Bio: Intro to Evolution

The Origin of The Universe and Earth

One of the greatest mysteries of our world. While we have no first-hand evidence of the universe’s formation, we have substantial secondary data.

• These various forms of evidence have led to the development of the Big Bang Theory

  1) First was the Big Bang (14 billion years ago)

  2) Inflation (Fractions of a second after big bang)

• The universe expanded faster than the speed of light, leading to a rapid cooling and the formation of fundamental particles.

• Made the universe smooth and uniform.

  3) Formation of fundamental Particles (first few seconds)

• energy turned into quarks, electrons, and neutrinos

• Quarks combine to form protons and neutrons

  4) Nucleosynthesis (3-20 minutes after)

• Protons and neutrons fused to create hydrogen, helium, and lithium nuclei

• The universe was too hot for atoms to form yet

  5) Recombination (380,000 years later)- formation of atoms

• Electrons joined with nuclei to form neutral atoms

• Light was finally able to travel freely, creating the Cosmic Microwave Background

  6) The Dark Ages

• The universe was mostly dark and filled with gas

• No stars or galaxies existed yet

  7) Formation of Stars and Galaxies (a few hundred million years later)

• Gravity pulled hydrogen and helium together to form the first stars

• Stars grouped into galaxies, including the Milky Way

  8) Formation of our Solar System

• A giant cloud of gas and dust collapsed, forming the Sun

• The leftover material formed planets, moons, and asteroids

  9) Present-Day Universe

• The universe continues to expand

• Stars are born and die, forming new elements

• Scientists study dark matter and dark energy to understand the future of the universe

  

The Formation of Chemical Elements

• They are any substance that cannot be decomposed into simpler substances by ordinary chemical processes

• The number of protons in the nucleus changes their identities

• Most common elements for life are: Carbon, Hydrogen, Oxygen, Nitrogen, and Phosphorus

• The first elements to form were the simplest; Hydrogen and Helium

• One of the main sources of energy in the universe is solar energy (during nuclear fusion in stars of hydrogen isotopes)

The Formation of the Earth

• The best theory for the formation of the solar system is the Solar Nebula Theory, that high density, high pressure core became a proto-star and eventually the sun.

• The bits of matter that were not part of the Sun became planetesimals and eventually the planets such as Earth

Evidence for Solar Nebula Theory:

• The placement of the rocky planets, then the gas giants both with the debris that never became a planet between them

• All planets orbit in the same direction

• Some meteorites are 4.6 billion years old, the same age as the Sun and planets

Early Earth

• The atmosphere was toxic (CH4, H2, H20, N2, and NH3)

• There was substantial volcanic activity

• Meteorite impacts were a regular occurrence

• Temperature changes were extreme (lack of ozone layer and previous factors)

Key events

• Formation of Earth (4.6 billion years ago)

• First life (prokaryotic bacteria, 3.5 billion years ago)

• Photosynthesis evolves (2.5 billion years ago)

• Oxygen revolution (2.4 billion years ago)

• First multicellular organisms (600 million years ago)

• First land plants and animals (500 million years ago)

• First mammals and dinosaurs (230 million years ago)

• First humans (200,000 years ago)

Evolution of Photosynthesis

• Mutation led to photosynthesis

• First time that an organism used sunlight to generate its own food and energy source

• Waste was oxygen, a toxic element to much of primal life

• Surviving creatures evolved to use oxygen as fuel, leading to more rapid evolution, leading to single-cell organisms developing into multicell organisms

• Oxygen reacted with the greenhouse gasses in the atmosphere, cooling the planet (snowball Earth) and then mellowed out to a good temperature

Photosynthesis

• The process by which plants and other autotrophs are able to convert solar energy into chemical energy

• The first organisms to evolve the ability to do photosynthesis were bacteria (cyanobacteria)

• One of the waste products is oxygen, changing the composition of Earth’s atmosphere

• Organisms that can exist in the presence of oxygen are called aerobes while those that cannot are anaerobes

The Rate of Speciation

• Speciation is the process through which new species form through evolution

• The rate is very inconsistent over the planet’s history

• Gradual vs. Punctuated Equilibrium

  

• The primary influencing factor on changes in speciation rate is environmental conditions

• Under some conditions, selection occurs quickly or radically

• ie: A species of snails living with the same basic form for thousands of years, their fossils would appear similar for a long time. When a change in the environment occurs, such as a drop in the water level, a small number are separated, creating two populations. Because the gene pool quickly became so small, any variation that helps with survival in new conditions will become predominant.