Quest flashcards

Origins and Early Life

• Spontaneous Generation: Early belief that life arises from nonlife (e.g., worms, insects, fish from mud). This idea was widely accepted until scientific experiments disproved it.

• Redi’s Experiment (1668): Tested the idea that flies arise from rotting meat; he placed meat in covered and uncovered jars, showing that only uncovered meat developed maggots, proving that flies come from other flies.

• Theory of Biogenesis (Louis Pasteur, 1861): Conducted experiments using swan-neck flasks to show that microorganisms come from other microorganisms, not spontaneous generation.

• Primordial Soup Hypothesis (1920s): Proposed that Earth’s early atmosphere contained gases such as methane, ammonia, hydrogen, and water vapor. With energy from UV light and lightning, these gases could react to form organic molecules, the precursors to life.

• Miller-Urey Experiment (1953): Simulated early Earth conditions and demonstrated that simple organic molecules, including amino acids, could form from inorganic substances when exposed to electric sparks (mimicking lightning).

• RNA: RNA may have been the first genetic material, capable of storing information and catalyzing chemical reactions (ribozymes). It could have played a key role in early life processes before DNA evolved.

• Membranes and Cells: Scientists investigate how molecules could have been enclosed in membranes, a step towards cellular life. The formation of protocells (primitive membrane-bound structures) may have led to the first living cells.

Cellular Evolution

• First Cells: Likely prokaryotic, resembling modern archaea, which thrive in extreme environments such as hydrothermal vents and hot springs.

• Endosymbiotic Theory (Lynn Margulis, 1967): Eukaryotic cells evolved when ancestral eukaryotes absorbed prokaryotic cells, which became mitochondria and chloroplasts. Evidence includes:

  • Mitochondria and chloroplasts have their own DNA, similar to bacterial DNA.

  • They reproduce independently through binary fission, like bacteria.

  • They have double membranes, suggesting they were once free-living prokaryotes.

Darwin’s Theory of Evolution by Natural Selection

• Natural Selection Principles:

  1. Variation: Individuals within a species differ from one another.

  2. Heritability: Traits must be genetically inherited.

  3. Overproduction: More offspring are produced than can survive.

  4. Differential Survival and Reproduction: Variations that enhance survival and reproduction become more common in the population.

• Artificial Selection: Humans selectively breed organisms to enhance desirable traits (e.g., domesticated dogs, crops like corn and wheat).

Evidence of Evolution

1. Fossil Record: Shows historical sequences of organisms and how species have changed over time.

   • Fossils form through permineralization, natural casts, trace fossils, amber preservation, and preserved remains.

   • Relative Dating: Determines fossil age by comparing its position in rock layers (older layers are deeper).

   • Radiometric Dating: Measures the decay of radioactive isotopes to determine a fossil’s absolute age (e.g., Carbon-14 dating for recent fossils, Uranium-238 for older fossils).

2. Comparative Anatomy:

   • Homologous Structures: Same structure, different function, indicating common ancestry (e.g., vertebrate forelimbs of humans, bats, and whales).

   • Analogous Structures: Different structure, same function, evolved separately (e.g., wings of birds and insects).

   • Vestigial Structures: Reduced or non-functional features, evidence of ancestral traits (e.g., human appendix, whale pelvic bones, flightless bird wings).

3. Comparative Embryology: Similar embryonic development in different species (e.g., vertebrate embryos have gill slits and tails, suggesting a common ancestor).

4. Molecular Biology: DNA and protein comparisons reveal evolutionary relationships; more genetic similarities indicate closer common ancestry.

Mechanisms of Evolution

• Gradualism: Evolution occurs slowly over long periods of time, supported by continuous fossil changes.

• Punctuated Equilibrium: Long periods of stability are interrupted by short bursts of rapid evolution (e.g., Cambrian Explosion).

• Examples of Natural Selection:

  • Darwin’s Finches: Different beak shapes evolved based on available food sources on the Galápagos Islands.

  • Industrial Melanism: Peppered moths evolved darker colors in polluted environments to better camouflage.

  • Pesticide Resistance: Insects develop resistance to pesticides over multiple generations.

  • Antibiotic Resistance: Bacteria evolve resistance to antibiotics through natural selection.

Adaptations

• Adaptation: A heritable trait that enhances survival and reproductive success in a specific environment.

• Fitness: The ability of an organism to survive and reproduce in its environment.

• Types of Adaptations:

  • Camouflage: Organisms blend into their surroundings (e.g., stick insects, chameleons).

  • Mimicry: A harmless species resembles a harmful one for protection (e.g., non-venomous king snake mimicking venomous coral snake).

  • Physiological Adaptations: Internal functions improve survival (e.g., hibernation, venom production, antibiotic resistance in bacteria).

Review Questions

1. What is the difference between homologous and analogous structures?

2. How does natural selection lead to evolution?

3. Explain the significance of the Miller-Urey experiment.

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

5. How does radiometric dating determine the age of fossils?

6. What is the difference between gradualism and punctuated equilibrium?

7. Give an example of artificial selection and explain how it differs from natural selection.

8. Describe an example of an organism adapting to its environment through natural selection.

9. How does comparative embryology provide evidence for evolution?

10. What are the main types of fossil formation, and how do they contribute to our understanding of evolution?