Intro/History of life

General Concepts

1. What is organismic biology?
   The study of biology at the level of the whole organism, considering its evolutionary history, anatomy, physiology, behavior, and life history.

2. How does organismic biology differ from other biological disciplines?
   It focuses on whole organisms rather than just their molecular or cellular components.

3. What are some interdisciplinary fields related to organismic biology?
   Evolutionary history, anatomy, behavior, life history, physiology, molecular biology.

4. What is the difference between macroevolution and microevolution?
   Macroevolution looks at large-scale evolutionary changes over long time periods, while microevolution studies evolutionary changes within populations over shorter timescales.

5. What are the key learning objectives of Chapter 25?
   Understanding the origins of life, conditions of early Earth, evolution of early life, and major evolutionary transitions.

Early Earth and Origins of Life

6. How old is the Earth?
   About 4.6 billion years old.

7. Why were seas unable to form before 4 billion years ago?
   Frequent bombardment by space debris vaporized water, preventing liquid oceans from forming.

8. What gases were likely present in Earth’s early atmosphere?
   Water vapor, nitrogen, carbon dioxide, methane, ammonia, hydrogen, and nitrogen oxides.

9. What are the four stages of the origin of early life?

   1. Abiotic synthesis of small organic molecules

   2. Formation of macromolecules

   3. Packaging into protocells

   4. Origin of self-replicating molecules

10. What is abiotic synthesis?
    The formation of organic molecules from non-living chemical sources.

11. What did the Miller-Urey experiment demonstrate?
    That organic molecules could form in a simulated early Earth environment.

12. Where might the first organic molecules have formed?
    Near volcanic openings, hydrothermal vents, or in shallow water pools.

13. How do deep-sea hydrothermal vents contribute to organic molecule formation?
    They release heat and minerals that provide energy for chemical reactions.

14. What is the difference between black smokers and alkaline vents?
    Black smokers release very hot (300–400°C) acidic water, while alkaline vents release warm (40–90°C), high-pH water more suitable for organic molecule formation.

15. Why are hydrothermal vents biodiversity hotspots?
    They support unique life forms that rely on chemosynthesis rather than photosynthesis.

16. What is the giant tube worm Riftia pachyptila and how does it survive?
    A deep-sea organism that relies on chemosynthetic bacteria for nutrition.

Protocells and Self-Replication

17. What are protocells?
    Simple cell-like structures with a lipid bilayer that could separate internal environments from the external world.

18. How do phospholipids contribute to protocell formation?
    They spontaneously form bilayer vesicles, which can encapsulate molecules.

19. Why is vesicle formation important for early metabolism?
    It allows molecules to be concentrated and interact in a controlled environment.

20. How does montmorillonite clay affect protocell formation?
    It speeds up vesicle formation and allows protocells to absorb organic molecules.

21. What was likely the first genetic material?
    RNA.

22. What are ribozymes?
    RNA molecules that can catalyze chemical reactions, including RNA replication.

23. How can ribozymes replicate RNA sequences?
    By catalyzing the formation of complementary RNA strands.

24. How did self-replicating RNA molecules evolve through natural selection?
    Mutations that improved replication efficiency became more common over time.

25. Why is DNA more stable than RNA?
    DNA is double-stranded, making it less prone to degradation and replication errors.

Fossil Record and Early Life

26. How does the fossil record provide evidence for evolution?
    It shows changes in species over time and reveals extinct organisms.

27. Why are sedimentary rocks important for fossils?
    They preserve layers of past life in strata.

28. What types of organisms are most likely to fossilize?
    Those that were abundant, had hard parts (e.g., shells, bones), and existed for long periods.

29. What are stromatolites?
    Layered structures formed by photosynthetic bacteria, among the oldest known fossils.

30. Why were prokaryotes Earth’s only inhabitants for 1.5 billion years?
    Because complex eukaryotic life had not yet evolved.

The Oxygen Revolution

31. What is the main source of atmospheric oxygen?
    Photosynthetic organisms, especially cyanobacteria.

32. How did photosynthesis lead to an oxygen increase in Earth’s atmosphere?
    Cyanobacteria released oxygen as a byproduct of photosynthesis.

33. What was the oxygen revolution?
    A period (2.7–2.4 billion years ago) when atmospheric oxygen levels drastically increased.

34. How did the oxygen revolution affect early prokaryotes?
    Many anaerobic species went extinct, while others adapted to use oxygen.

35. Why is oxygen toxic to some organisms?
    It can damage biological molecules through oxidation.

36. How did some prokaryotes survive the oxygen revolution?
    By evolving aerobic respiration or remaining in anaerobic environments.

The First Eukaryotes and Endosymbiosis

37. When did the first eukaryotic cells appear?
    About 1.8 billion years ago.

38. What are key features of eukaryotic cells?
    Nuclear envelope, mitochondria, endoplasmic reticulum, and cytoskeleton.

39. What is endosymbiosis?
    A process where one cell engulfs another, leading to a symbiotic relationship.

40. How did mitochondria originate?
    From aerobic prokaryotes that were engulfed by larger cells.

41. What is an endosymbiont?
    A cell living inside another cell in a mutually beneficial relationship.

42. Why did early host cells benefit from endosymbionts?
    They could use oxygen more efficiently for energy production.

43. What is serial endosymbiosis?
    The theory that mitochondria evolved before plastids through multiple endosymbiotic events.

44. How do mitochondria and plastids provide evidence for endosymbiosis?
    They have bacterial-like DNA, ribosomes, and reproduce independently within cells.

45. How do mitochondria and plastids resemble bacteria?
    They have double membranes and divide like bacteria.

Multicellularity

46. How does multicellularity benefit organisms?
    It allows for specialization and division of labor among cells.

47. What lineages evolved due to multicellularity?
    Plants, fungi, algae, and animals.

48. How did yeast demonstrate multicellular evolution in Lenski’s study?
    Single-celled yeast developed multicellular clusters under selective conditions.

49. How does cell specialization contribute to multicellular life?
    It allows different cells to perform unique functions efficiently.

50. Why did multicellularity lead to an increase in biodiversity?
    It enabled more complex body structures and ecological roles.