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Questions and Answers
What does the length of a branch in a cladogram represent?
What does the length of a branch in a cladogram represent?
Which principle states that the simplest tree with the fewest evolutionary events is preferred?
Which principle states that the simplest tree with the fewest evolutionary events is preferred?
How do molecular clocks assist systematists?
How do molecular clocks assist systematists?
What was the classification system before the three-domain system was adopted?
What was the classification system before the three-domain system was adopted?
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What role do computer programs play in constructing phylogenetic trees?
What role do computer programs play in constructing phylogenetic trees?
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What does phylogeny represent?
What does phylogeny represent?
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Which scientist developed the binomial naming system for species?
Which scientist developed the binomial naming system for species?
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What is the highest taxonomic group that includes all organisms with eukaryotic cells?
What is the highest taxonomic group that includes all organisms with eukaryotic cells?
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In the scientific name Homo sapiens, what does 'Homo' represent?
In the scientific name Homo sapiens, what does 'Homo' represent?
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Which of the following statements about systematics is true?
Which of the following statements about systematics is true?
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What does a phylogenetic tree represent?
What does a phylogenetic tree represent?
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How many primary taxonomic groups exist in biological classification?
How many primary taxonomic groups exist in biological classification?
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Which taxonomic group is the least inclusive?
Which taxonomic group is the least inclusive?
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What do phylogenetic trees primarily show?
What do phylogenetic trees primarily show?
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Why is it incorrect to assume that a taxon evolved from the taxon next to it in a phylogenetic tree?
Why is it incorrect to assume that a taxon evolved from the taxon next to it in a phylogenetic tree?
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What does homology indicate in the context of organism relationships?
What does homology indicate in the context of organism relationships?
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What is the main difference between homology and analogy?
What is the main difference between homology and analogy?
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Which of these is NOT a type of data that systematists use to infer phylogenies?
Which of these is NOT a type of data that systematists use to infer phylogenies?
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What does the term 'sister taxa' refer to in a phylogenetic tree?
What does the term 'sister taxa' refer to in a phylogenetic tree?
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What is an unresolved pattern of divergence called in a phylogenetic tree?
What is an unresolved pattern of divergence called in a phylogenetic tree?
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Which of the following statements is true about morphological similarities among species?
Which of the following statements is true about morphological similarities among species?
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What type of group is characterized by including a common ancestor and all its descendants?
What type of group is characterized by including a common ancestor and all its descendants?
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Which of the following is an example of a shared derived character?
Which of the following is an example of a shared derived character?
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Which group of organisms is directly considered a part of Eukarya?
Which group of organisms is directly considered a part of Eukarya?
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What represents the ingroup in a cladogram?
What represents the ingroup in a cladogram?
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Which of the following best describes a shared ancestral character?
Which of the following best describes a shared ancestral character?
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Which of the following organisms is a type of green algae?
Which of the following organisms is a type of green algae?
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What is the significance of the 'COMMON ANCESTOR OF ALL LIFE' in the figure?
What is the significance of the 'COMMON ANCESTOR OF ALL LIFE' in the figure?
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In the scenario where leopard and domestic cat are the ingroup, which of the following would be classified as the outgroup?
In the scenario where leopard and domestic cat are the ingroup, which of the following would be classified as the outgroup?
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Which characteristic is NOT used to differentiate between shared derived and shared ancestral characteristics?
Which characteristic is NOT used to differentiate between shared derived and shared ancestral characteristics?
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Which of these is classified as a thermophile?
Which of these is classified as a thermophile?
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Which of the following statements is true regarding a polyphyletic group?
Which of the following statements is true regarding a polyphyletic group?
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Which type of bacteria is represented by 'Spirochetes' in the figure?
Which type of bacteria is represented by 'Spirochetes' in the figure?
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What is the role of an outgroup in systematics?
What is the role of an outgroup in systematics?
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Which of the following is NOT a group under Bacteria in the figure?
Which of the following is NOT a group under Bacteria in the figure?
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Which organism is represented as a part of organisms that feed through phagocytosis?
Which organism is represented as a part of organisms that feed through phagocytosis?
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What distinguishes Euglena from other microorganisms?
What distinguishes Euglena from other microorganisms?
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What does each branch point in a phylogenetic tree represent?
What does each branch point in a phylogenetic tree represent?
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What defines sister taxa in a phylogenetic tree?
What defines sister taxa in a phylogenetic tree?
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Which of the following is an example of a basal taxon?
Which of the following is an example of a basal taxon?
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What is a polytomy in the context of a phylogenetic tree?
What is a polytomy in the context of a phylogenetic tree?
