BIO-202 Origin of Life Lecture

What three things does life do

grow, metabolize, reproduce

When was the Earth in its infancy

4.6 bya

How do we know the age of the Earth

radiometric dating of minerals in rocks

Why aren’t all rocks on Earth the same age

plate tectonics

How do we know what Earth was like when life arose

volcanoes

What 2 large roles did volcanoes play from early Earth to now

1. Volcanic gases help scientists reconstruct the atmosphere of early Earth

2. volcanoes created habitats where life could start (ex. hydrothermal vents, geysers)

From 3.8 to 3.3 bya

primordial soup microbes live deep, atmosphere = N2, CO2, H2O vapor, no O3

Early life underwent (Anaerobic/Aerobic) Respiration

Anaerobic (little ATP)

What started to happen to the primoridal soup after a while and what did it lead to

it became thin (started to run out) which led to some bacteria evolving to create their own food using light

What were the beliefs during the 1800s

Spontaneous generation: living things can arise from non-living things (ex. rotting meat turns into flies)

What were the beliefs during the 1920s

Primordial Soup hypothesis arose

What was done to test the primordial soup hypothesis

Miller-Urey experiment: simulated early earth by sealing water and simple gases in a closed system, zapping them with electrical sparks, and showing that this setup naturally produced amino acids

Phlogiston theory

Old idea that said anything that burns contains a substance called phlogiston, which is released during combustion

What bacteria led to the origin of photosynthesis

Cyanobacteria

What connection does O2 have with iron

O2 reacts with Fe2+ to turn into ferrous iron (rust) which is insoluble, this reaction absorbs O2 for ~1 billion years, resulted in a banded iron formation on the ocean floor

What happens after all of the iron is gone

O2 builds up (bad bc its deadly to anaerobes), forces evolution of aerobic heterotrophs, O2 becomes present in atmosphere and O3 layer forms, aerobic orgs take over

Whats the significance of the formation of the ozone layer

animals can live closer to the surface

The evolution of aerobes allowed what process to be accelerated and why

The evolutionary process because more ATP was produced

Endosymbiosis Hypothesis

Mitochondria enters a prokaryotic cell, chloroplasts enter an animal cell and become plants

What are the benefits of sexual reproduction over asexual

In asexual reproduction, the animals cant deal with changes = no natural selection, only evolve through mutation, so less diversification and slower evolution

What is the colonial flagellate hypothesis

flagellated unicellular organisms make a colony from which specialized cells and tissues are made to form a multicellular body (ex. volvox)

Ediacaran Period

No hard parts (soft bodies leave imprints in mudstone)

Cambrian Period (3 points)

Animals developed hard parts (huge fossil record)

O2 levels are above ~5%

34 phyla from this point onward

Primordial Soup Hypothesis

Life began in Earth’s early oceans, where NH3, H2O, CH4, H2—energized by lightning, UV light, and volcanic heat—reacted to form the first organic molecules

6 Global mass extinction events

Paleozoic (3 events)

Mesozoic

Cenozoic

Which extinction event is titled “the great dying” and what happened

Paleozoic, loss of 96% of species, all 34 phyla survived

Which extinction event marked the end of the cretaceous period

Mesozoic, killed ~75% of species, killed dinosaurs

What extinction event is known as the holocene extinction

Cenozoic, human-caused, 10,000 mya - present

What did all 34 phyla evolve from

a common protist ancestor

No new phyla have evolved since the _________ period

Cambrian