Bell-Ringers: Biological Evolution

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The Fossil Record

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  1. Every Organism Becomes a Fossil: In reality, the fossilization process is rare. A large number of organisms decompose before they have a chance to become fossilized. Therefore, the fossil record is incomplete and represents only a small fraction of all the organisms that have ever lived.

  2. The Fossil Record is Complete: Some people might believe that we have found and cataloged every type of fossil out there. In truth, new fossils are being discovered regularly, and our understanding of the history of life is constantly evolving as a result.

  3. All Sedimentary Layers Are Chronologically Ordered Everywhere: While sedimentary layers can show chronological order in a specific location, they can be disrupted by geological processes like folding, faulting, or erosion. As a result, layers in one location may not perfectly align with layers in another.

  4. Radioactive Dating Determines the Age of All Fossils: Radioactive dating (or radiometric dating) is a powerful tool for determining the age of certain rocks and fossils, but it isn’t used for all fossils. The method depends on the presence of certain isotopes, which may not be present in all specimens.

  5. All Extinctions Are Evident in the Fossil Record: While significant extinction events (like the one that wiped out the dinosaurs) are well-documented, not all extinctions are clearly reflected in the fossil record due to its incomplete nature.

  6. All Evolutionary Changes Are Gradual and Continuous: Some interpret the fossil record to mean that evolutionary changes always happen slowly and steadily over long periods. While many changes do occur this way, the theory of punctuated equilibrium suggests that species might exhibit long periods of stability interrupted by shorter periods of rapid change.

  7. A Higher Position in the Sedimentary Layer Means a More Advanced Organism: Some might mistakenly think that organisms in upper sedimentary layers are more “advanced” than those below. In reality, the position in the layer primarily indicates age, not complexity or advancement.

  8. The Fossil Record Only Documents Past Life: While the fossil record is a critical tool for understanding past life, it also informs our understanding of current biodiversity, ecological relationships, and potential future evolutionary trends.

  9. Fossils Are Always Bones: While many fossils are indeed bones or teeth, a fossil can be any trace of an ancient organism. This includes footprints, burrows, and even imprints of soft-bodied organisms.

Evolutionary Relationships

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  1. All similarities are due to common ancestry. While many anatomical similarities can be attributed to common ancestry (homology), some are due to convergent evolution, where unrelated organisms independently evolve similar traits as a result of adapting to similar environments or ecological niches (analogy). For example, the wings of birds and the wings of bats are analogous structures, not homologous.

  2. Fossils give a complete picture of past life. The fossil record is actually incomplete, and there are numerous gaps. This is because not all organisms fossilize well, and even when they do, many fossils are yet to be discovered or may be destroyed by geological processes.

  3. The presence of transitional fossils means we’ve found the “missing link.” The term “missing link” is a misleading one. Evolution is a branching process, not a linear one. While transitional fossils can show intermediate forms between two groups, they might not necessarily represent the direct ancestor of a modern organism.

  4. If two organisms look alike, they must be closely related. As mentioned above with convergent evolution, similar environmental pressures can lead to similar adaptations in unrelated organisms. This can make them look more alike than their actual evolutionary relationship would suggest.

  5. Complex structures could not have evolved step by step. Some people struggle to understand how complex structures, like the eye, could have evolved gradually. However, intermediate forms of these structures can and do exist, suggesting that they evolved through a series of functional stages.

  6. Evolution always leads to more complexity. This is not necessarily true. Organisms can also evolve to be simpler if it’s beneficial for their survival and reproduction.

  7. All traits of an organism are adaptive. Not every trait is necessarily a result of natural selection. Some traits might be neutral, or they could be byproducts of other adaptive traits. Additionally, some traits might be vestigial, having once had a function in an ancestor but no longer being of use.

  8. Anatomical structures that are similar in function are always similar in structure. This isn’t always the case. For example, the wings of insects, bats, and birds are used for flying but have different structural designs.

  9. If we don’t have fossils of a certain transitional form, that means it never existed. Absence of evidence is not evidence of absence. Just because a fossil hasn’t been found doesn’t mean the organism didn’t exist. It could be that the conditions for fossilization weren’t met or that the fossil hasn’t been discovered yet.

  10. Evolutionary trees are set in stone. Phylogenetic trees, which represent the evolutionary relationships among groups of organisms, are hypotheses based on current evidence. As more data (from fossils, DNA, etc.) becomes available, these trees can and do get refined.

Natural Selection

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  1. Natural Selection Equals Evolution: While natural selection is a driving force behind evolution, they aren’t synonymous. Evolution refers to the change in the genetic composition of a population over time. Natural selection is just one mechanism (alongside genetic drift, gene flow, and mutation) that can lead to such changes.

  2. “Survival of the Fittest” Misunderstanding: The phrase can suggest that only the “strongest” individuals survive. In reality, “fittest” refers to reproductive fitness, meaning those who leave the most offspring, regardless of strength or size.

  3. Natural Selection Produces Perfect Organisms: No organism is perfectly adapted. Natural selection works with available genetic variation, which might not lead to an optimal outcome. An organism just needs to be “good enough” to survive and reproduce.

  4. Natural Selection Has a Set Goal or Direction: There’s a misconception that evolution moves towards a pre-determined “end goal” or that it always results in more complexity. Evolution has no foresight; it’s a response to current environmental pressures.

