Podcast
Questions and Answers
How old is the universe?
How old is the universe?
13 billion years
How old is earth?
How old is earth?
4.6 billion years old
What is the name of the first divergence that occurred during prokaryote domination?
What is the name of the first divergence that occurred during prokaryote domination?
Bacteria and Archaea
What are the three theories regarding the evolution of life?
What are the three theories regarding the evolution of life?
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What does the special creation theory believe?
What does the special creation theory believe?
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What is the Cosmozoic Theory?
What is the Cosmozoic Theory?
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The Panspermia Theory suggests that life originated from another planet.
The Panspermia Theory suggests that life originated from another planet.
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What is the scientific term for spontaneous generation?
What is the scientific term for spontaneous generation?
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What is the name of the hypothesis that life arises regularly from non-living things?
What is the name of the hypothesis that life arises regularly from non-living things?
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What does the RNA World Hypothesis propose?
What does the RNA World Hypothesis propose?
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What is the proposed first step in the origin of life?
What is the proposed first step in the origin of life?
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What are protobionts?
What are protobionts?
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The Miller-Urey experiment provided conclusive evidence of the early Earth’s atmosphere being a reducing environment.
The Miller-Urey experiment provided conclusive evidence of the early Earth’s atmosphere being a reducing environment.
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The Miller-Urey experiment used energy mimicking lightning to create a primordial soup from a mixture of gases thought to have existed in the early atmosphere.
The Miller-Urey experiment used energy mimicking lightning to create a primordial soup from a mixture of gases thought to have existed in the early atmosphere.
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Name two scientists who were behind the Miller-Urey experiment in 1953.
Name two scientists who were behind the Miller-Urey experiment in 1953.
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The first genetic material was probably RNA.
The first genetic material was probably RNA.
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What are ribozymes?
What are ribozymes?
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What are eons, eras, and periods?
What are eons, eras, and periods?
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What is the name of the oldest known eon?
What is the name of the oldest known eon?
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What happened during the Archean Eon?
What happened during the Archean Eon?
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What happened during the Proterozoic Eon?
What happened during the Proterozoic Eon?
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What is the name of the current eon?
What is the name of the current eon?
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What event marked the end of the Mesozoic Era?
What event marked the end of the Mesozoic Era?
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What is the currently ongoing event in the geologic time scale?
What is the currently ongoing event in the geologic time scale?
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How many major extinction events have occurred in the last 500 million years?
How many major extinction events have occurred in the last 500 million years?
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Study Notes
Tracing Evolutionary History: Origins of Life
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Objectives:
- Discuss the timing, location, and process of life's origins.
- Describe how early atmospheres and climates influenced prebiotic evolution.
- Explain the Miller-Urey Experiment.
- Discuss the RNA-world hypothesis.
- Detail the characteristics of early organisms.
- Present a timeline of key events.
Overview: Lost Worlds
- Past life forms differed significantly from present-day organisms.
- The fossil record reveals macroevolutionary changes across extended time scales, such as:
- Emergence of terrestrial vertebrates.
- Impact events of mass extinctions.
- Bird flight origins.
Early Earth and the Origin of Life
- Information about the conditions on Earth during the early stages of life's development.
Conditions on Early Earth
- Details about the geological characteristics, like volcanoes, atmosphere, and presence of water at the time.
Earth's Early Atmosphere
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4.6 Billion Years Old:
- Earth's formation is approximately 4.6 billion years ago (BYA), as indicated by geologic evidence.
- The early atmosphere likely contained carbon dioxide (CO2), carbon monoxide (CO), nitrogen, ammonia, methane, but not oxygen—a condition unsuitable for most life forms.
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3.8 Billion Years Ago:
- The cooling of Earth allowed the formation of liquid water.
How Old is This Planet?
- The universe is estimated to be around 13 billion years old.
- Earth is roughly 4.6 billion years old.
- Early Earth bombardment by rocks and ice prevented seas from forming or existing from approximately 4.2 to 3.9 billion years ago.
- The oldest known records of life on Earth are around 3.5 to 3.8 billion years ago (ByA).
When Did Life Begin?
- Prokaryotes, like bacteria and archaea, were dominant from 3.5 to 2 billion years ago.
- During this time, the first divergence of Bacteria and Archaea occurred.
How Did Life Evolve?
- Three theories:
- Creationism
- Extraterrestrial origin (Panspermia)
- Spontaneous origin (Abiogenesis)
Theories of Early Earth
- Details on hypothetical models related to Earth's early development
Special Creation Theory
- This theory, deeply rooted in religious beliefs, asserts that living things have not changed significantly since their creation.
- It lacks scientific support.
Panspermia Theory
- This theory suggests that life on Earth originated from other celestial bodies.
- Microorganisms could travel through space, carried by comets or interstellar dust.
- This material can contain organic chemicals.
