Cosmic Perspective and Evolution: From Big Bang to Modern Diseases
1. Cosmic Perspective and the Evolution of Life
1.1 Anthropocentric vs. Geocentric View
The anthropocentric perspective places humans at the center of the universe, while the geocentric system, like Ptolemy’s model, positions Earth at the center.
1.2 The Copernican Revolution
The Copernican Revolution shifted from a geocentric to a heliocentric system, with the sun at the center, resolving issues with Ptolemy’s model and explaining the movement of stars.
1.3 The Immensity of the Universe
Our sun is a star within the Milky Way galaxy. Our solar system resides in one of its arms, rotating around the galactic axis at a speed of 230 million km/h, taking 76,000 years to complete one Galactic Year.
1.4 Deep Time and Biological Evolution
Previous beliefs placed Earth’s age at 6,000 years. However, the discovery of deep time revealed a much older Earth. Up until the mid-19th century, each biological species was thought to be individually created. Charles Darwin demonstrated that species change over time through biological evolution.
1.5 Planets and Dwarf Planets
A planet is a celestial body orbiting a star, with sufficient mass to be nearly spherical and to have cleared its orbit. A dwarf planet meets the spherical requirement but has not cleared its orbit.
1.6 Composition of the Solar System
1.6.1 Sun
The sun is a sphere of incandescent gas (mostly hydrogen) generating energy through thermonuclear reactions in its core at over 15 million °C, with a surface temperature of 6,000 °C.
1.6.2 Planets
Planets orbit the sun and are nearly spherical. Inner/terrestrial planets (Mercury, Venus, Earth, Mars) are smaller, rocky, and closer to the sun. Outer/giant planets (Jupiter, Saturn, Uranus, Neptune) are larger, gaseous or liquid, and farther from the sun.
1.6.3 Dwarf Planets
Dwarf planets (Ceres, Pluto, Eris) orbit the sun and are spherical but haven’t cleared their orbits.
1.6.4 Satellites
Satellites are celestial bodies that orbit planets, like Earth’s moon.
1.6.5 Minor Bodies
Asteroids are small, irregularly shaped rocky bodies found mainly in the asteroid belt between Mars and Jupiter. Comets are small icy bodies orbiting beyond Neptune (Kuiper Belt).
1.7 Planetesimal and Nebula Theory
- Nebula: 4.6 billion years ago, a nebula of gas and dust began to concentrate.
- Gravitational Collapse: Mass concentrated in the center, forming a rotating disk.
- Protosun Formation: Particle collisions released heat, initiating nuclear fusion and forming the protosun.
- Planetesimal Formation: Dust and gas particles clumped together.
- Protoplanet Formation: Planetesimals collided to form protoplanets.
- Orbit Clearing: Protoplanets cleared planetesimals from their orbits.
1.8 Origin of the Moon
- Sister/Adopted: Formed simultaneously with Earth through gravity.
- Daughter: Formed from debris ejected after a collision with Earth.
1.9 Star Evolution
Stars consume hydrogen for energy. When depleted, they expand into red giants. Eventually, they shrink and become dense white dwarfs.
1.10 Prebiotic Synthesis
Oparin and Haldane independently hypothesized that life arose through stages:
- Simple Organic Molecules: Primitive atmosphere components reacted under solar radiation and electrical discharges.
- Complex Organic Molecules: Simple molecules combined.
- Coacervates: Compounds in the primordial soup formed spherical coacervates.
2. Theories of Evolution
2.1 Fixism
Fixism asserts that species have remained unchanged since creation, based on an anthropocentric worldview, a young Earth, and flawed evidence.
2.2 Lamarckism
Lamarckism proposes a natural tendency towards complexity. Species change habits and needs due to environmental changes, and these acquired changes are inherited.
2.3 Darwinism
Darwin’s theory of evolution centers on natural selection. More individuals are born than can survive, leading to competition. Heritable variations exist, and natural selection favors the most fit, gradually changing the population.
2.4 Natural Selection and Adaptation
Darwin: Nature constantly selects the most advantageous traits. Lamarck: The environment induces changes in organisms. Darwin’s view emphasizes variability and environmental selection, while Lamarck’s suggests a directed process.
2.5 Synthetic Theory
This theory combines Darwin’s ideas with genetics. The unit of evolution is the population, and variability arises from mutations. Evolution is not always gradual.
2.6 Gradual vs. Punctuated Evolution
Gradualism posits slow, incremental changes. Gould and Eldredge argue for punctuated equilibrium, where periods of stability are interrupted by rapid change, explaining the lack of intermediate forms in the fossil record.
2.7 Evo-Devo
Evo-devo (evolution and development) explores how gene hierarchies control development, influencing body design.
2.8 Human Ancestors
- Homo habilis
- Homo ergaster
- Homo erectus
- Homo antecessor
- Homo neanderthalensis
3. Emerging and Re-emerging Diseases
3.1 Emerging and Re-emerging Diseases
Emerging diseases are caused by previously unknown germs. Re-emerging diseases are past diseases that persist (cholera, tuberculosis, dengue, malaria).
3.2 Germ Theory of Disease
Pasteur linked diseases to microorganisms. Koch experimentally confirmed this, showing that specific organisms cause specific diseases.
3.3 Infectious Agents
Viruses: Cellular parasites requiring host cells to reproduce. Bacteria: Unicellular prokaryotes reproducing independently. Protozoa: Unicellular eukaryotes. Fungi: Unicellular or multicellular.
3.4 Transmission
Direct: Contact between sick and healthy individuals. Indirect: Germs transmitted through a medium (water, food).
3.5 Antibiotics and Antivirals
Antibiotics: Chemicals killing or inhibiting bacteria. Fleming discovered penicillin. Antivirals: Target viruses, which are harder to eliminate due to their intracellular reproduction.
3.6 Antibiotic Resistance
Resistance can arise through mutation or gene exchange. These are natural phenomena. Avoidable factors include inadequate treatment and antibiotic use in agriculture.
3.7 New Drug Development
Preclinical Stage: Research and testing of natural substances or new molecules. Clinical Stage: Testing on volunteers in three phases.
3.8 Influenza
Influenza viruses are characterized by: a) Genetic information in 8 RNA molecules. b) Surface molecules H (hemagglutinin) and N (neuraminidase) defining virus types.