WHAT ARE THE EVIDENCES FOR EVOLUTION?
1. Paleontological Evidence
- Fossils found in rocks, remains of hard parts of life-forms.
- Different-aged rock sediments contain fossils of different life-forms.
- Fossils provide evidence of extinct organisms like Dinosaurs.
- Study of fossils in sedimentary layers helps determine geological periods.
2. Embryological Support
- Ernst Heckel proposed embryological support for evolution.
- Common features observed in vertebrate embryos, absent in adults.
- For example, vestigial gill slits in vertebrate embryos.
3. Comparative Anatomy and Morphology
- Similarities and differences among organisms provide insights into common ancestry.
- Example: Mammals like whales, bats, Cheetah, and humans share similarities in forelimb bones.
- Divergent evolution: Structures with common ancestry (homologous structures).
- Analogy: Similar functions with different structures (analogous structures).
4. Biochemical Similarities
- Similarities in proteins and genes among diverse organisms.
- Indicate common ancestry, similar to structural similarities.
5. Artificial Selection
- Humans have bred and selected plants and animals.
- Created distinct breeds within the same species.
- Suggests that nature, over millions of years, could also drive evolution.
6. Industrial Melanism
- Observation in England: Moth populations.
- Before industrialization, more white-winged moths.
- After industrialization, more dark-winged moths.
- Shows shifts in populations due to environmental changes.
Comparison between homologous and analogous structures:
| Aspect | Homologous Structures | Analogous Structures |
|---|---|---|
| Definition | Structures in different species with a common evolutionary origin but may serve different functions. | Structures in different species with similar functions but different evolutionary origins. |
| Evolutionary Origin | Arise from a common ancestor, indicating shared ancestry. | Arise independently in different lineages, indicating convergent evolution. |
| Anatomical Similarity | Similar in basic structure and organization (e.g., bone arrangement, genetic basis). | Similar in function but may differ in basic structure (e.g., butterfly and bird wings). |
| Example (1) | The forelimbs of vertebrates (e.g., human, whale, bat) share a common skeletal structure. | Wings of butterflies and birds both allow for flight but have different underlying structures. |
| Example (2) | The pentadactyl limb with the same set of bones found in human, cat, whale, and bat forelimbs. | The flippers of penguins and dolphins both facilitate swimming but have different structures. |
| Supports Evolution | Provides evidence for common ancestry and divergent evolution. | Provides evidence for convergent evolution in response to similar environmental pressures. |
Comparison between convergent and divergent evolution:
| Aspect | Convergent Evolution | Divergent Evolution |
|---|---|---|
| Definition | Independent development of similar traits or characteristics in different lineages in response to similar environmental pressures. | Evolutionary process where two or more species that share a common ancestor become increasingly different from one another. |
| Key Characteristics | – Organisms from different lineages develop similar traits or structures. | – Organisms from a common ancestor evolve to have different traits or structures. |
| Result | – Different species may appear similar due to adaptations to similar environments. | – Different species diverge from each other, becoming more distinct over time. |
| Example (1) | The wings of bats and birds, which have evolved separately for flight but have similar functions. | Darwin’s finches in the Galapagos Islands that evolved distinct beak shapes based on their diets. |
| Example (2) | The streamlined bodies of dolphins and fish, which aid in swimming but have different evolutionary origins. | The diversity of species resulting from a single ancestral population, leading to various adaptations. |
| Mechanism | Environmental factors and pressures drive organisms to develop similar traits for survival. | Environmental factors and selective pressures drive species to adapt and diversify over time. |
| Time Scale | Faster, as it involves adaptations to current environmental pressures. | Slower, occurring over extended periods as species accumulate genetic differences. |
| Genetic Basis | May involve different genetic pathways and molecular mechanisms. | Results in genetic differences and variation among populations within a species. |
The Tale of Industrial Melanism
Once upon a time in a serene English countryside, there existed a lush forest filled with an abundance of trees and various species of moths. The moths, known as the “Peppered Moths,” were predominantly of a light, speckled coloration, which provided them with excellent camouflage against the lichen-covered bark of the trees. These light-colored moths were perfectly adapted to their environment, and they thrived without fear of predators.
