Unit 5 Flashcards
Describe the conditions present in primordial Earth and explain how and why they may have favored the appearance of the first organic molecules.
Primordial Earth was marked by extreme volcanic activity, frequent bombardment by meteors, and a reducing atmosphere lacking oxygen. These conditions facilitated the formation of organic molecules as the reducing environment allowed simpler molecules like methane, ammonia, and hydrogen to react and form more complex compounds. High energy from lightning, UV radiation, and geothermal heat acted as catalysts for these reactions.
- Explain how the Miller-Urey experiment is a key step in understanding the appearance of life on Earth.
The Miller-Urey experiment simulated early Earth’s conditions by circulating a mixture of water, methane, ammonia, and hydrogen in a closed system, exposing it to electrical sparks to mimic lightning. This experiment resulted in the synthesis of amino acids, demonstrating that organic molecules essential for life could form under abiotic conditions.
- Explain how an RNA world would be a self-sustainable system without the presence of DNA or proteins and what evidence we have in cells that support the RNA world hypothesis.
The RNA world hypothesis posits that RNA served as both the genetic material and a catalyst for metabolic reactions through ribozymes. RNA could replicate itself, store genetic information, and catalyze essential biochemical reactions. Evidence includes ribosomes, where RNA is the active site, and the existence of ribozymes in modern cells, showing RNA’s dual functionality.
- Define the major evolutionary transitions that occurred in Earth’s history.
Formation of prokaryotic life (~3.5 billion years ago).
Emergence of eukaryotic cells (~2 billion years ago).
Development of multicellular life (~1 billion years ago).
Appearance of animals (~525 million years ago).
Evolution of modern humans (~150,000 years ago).
- Explain how multicellular life might have appeared and what were its advantages.
Multicellular life likely arose from single-celled organisms forming colonies where cells specialized for specific tasks. This provided advantages like greater efficiency, larger organism size, improved protection against predators, and the ability to exploit diverse environments.
- Explain how cooperation can be selected by natural selection.
Cooperation can arise when it benefits the survival and reproduction of individuals. For example, by helping relatives (kin selection), individuals ensure the propagation of shared genes. Reciprocal altruism also allows cooperation to be mutually beneficial when organisms help each other over time.
- Explain why the diversity and stability of ecosystems are so important for mankind.
Ecosystem diversity ensures resilience to environmental changes, provides essential resources like food, medicine, and clean water, and supports ecological services like pollination and carbon sequestration. Stability in ecosystems helps sustain human life by maintaining these services over time.
