characteristics and origins of life

the origin of life

No one knows how or when life first began on the turbulent early Earth. There is little hard evidence from so long ago. Scientists think that it is extremely likely that life began and was wiped out more than once; for example, by the impact that created the Moon. This issue of whats living and whats not becomes important when talking about the origin of life. If were going to know when a blob of organic material crossed over into being alive, we need to have a definition of life.

learning about the origin of life

To look for information regarding the origin of life, scientists: perform experiments to recreate the environmental conditions found at that time. study the living creatures that make their homes in the types of extreme environments that were typical in Earths early days. seek traces of life left by ancient microorganisms, also called microbes, such as microscopic features or isotopic ratios indicative of life. Any traces of life from this time period are so ancient it is difficult to be certain whether they originated by biological or non-biological means. Click image to the left or use the URL below. URL:

characteristics of life

To be considered alive a molecule must: be organic. The organic molecules needed are amino acids, the building blocks of life. have a metabolism. be capable of replication (be able to reproduce).

millerurey experiment

To see if amino acids could originate in the environment thought to be present in the first years of Earths existence, Stanley Miller and Harold Urey performed a famous experiment in 1953. To simulate the early atmosphere they Amino acids form polypeptide chains. The setup of the Miller-Urey experiment. placed hydrogen, methane, and ammonia in a flask of heated water that created water vapor, which they called the primordial soup. Sparks simulated lightning, which the scientists thought could have been the energy that drove the chemical reactions that created the amino acids. It worked! The gases combined to form water-soluble organic compounds including amino acids. Amino acids might also have originated at hydrothermal vents or deep in the crust where Earths internal heat is the energy source. Meteorites containing amino acids currently enter the Earth system and so meteorites could have delivered amino acids to the planet from elsewhere in the solar system (where they would have formed by processes similar to those outlined here).

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amino acids

Amino acids are the building blocks of life because they create proteins. To form proteins, the amino acids are linked together by covalent bonds to form polymers called polypeptide chains (Figure 1.1). These chains are arranged in a specific order to form each different type of protein. Proteins are the most abundant class of biological molecules. An important question facing scientists is where the first amino acids came from: did they originate on Earth or did they fly in from outer space? No matter where they originated, the creation of amino acids requires the right starting materials and some energy.

instructional diagrams

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questions

which is not a characteristic of all life?

a) be organic

b) have a metabolism

c) be capable of replication/reproduction

-->  d) have a heartbeat

to learn about the origin of life, scientists do not

a) perform experiments to recreate the environmental conditions found at that time

-->  b) create stories from their imaginations

c) study organisms living in extreme environments

d) study ancient microorganisms

amino acids are the building blocks of life because they create

-->  a) proteins

b) lipids

c) carbohydrates

d) sucrose

amino acids are linked together by ionic bonds to form monomers called polypeptides.

a) true

-->  b) false

what did the miller-urey experiment help determine?

a) to see if carbohydrates could originate in an early earth environment.

b) to see if amino acids landed on earth from outer space.

-->  c) to see if amino acids could originate in an early earth environment.

d) to see if hydrogen was the first building block of proteins before amino acids.

in the miller-urey experiment, electric sparks provided the energy that drove the chemical reactions.

-->  a) true

b) false

scientists think that life on earth originated once.

a) true

-->  b) false

proteins are important because they

a) were the living organisms to originate on earth.

-->  b) are the most abundant class of biological molecules.

c) are known to have originated in outer space, rather than on earth.

d) all of these.

early amino acids may have originated

a) at hydrothermal vents.

b) deep in the crust.

c) elsewhere in the solar system.

-->  d) all of these.

a primary protein structure is a sequence of a chain of amino acids.

-->  a) true

b) false

diagram questions

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