Spontaneous Generation (Abiogenesis)
- This theory proposes that life arises periodically from non-living matter.
- Prebiotic conditions on early Earth could have supported the development of simple cells.
Objective: Describe the prebiotic evolution
- Chemical and physical processes on early Earth likely produced very simple cells in stages:
- Abiotic synthesis of small organic molecules.
- Joining small molecules into macromolecules (e.g. polymers).
- Packaging of molecules into protobionts.
- The origin of self-replicating molecules.
Synthesis of Organic Compounds on Early Earth
- Early Earth's atmosphere contained water vapor and various volcanic gases (e.g., nitrogen, nitrogen oxides, carbon dioxide, methane, ammonia, hydrogen, hydrogen sulfide).
- Oparin and Haldane proposed a "reducing atmosphere" where oxygen was absent, preventing oxidation.
- Miller and Urey conducted experiments demonstrating the abiotic synthesis of organic molecules in reducing atmospheres.
- Evidence suggests the first organic compounds formed in environments near volcanoes or deep-sea vents, not necessarily in the upper atmosphere.
- Amino acids have also been found in meteorites.
Primordial Soup
- This theory proposes life evolved in warm ponds or oceans from a combination of chemicals, forming amino acids and ultimately proteins.
- This process, based on Haldane's work in the 1920s, postulates that early atmospheric lightning and rain energized simple molecules that formed within the early atmosphere and created an "organic soup".
- These theoretical mechanisms led Miller and Urey to conduct their famous experiments.
Deep Sea Vents
- Vents as potential locations for the development of life’s building blocks.
Miller-Urey Experiment
- A 1953 experiment by Stanley Miller and Harold Urey simulating early Earth conditions.
- Simulated a "reducing atmosphere" to generate simple organic molecules like amino acids from inorganic precursors.
Variations of Miller-Urey Experiment
- Different mixes of gases were used to represent possible atmospheres.
- Different energy sources, such as ultraviolet light, were also investigated.
- The results found consistent formation of amino acids and organic molecules, though not as dramatically as the original setup.
- It emphasized the need to consider other potential sources of organic molecules.
Origin of the First Cell(s)
- Stages in the development of the first cells, including polymer formation, protocell development, and self-replicating RNA.
- The development of monomers, resulting in macromolecules, protocells (precursor cells), and self-replicating RNA are essential aspects of this origin of cells.
Protocells May Have Formed Spontaneously
- Illustrates mechanisms describing formation of early cells.
STEP 4: Ribozymes
- Self-replicating RNA (ribozymes) molecules that can catalyze biochemical reactions.
- Ribozymes played a likely crucial role in the early stages of life, storing information and catalyzing the formation of the first proteins.
Complementary Base Pairing: RNA
- Describes the pairing rules for RNA nucleotides.
The RNA World Hypothesis
- This theory proposes that RNA, not DNA, was the initial genetic material.
- Supports the idea of RNA playing a catalytic role as well as a genetic role, acting as both an enzyme and a genetic material.
Major Events in the History of Life
- A timeline of key events in the evolution of life on Earth.
Geologic Time Spans
- Eons, eras, periods, Epochs, and their corresponding durations as divisions of geologic time, representing Earth's history.
Precambrian "Age of Early Life"
- A period in Earth history prior to 542 million years ago (mya).
- Key events included:
- Formation of early Earth and the atmosphere.
- Formation of the earliest prokaryotes.
- Development of photosynthesis and the production of oxygen (Great Oxygenation Event).
- Formation of the earliest eukaryotes and multicellular organisms.
Hadean Eon
- Earth's formation and subsequent cooling events.
- Early crust solidification.
- Absence of liquid water and high volcanic activity characterized this period.
Archean Eon
- Dropped temperatures and formation of the Earth's crust from approximately 4 Billion to 2.5 Billion years ago.
- Formation of the first oceans.
- Earliest forms of life emerge in oceans, specifically prokaryotes.
Proterozoic Eon
- Oxygen accumulation in Earth's atmosphere.
- Development of the first multicellular organisms.
Phanerozoic Eon
- Evolution of life forms with hard body parts.
5 Major Extinctions
- Major extinction events during Earth’s history and their potential causes.
Timeline of Events (Illustrative example from a 24-hour clock)
- A graphic representation of the major events in life’s history, from the formation of Earth to other significant points like the appearance of complex life, sexual reproduction, and human development.
15.4, Origins of Single-celled and Multicellular Organisms and Colonization of Land
- Highlighted critical evolutionary events:
- Origin of single-celled and multicellular organisms.
- Colonization of land by life forms.
15.6 Timeline of Life Events
- Timeline of key events in life's history on Earth.
Additional Information
- Other illustrative details about the evolution of life and the supporting evidence (e.g., from Table 15.6).
- Diagrammatic representations of the progression of events during life’s history.
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