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Evolutionary History and Systematics
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Evolutionary History and Systematics
Bio 2 Exam 1 prep
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1
Question
How does the geological record differ fundamentally from the fossil record?
Page 2
Answer
The geological record documents Earth's physical history through crustal rock layers. The fossil record specifically documents the occurrence and evolutionary change of living organisms over time.
2
Question
What is the chronological sequence of Earth's four major geological eons from oldest to newest?
Page 2
Answer
Hadean eon, followed by Archaean, Proterozoic, and Phanerozoic eons.
3
Question
Why do boundaries between major divisions in the geological record frequently correspond to mass extinction events?
Page 3
Answer
Mass extinctions rapidly eliminate large numbers of species due to catastrophic events. This creates sharp transitions in the types of fossilized organisms preserved across adjacent rock strata.
4
Question
How are stromatolites structured and what is their evolutionary significance?
Page 3
Answer
Stromatolites are layered rocky mounds formed by lime-secreting bacteria and trapped sediment. They represent the oldest known fossils, dating back approximately 3.5 billion years.
5
Question
What does the acronym LUCA represent in the context of early cellular evolution?
Page 3
Answer
Last Universal Common Ancestor, the single ancestral lineage from which two distinct types of modern prokaryotes diverged.
6
Question
How did early photosynthetic cyanobacteria trigger the Oxygen Revolution approximately 2.7 to 2.4 billion years ago?
Page 4
Answer
Cyanobacteria produced molecular oxygen through photosynthesis, which accumulated in the atmosphere. This transformed the atmospheric chemistry from weakly reducing to oxidizing and caused many anaerobic species to die out.
7
Question
To what level did atmospheric oxygen rise during the Oxygen Revolution relative to current levels?
Page 4
Answer
Atmospheric oxygen rapidly reached approximately 1% to 10% of its present-day level.
8
Question
What structural innovations distinguish early eukaryotic cells from their prokaryotic ancestors?
Page 5
Answer
Eukaryotic cells possess larger sizes, a nuclear envelope, mitochondria, an endoplasmic reticulum, and a complex cytoskeleton.
9
Question
Which fossil organism provides an early example of single-celled eukaryotic life approximately 1.8 billion years ago?
Page 5
Answer
Tappania serves as an early eukaryotic fossil example.
10
Question
What morphological characteristics defined the Ediacaran biota that appeared roughly 635 to 541 million years ago?
Page 5
Answer
They were larger, more diverse, soft-bodied multicellular organisms, exemplified by fossils such as Dickinsonia costata.
11
Question
What conditions characterize the Snowball Earth hypothesis during the Cryogenian period?
Page 5
Answer
Earth's surface became entirely or nearly entirely frozen for episodes lasting roughly 10 million years between 710 and 640 million years ago.
12
Question
What three primary environmental challenges did ancestral plants confront during the terrestrial colonization around 500 million years ago?
Page 6
Answer
Plants needed physiological adaptations to reproduce on land, avoid dehydration, and transport materials throughout their bodies.
13
Question
Why was the evolution of a vascular system around 420 million years ago critical for land plants?
Page 6
Answer
A vascular system provided specialized internal conductive tissues that allowed plants to transport water and nutrients efficiently throughout their bodies on land.
14
Question
From which ancestral vertebrate group did tetrapods evolve approximately 365 million years ago?
Page 6
Answer
Tetrapods evolved directly from lobe-finned fishes.
15
Question
How does the timeline of the human lineage compare with the emergence of anatomically modern humans?
Page 6
Answer
The broader human lineage of tetrapods emerged approximately 6 to 7 million years ago. Modern humans appeared very recently, roughly 195,000 years ago.
16
Question
What is the broad developmental sequence of major biological milestones across the history of life?
Page 7
Answer
Prokaryotes arose first, followed by atmospheric oxygen accumulation, single-celled eukaryotes, multicellular eukaryotes, animals, the colonization of land, and finally humans.
17
Question
How does the current estimated extinction rate compare with the historical background extinction rate?
Page 7
Answer
The current extinction rate is estimated to be 100 to 1,000 times higher than the typical background extinction rate recorded in fossils.
18
Question
What historical correlation exists between global climate changes and extinction intensity?
Page 8
Answer
Historically, higher global temperatures correlate with higher rates of species extinction.
19
Question
Why does the RNA world hypothesis propose that RNA preceded DNA and proteins in early life?
Page 8
Answer
RNA uniquely combines genetic information storage with enzymatic catalytic activity. Unlike DNA, which requires protein enzymes to replicate, RNA can perform self-replication and catalyze chemical reactions independently.
20
Question
How did the discovery of ribozymes provide empirical support for the RNA world model?
Page 9
Answer
Ribozymes proved that RNA molecules can act as catalytic enzymes. This demonstrated that early primitive life could carry out metabolic reactions without relying on complex protein machinery.
21
Question
What four primary lines of cellular evidence support the endosymbiotic origin of mitochondria and chloroplasts?
Page 9
Answer
Both organelles possess their own circular DNA, contain bacterial-like ribosomes, reproduce independently via binary fission, and have double membranes.
22
Question
How does organelle evolution under endosymbiosis illustrate horizontal gene transfer rather than vertical gene transfer?
Page 9
Answer
Genes were transferred directly from engulfed symbiotic bacteria into the host cell's nuclear genome over evolutionary time, moving genetic material between cohabiting organisms rather than from parent to offspring.
23
Question
How do taxonomy, phylogeny, and systematics differ in their approach to biological diversity?
Page 10
Answer
Taxonomy focuses on naming and classifying organisms into groups. Phylogeny describes the evolutionary history and relationships of lineages. Systematics applies evolutionary relationships to build unified classification frameworks.
24
Question
What is the correct Linnaean taxonomic hierarchy arranged from the broadest rank to the most specific?
Page 10
Answer
Domain, Kingdom, Phylum, Class, Order, Family, Genus, and Species.
25
Question
How does inclusiveness change when moving through the taxonomic hierarchy from domain to species?
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Answer
Groups become progressively less inclusive. Domain represents the broadest, most inclusive level, while species is the least inclusive category.
26
Question
If two organisms belong to the same phylum, which taxonomic levels must they also share?
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Answer
They must share the same kingdom and domain. They do not necessarily share the same class, order, family, genus, or species.
27
Question
How does phylogeny differ from taxonomy in the study of biological organisms?
Page 11
Answer
Phylogeny focuses on the evolutionary history and relationships of organisms. Taxonomy focuses on naming and classifying organisms into groups.
28
Question
What criteria define a valid clade in cladistics?
Page 11
Answer
A clade must consist of an ancestral species and all of its descendants.
29
Question
What structural composition distinguishes a monophyletic taxon in phylogenetic classification?
Page 12
Answer
A monophyletic group includes a common ancestor and all of its descendants. It constitutes a complete, valid clade.
30
Question
Why is a paraphyletic grouping considered an invalid clade in cladistics?
Page 12
Answer
It contains an ancestral species and some, but not all, of its descendants. Leaving out descendants violates the definition of a complete clade.