  5. Only Beneficial Traits are Passed On: While beneficial traits become more common, neutral traits (which don’t confer a specific advantage or disadvantage) can also spread through a population.

  6. All Traits are a Result of Natural Selection: Some traits may arise due to other evolutionary mechanisms like genetic drift (random changes).

  7. Quick Response Misconception: Some believe that if a sudden environmental change occurs, organisms will quickly develop beneficial mutations in response. In reality, mutations are random and can’t be “willed” into existence. Populations either already have beneficial variations, or they might develop them by chance.

  8. Only Physical Traits are Selected: Both behavioral and physical traits can be acted upon by natural selection. For example, a particular behavior that increases the chance of survival or reproduction can become more common over generations.

  9. Use and Disuse Idea: Some think that if an animal uses a particular organ or feature more frequently, it will develop or strengthen in their offspring (e.g., the idea that giraffes got long necks by stretching to reach tall trees). This Lamarckian idea has been discredited in favor of the genetic basis of inheritance.

  10. Individuals Evolve: This misconception is the idea that individual organisms can change in response to their environment and then pass on these changes. In reality, populations evolve, not individual organisms.

Artificial Selection

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  1. Perfect Control: One of the biggest misconceptions is that humans have perfect control over the traits of organisms through artificial selection. While humans can influence traits, there’s still a lot of genetic variability, and not all offspring will perfectly exhibit the desired traits.

  2. Speed of Results: Some people think that artificial selection can produce desired results in just one or a few generations. In reality, certain traits might take many generations of selective breeding to become firmly established.

  3. All Traits are Equally Heritable: Some traits are more strongly influenced by genetics than others. Just because a trait is present in one generation doesn’t mean it’s 100% certain to appear in the next, even with selective breeding.

  4. Artificial Selection Produces “Unnatural” Organisms: Some people believe that organisms bred through artificial selection are “unnatural” or “man-made.” While humans guide the selection process, the underlying genetic mechanisms are natural processes.

  5. Artificially Selected Organisms are Always Weaker: There’s a belief that organisms bred for specific traits (like large fruit) are necessarily weaker or more susceptible to diseases. While narrowing genetic diversity can increase susceptibility to specific threats, not all artificially selected organisms are inherently weaker.

  6. Only Physical Traits are Selected: Some think that artificial selection only influences physical traits. However, organisms can also be selectively bred for behavioral traits, like docility in domesticated animals.

  7. Artificial Selection is a Modern Concept: Some might believe that artificial selection is a result of modern science. In reality, humans have been practicing artificial selection for thousands of years, long before the underlying genetic mechanisms were understood.

  8. It’s the Same as Genetic Modification: People often conflate artificial selection with genetic engineering. While both influence an organism’s traits, artificial selection is about choosing specific organisms to reproduce based on existing traits, whereas genetic engineering involves directly manipulating an organism’s genetic material.

  9. No Negative Consequences: A misconception is that artificial selection has no downsides. In reality, overly narrow breeding can lead to unintended consequences, such as genetic disorders in certain purebred dogs.

  10. All Traits Can be Bred Simultaneously: There’s an idea that one can selectively breed for multiple traits all at once easily. In reality, selecting for one trait might inadvertently impact another, making it a balancing act to achieve the desired outcomes.


Use the arrows located at the bottom of the presentation to navigate through all the bell ringer questions.

  1. Individuals Adapt: One common misconception is that individual organisms can adapt (in a genetic sense) to their environment during their lifetime and then pass these adaptations onto their offspring. In fact, it’s populations that adapt over many generations, not individual organisms within a single lifetime.

  2. Evolution is Goal-Oriented: Some people believe that evolution has a specific ‘goal’ or ‘end point’ in mind. In reality, evolution is not goal-directed. It simply results from the differential survival and reproduction of individuals in a population.

  3. All Traits are Adaptive: Not all traits an organism has are necessarily adaptive or beneficial. Some traits might be neutral, some might be by-products of other adaptive traits, and some currently maladaptive traits may have been beneficial in past environments.

  4. Use and Disuse: A throwback to Lamarck’s theory, some believe that characteristics acquired or unused during an organism’s lifetime can be passed on to its offspring. For instance, the mistaken idea that if someone loses a limb, their children will be born without that limb.

  5. Evolution Leads to Perfection: There’s a belief that natural selection will produce perfectly adapted organisms. However, evolution works with what’s already present, so organisms are often “good enough” rather than “perfect.”

  6. Natural Selection is the Only Mechanism: While natural selection is a primary driver of evolution, there are other mechanisms at play too, such as genetic drift, gene flow, and mutation.

  7. Survival of the Fittest means Only the Strong Survive: The phrase “survival of the fittest” can be misleading. “Fittest” in evolutionary terms means being best suited to the environment and leaving the most offspring, not necessarily being the strongest or fastest.

  8. Only Large Changes Matter: Some think that only major mutations or changes can drive evolution. In reality, small changes accumulated over long periods can lead to significant evolutionary shifts.

  9. Humans are the End Product of Evolution: Some people view humans as the pinnacle or end point of evolution. In reality, all organisms are continuously evolving, and there’s no “end point” in evolution.

  10. Environment Dictates Evolution: There’s a misconception that the environment ‘dictates’ specific adaptations. In reality, while the environment exerts pressures, the genetic variation present in the population plays a crucial role in determining how the population adapts.