Origin of Life Flashcards
When was the earth formed?
at least 4.6 billion years ago
How do we know when the earth was formed?
radioactive emissions from meteorites found on the Earth and the Moon leads us to infer that the Earth formed at
least 4.6 billion years ago
What techniques study the structure of the earth?
Advanced techniques in analysing seismic
waves, the Earth’s magnetic field, and geomagnetic
and gravity measurements
Why are rocks important to scientists?
Rocks can be dated by both absolute and relative
techniques
Why do living organisms affect changes in the Earth?
taking in liquid water and releasing water vapour to the atmosphere. Aquatic living organisms also affect the levels of dissolved gases and the levels of dissolved solids.
How did the concept of plate tectonics form?
gradually built up over the years based on:
- complementary shape of parts of the present continents
- similarities in rock formations and plant species,
though much of the scientific community was initially
sceptical
What led to the acceptance of plate tectonics?
paleomagnetism, especially critical evidence concerning the magnetic orientation of rocks from either side of the
mid-Atlantic ridge
What is paleomagnetism?
the branch of geophysics concerned with the magnetism in rocks that was induced by the earth’s magnetic field at the time of their formation
How are tectonic plates observed?
As a result of new technologies to measure distance
and position very precisely
What is the Earth’s crust made of?
The Earth’s crust is comprised of a number of
separate plates that gradually move relative to each
other.
What has happened to tectonic plates over time?
Over geological time the number and shape of the
plates, as well as the positions of these, have
undergone many changes.
What do tectonic plates cause?
Interactions of the plates are responsible for
earthquakes and physical features such as volcanoes
and mountain ranges.
What surrounds the Earth?
The Earth is surrounded by an atmosphere, the
composition of which has changed and continues to
change
What causes the ozone layer?
Radiation from the Sun, especially UV light, causes
chemical reactions between components of the
atmosphere
What causes gases in water?
Equilibrium exists between gases in the atmosphere
and gases dissolved in water on the surface of the
Earth, which hence acts as a reservoir of gases
What has a detailed study of the atmosphere enabled us to do?
develop models that can predict the effects of
changes in gas composition that may occur in the
future
Where do recent changes in Earth’s atmosphere come from?
ice core samples, especially from the Antarctic, which contain trapped air.
What causes change in sea levels?
The total amount of water, and the ratio of water to
ice
Where does most of Earth’s energy come from?
Most of the energy on Earth originates from the
Sun.
What causes green house gases?
Solar radiation is absorbed by the Earth’s
surface and transferred to the atmosphere. The
Earth emits infrared radiation, some of which is absorbed and re-radiated by some gases in the
atmosphere, creating a greenhouse effect.
What makes the surface temperature steady?
The balance between absorbed and emitted
radiation results in a surface temperature that
makes life possible.
How does the sun affect the global climate?
Variations in solar activity are hypothesized to affect
global climate by 5%
What objects provide information on how the Earth’s climate has changed over time?
Fossils and sediments
Does human activity affect the climate?
Yes, Changes to the atmosphere that result from human
activity have a significant effect on the climate.
How many greenhouse gases are there?
There are several greenhouse gases, each with a
different contribution to global warming
What gases did Miller and Urey originally use in 1953 to show that amino acids could be made from simple inorganic molecules?
Hydrogen, methane and ammonia
What was absent in Earth’s early atmosphere that allowed ultra violet light to shine on the Earth’s surface?
Ozone layer
What did the electrodes simulate in the Miller Urey Experiment?
Lightening
How many amino acids did Miller and Urey originally detect?
Five
What gases did Miller and Urey use in their 1958 experiment?
Carbon dioxide, hydrogen sulphide, methane and ammonia
What amino acid has been indirectly detected in nebula?
Glycine
What does molecular Panspermia mean?
The first organic molecules originated from space
How many strands does a RNA molecule have?
One
What is RNA world theory?
RNA was the precursor to DNA as the molecule that held genetic information
What is the primordial soup?
a solution rich in organic compounds in the primitive oceans of the earth, from which life is thought to have originated
What are the main criticisms of Miller Urey’s experiment?
Results did not match the early earth
- gases did not represent those in the atmosphere
- only five amino acids found (compared to 20 in living things)
- No methionine found (starter amino acid found in all proteins)
What was Miller Urey’s experiment?
An experiment to show that conditions believed to exist in the early earth could create complex organic molecules. They created a primordial soup by:
- Introducing gases
- Recreating the water cycle by evaporating and condensing water
- Keeping the environment warm
- Exposing the chemicals to UV (no ozone layer in early atmosphere)
- Recreating lightning by generating electrical sparks
What happened when Miller and Urey’s ‘primordial soup’ was analysed 50 years later?
22 amino acids were found
What is the endosymbiotic theory?
It proposes that 2 billion years, a prokaryote cell absorbed a smaller prokaryote cell. This smaller cell survived and the cells lived symbiotically (giving services to each other)
What is the evidence for endosymbiosis?
Organelles that to be derived from engulfed prokaryotes:
- have double membranes
- have their own DNA
- can replicate themselves within the host cell
- can perform their own independent protein synthesis using small ribosomes
