Evolution Lecture 1

Study Notes

The evolution of the environment with definite biosphere zones facilitated the evolution of higher animals, including humans.
Oparin (1938) suggested the following phases of evolution:
- Atomic phase
- Molecular phase
- Organic phase
- Colloidal phase
- Autocatalytic phase
- Primordial cellular phase
- Autotrophic phase
- Prokaryotic phase
- Eukaryotic phase

The Earth is also known as 'the blue planet' or 'the planet with life', originating about 4.8 billion years ago.
The primitive atmosphere of the Earth contained nitrogen, hydrogen, and carbon, but no oxygen or ozone, all found in the atomic state due to extreme heat and ultraviolet insulation.
Chemical evolution continued for about 2,000 million years, resulting in the appearance of various inorganic and organic compounds, including N2, H2, CH4, NH3, CO, CO2, H2O, etc.

Lamarckian theory is also known as the 'Theory of Inheritance of Acquired Characters' or the 'Theory of Use or Disuse of Organs'.
According to Lamarck's theory, as giraffes stretched to reach high branches, their necks lengthened, and this was passed on to their offspring.
The basic ideas of Lamarckism are:
- Complex plants and animals are produced from simpler ones over time under the influence of nature.
- Living organisms have a tendency to continuously increase in size.
- There is a change in the needs of an animal due to changes in the surrounding environment, resulting in the formation of new organs to cater to the needs of the animal.
- If an organ is used continuously, it will become more powerful, but if it is not used for a long time, it will gradually weaken and eventually disappear.
- The characters acquired during the lifetime of individuals will be transmitted to the next generation.

Lamarck based his idea of use and disuse on the evidence of vestigial organs and rudimentary organs.
Weismann (1890) provided experimental proof against the assumption of inheritance of acquired characters.
Weismann proposed the 'Theory of Continuity of Germplasm', stating that only changes in the germ cells are inherited, and somatic changes are not inherited.

A few scientists, notably Herbert Spencer, Haeckel, Gadow, etc., have supported Lamarckism in a modified form, known as Neo-Lamarckism.

Malthus' "Essay of the Principle of Population" (1798) influenced Darwin's idea of natural selection.
Darwin hypothesized natural selection as a means by which selective survival of individuals with superior attributes gradually changes the average characters of the population over many generations.

Molecular biology, DNA, and genetic code, gene expression support the theory of evolution.
Developmental biology provides insights into an organism's evolutionary history.
Human embryos with gills, tails, and fur demonstrate evolutionary connections.

Charles Darwin (1809-1882) categorically explained organic evolution in detail.
Darwin's theory of evolution was shaped by the gradual changes in scientific beliefs during the 18th and 19th centuries.

Galapagos tortoises have distinct shell shapes varying according to their island of origin.
Examples of distinct species include the Rhea of South America, the Emu of Australia, and African ostriches.

Alfred Russel Wallace (1823-1913) independently came up with the idea of natural selection.
Darwin and Wallace published a joint presentation on their ideas in 1858, and Darwin published a detailed treatment in the Origin of the Species in 1859.