Question

1. Explain Darwin’s two observations and two inferences that led to the understanding of natural selection as the mechanism of evolution.

2. Explain the characteristics of early Earth (before life evolved) and what four steps led to the origin of life.

Answer 1

Darwin's 2 observations and inferences of evolution

Observation 1. Individuals in a population vary in their heritable characteristics.

Inference 1 . Individuals that are well suited to their environment tend to leave more offspring than other individuals.

Observation 2. All species can produce more offspring than the environment can support , and many of these offspring fail to survive and reproduce .

Inference 2. This unequal ability of individuals to survive and reproduce will lead to the accumulation of favourable traits in the population over generations.

Characteristics of early earth ( History of early earth Hadean period):

At first(4.54 billion years ago) earth was not even able to support the life .The earth was without form and void ; and the darkness was on the face of the deep. There was no oxygen in the admosphere. There was no ozone layer in the earth hence the earth was extremely hot . It contains nitrogen, carbon dioxide, hydrogen and water vapour at initially.

Much of the earth was molten because of frequent collisions with other bodies which will leads to extream volconism.

Within the first billion years life appeared in it's ocean and begun to affect it's admosphere and surface promoting the proliferation of aerobic and anaerobic organisms.

Four steps led to the origin of life :

1 . Formation of the organic compounds from inorganic compounds . That is at initially a significant molecules which is necessary for life was produced . ( Before the first cell -chemical evolution)

2. From those monomers by the bonding polymers were formed . Phosphoric acid can bond molecules to form long chain molecules.

3. Amino acids form first since they do not form if oxygen present . Probably formed on clay surfaces since they are attractive and absorptive, also protection from UV.

4. Finally larger molecules produced by linking of amino acids by dehydration synthesize ( water loss) ,Clay's have potential to absorb water , thus amino acids could be linked on clay surfaces .They can replicate .

Those polymers can function as a enzyme to carryout metabolic reactions , encode hereditary information and possibly replicate( eg: protein , RNA strands) . Concentration of organic molecules and polymers carryout the metabolic reactions within the enclosed system , seperated from the environment by semipermeable membrane , such as lipid bilayer membrane. Hence protocells were formed .