TERM 1 - WEEK 10

Development of the Theory of Evolution

The theory of evolution developed gradually as scientists gathered evidence about how living organisms change over generations. Early thinkers proposed that organisms might change over time, but these ideas were not yet supported by strong scientific evidence. In the 18th century, Carolus Linnaeus developed a system for classifying organisms, which helped scientists compare similarities among species. Georges-Louis Leclerc, Comte de Buffon suggested that species could change in response to their environment. Later, Jean-Baptiste Lamarck proposed that organisms change through the use and disuse of body parts and that acquired characteristics could be inherited, although this mechanism was later rejected.

In the 19th century, Charles Darwin and Alfred Russel Wallace independently developed the idea of evolution by natural selection. Darwin explained that individuals in a population have heritable variations, and those with traits that improve survival and reproduction are more likely to pass those traits to their offspring. Over many generations, these advantageous traits can become more common in a population. Later discoveries in genetics, DNA, fossils, and molecular biology provided additional evidence and helped establish the modern understanding of evolution, often called the modern evolutionary synthesis.

DAY 1: Define evolution as the heritable change in populations and species over time

What is Evolution?

Evolution refers to the heritable change in populations and species over time. It explains how living organisms gradually change through generations as traits are passed from parents to offspring. These changes may involve physical structures, behaviors, and physiological processes that help organisms survive in their environment. Evolution also explains the diversity of life on Earth and the existence of similarities among organisms. Scientists believe that present-day organisms evolved from earlier life forms through a long process of gradual change

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Evolution is the heritable change in the characteristics of a population over generations. These changes are passed from parents to offspring through genetic information and can cause populations to become better adapted to their environments over time. Evolution occurs in populations, not individual organisms, and over many generations, accumulated changes can contribute to the formation of new species.

DAY 2: Explain the occurrence of evolution according to Darwin’s ideas.

Charles Darwin and the Theory of Evolution

Charles Darwin developed the theory of evolution by natural selection based on observations he made during his voyage aboard the HMS Beagle. His observations in the Galápagos Islands were especially important in developing his ideas. Darwin noticed that finches on different islands had different beak shapes and sizes. These differences were related to the types of food available in their environments. For example, some finches had large, strong beaks that helped them crush hard seeds, while others had longer, narrower beaks suited for feeding on insects or other food sources. These observations led Darwin to propose that populations change over generations as organisms with advantageous inherited traits are more likely to survive and reproduce.

DAY 3: Describe natural selection as the mechanism by which species adjust to their environment through evolutionary changes.

Darwin and Natural Selection

Charles Darwin explained that natural selection is the mechanism that drives evolution. Based on his observations of organisms, Darwin proposed that individuals within a population have natural variations in their traits. Because organisms compete for limited resources and face environmental challenges, individuals with traits that give them an advantage are more likely to survive and reproduce. Their favorable traits can be passed to their offspring. Over many generations, these advantageous traits become more common in the population, causing the population to change and become better adapted to its environment. Thus, Darwin's theory of natural selection explains how evolutionary changes occur gradually over time.

DAY 4-5: Identify and Analyze the key concepts associated with evolution: variation, heredity, isolation, selection, and adaptation

Key factors of the Theory of Natural Selection

Variation

Darwin’s ideas depend on a key biological reality: variation exists within every species. Variation refers to differences among individuals, such as size, strength, or resistance to disease. In the finches he studied, differences in beak shape allowed some individuals to access certain types of food better than others. Without variation, there would be no traits for natural selection to act upon, and evolution would not occur.

Heredity

is the transfer of traits from parents to offspring. Through heredity, advantageous traits that help organisms survive are passed on to future generations. For example, if a particular trait increases an organism’s chance of surviving in a harsh environment, the offspring may inherit the same beneficial characteristic. Over time, these inherited traits become more common within the population, contributing to evolutionary change.

Isolation

occurs when groups of the same species become separated by physical or environmental barriers such as mountains, rivers, oceans, deserts, storms, or earthquakes. When populations are isolated, they can no longer reproduce with one another. Over time, the separated groups may develop different traits due to different environmental conditions and selective pressures. Isolation can eventually lead to the formation of new species.

Selection

occurs when environmental conditions favor organisms with specific traits. Individuals with beneficial traits survive and reproduce more successfully than others. This process is commonly referred to as “survival of the fittest.” In evolution, “fitness” refers to how well an organism is adapted to its environment. Organisms that are better adapted have a greater chance of passing their genes to the next generation. Through continuous selection, populations gradually change over time.

Adaptation

is the biological mechanism by which organisms adjust to changes in their environment. Adaptations are traits or behaviors that improve an organism’s ability to survive and reproduce. These adaptations may be structural, behavioral, or physiological. Structural adaptations involve physical features such as the thick fur of polar bears. Behavioral adaptations include migration and hibernation, while physiological adaptations involve internal body processes such as water conservation in camels. Adaptations develop over many generations through natural selection.

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