Biology Option D 1

Question 1

D. 1.1

Describe four processes needed for the spontaneous origin of life on Earth

Answer 1

1. The non-living synthesis of simple organic molecules to monomers
2. The assembly of the monomers to polymers
3. Enabling inheritance through the formation of polymers that can self-replicate
4. Packaging of the molecules into membranes with internal chemistry different from their surroundings.

Question 2

D. 1.2

Outline the experiments of Miller and Urey into the origin of organic compounds

Answer 2

Miller and Urey

Created a situation of pre-biotic Earth in a closed system of flasks and tubes. Conditions included low oxygen, high radiation levels, and high temperatures. Water was boiled and mixed with methane, ammonia, and hydrogen. And then gas were exposed to electrical discharge to produce lightning. The mixture was allowed to cool down for a week. Amino acids and oily hydrocarbon were formed which showed that organic molecules could be formed under hypothesized pre-biotic Earth.

Question 3

D. 1.3

What is one way organic compounds were delivered to Earth

Answer 3

Comets

Question 4

D. 1.4

Discuss possible locations where conditions would have allowed for the synthesis of organic compounds

Answer 4

Organic synthesis requires a range of inorganic molecules as well as energy to combine them into organic forms.
Some of the locations include:
Volcanoes, hydrothermal vents, and extraterrestrial locations.

Question 5

D. 1.5

Outline two properties of RNA that would have allowed it to play a role in the origin of life.

Answer 5

It is hypothesized that RNA came before DNA.
1) Self-replication:
Allows duplication of other RNAs and ables RNA to store information in a sequence of four nucleotides.
2) Acting as a catalyst

*DNA took over the storage of information and protein took over the role of catalytic form.

Question 6

D. 1.6

What may have been preceding living cells?

Answer 6

Protobionts with internal chemistry different to their surroundings.
Examples: coacervates and microspheres.

Question 7

D. 1.7

Outline the contribution of prokaryotes to the creation of an oxygen-rich atmosphere

Answer 7

Pre-biotic Earth has an atmosphere of very low oxygen. A from of chlorophyll evolved into prokaryotes. This allows photosynthesis to occur, which ultimately creates oxygen through photolysis of water.
More oxygen in time meant breaking down of chemicals which would allow more and more oxygen as well as the formation of ozone layer, restricting UV radiation, which helps in the formation of oxygen-rich atmosphere.

Question 8

D. 1.8

Discuss the endosymbiotic theory for the origin of eukaryotes

Answer 8

An endosymbiont cell is a cell that lives within another cell for mutual benefit. Eukaryotes are believed to have evolved from aerobic prokaryotes that were engulfed by endocytosis. Mitochondria and chloroplasts are suggested to have originated by endosymbiosis. Some evidence that support the endosymbiotic theory are the idea that mitochondria and chloroplasts have their own DNA which is naked and circular. Also, both of them have a double membrane with proteins of inner membrane similar to that of prokaryotes. They are also roughly the same size as bacteria which shows that they were originally prokaryotes engulfed through the endosymbiotic theory.