Biology & Life Sciences
3 MAXE · 171 OIB
◆ ◆
Department of Ecology & Evolutionary Biology
BIOLOGY
EXPLORING THE SCIENCE OF LIFE
BIO 171 Exam 3 — Evolution, Population Ecology &
Phylogenetics
CO M P R E H E N S I V E E X A M I N AT I O N : FO SS I L R E CO R D · P O P U L AT I O N DY N A M I CS ·
S P E C I E S I N T E RACT I O N S · E VO LU T I O N A RY H I STO RY
INSTITUTION [UNCONFIRMED] — BIO 171 COURSE CODE BIO 171
General Biology
PROGRAM [INFERRED] — Associate / ACADEMIC YEAR
Bachelor of Science
EXAM TITLE BIO 171 Exam 3 — Evolution & TOTAL QUESTIONS 48 Questions
Population Ecology
COURSE TITLE General Biology II — Ecology & FORMAT Multiple Choice — Select the
Evolution Single Best Answer
EXAMINATION INSTRUCTIONS
▸ Select the single best answer for each question based on BIO 171 Exam 3 content.
▸ Questions cover fossil records, phylogenetics, population ecology, species interactions, and
evolutionary history.
▸ Correct answers and detailed rationales provided for comprehensive exam preparation.
, SECTION I — BIO 171 EXAM 3: EVOLUTION &
Questions 1 – 48
POPULATION ECOLOGY
1. When did all of the modern animal phyla first appear?
A. About 65 million years ago, after the extinction of the dinosaurs
B. About 3.5 billion years ago, following the evolution of photosynthesis
C. About 200,000 years ago, following the evolution of Homo sapiens
D. About 540 million years ago, during the adaptive radiation known as the Cambrian
explosion, due in part to an increase in oxygen in the atmosphere
CORRECT ANSWER D — About 540 million years ago, during the adaptive radiation known as
the Cambrian explosion, due in part to an increase in oxygen in the
atmosphere
RATIONALE The Cambrian explosion (~540 million years ago) represents one of the most
dramatic events in the history of life — a relatively rapid (over ~20–25 million
years) diversification of animal body plans during which virtually all modern
animal phyla first appeared in the fossil record. This adaptive radiation was likely
driven by several factors: increasing atmospheric oxygen levels (enabling larger
body sizes and more active metabolisms), the evolution of Hox genes (enabling
diverse body plans), ecological interactions (predator-prey arms races), and the
availability of empty niches following the end-Ediacaran extinction. The Cambrian
explosion marks the beginning of the Phanerozoic eon and produced the
fundamental animal body plans that have persisted for over half a billion years.
,2. Mitochondria are thought to have evolved from:
A. Amoeba
B. Cyanobacteria
C. Heterotrophic protists
D. Proteobacteria
CORRECT ANSWER D — Proteobacteria
RATIONALE Mitochondria evolved from an ancestral alpha-proteobacterium that was
engulfed by an early eukaryotic cell approximately 1.5–2 billion years ago — the
first endosymbiotic event. Evidence includes: mitochondria have their own
circular DNA similar to proteobacterial DNA, 70S ribosomes (bacterial-type),
double membranes (consistent with engulfment), and divide by binary fission.
Molecular phylogenies consistently place mitochondrial DNA within the alpha-
proteobacteria group. This event was transformative — it provided eukaryotic
cells with aerobic respiration, producing far more ATP per glucose than anaerobic
metabolism. Chloroplasts (option B) evolved from cyanobacteria in a separate,
later endosymbiotic event in the lineage leading to photosynthetic eukaryotes.
, 3. Which of the following apply to the MC1R gene? Choose all that apply.
A. Codes for the protein melanin
B. Affects the type of melanin produced by human skin cells; shows the most variation
among populations outside Africa; does not show much variation in most African
populations; has polymorphisms that evolved since the origin of modern humans
C. Is a gene that all humans have but is not present in other mammals
D. Does not show much variation among populations of humans around the globe
CORRECT ANSWER B — Affects the type of melanin produced by human skin cells; shows the
most variation among populations outside Africa; does not show much
variation in most African populations; has polymorphisms that evolved
since the origin of modern humans
RATIONALE The MC1R gene codes for the melanocortin 1 receptor (NOT melanin itself —
option A is incorrect). This receptor affects the type of melanin produced:
activation leads to eumelanin (dark brown/black); reduced activity leads to
pheomelanin (red/yellow). In African populations, MC1R shows little variation
because dark skin was maintained by natural selection (protecting folate from UV
degradation). Outside Africa, MC1R shows greater variation, with polymorphisms
that produce lighter skin — these variants evolved relatively recently as humans
migrated to higher latitudes where UV is less intense and lighter skin enables
sufficient vitamin D synthesis. MC1R is present in other mammals (option C is
false).
