Exam 1

Question 1

How long did the Hadean Eon last?

Answer 1

From 4.6 bya- 3.8 bya

Question 2

How long did the Archean Eon last?

Answer 2

From 3.8 bya -2.5 bya

Question 3

What eon lasted from 2.5bya-543mya?

Answer 3

Proterozoic Eon

Question 4

What eon lasts from 543mya-0.01mya/today?

Answer 4

The Phanerozoic Eon

Question 5

What eons make up the Precambrian Supereon?

Answer 5

The Hadean, Archean, and Proterozoic eons

Question 6

what are the four steps that likely took place to form living things? In order?

Answer 6

1. Abiotic synthesis of small, organic molecules (amino acids & nucleotides)
2. joining small organic molecules into macromolecules/polymers (proteins & nucleic acids)
3. Formation of self-replicating molecules (RNA)
4. Encapsulation into lipid spheres, forming protocells

Question 7

What are the levels of the geologic timescale in order from largest to smallest?

Answer 7

Eon, Era, Period

Question 8

What happened during the Theia collision?

Answer 8

Massive collision between Earth and Theia, Earth’s surface then turned molten, and that led to the formation of the tilt of Earth’s rotational axis and the Moon

Question 9

What takes place during the water condensation?

Answer 9

After Earth cooled, water was able to condense into clouds. Eventually, the temperature lowered even further, allowing water to accumulate on the surface in liquid form.

Question 10

What gases were present in the atmosphere during the Hadean eon?

Answer 10

Carbon dioxide, ammonia(NH3), neon, helium, water, methane(CH4)

Question 11

Explain why the Precambrian Supereon is significant in Earth’s history.

Answer 11

The Precambrian Supereon encompasses the majority of Earth’s history, including the formation of the planet and the origin of life.

Question 12

During the Hadean eon, Earth’s atmosphere was quite different from today. List the gases present and explain why the absence of oxygen was crucial for early chemical processes.

Answer 12

The atmosphere consisted of carbon dioxide, ammonia, neon, helium, water, and methane. The absence of oxygen was crucial because oxygen is highly reactive and would have disrupted the formation of organic molecules necessary for life.

Question 13

The Hadean eon is known for three pivotal events. Name these events and describe how each one contributed to Earth’s early environment.

Answer 13

1. Theia collision – Created the moon and reshaped Earth’s surface.
2. Water condensation – Allowed for the formation of oceans.
3. Formation of the first living organisms – Set the stage for the emergence of life.

Question 14

Several hypotheses exist for the origin of organic molecules. Which hypothesis involves extraterrestrial delivery, and why does this idea remain scientifically viable?

Answer 14

The meteor hypothesis suggests that organic molecules were delivered to Earth by meteors. It remains viable because meteors have been found to contain amino acids and other organic compounds, providing a potential external source for life’s building blocks.

Question 15

Clay played a role in the polymerization of organic molecules. Describe how this could have occurred and what of clay’s properties are particularly suited to this process.

Answer 15

Clay surfaces could have been a mold for organic molecules, concentrating them, and catalyzing their polymerization. The charged surfaces of clay attract molecules, helping align them and promote reactions, essentially acting as a scaffold for early biochemical processes.

Question 16

RNA’s self-replicating ability might have been a key step in the formation of life. Explain how RNA’s dual function contributes to both replication and catalysis and how this could have led to the formation of the first cells.

Answer 16

RNA can both store genetic information and catalyze reactions (ribozymes). This dual role means RNA could self-replicate and assist in forming lipid spheres, which could eventually enclose these molecules, forming the first protocells.

Question 17

What is the significance of the fossil record dating back to the Archean eon, and what does the oldest fossil tell us about the nature of life at that time?

Answer 17

The oldest fossil, dating back approximately 3.5 billion years, suggests that life emerged early in Earth’s history, likely as simple prokaryotic organisms that thrived in an anoxic environment.

Question 18

The Oxygen Revolution dramatically altered Earth’s atmosphere. What was the source of this oxygen, and how did its gradual accumulation lead to two major biological innovations?

