Correct Answer - Option 1 : Natural hazard
The theory of evolution is one of the great intellectual revolutions of human history, drastically changing our perception of the world and of our place in it.
Charles Darwin put forth a coherent theory of evolution and amassed a great body of evidence in support of this theory. In Darwin's time, most scientists fully believed that each organism and each adaptation was the work of the creator.
Darwin's Theory
- Darwin’s theory of evolution entails the following fundamental ideas. The first three ideas were already under discussion among earlier and contemporaneous naturalists working on the “species problem” as Darwin began his research.
- Darwin’s original contributions were the mechanism of natural selection and copious amounts of evidence for evolutionary change from many sources. He also provided thoughtful explanations of the consequences of evolution for our understanding of the history of life and modern biological diversity.
- Species (populations of interbreeding organisms) change over time and space. The representatives of species living today differ from those that lived in the recent past, and populations in different geographic regions today differ slightly in form or behaviour.
- These differences extend into the fossil record, which provides ample support for this claim. All organisms share common ancestors with other organisms. Over time, populations may divide into different species, which share a common ancestral population. Far enough back in time, any pair of organisms shares a common ancestor.
- For example, humans shared a common ancestor with chimpanzees about eight million years ago, with whales about 60 million years ago, and with kangaroos over 100 million years ago. Shared ancestry explains the similarities of organisms that are classified together: their similarities reflect the inheritance of traits from a common ancestor.
- Evolutionary change is gradual and slow in Darwin’s view. This claim was supported by the long episodes of gradual change in organisms in the fossil record and the fact that no naturalist had observed the sudden appearance of a new species in Darwin’s time.
- Since then, biologists and palaeontologists have documented a broad spectrum of slow to rapid rates of evolutionary change within lineages. The primary mechanism of change over time is natural selection. This mechanism causes changes in the properties (traits) of organisms within lineages from generation to generation.
Darwin’s process of natural selection has four components.
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Variation. Organisms (within populations) exhibit individual variation in appearance and behavior. These variations may involve body size, hair color, facial markings, voice properties, or number of offspring. On the other hand, some traits show little to no variation among individuals—for example, number of eyes in vertebrates.
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Inheritance. Some traits are consistently passed on from parent to offspring. Such traits are heritable, whereas other traits are strongly influenced by environmental conditions and show weak heritability.
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High rate of population growth. Most populations have more offspring each year than local resources can support leading to a struggle for resources. Each generation experiences substantial mortality.
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Differential survival and reproduction. Individuals possessing traits well suited for the struggle for local resources will contribute more offspring to the next generation.
From one generation to the next, the struggle for resources (what Darwin called the “struggle for existence”) will favour individuals with some variations over others and thereby change the frequency of traits within the population. This process is natural selection. The traits that confer an advantage to those individuals who leave more offspring are called adaptations.
- 'Survival of the fittest' is a phrase that describes the mechanism of natural selection.
- It originated from the Darwinian Evolutionary theory and reproductive success is the biological concept of it.
- In simpler terms, it means, that the form which will leave the most copies of itself in the successive generations will survive.
