life & Universal Features

This question tests your knowledge of the classification of life and the evidence for a universal common ancestor.

Key Terms:

• Domain: Highest taxonomic rank; Bacteria, Archaea, Eukarya.

• Universal features: Traits shared by all living organisms.

• Common ancestor: The original organism from which all life descended.

Step-by-Step Guidance

1. Recall the three domains: Bacteria, Archaea, and Eukarya.

2. List features shared by all domains, such as the use of DNA as genetic material, ribosomes for protein synthesis, and a universal genetic code.

3. Consider other universal cellular processes, like transcription and translation.

4. Think about how these shared features support the idea of a single common ancestor.

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Q6. List the key differences between prokaryotes and eukaryotes and the key differences between bacteria and archaea.

Background

Topic: Cell Structure & Classification

This question is about distinguishing between major cell types and between two prokaryotic groups.

Key Terms:

• Prokaryote: Cell without a nucleus or membrane-bound organelles.

• Eukaryote: Cell with a nucleus and membrane-bound organelles.

• Bacteria vs. Archaea: Two domains of prokaryotes with distinct molecular and structural features.

Step-by-Step Guidance

1. Identify structural differences: prokaryotes lack a nucleus, while eukaryotes have one.

2. Compare organelles: eukaryotes have membrane-bound organelles; prokaryotes do not.

3. For bacteria vs. archaea, consider differences in cell wall composition, membrane lipids, and genetic machinery.

4. Think about environmental adaptations unique to archaea.

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Q8. Describe the four criteria that Koch asserted should be met to establish that a particular type of microorganism causes a particular disease, and explain how a modern application of this approach led to a Nobel prize.

Background

Topic: Koch's Postulates & Disease Causation

This question tests your understanding of the scientific method for linking microbes to diseases and its historical significance.

Key Terms:

• Koch's postulates: Four criteria for establishing causation.

• Pathogen: Disease-causing microorganism.

• Nobel prize: Recognition for scientific achievement.

Step-by-Step Guidance

1. Recall the four postulates: (1) The microorganism must be found in all cases of the disease, (2) It must be isolated and grown in pure culture, (3) It must cause the disease when introduced into a healthy host, (4) It must be re-isolated from the experimentally infected host.

2. Think about how these steps establish a causal relationship between microbe and disease.

3. Consider a modern example where these postulates were applied, such as the discovery of Helicobacter pylori causing ulcers.

4. Reflect on how this led to a Nobel prize for the researchers involved.

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