Answer 18

Oxygen was produced by photosynthetic bacteria. Its accumulation allowed organisms to perform aerobic respiration, which is more efficient than anaerobic processes, and the formation of the ozone layer, which protected life from harmful UV radiation.

Question 19

Fossil evidence places the origin of eukaryotic organisms at around 1.5 billion years ago. Describe the two main hypotheses for the origin of eukaryotic organelles and how each hypothesis accounts for the complexity of modern eukaryotic cells.

Answer 19

1. Membrane infolding hypothesis – Proposes that the eukaryotic cell’s internal membranes (like the nucleus and ER) formed from the inward folding of the plasma membrane.
2. Endosymbiont theory – Suggests that organelles like mitochondria and chloroplasts originated as prokaryotic cells that were engulfed by an ancestral eukaryotic cell and formed a symbiotic relationship.

Question 20

Multicellularity evolved independently in several lineages. Identify the eon during which multicellular organisms first appeared, and explain how this trait may have provided an evolutionary advantage.

Answer 20

Multicellular organisms first appeared during the Proterozoic eon, around 1.2 billion years ago. Multicellularity allowed for cellular specialization, which improved efficiency in resource utilization, reproduction, and adaptation to complex environments.

Question 21

The Phanerozoic eon is marked by major biological changes. What key event initiated the Paleozoic era, and how did this event influence the evolution of life in subsequent periods?

Answer 21

The Cambrian Explosion initiated the Paleozoic era, a rapid diversification of life forms. This event led to the evolution of most major animal phyla and set the stage for the dominance of complex organisms, including the emergence of vertebrates and land plants.

Question 22

The Mesozoic era is often referred to as the “Age of Reptiles.” However, this era also saw the rise of other significant life forms. Identify two major developments in life during the Mesozoic, aside from reptiles, and explain their evolutionary significance.

Answer 22

1. The evolution of the first mammals – These small, nocturnal creatures eventually diversified and became dominant after the mass extinction at the end of the Mesozoic.
2. The evolution of flowering plants – Flowering plants (angiosperms) greatly diversified during this era, leading to new ecological interactions, particularly with pollinators.

Question 23

Natural selection operates in different patterns. Describe the three main patterns of natural selection and give an example of each.

Answer 23

Directional selection: Favors one extreme phenotype, leading to a shift in the population (e.g., peppered moths during the Industrial Revolution).

Stabilizing selection: Favors intermediate phenotypes, reducing variation (e.g., human birth weight, where extremes are less favorable).

Disruptive selection: Favors both extremes over the intermediate phenotype, leading to population divergence (e.g., beak sizes in a bird population where small and large seeds are the only food sources).

Question 24

Genetic drift can have a significant impact on small populations. Compare and contrast the founder effect and the bottleneck effect as mechanisms of genetic drift, and provide an example of each.

Answer 24

Founder effect: Occurs when a small group from a larger population establishes a new population with different allele frequencies (e.g., a small group of colonists forming a new settlement).

Bottleneck effect: Happens when a population is drastically reduced by a catastrophe, and the survivors’ gene pool may not represent the original population’s genetic diversity (e.g., a natural disaster reducing a species’ population).

Question 25

Using the Hardy-Weinberg equation, 𝑝^2 + 2𝑝𝑞 + 𝑞^2 =1, identify what each variable represents, and explain how you would use this equation to determine if a population is evolving.

Answer 25

p^2 = frequency of homozygous dominant genotype
2pq = frequency of heterozygous genotype
q^2 = frequency of homozygous recessive genotype
If observed genotype frequencies differ from those predicted by the equation, the population is not in Hardy-Weinberg equilibrium and is evolving.

Question 26

The Hardy-Weinberg equilibrium describes a population that is not evolving. Identify the five conditions required to maintain Hardy-Weinberg equilibrium and explain why any deviation from these conditions results in evolution.

