ORIGIN OF LIFE Flashcards
Theories on the Origin of Life
Panspermia
Spontaneous Generation Theory
Chemosynthesis
the biological production of organic compounds from C-1 compounds and nutrients, using the energy generated by the oxidation of inorganic (e.g., hydrogen gas, hydrogen sulfide, ammonium) or C-1 organic (e.g., methane, methanol) molecules.
Chemosynthesis
implies that the development of life is probable wherever the proper physical and chemical conditions are in place.
Chemosynthesis
seeds everywhere” life exists throughout the Universe; distributed by space dust, meteoroids, asteroids, comets, planetoids, and also by contaminated spacecraft.
Panspermia
an extremophilic bacterium and one of the most radiation-resistant organisms known. It can survive cold, dehydration, vacuum, and acid.*
Deinococcus radiodurans
It has been listed as the world’s toughest known bacterium in The Guinness Book Of World Records. · Found to withstand harsh space
Deinococcus radiodurans
Life can arise from nonliving matter.
Spontaneous Generation Theory
proposed that life arose from nonliving material if the material contained pneuma (“vital heat”). Evidences described:
Life can arise from nonliving matter.
- Bivalves / fishes form spontaneously in mud or sand
- Insects generated on dew falling on leaves
Aristotle (384-322 BC)
supports Spontaneous Generation
Each species arose from an independent event of spontaneous generation. - Spontaneous generation continues today.
19th Century Lamarck (1724-1829)
Demonstrated experimentally that microbes would not appear in swan neck flasks protected from dust and other small particles. Spontaneous generation does not happen today on experimental time scales.
Pasteur (1822 - 1895)
Conditions on early Earth made the origin of life possible
Earth formed about 4.6 billion years ago, along with the rest of the solar system
Bombardment of Earth by rocks and ice likely vaporized water and prevented seas from forming before 4.2 to 3.9 billion years ago
Earth’s early atmosphere likely contained water vapor and chemicals released by volcanic eruptions (nitrogen, nitrogen oxides, carbon dioxide, methane, ammonia, hydrogen, hydrogen sulfide)
Synthesis of Organic Compounds on Early Earth
A. I. Oparin and J. B. S. Haldane 1920s
hypothesized that the early atmosphere was a reducing environment and could produce organics
A. I. Oparin and J. B. S. Haldane 1920s
suggests that life arose gradually from inorganic molecules, with “building blocks” like amino acids forming first and then combining to make complex polymers.
Oparin-Haldane hypothesis
conducted lab experiments that showed that the abiotic synthesis of organic molecules (amino acids) in a reducing atmosphere is possible
Stanley Miller and Harold Urey (1953)
simulated early earth with a strongly reducing atmosphere, an ocean, and a hydrologic cycle.
- Energy inputs via heating & an electrical discharge.
- Inorganic reactants CH4, NH3, and H2 Amino acids and other organic molecules formed spontaneously under these conditions.
- The building blocks of living organisms can form spontaneously on short time scales.
Mike and Urey Experiment
Amino acids have also been found in meteorites
true
RNA monomers have been produced spontaneously from simple molecules
true
can spontaneously form vesicles with a lipid bilayer
In water, lipids and other organic molecules
Adding ______ can increase the rate of vesicle formation
clay
exhibit simple reproduction and metabolism and maintain an internal chemical environment
Result protocells
Vesicles
Chemical and physical processes on early Earth may have produced very simple cells through a sequence of stages:
a. Abiotic synthesis of small organic molecules
b. Joining of these small molecules into macromolecules
c. Packaging of molecules into protocells
d. Origin of self-replicating molecules
All organisms we know of on Earth today are descended from a common ancestor that lived about 4 billion years ago.
true
formation of Three Domains of Life
1 Last common ancestor of all living things (LUCA)
2 Symbiosis of chloroplast ancestor with ancestor of green plants
3 Symbiosis of mitochondrial ancestor with ancestor of eukaryotes
4 Possible fusion of bacterium and archaean, yielding ancestor of eukaryotic cells
The rise and fall of groups of organisms reflect differences in speciation and extinction rates.
