7.13 Abiogenesis

When you leave a steak out, where do the maggots come from?

• they result from spontaneous generation --> life forming from an inanimate object

• Flies land on the steak and lay their eggs.  Maggots are the larvae form of baby flies.

Do scientists argue that life could have emerged in one step?  (No life... then all of sudden, cells exist as we know them today)?

• Yes, that is the theory of abiogenesis

• No, scientists have evidence that a series of steps occurred over a long period of time, starting with the chemical formation of monomers.

The early atmosphere was a REDUCING atmosphere (molecules tended to GAIN electrons).  Our current atmosphere is an OXIDIZING atmosphere because...  (CHECK TWO CORRECT ANSWERS)

• there is an abundance of oxygen

• oxygen always loses its electrons to other molecules

• oxygen is very electronegative and pulls electrons away from other molecules

• there is not enough oxygen

The monomer known as amino acids are used by living things to build which polymer?

• nucleic acids

• lipids

• proteins

• carbohydrates

Be careful:

True or False, the Miller-Urey experiment directly shows that life could have formed abiotically.

• False.  It showed that monomers could have formed in the conditions of early Earth.  This would have been the first required step in the progression of steps leading towards life.

• True.  Miller and Urey observed the creation of life in their lab.

Review: What is the overall purpose of the Kreb's cycle?

• release energy from carbohydrates

• store energy in carbohydrates