Answer 26

1. No mutations
2. Random mating
3. No natural selection
4. Extremely large population size
5. No gene flow
   Deviations from these conditions introduce new genetic variations or alter allele frequencies, increasing the possibility of evolution in the population.

Question 27

Darwin’s theory of natural selection introduced a key concept that contrasts with earlier ideas of evolution. Explain Darwin’s definition of natural selection and how it differed from Lamarck’s theory of inheritance of acquired characteristics.

Answer 27

Darwin’s natural selection is the process by which organisms with traits that increase their fitness are more likely to survive and reproduce, passing those traits to the next generation. In contrast, Lamarck believed that organisms acquire traits during their lifetime through use and disuse and then pass these traits directly to their offspring, which is incorrect.

Question 28

Contrast the causes of mass extinction events vs background extinction. What is the primary difference between these two types of extinction, and how does adaptive radiation relate to the aftermath of mass extinctions?

Answer 28

Mass extinction is caused by catastrophic events (e.g., asteroid impacts or volcanic activity) that rapidly wipe out a large percentage of species, while background extinction occurs at a slower, more constant rate due to environmental or biological factors. After mass extinctions, adaptive radiation occurs as surviving species rapidly diversify to fill vacant ecological niches/roles.

Question 29

Mutation is one of the mechanisms driving evolution. Explain how mutations contribute to genetic variation and provide an example of a type of mutation that could have a significant evolutionary impact.

Answer 29

Mutations introduce new alleles into a population’s gene pool by altering DNA sequences. A significant mutation, such as a point mutation in a regulatory gene, could drastically alter an organism’s development or traits (e.g., a mutation in the Hox gene affecting body plan segmentation in animals).

Question 30

Sexual selection is a specific type of nonrandom mating. Distinguish between intrasexual and intersexual selection, providing an example for each, and explain how these processes lead to sexual dimorphism.

Answer 30

-Intrasexual selection involves competition between members of the same sex
-Intersexual selection involves one sex choosing mates based on traits
Both lead to sexual dimorphism, where males and females of a species show distinct physical differences due to selection pressures favoring different traits.

Question 31

Gene flow can either enhance or reduce genetic diversity. Explain how gene flow operates between populations and describe a scenario in which gene flow could prevent speciation.

Answer 31

Gene flow is the transfer of alleles between populations via migration. If gene flow occurs frequently between two populations, it prevents genetic divergence by mixing their gene pools, which can prevent speciation or distinct differences between the two populations. For example, if two bird populations frequently interbreed, they may not develop into distinct species.

Question 32

Compare and contrast the evolutionary concepts of adaptation and exaptation, giving a specific example of each.

Answer 32

Adaptation: A trait that evolves because it enhances survival or reproduction in a specific environment (e.g., the long neck of a giraffe for reaching high foliage).

Exaptation: A trait that evolved for one purpose but is co-opted for another use (e.g., feathers originally evolved for temperature regulation but later adapted for flight in birds).

Question 33

Describe heterozygote advantage and explain how this form of selection maintains genetic variation within a population. Provide an example of a condition where heterozygote advantage is observed.

Answer 33

Heterozygote advantage occurs when individuals with heterozygous genotypes have higher fitness than either homozygous genotype, maintaining both alleles in the population. An example is sickle cell trait, where heterozygotes (AS) are resistant to malaria, providing a survival advantage in regions where malaria is prevalent.

Question 34

Fossils provide critical evidence for evolution, but the fossil record is incomplete. Explain two reasons why the fossil record is biased and incomplete, and discuss the significance of transitional fossils like Archaeopteryx.

Answer 34

The fossil record is biased because (1) only organisms with hard parts like bones or shells are more likely to fossilize, and (2) fossils form best in environments where sediment rapidly covers remains, such as in lakes or rivers. Transitional fossils like Archaeopteryx are significant because they show intermediate traits, linking birds and reptiles and illustrating the evolutionary transition between major groups.

Question 35

Biogeography is one of the key pieces of evidence supporting evolution. Describe how the distribution of species across geographic regions supports evolutionary theory, and provide an example involving an endemic species.

