Learning Outcomes:
i. Explain the key principles of Darwin's theory of natural selection.
ii. Understand how natural selection operates in the context of adaptive evolution.
Introduction:
In this lesson, we will unravel the profound insights that Charles Darwin brought to the field of biology through his theory of natural selection. We will explore the fundamental principles that underlie this theory and how it explains the mechanism driving the adaptive evolution of species.
i. Variation within Populations:
Darwin observed that within any population, there is natural variation among individuals. No two individuals are exactly alike, and this variation can be attributed to genetic differences. For example, in a population of finches, there may be variations in beak size, shape, and color.
ii. Struggle for Existence:
Darwin noted that populations have the potential to produce more offspring than the environment can support. This leads to competition for resources, such as food, water, and shelter. The struggle for existence is a central concept in natural selection, where individuals with advantageous traits have a better chance of surviving and reproducing.
iii. Differential Reproduction:
Individuals with traits that confer a higher probability of survival and reproduction are more likely to pass those traits to their offspring. Over time, these advantageous traits become more prevalent in the population, leading to the concept of differential reproduction. For instance, in a population of moths, those with better camouflage against predators are more likely to survive and produce offspring with similar traits.
iv. Adaptation to the Environment:
Natural selection results in the accumulation of traits that enhance an organism's fitness in its specific environment. The process of adaptation involves the development of traits that improve an organism's ability to survive and reproduce. A classic example is the peppered moth during the Industrial Revolution, where darker moths had a survival advantage in polluted environments.