Questions and Answers
Why do some scientists believe that RNA, rather than DNA, was the first genetic material?
RNA has both information storage and catalytic properties.
In the origin of the eukaryotes, how did endosymbiosis most likely begin?
A heterotrophic endosymbiont entering the cell as undigested prey or as an internal parasite.
During the origin of the eukaryotic cell, what was thought about engulfed bacteria?
They did not initially have a mutually beneficial relationship with their hosts, but later evolved one.
What three components distinguish a eukaryotic cell?
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Earth probably formed _____ years ago, and the first life evolved as early as _____ years ago.
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How was early Earth from more than three billion years ago different from today's Earth?
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Which of the following is the correct sequence of events in the origin of life?
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The earliest organisms were most likely _____?
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The atmosphere of early Earth probably contained no O2 until the emergence of organisms that _____?
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Which characteristics are expected in the first animals to have colonized land?
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The oxygen revolution changed Earth's environment dramatically. Which of the following took advantage of the presence of free oxygen in the oceans and atmosphere?
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Which of the following steps has not yet been accomplished by scientists studying the origin of life?
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Which statement about natural selection on early Earth is correct?
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Study Notes
Origin of Genetic Material
- RNA is believed to be the first genetic material due to its dual role in information storage and catalytic functions.
Endosymbiosis and Eukaryotic Origin
- Eukaryotes likely originated through endosymbiosis, starting with a heterotrophic endosymbiont that entered a cell as an undigested prey or parasite.
- Initially, engulfed bacteria had a non-mutual relationship with their hosts, which later developed into mutualism.
Characteristics of Eukaryotic Cells
- Eukaryotic cells are distinguished by three key components: a nucleus, an endomembrane system, and mitochondria.
Earth's Timeline
- Earth is estimated to have formed about 4.5 billion years ago, with the first life forms appearing around 3.9 billion years ago.
Early Earth's Atmosphere
- Early Earth featured a volcanic atmosphere rich in various gases, contrasting sharply with the oxygen-rich atmosphere of today.
Sequence of Life's Origin
- The correct sequence in the origin of life involves:
- Synthesis of organic monomers
- Synthesis of organic polymers
- Formation of protocells
- Development of DNA-based genetic systems.
Prokaryotic Dominance
- The earliest life forms were likely prokaryotic organisms.
Oxygen's Role in Evolution
- The atmosphere of early Earth lacked free oxygen until organisms capable of using water in photosynthesis emerged.
Evolutionary Timeline
- The sequence of events in early life evolution is as follows:
- Origin of cyanobacteria
- Origin of mitochondria
- Origin of chloroplasts
- Origin of multicellular eukaryotes
- Origin of fungal-plant symbioses.
Characteristics of Early Land Animals
- The first land animals likely exhibited certain traits:
- Herbivorous diet
- Ability to resist dehydration
- Ancestors were lobe-finned fishes and included invertebrates.
Effects of the Oxygen Revolution
- The increase in free oxygen led to the evolution of cellular respiration, enabling organisms to extract energy from organic molecules more efficiently.
Ongoing Research in Origin of Life
- Current research has yet to achieve the formation of protocells that utilize DNA for directing amino acid polymerization.
Natural Selection on Early Earth
- Natural selection could operate on populations of proto-cells, favoring stability and self-replicating, catalytic RNA capable of growth and division.
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Description
Test your knowledge with flashcards covering key concepts from Biology Chapter 25. This chapter focuses on the origins of genetic material, particularly the role of RNA, and the concept of endosymbiosis in the development of eukaryotic cells. Perfect for reinforcing your understanding of these fundamental biological principles.
