Heredity - Evolution

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Differences in characters within very closely related groups of organisms are called variations. Variations can be inherited and they help organisms survive in changing conditions.

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Variations give some individuals a survival advantage. Useful variations help organisms live longer, reproduce, and pass the trait to the next generation. Over time, this leads to evolution.

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Mendel studied inheritance of variations in pea plants. He worked in a monastery garden, used nearly 10,000 pea plants of 34 varieties, and studied seven contrasting characters.

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Pea plants had well defined characters, bisexual flowers, predominant self-pollination, suitability for cross-pollination, and an annual life cycle. These features made them suitable for studying inhe…

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Flower colour: purple or white; flower position: axial or terminal; seed colour: yellow or green; seed shape: round or wrinkled; pod shape: inflated or constricted; pod colour: green or yellow; stem l…

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A monohybrid cross is a cross between two plants differing in one pair of contrasting characters. It is used to study inheritance of one trait at a time.

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All F1 seeds are yellow because yellow is dominant over green. The trait expressed in F1 is called dominant, and the unexpressed trait is called recessive.

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The F2 phenotypic ratio is 3:1, meaning about 75% show the dominant trait and 25% show the recessive trait.