Natural Selection and Evolution

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Questions and Answers

Which of the following scenarios would LEAST likely lead to natural selection?

  • A population of birds with beaks of various sizes living in an environment where only small seeds are available.
  • A population of fish where individuals with brighter coloration are more attractive to mates and reproduce more successfully.
  • A population of trees in a forest with uniform height and identical resistance to a common fungal disease. (correct)
  • A population of insects displaying different camouflage patterns in a habitat with varied foliage colors.

A population of butterflies exhibits two distinct wing colorations: vibrant orange and dull brown. Over several generations, the frequency of the orange coloration increases. Which factor would suggest this change is due to natural selection rather than genetic drift?

  • The orange coloration is linked to a gene that also enhances toxin resistance against predators. (correct)
  • The change in coloration frequency occurs rapidly over just a few generations.
  • The butterfly population experienced a bottleneck event, drastically reducing its size.
  • There is random mating within the butterfly population, without preference for color.

Which of the following describes a key difference between microevolution and macroevolution?

  • Microevolution is driven by natural selection, whereas macroevolution is driven by genetic drift.
  • Microevolution involves changes in allele frequencies within a population, while macroevolution involves the formation of brand new species and higher taxonomic groups. (correct)
  • Microevolution is observable in the fossil record, whereas macroevolution cannot be directly observed.
  • Microevolution occurs over geological timescales, while macroevolution occurs over shorter periods.

A species of frog exhibits significant genetic diversity. Which of the following environmental changes would pose the LEAST threat to the survival of this frog population?

<p>A slow shift towards increased rainfall enabling them to slowly adapt. (D)</p> Signup and view all the answers

In a population of birds, larger beaks are more efficient for cracking open tough seeds. Over time, the average beak size increases. What must be true for this to be considered an example of evolution by natural selection?

<p>Birds with larger beaks have higher reproductive success, and beak size is a heritable trait. (B)</p> Signup and view all the answers

Which of the following is an example of convergent evolution?

<p>The flippers of dolphins and the fins of sharks which both live in acquatic environments. (A)</p> Signup and view all the answers

A small group of individuals migrates from a large mainland population to a isolated island. The allele frequencies in the island population are noticeably different from those in the mainland population. What is this an example of?

<p>Founder Effect (A)</p> Signup and view all the answers

Which of following best describes the role of mutations in the process of evolution?

<p>Mutations provide the raw genetic variation upon which other evolutionary forces can act. (D)</p> Signup and view all the answers

A population of plants is exposed to a new disease. Some individuals have a gene that confers resistance, while others are susceptible. Over time, the proportion of resistant individuals increases. What evolutionary mechanism is at play?

<p>Natural Selection (D)</p> Signup and view all the answers

Which of these provides the best evidence for common ancestry between two different species?

<p>Highly similar DNA sequences and conserved metabolic pathways. (C)</p> Signup and view all the answers

Which of the following is an example of a vestigial structure?

<p>The appendix in humans, which has no significant digestive function. (A)</p> Signup and view all the answers

Two populations of squirrels are geographically separated by a large river. Initially, they were the same species, but over time, they develop distinct characteristics due to different environmental pressures. What process is occurring?

<p>Divergent Evolution (A)</p> Signup and view all the answers

A population of insects is sprayed with a new insecticide. Initially, most insects are killed, but a few survive. Over time, the insecticide becomes less effective. What is the most likely explanation?

<p>The surviving insects had genes that made them resistant, and they passed those genes on to their offspring. (C)</p> Signup and view all the answers

How is evolutionary fitness best measured?

<p>By an organism's reproductive success and contribution to the gene pool of the next generation. (B)</p> Signup and view all the answers

Which of the following is NOT a condition necessary for natural selection to occur?

<p>The population must be in Hardy-Weinberg equilibrium. (D)</p> Signup and view all the answers

Why is genetic variation important for the survival of a species?

<p>It allows the species to adapt to changing environmental conditions. (A)</p> Signup and view all the answers

Which of the following processes is considered a random mechanism of evolution?

<p>Mutation (C)</p> Signup and view all the answers

Which of the following is an example of gene flow?

<p>The migration of birds from one island to another, introducing new alleles to the island population. (A)</p> Signup and view all the answers

Fossils can be dated using radioactive dating. What is this process based on?

<p>The known decay rates of radioactive elements found in fossils. (C)</p> Signup and view all the answers

Homologous structures provide evidence for evolution because they demonstrate:

<p>Shared ancestry and common evolutionary origins, even if functions diverge. (C)</p> Signup and view all the answers

Flashcards

Evolution

Change in allele frequency of a gene pool in a population over time.

Microevolution

Small-scale changes in a population's gene frequency.

Macroevolution

Large-scale changes, like speciation.

Natural Selection

Individuals with favorable traits are more likely to survive and reproduce.

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Conditions for Natural Selection

Reproduction, inheritable traits, variation, and varied fitness.

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Evolutionary Fitness

Measured by reproductive success.

