Evolutionary Biology Quiz

Origin of Earth and Evolution of Life

• Universe Origin (Big Bang Theory): All mass and energy were concentrated at a point at the beginning of time and space. Expansion started 13.7 billion years ago. The cause of this is unknown. The early universe was hot, but cooled as it expanded.
• Formation of Atoms: A million years after the Big Bang, temperatures cooled enough for atoms (mostly hydrogen) to form from the energy and particles of the expanding universe. Hydrogen is abundant in both early and current universe.
• Galaxy Formation: A billion years after the Big Bang, matter started coalescing into the first galaxies and stars.
• Galaxies: Huge, rotating collections of stars, dust, gas, held together by gravity. Spiral, elliptical, or irregular in shape. There are approximately 100 billion galaxies and 100 billion stars in each. Our spiral galaxy is the Milky Way.
• Solar System Origin (Nebular Condensation Theory): Our solar system formed from a nebular (dust and gas cloud) cloud after a previous star's death. The cloud condensed, shrunk, heated up due to gravity, becoming a protostar. Eventually, nuclear fusion started forming a star, with remaining material forming planets.
• Star Birth: Spinning nebulae shrink and heat due to their gravity. The cloud condenses at the center, forming a protostar. Increased internal pressure and temperature initiate nuclear fusion (hydrogen to helium). This stops the star's contraction.
• Star Death (Small/Medium): Stars convert hydrogen to other fusion products (helium, carbon, etc.) over long periods, becoming stable. Their energy output increases, swelling into a red giant. Eventually it pulsates, expelling its outer layers of light gases. The core cools to form a 'cooling ember'
• Star Death (Large): Stars much larger than the sun fuse hydrogen to heavier elements faster, reaching higher core temperatures. The core collapses causing a catastrophic expansion (supernova). In this process, a lot of energy is released and elements heavier than iron are formed.
• Solar System Formation: The remnants of a supernova explosion formed the solar nebula, which condensed and spun. It formed a rotating disk shape, where the center became the proto-sun. Materials close to the protosun (center) condensed into denser forms. Materials farther from the center condensed to form gas giant planets composed of ices.
• Earth's Formation: As the solar system cooled, heavier materials (iron, nickel) sank towards the core. Light materials (silicon, magnesium) formed the crust. This process called density stratification takes approximately 100 million years to complete. Earth's surface cools about 4.6 billion years ago.
• Moon's Formation: A Mars-sized object collided with the young Earth, ejecting material that condensed into the moon about 30 million years after Earth formed.
• Earliest Atmosphere: Early Earth's atmosphere consisted of gases common in the early solar system (hydrogen, helium, methane, ammonia, carbon dioxide, water vapor). Most of these gases escaped into space.
• Second Atmosphere: Volcanic outgassing released gases from Earth's interior into the atmosphere (water vapor, carbon dioxide, sulfur dioxide, nitrogen, traces of ammonia and methane). This atmosphere was anoxic (lacked free oxygen).
• Third Atmosphere: Photosynthetic organisms (cyanobacteria) evolved about 2.8 billion years ago, producing free oxygen. This oxygen formed the ozone layer, protecting the Earth's surface from UV radiation.
• Ocean Formation: Water vapor condensed into clouds, then rained, resulting in early oceans about 4 billion years ago.

Origin of Earliest Life Forms

• Theories of origin of life include: Special Creation, Spontaneous Generation/Abiogenesis, Catastrophism, Cosmozoic Theory, Biogenesis, Chemosynthetic/Naturalistic theory.
• Chemosynthetic Theory (most recent): Coacervates (clusters of organic molecules) in the primordial soup could have evolved into simple cells. These early forms lacked nucleic acids and metabolism. RNA likely preceded DNA in genetic material.
• Formation of cells: Coacervates acquired RNA which evolved into more stable DNA, forming early prokaryotes.
• Early life: Anoxygenic photoautotrophs (bacteria) may have evolved around 3.85-3.5 billion years ago. Stromatolites are fossilized bacterial mats.

Evolution of Early Earth and its Atmosphere

• Formation of Atmosphere: The early atmosphere contained gases like water vapor, carbon dioxide, sulfur dioxide, and trace amounts of ammonia and methane.
• Formation of Oceans: As Earth cooled, water vapor condensed and rained, forming oceans.
• Presence of Oxygen: Photosynthetic organisms (cyanobacteria) added oxygen to the atmosphere around 2.8 billion years ago.
• Origin of Life: Life likely originated in the early oceans, perhaps from organic molecules generated by chemical processes.

Mass Extinctions

• Definition: Mass extinction is a significant increase in the rate of extinction compared to the normal background rate.
• Past events: Events occurring millions of years ago. Evidence shows these events can be linked to major habitat destruction.
• Causes: Various factors may trigger mass extinctions (glacier formation, changes in sea levels, meteorite/asteroid impact, volcanism, warming). These have all resulted in significant biodiversity reductions.

Theories of Biological Evolution

• Lamarckism: Organisms change over time in response to their environment. Acquired characteristics are inherited by offspring (e.g., giraffes' necks extending). (disproven)
• Darwinism/Natural Selection: Organisms with favorable traits are more likely to survive and reproduce, passing those traits to their offspring. The environment causes some variations to disappear and others to persist. The species changes gradually through accumulated favorable variations.
• Mutation Theory (de Vries): Variations (mutations) arise suddenly and directly contribute to evolutionary change; they are not continuous but discontinuous.

Hardy-Weinberg Equilibrium

• Concept: A theoretical state where allele and genotype frequencies in a population remain constant from one generation to the next, in the absence of evolutionary influences.
• Conditions: No mutations, no gene flow (migration), random mating, no genetic drift, and no natural selection.
• Equilibrium: Genotype frequencies (AA, Aa, and aa) can be calculated using allele frequencies (p and q). The condition (p^2 + 2pq + q^2 = 1) holds true under these conditions.

Evolution of Humans

• Primates: Group of mammals characterized by features such as flexible shoulders, hands with opposable digits, and large brains.
• Diversification: From common primate ancestors, primates diversified in various features (e.g., locomotion, sensory systems, and brain size) through speciation, including the hominins (precursors) of humans.
• Human Evolution: Significant stages in evolution (e.g., hominins) and key characteristics of these groups (e.g., bipedalism, brain size, tool use).
• Modern Humans: Emergence of Homo sapiens, distinguishing characteristics, and their dispersal across different parts of the globe.

Test your knowledge on key concepts in evolutionary biology, focusing on the ideas of Darwin and Weismann. Explore important events in Earth's history and understand the significance of various scientific observations. This quiz challenges you with matching questions and insightful inquiries into the mechanisms of evolution.