3 MAXE · 171 OIB
◆ ◆
Department of Ecology & Evolutionary Biology
BIOLOGY
EXPLORING THE SCIENCE OF LIFE
BIO 171 Exam 3 — Evolution, Population Ecology &
Phylogenetics
CO M P R E H E N S I V E E X A M I N AT I O N : FO SS I L R E CO R D · P O P U L AT I O N DY N A M I CS ·
S P E C I E S I N T E RACT I O N S · E VO LU T I O N A RY H I STO RY
INSTITUTION [UNCONFIRMED] — BIO 171 COURSE CODE BIO 171
General Biology
PROGRAM [INFERRED] — Associate / ACADEMIC YEAR
Bachelor of Science
EXAM TITLE BIO 171 Exam 3 — Evolution & TOTAL QUESTIONS 48 Questions
Population Ecology
COURSE TITLE General Biology II — Ecology & FORMAT Multiple Choice — Select the
Evolution Single Best Answer
EXAMINATION INSTRUCTIONS
▸ Select the single best answer for each question based on BIO 171 Exam 3 content.
▸ Questions cover fossil records, phylogenetics, population ecology, species interactions, and
evolutionary history.
▸ Correct answers and detailed rationales provided for comprehensive exam preparation.
, SECTION I — BIO 171 EXAM 3: EVOLUTION &
Questions 1 – 48
POPULATION ECOLOGY
1. When did all of the modern animal phyla first appear?
A. About 65 million years ago, after the extinction of the dinosaurs
B. About 3.5 billion years ago, following the evolution of photosynthesis
C. About 200,000 years ago, following the evolution of Homo sapiens
D. About 540 million years ago, during the adaptive radiation known as the Cambrian
explosion, due in part to an increase in oxygen in the atmosphere
CORRECT ANSWER D — About 540 million years ago, during the adaptive radiation known as
the Cambrian explosion, due in part to an increase in oxygen in the
atmosphere
RATIONALE The Cambrian explosion (~540 million years ago) represents one of the most
dramatic events in the history of life — a relatively rapid (over ~20–25 million
years) diversification of animal body plans during which virtually all modern
animal phyla first appeared in the fossil record. This adaptive radiation was likely
driven by several factors: increasing atmospheric oxygen levels (enabling larger
body sizes and more active metabolisms), the evolution of Hox genes (enabling
diverse body plans), ecological interactions (predator-prey arms races), and the
availability of empty niches following the end-Ediacaran extinction. The Cambrian
explosion marks the beginning of the Phanerozoic eon and produced the
fundamental animal body plans that have persisted for over half a billion years.
,2. Mitochondria are thought to have evolved from:
A. Amoeba
B. Cyanobacteria
C. Heterotrophic protists
D. Proteobacteria
CORRECT ANSWER D — Proteobacteria
RATIONALE Mitochondria evolved from an ancestral alpha-proteobacterium that was
engulfed by an early eukaryotic cell approximately 1.5–2 billion years ago — the
first endosymbiotic event. Evidence includes: mitochondria have their own
circular DNA similar to proteobacterial DNA, 70S ribosomes (bacterial-type),
double membranes (consistent with engulfment), and divide by binary fission.
Molecular phylogenies consistently place mitochondrial DNA within the alpha-
proteobacteria group. This event was transformative — it provided eukaryotic
cells with aerobic respiration, producing far more ATP per glucose than anaerobic
metabolism. Chloroplasts (option B) evolved from cyanobacteria in a separate,
later endosymbiotic event in the lineage leading to photosynthetic eukaryotes.
, 3. Which of the following apply to the MC1R gene? Choose all that apply.
A. Codes for the protein melanin
B. Affects the type of melanin produced by human skin cells; shows the most variation
among populations outside Africa; does not show much variation in most African
populations; has polymorphisms that evolved since the origin of modern humans
C. Is a gene that all humans have but is not present in other mammals
D. Does not show much variation among populations of humans around the globe
CORRECT ANSWER B — Affects the type of melanin produced by human skin cells; shows the
most variation among populations outside Africa; does not show much
variation in most African populations; has polymorphisms that evolved
since the origin of modern humans
RATIONALE The MC1R gene codes for the melanocortin 1 receptor (NOT melanin itself —
option A is incorrect). This receptor affects the type of melanin produced:
activation leads to eumelanin (dark brown/black); reduced activity leads to
pheomelanin (red/yellow). In African populations, MC1R shows little variation
because dark skin was maintained by natural selection (protecting folate from UV
degradation). Outside Africa, MC1R shows greater variation, with polymorphisms
that produce lighter skin — these variants evolved relatively recently as humans
migrated to higher latitudes where UV is less intense and lighter skin enables
sufficient vitamin D synthesis. MC1R is present in other mammals (option C is
false).