However, as the Industrial Revolution unfolded in the 19th century, the landscape around the forest transformed dramatically. Factories and industrialization brought pollution, and soon, the once-pristine trees became dark and soot-covered due to the industrial emissions. The forest that had once provided a harmonious home for the light-colored Peppered Moths was now undergoing a significant transformation.
In this changing environment, a new variant of Peppered Moths began to emerge. These moths, with dark black wings, were far less camouflaged against the now-darkened trees. Predators, particularly birds, could now easily spot the dark moths against the soot-covered trunks. For a while, it seemed like the dark Peppered Moths were at a disadvantage.
However, nature had a way of selecting those individuals best suited to their environment. With their surroundings favoring darker moths, the dark variant had an advantage. Birds would prey on the lighter moths, as they were less well-camouflaged against the darkened trees. The dark Peppered Moths, on the other hand, were less likely to be spotted and devoured.
Over time, the population of dark Peppered Moths began to grow, while the light-colored moths dwindled. The story of the Peppered Moths illustrated the concept of “industrial melanism,” where the darker, previously rare variant of moths became predominant in response to changes in their environment.
As decades passed, the environment gradually improved. Clean air acts and reduced pollution led to the restoration of the forest’s trees, which regained their natural coloration. As the trees lightened, the dark Peppered Moths became more visible to predators. The tables had turned, and the light-colored moths now had the advantage.
The tale of industrial melanism serves as a striking example of how evolution by natural selection can occur rapidly in response to environmental changes. It also reminds us of the delicate balance between species and their surroundings in the ever-changing world of nature.
Examples of evolution by anthropogenic action
Evolution by anthropogenic (human-induced) action is a fascinating field of study that demonstrates how human activities can influence the evolutionary trajectories of various species. Here are some examples of evolution driven by human actions:
Antibiotic Resistance in Bacteria:
- Overuse and misuse of antibiotics in medicine and agriculture have led to the development of antibiotic-resistant bacteria. Bacteria that survive antibiotic treatments pass on their resistance genes to subsequent generations, resulting in the emergence of superbugs that are challenging to treat.
Pesticide Resistance in Insects:
- The widespread use of pesticides in agriculture has led to the evolution of pesticide-resistant insects. Insects with genetic variations that allow them to survive pesticide exposure pass on their resistant traits, rendering some pesticides ineffective over time.
Urban Evolution in Wildlife:
- Animals living in urban environments have adapted to the challenges posed by cities. Examples include birds with altered songs to communicate in noisy urban settings, and urban-dwelling rodents developing resistance to toxins found in human waste.
Commercial Fishing and Fish Evolution:
- Intensive commercial fishing practices have led to the selective removal of large fish from populations. This has caused some fish species to evolve towards smaller sizes at maturity, which has implications for their reproductive and ecological dynamics.
Artificial Selection in Agriculture:
- Humans have selectively bred crops and livestock for desirable traits such as higher yields, disease resistance, or specific physical characteristics. This has led to the evolution of new varieties and breeds.
Invasive Species Evolution:
- Some invasive species adapt and evolve to thrive in new environments, which can further enhance their invasive capabilities. For example, the cane toad in Australia has rapidly evolved longer legs to disperse more effectively.
Climate Change Adaptation:
- Climate change has led to shifts in the geographic ranges of various species. Many animals and plants are evolving to adapt to changing temperature and ecological conditions, such as shifting breeding seasons or moving to higher elevations.
Industrial Melanism in Peppered Moths (as mentioned earlier):
- The darkening of the peppered moth population in response to industrial pollution is a classic example of rapid evolution due to environmental changes caused by human industrialization.