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Adaptation

A genetic variation favored by selection that gives organism advantages in an environment.

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Natural Selection Acts on Phenotype

Acts on observable traits because they interact with the environment.

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Why is genetic variation important?

A diverse gene pool increases species survival chances in changing environments.

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Genetic Drift

Random changes due to chance events that alter allele frequencies.

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Bottleneck Effect

Natural disaster shrinks original population size.

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Founder Effect

A small group establishes a new colony separated from the original population.

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Gene Flow

Movement of genes into or out of a population.

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Radioactive Dating

Using radioactive elements in fossils to estimate their age.

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Homologous Structures

Similar body parts showing common ancestry.

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Vestigial Structures

Remnants of structures that had a function in ancestral species

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Convergent Evolution

Unrelated species develop similar traits due to similar environments.

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Divergent Evolution

Species from a common ancestor evolve distinct characteristics, often due to different environments.

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Molecular Evidence

Analysis of DNA/protein sequences determining evolutionary relationships.

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Study Notes

  • Natural selection is a primary driver of evolution, operating on phenotypic variations within populations.

Evolution Defined

  • Evolution is defined as changes in allele frequencies within a population's gene pool over time.

Five Processes of Evolution

  • Population shrinkage can lead to genetic drift due to chance events.
  • Non-random mating can alter allele frequencies.
  • Mutations introduce new genetic variations.
  • Gene flow, through movement of individuals or gametes, can change allele frequencies.
  • Natural selection leads to adaptation by favoring beneficial traits.

Microevolution

  • Microevolution involves small-scale changes in a population, specifically changes in gene frequency.
  • These changes are subtle, occur rapidly, and may not be immediately apparent.

Macroevolution

  • Macroevolution involves large-scale changes, such as speciation (the formation of new species).
  • Macroevolution encompasses major evolutionary trends and transformations.

Natural Selection

  • Individuals with favorable phenotypes are more likely to survive, reproduce, and pass on their traits.
  • Natural selection is a mechanism of evolution, where organisms better adapted to their environment are more likely to pass on their genes.

Conditions for Natural Selection

  • Reproduction must occur.
  • Traits must be inheritable.
  • Variation must exist among individuals.
  • Variation in fitness among individuals must be present.

Evolutionary Fitness

  • Fitness is defined by reproductive success.

Adaptation

  • Adaptation is the modification of an organism or its parts to better suit its environment.
  • It is a genetic variation that provides an advantage in a specific environment and is favored by selection.
  • Adaptations occur naturally due to environmental pressures.

Natural Selection and Phenotype

  • Natural selection acts on the phenotype because observable traits interact with the environment.
  • Changing environments act as selective mechanisms on populations.

Importance of Genetic Variation

  • A diverse gene pool enhances a species' ability to survive environmental changes.

Randomness in Evolution

  • Evolution can be influenced by random processes, like mutations.

Mutations Explained

  • Mutations, alterations in genetic information that can be random or caused by mutagens, and can be positive, negative, or neutral.

Genetic Drift Defined

  • Genetic drift is caused by random changes (bottleneck and founder effects).

Bottleneck Effect

  • Bottleneck effect occurs when a natural disaster reduces the size of an original, larger population, reducing genetic diversity.

Founder Effect

  • Founder effect: a subpopulation establishes a new colony drawn from a larger population, resulting from migration.

Gene Flow Described

  • Gene flow: the movement of genes into or out of a population through migration of individuals or gametes.

Fossil Record

  • Ardi (Ardipithecus ramidus) lived approximately 4.4 million years ago.
  • Lucy (Australopithecus afarensis) lived approximately 3.2 million years ago.
  • Radioactive dating, using elements like Carbon-14, is used to determine the age of fossils.
  • Morphologies are compared to determine the age of fossils.

Homologous Structures

  • Sharing similar body parts indicates common ancestry.
  • Homologous structures can be internal or external and might not have the same function.

Vestigial Structures

  • Vestigial structures are remnants of functional structures in ancestors.
  • Analysis of vestigial structures is used for comparisons with fossils, providing evolutionary proof.
  • Embryology, the study of embryos and their development, contributes to comparative anatomy.

Convergent and Divergent Evolution

  • Convergent evolution occurs when unrelated species develop similar traits due to similar environmental pressures.
  • Divergent evolution occurs when species with a common ancestor evolve distinct characteristics, often adapting to different environments.

Genetic Material

  • Genetic material: DNA or RNA, composed of A, T, C, G, sugar, and phosphate.
  • Metabolic pathways, such as photosynthesis or respiration, provide molecular evidence.

Eukaryotic Features

  • Eukaryotes possess a cytoskeleton, membrane-bound organelles, linear chromosomes, and endomembrane systems (including the nuclear envelope).

Molecular Evidence

  • Analysis of DNA nucleotide or protein sequences (e.g., cytochrome c) provides molecular evidence.
  • Similar sequences indicate closer evolutionary relationships.

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