BIO 1108 LOS | UPDATED Questions with 100% Verified
Answers
Q1: Label the roots, nodes, branches, and tips used in phylogenetic trees and their interpretation, and avoid
common misconceptions in interpreting phylogenetic trees
A: Root: oldest part of the tree; represents the common ancestor of all taxa shown.
Node: point where lineages diverge; represents a common ancestor/speciation event.
Branch: evolutionary lineage connecting ancestors and descendants.
Tip: endpoint representing a taxon/lineage.
MRCA: most recent common ancestor of two or more taxa.
Outgroup: the leastrelated taxon included for comparison.
In the reading's tree, time goes from older at the root → more recent at the tips.
However, trees can be drawn in different orientations.
The shape/orientation itself does not determine relatedness.
Rotating branches around a node does not change evolutionary relationships.
Do not assume organisms at the top/right are "more evolved.
Q2: Distinguish the different types of data used to construct phylogenetic trees, define homology, and
explain how the principle of parsimony is used to construct phylogenetic trees
A: Morphological data: structural features, organs, skeletal arrangements, etc.
Genetic data: mtDNA, rRNA sequences, genomic genes, etc.
Homology: similarity due to common ancestry.
Parsimony: prefer the evolutionary hypothesis/tree requiring the fewest evolutionary
changes.
A phylogenetic tree is a hypothesis about evolutionary relationships and can change
when new evidence appears
Q3: Distinguish monophyletic and nonmonophyletic groups, and identify shared, derived traits that identify
a monophyletic group
A: Monophyletic group/clade: common ancestor + ALL descendants.
Derived trait: trait that first appears in the MRCA of a group.
Shared, derived trait/synapomorphy: trait shared by members of a clade because they
inherited it from their common ancestor.
Paraphyletic: common ancestor + some, but not all, descendants.
Polyphyletic: group does not include the common ancestor and groups organisms based
on traits that evolved separately.
Q4: Identify and use the most recent common ancestor (MRCA) to evaluate the relatedness of taxa
A: To determine relatedness:
Find the two taxa.
Trace backward through the tree.
Find their MRCA.
The pair with the more recent MRCA is more closely related.
, Q5: Define and identify features of adaptive radiations
A: Adaptive radiation: rapid speciation and increase in biodiversity.
Often occurs when new ecological niches become available.
On a tree, it can look "tufty", with many short branches coming from one lineage.
Examples in this module include the Cambrian radiation and diversification after mass
Q6: Identify the four eons of geologic time by the major events of life (or absence thereof) that define them,
and list the eons in chronological order
A: Hadean → Archean → Proterozoic → Phanerozoic
Hadean (4.64.0 BYA): before compelling evidence of life.
Archean (4.02.5 BYA): early life, including Bacteria, Archaea, and cyanobacteria.
Proterozoic (2.5 BYA542 MYA): oxygen accumulation, eukaryotes, and multicellular life.
Phanerozoic (542 MYApresent): begins with the Cambrian explosion and includes major
diversification of animals and plants.
Q7: Identify the fossil, chemical, and genetic evidence for key events for evolution of the three domains of
life (Bacteria, Archaea, and Eukarya)
A: Fossil evidence: physical remains/traces of ancient life.
Chemical evidence: chemical signatures preserved in ancient rocks that reveal past
environments/life.
Genetic evidence: DNA/RNA sequence comparisons reveal evolutionary relationships.
Example: rRNA sequencing supported the traditional threedomain model.
Genomelevel comparisons later provided evidence for Eukarya nested within Archaea.
Q8: Describe the processes that caused the oxygenation of the atmosphere and the evidence for it
A: Early Earth had little/no free atmospheric oxygen.
Cyanobacteria evolved oxygenic photosynthesis, releasing O₂.
O₂ accumulated over time.
Oxygen initially reacted with materials such as iron before accumulating in the
atmosphere.
Evidence includes banded iron formations and chemical changes in ancient rocks.
Oxygen caused extinction of many anaerobic organisms.
Oxygen also allowed larger, more metabolically active organisms to evolve.
Q9: Describe the hypotheses explaining the causes and results of the Cambrian explosion
A: The Cambrian explosion/radiation occurred around 542 MYA.
Nearly all modern animal phyla emerged/diversified during this period.
It was not literally simultaneous; it occurred over millions of years, which is rapid on a
geologic timescale.
Leading hypothesis in your reading: increased atmospheric oxygen.
More O₂ allowed larger bodies, organs, tissues, and higher metabolic rates.
