Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
The universe is approximately billion years old, and Earth was formed about billion years ago.
Conditions on primitive Earth included high temperatures, volcanic storms, and a reducing atmosphere containing , , , and (water vapor), but no free .
The Theory of Chemical Evolution (Oparin-Haldane) proposes that the first forms of life arose from pre-existing non-living organic molecules like and proteins.
S.L. Miller's experiment () provided experimental evidence for chemical evolution by creating electric discharges in a closed flask containing , , , and water vapor at .
Miller observed the formation of amino acids; similar experiments by others yielded sugars, nitrogen bases, pigments, and fats.
The first non-cellular forms of life could have originated billion years ago as large molecules like , proteins, or polysaccharides.
The first cellular forms of life probably originated in a liquid medium about million ( billion) years ago and were likely single-celled.
Louis Pasteur disproved the theory of 'Spontaneous Generation' using swan-neck flasks, demonstrating that life comes only from pre-existing life (Biogenesis).
📐Formulae
💡Examples
Problem 1:
In the Miller-Urey experiment, what was the temperature maintained in the flask, and which organic compounds were specifically identified after the reaction?
Solution:
The temperature was maintained at . The organic compounds identified were amino acids (specifically Glycine, Alanine, and Aspartic acid).
Explanation:
High temperature and electric discharge simulated the volcanic storms and lightning of primitive Earth, facilitating the synthesis of monomers of proteins.
Problem 2:
Arrange the following in the correct chronological order of their appearance on Earth: (i) Free , (ii) Non-cellular life, (iii) layer, (iv) Cellular life.
Solution:
(ii) Non-cellular life (iv) Cellular life (i) Free (iii) layer.
Explanation:
Non-cellular life appeared billion years ago, followed by cellular life billion years ago. Photosynthetic organisms later released , which subsequently formed the (ozone) layer.