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What is the classification level of Panthera pardus?
What is the classification level of Panthera pardus?
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Which of the following statements about taxa is incorrect?
Which of the following statements about taxa is incorrect?
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What does a rooted tree in phylogenetics illustrate?
What does a rooted tree in phylogenetics illustrate?
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Which of the following is NOT a characteristic of a sister taxon?
Which of the following is NOT a characteristic of a sister taxon?
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Study Notes
Phylogeny and the Tree of Life
- Biologists estimate 5 to 100 million species of organisms live on Earth today.
- Evidence from morphology, biochemistry and gene sequences suggests all organisms are genetically related.
- Evolutionary relationships represented by a Tree of Life.
- The Tree of Life depicts the phylogeny of organisms.
- Phylogeny is the evolutionary history of a species or group.
- All life arises from a previous ancestor.
- All organisms (bacteria, fungi, protists, plants, and animals) are connected by gene passage along the phylogenetic tree.
Systematics
- Systematics classifies organisms and determines evolutionary relationships.
- Systematists use fossil, molecular, and genetic data to infer evolutionary relationships.
- Systematists depict relationships using branching phylogenetic trees.
Phylogenetic Tree
- A phylogenetic tree is a hypothesis about evolutionary relationships.
- Each branch point represents the divergence (separation) of two or more species.
- A rooted tree includes a branch to represent the last common ancestor of all taxa (group) in the tree.
Sister Taxa
- Sister taxa are groups that share an immediate common ancestor.
- In the phylogenetic tree below, domestic dog and wolf are sister taxa.
Taxon
- A taxon or taxa is a taxonomic unit (group of related organisms) at any level of hierarchy.
- Examples include Kingdom, Panthera, Felidae, Carnivora, Canis, Lutra, Mephitis.
Basal Taxon
- A basal taxon is a taxon that diverges early in the history of that group.
- A basal taxon typically originates near the common ancestor of the group.
Polytomy
- A polytomy is a branch from which more than two groups or taxa emerged.
- Polytomies represent an unknown cause of the divergence.
Phylogenetic Tree Limitations
- Phylogenetic trees show patterns of descent, not phenotypic similarity.
- Phylogenetic trees don't indicate when species evolved or how much change occurred.
- It should not be assumed that a taxon evolved from the taxon next to it.
Phylogenies from Data
- Phylogenies are inferred from morphological and molecular data.
- Organisms with similar morphologies or molecular sequences are likely more closely related.
- Phenotypic and molecular similarities are homologies that indicate a shared or common ancestry.
- The more complex two similar structures are, the more likely they are homologous.
Molecular Homology
- Molecular homology shows similarities in DNA sequence across different species.
Morphological Homology
- Morphological homology shows similarities in anatomical structures in different species.
Analogy vs Homology
- Homology is similarity due to shared ancestry.
- Analogy is similarity due to convergent evolution.
Convergent Evolution
- Convergent evolution happens when unrelated organisms face similar pressures in similar environments, leading to similar adaptations.
- Examples include wings of insects and birds, or tails of whales and fish.
Classifying Organisms
- Taxonomists classify organisms by shared characteristics or evolutionary relationships.
- Phenetic classification focuses primarily on shared traits.
- Cladistic classification focuses primarily on evolutionary relationships and shared characteristics.
Cladistics
- Cladistics aims to provide a scheme (cladogram) that shows the most likely evolutionary pathway for a species.
- A clade includes an ancestral species and all its descendants.
Monophyletic
- Monophyletic clade includes only an ancestral species and all its descendents.
Paraphyletic
- A paraphyletic group includes an ancestral species and some, but not all of its descendants
Polyphyletic
- A polyphyletic group includes various species with different ancestors.
Shared Ancestral and Derived Characters
- Organisms have shared and different characteristics compared to ancestors.
- Shared ancestral character is a character that originates in an ancestor of that taxon.
- A shared derived character is an evolutionary new trait unique to a particular clade.
Molecular Clocks
- Molecular clocks help determine how long ago two or more groups or taxa diverged from a common ancestor.
- These methods use the rate of genetic mutation in a shared ancestral gene.
From Two Kingdoms to Three Domains
- Early taxonomists classified species as either plants or animals.
- Later five kingdoms were recognized (Monera, Protista, Plantae, Fungi, Animalia).
- More recently the three-domain system was adopted (Bacteria, Archaea, Eukarya).
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Description
Test your knowledge on the concepts of phylogeny and the Tree of Life. This quiz covers the evolutionary relationships of organisms and how systematics classifies species based on various data. Explore the connections among all life forms and their historical evolution.