Oxygen also caused extinction of obligate anaerobes.
Answers
Q1: Label the roots, nodes, branches, and tips used in phylogenetic trees and their interpretation, and avoid
common misconceptions in interpreting phylogenetic trees
A: Root: oldest part of the tree; represents the common ancestor of all taxa shown.
Node: point where lineages diverge; represents a common ancestor/speciation event.
Branch: evolutionary lineage connecting ancestors and descendants.
Tip: endpoint representing a taxon/lineage.
MRCA: most recent common ancestor of two or more taxa.
Outgroup: the leastrelated taxon included for comparison.
In the reading's tree, time goes from older at the root → more recent at the tips.
However, trees can be drawn in different orientations.
The shape/orientation itself does not determine relatedness.
Rotating branches around a node does not change evolutionary relationships.
Do not assume organisms at the top/right are "more evolved.
Q2: Distinguish the different types of data used to construct phylogenetic trees, define homology, and
explain how the principle of parsimony is used to construct phylogenetic trees
A: Morphological data: structural features, organs, skeletal arrangements, etc.
Genetic data: mtDNA, rRNA sequences, genomic genes, etc.
Homology: similarity due to common ancestry.
Parsimony: prefer the evolutionary hypothesis/tree requiring the fewest evolutionary
changes.
A phylogenetic tree is a hypothesis about evolutionary relationships and can change
when new evidence appears
Q3: Distinguish monophyletic and nonmonophyletic groups, and identify shared, derived traits that identify
a monophyletic group
A: Monophyletic group/clade: common ancestor + ALL descendants.
Derived trait: trait that first appears in the MRCA of a group.
Shared, derived trait/synapomorphy: trait shared by members of a clade because they
inherited it from their common ancestor.
Paraphyletic: common ancestor + some, but not all, descendants.
Polyphyletic: group does not include the common ancestor and groups organisms based
on traits that evolved separately.
Q4: Identify and use the most recent common ancestor (MRCA) to evaluate the relatedness of taxa
A: To determine relatedness:
Find the two taxa.
Trace backward through the tree.
Find their MRCA.
The pair with the more recent MRCA is more closely related.
, Q5: Define and identify features of adaptive radiations
A: Adaptive radiation: rapid speciation and increase in biodiversity.
Often occurs when new ecological niches become available.
On a tree, it can look "tufty", with many short branches coming from one lineage.
Examples in this module include the Cambrian radiation and diversification after mass
Q6: Identify the four eons of geologic time by the major events of life (or absence thereof) that define them,
and list the eons in chronological order
A: Hadean → Archean → Proterozoic → Phanerozoic
Hadean (4.64.0 BYA): before compelling evidence of life.
Archean (4.02.5 BYA): early life, including Bacteria, Archaea, and cyanobacteria.
Proterozoic (2.5 BYA542 MYA): oxygen accumulation, eukaryotes, and multicellular life.
Phanerozoic (542 MYApresent): begins with the Cambrian explosion and includes major
diversification of animals and plants.
Q7: Identify the fossil, chemical, and genetic evidence for key events for evolution of the three domains of
life (Bacteria, Archaea, and Eukarya)
A: Fossil evidence: physical remains/traces of ancient life.
Chemical evidence: chemical signatures preserved in ancient rocks that reveal past
environments/life.
Genetic evidence: DNA/RNA sequence comparisons reveal evolutionary relationships.
Example: rRNA sequencing supported the traditional threedomain model.
Genomelevel comparisons later provided evidence for Eukarya nested within Archaea.
Q8: Describe the processes that caused the oxygenation of the atmosphere and the evidence for it
A: Early Earth had little/no free atmospheric oxygen.
Cyanobacteria evolved oxygenic photosynthesis, releasing O₂.
O₂ accumulated over time.
Oxygen initially reacted with materials such as iron before accumulating in the
atmosphere.
Evidence includes banded iron formations and chemical changes in ancient rocks.
Oxygen caused extinction of many anaerobic organisms.
Oxygen also allowed larger, more metabolically active organisms to evolve.
Q9: Describe the hypotheses explaining the causes and results of the Cambrian explosion
A: The Cambrian explosion/radiation occurred around 542 MYA.
Nearly all modern animal phyla emerged/diversified during this period.
It was not literally simultaneous; it occurred over millions of years, which is rapid on a
geologic timescale.
Leading hypothesis in your reading: increased atmospheric oxygen.
More O₂ allowed larger bodies, organs, tissues, and higher metabolic rates.
Oxygen also caused extinction of obligate anaerobes.
