Evolutionary Biology Quiz

Earliest Ideas About Life's Origin

• Creationism: Life arises suddenly and directly from a divine being.
• Spontaneous Generation: Life arises from nonliving material. This idea posited that life could appear suddenly from nonliving things.

How the Earth Formed

• Nebular Hypothesis: The most widely accepted theory. The solar system formed from a collapsing nebula of gas and dust.
• Supported by Hubble Space Telescope Data: The collapsing nebula's temperature increases due to gravitational compression as it collapses; the rotation speed increases, flattening it into a disk-shape. The sun forms at the center, and dust particles outside form planetesimals, which are several kilometers across.

Early Earth Conditions

• Hadean Eon (4.6-3.8 BYA): Earth was a molten planet frequently bombarded by asteroids and meteors.
• Initial Atmosphere: Primarily ammonia, water vapor, methane, and other simple gases.
• Oxygen Accumulation: Oxygen gradually accumulated approximately 2 billion years ago, becoming more abundant in later periods. Early earth's atmosphere lacked free oxygen.

Organic Molecule Hypotheses

• Life arose gradually from inorganic molecules.
  • Building blocks like amino acids combined to make more complex polymers.
• Two Hypotheses:
  • Miller-Urey Experiment: Simulated early Earth conditions to show that organic molecules (amino acids) could be made from inorganic compounds using energy from lightning.
  • Meteorite Hypothesis: Amino acids may have arrived on Earth through meteorites or asteroids. A significant number of amino acids (90, including 19 naturally found on Earth) were found in a meteorite collected in 1969.

Further Experiments on Organic Molecule Formation

• Sidney Fox (1964): Built on the Miller-Urey experiment; showed that amino acids could spontaneously form small peptides under specific conditions.

Meteorite Hypothesis (1969)

• A meteorite found in Austria contained more than 90 amino acids, 19 of which occur naturally on Earth.
• Possible Interpretations: Amino acids could have been present on Earth before, formed from early Earth's materials, or arrived from meteors and asteroids.

Iron-Sulfide Bubbles Hypothesis

• Suggests hydrothermal sea vents produced sulfur compounds, which mixed with water to form compartments within rock. These compartments may have housed the first living cells, a`cting as a membrane-like structure.

Lipid Membrane Hypothesis

• Proposed that liposomes (spheres formed from phospholipids) could have created the first cell membranes, separating the internal and external environments of early cells.

RNA World Hypothesis

• Ribozymes (RNA molecules) can replicate and form proteins without the help of DNA or proteins, thus were potentially critical early in evolution.
• DNA formation requires enzymes (polymerase and helicase).
• RNA can be synthesized from inorganic compounds; however, DNA stores information more efficiently and is more stable.

Microbes Changed Earth's Conditions

• Oldest known fossils: Cyanobacteria (3.5 BYA)
• Formed Stromatolites: layered sediments trapped by cyanobacteria, providing evidence of early colonies. This process was enhanced by cyanobacteria.
• Added Oxygen: Photosynthesis by cyanobacteria added oxygen to the atmosphere, causing a significant alteration in the Earth's atmosphere. This process, called oxygenation, had many important effects including making more complex life possible.

Eukaryotes Evolved by Endosymbiosis

• Endosymbiosis: One organism living inside another.
• Lynn Margulis (1970s): First to support Endosymbiotic Theory, explaining how mitochondria and chloroplasts evolved from prokaryotic organisms through endosymbiosis.
• Evidence: Own DNA and ribosomes, circular DNA like prokaryotes, self-replication, similar size and structure to prokaryotes.

Theory of Endosymbiosis

• Diagram showing the evolution from ancestral prokaryotes to eukaryotes through the infolding of the plasma membrane and subsequent engulfment, leading to the development of the nucleus and the formation of mitochondria and chloroplasts.

The Story of Life on Earth (Timeline)

• Prokaryotic Anaerobic
• Oldest known fossils (cyanobacteria) make oxygen.
• Prokaryotic aerobic
• Eukaryotic unicellular
• Multicellular life

Sexual Reproduction's Impact

• Genetic variation is advantageous, increasing the diversity and adaptability of a species across different environments.
• Led to the evolution of complex multicellular life.

What are Primates?

• Mammals with flexible hands and feet, forward-facing eyes for depth perception, and large brains relative to their body size.
• Rotating shoulder joints and opposable thumbs.

Prosimians

• Oldest primate group (40 million years ago).
• Small and nocturnal.

Walking Upright (Bipedalism)

• Bipedal locomotion required skeletal adaptations.
• Advantages: Free hands for other activities, higher reach for foraging, carrying objects (infants, food, tools), predator avoidance, and protection of infants, improving both mobility and efficiency.

Fossils of Hominids

• Most are either Australopithecus or Homo.
• Australopithecines lived 3-4 million years ago in Africa, had small brains.
• Homo genus evolved 2.4 million years ago.
• Homo habilis: First stone tools, signifying an important step in human evolution.
• Homo neanderthalensis: Latest extinct human group.

Changes in the Human Skull Fossils

• Increased brain size in hominids over time, signifying increased cognitive ability and enhanced behavioral capabilities
• Less protruding jaw. Smaller jaw in newer hominid species, indicating evolutionary changes in the skull's structure and adapting to new food sources.