true
Not only geologic time but also continental movement had profound effects on these rates
true
A continent’s climate can change as it moves north or south
true
- Separation of land masses can lead to allopatric speciation
true
shows that most species that have ever lived are now extinct
fossil record
The “Big Five” Mass Extinction
End Ordovician
Late Devonian
End Permian
End Triassic
End Cretaceous
That is, the 1 percent of species on Earth not yet extinct: For the last 3.5 billion or so years, about 99 percent of the estimated 4 billion species that ever evolved are no longer around.
true
ca. 443 Climate change (Ice)
best 86% of species and 57% of genera, e.g. Trilobites, corals,
Sponges
ORDOVICIAN
359-380
climate change for >20 million- plus years: volcanic activity in Siberia, reduced oxygen levels in the oceans
etc. 75% of species and 35% of genera; placoderms, corals, trilobites
Small vertebrates, tetrapods → amphibians, reptiles,
DEVONIAN
251
Volcanic activity in Siberia; global warming; apocalypse unfolded over a span of about 50,000 years.
96 % of species and 56 % of genera; vast forests; amphibians; marine life
Fungi; early ancestors of dinosaurs
PERMIAN
201
Massive volcanic eruptions in what would become Atlantic Ocean
80% of species and 47% of genera; ribbonlike fish conodont, reptiles
Dinosaurs
TRIASSIC
65.5
Asteroid; volcanic eruptions
76% of species and 40% Mammals of genera; dinosaurs, ammonites, etc..
mammals
CRETACEOUS
A number of factors might have contributed to these extinctions i. Intense volcanism in what is now Siberia ii. Global warming resulting from the emission of large amounts of CO2 from the volcanoes iii. Reduced temperature gradient from equator to poles iv. Oceanic anoxia from reduced mixing of ocean waters
Permian extinctions
- Dinosaurs went extinct after living for ca. 165 MY on earth. 2. Planetwide volcanism; large-scale volcanic eruption in the Indian Deccan Traps * a spike in carbon dioxide and a drop in ocean oxygen levels 3. An asteroid (or comet) hit the earth and created a cloud of debris that blocked out sunlight for months. Temperatures dropped and plants died.
Cretaceous extinction
The ________ is located in the Caribbean Sea near the Yucatan Peninsula of Mexico.
This artists interpretation represents the impact and its immediate effect - a cloud of hot vapor and debris that could have killed most of the plants and animals in North America within hours.
65-million-year-old Chicxulub impact crater
65 Million years ago the curtain came down on the Age of Dinosaurs when a cataclysmic event led to mass extinctions. This interval of abrupt change in Earth’s history, called the __________, closed the Cretaceous (K) Period and opened the Tertiary (T) Period.
K/T Boundary
are single-celled organisms that have inhabited the oceans for more than 500 million years. Both living and fossil __________come in a variety of shapes and sizes and occur in many different marine environments.
good indicators of climate change
Foraminifera
Sediments containing microfossils from after the dinosaurs
Post-extinction Layer
Dust and ash fallout from the asteroid impact
Fireball Layer
Material blasted from the crater and deposited here within days to months
Ejecta Layer
Sediments containing microfossils from the time of the dinosaurs
Pre-extinction Layer
Scientists estimate that the current rate of extinction is 1,000 to 10,000 times the typical background rate (IUCN)
true
All of the 17 freshwater fish species endemic to Lake Lanao and its outlet in the Philippines are now Extinct (15 species) or Critically Endangered (Possibly Extinct) (two species). The extinctions were caused by predatory introduced species, compounded by overharvesting and destructive fishing methods.
true
Evolutionary Milestones
- Life arose from nonlife
- The first organisms were single cells
- Speciation has generated the diversity of life
- Eukaryotes are “cells within cells”
- Photosynthesis changed the course of evolution - and the planet
- Multicellular organisms developed relatively late in Earth history.