Answer 35

Biogeography shows how species that are geographically isolated evolve differently due to varying selection pressures. An example is the Nene goose in Hawaii, which evolved from the Canadian goose but adapted to Hawaii’s unique environment, becoming its own unique species & now native to the islands.

Question 36

Explain the concept of convergent evolution and how it differs from homologous structures. Provide an example of an analogous structure that demonstrates convergent evolution.

Answer 36

Convergent evolution occurs when unrelated species evolve similar traits due to similar environmental pressures, while homologous structures are traits inherited from a common ancestor. An example of an analogous structure is the wings of bats and insects—both are used for flight but evolved independently in different lineages.

Question 37

Molecular evidence provides one of the most precise ways to trace evolutionary relationships. Discuss how homologous genes and proteins serve as evidence for common ancestry, and explain the importance of highly conserved genes like Hox genes.

Answer 37

Homologous genes and proteins are similar due to shared ancestry, indicating evolutionary relationships across species. Highly conserved genes like Hox genes are crucial because they control the development of body plans, and their similarities across different species suggest a common evolutionary origin.

Question 38

Direct observation of evolution occurs in various ways. Describe two real-world examples where evolution has been observed in nature, and explain how these examples provide direct evidence of natural selection in action.

Answer 38

1. Soapberry bugs evolved shorter beaks to feed on introduced plant species with smaller fruit.
2. Staphylococcus aureus bacteria evolved resistance to antibiotics due to selective pressure from drug treatments.
   Both examples show how environmental changes (new food sources or antibiotics) exert selective pressure, leading to observable evolutionary changes within populations.

Question 39

How does the fossil record support the theory of evolution?

Answer 39

Fossils provide evidence of past organisms, showing changes over time and documenting intermediate forms between species (e.g., transitional fossils).

Question 40

What are the two main types of fossil dating, and how do they differ?

Answer 40

1. Relative dating estimates a fossil’s age by its location in rock layers.
2. Absolute dating uses radiometric techniques to determine the actual age of a fossil.

Question 41

What is artificial selection and how does it differ from natural selection?

Answer 41

Artificial selection is when humans breed organisms for specific traits, whereas natural selection is when traits evolve based on survival and reproduction in nature.

Question 42

What is biogeography and how does it provide evidence for evolution?

Answer 42

Biogeography is the study of species distribution across the world. It shows how species that are isolated from each other evolve differently due to different environments.

Question 43

What are homologous structures and how do they differ from analogous structures?

Answer 43

Homologous structures are similar due to shared ancestry, while analogous structures evolve independently but serve similar functions (e.g., bird wings vs. insect wings).

Question 44

What are vestigial structures, and what do they tell us about evolution?

Answer 44

Vestigial structures are body parts that have lost their original function (e.g., the human appendix), showing that species can change over time.

Question 45

How does molecular evidence, such as DNA and protein similarities, support the theory of evolution?

Answer 45

Similarities in DNA sequences and proteins, such as homologous genes, show that different species have common ancestors.

Question 45

How does embryological evidence support evolution?

Answer 45

Similarities in early development stages across different species suggest that they share a common ancestor.

Question 46

What are Hox genes and why are they important in understanding evolution?

Answer 46

Hox genes control the development of body plans and are highly conserved across species, indicating a common evolutionary origin.

Question 47

How do the Cytochrome C proteins provide evidence of evolution?

Answer 47

Cytochrome C proteins are found in many species, and similarities in their sequences indicate shared ancestry among species.

Question 48

What is an example of evolution observed through experiments?

Answer 48

In experiments with bacteria, scientists have observed mutations that allow them to survive in new environments, demonstrating evolutionary change over time.

Question 49

What is an endemic species, and how does it relate to evolution?

Answer 49

An endemic species is one that is found in a specific location and nowhere else, often due to isolation that leads to unique evolutionary changes.

Question 50

What role does artificial selection play in evolution experiments?

Answer 50

Artificial selection allows scientists to observe how traits change when they control which organisms reproduce, providing a model for natural selection.