7.3 Artificial Selection
Keywords
| English Term | 中文翻译 | Definition & Explanation |
|---|---|---|
| Artificial Selection | 人工选择 | The selective breeding of domesticated plants and animals to encourage the occurrence of desirable traits. |
| Convergent Evolution | 趋同进化 | The independent evolution of similar features in species of different lineages. |
| Analogous Structures | 同功器官 | Structures that share similar functions and appearances due to convergent evolution, but evolved independently from different ancestors. |
1. Humans as the Selective Pressure
While natural selection is driven by environmental factors, humans can also drive evolution. Artificial selection is the process by which humans deliberately impact the variation in other species.
Instead of nature deciding which traits provide the highest survival fitness, humans select individuals with traits they find desirable and breed them together.
- Agriculture: Farmers have selectively bred crops for thousands of years. For example, wild mustard has been artificially selected to produce broccoli, cabbage, kale, and cauliflower—all radically different phenotypes derived from the same ancestral species.
- Domestication: All modern dog breeds, from Great Danes to Chihuahuas, were artificially selected by humans from a common wolf ancestor. Humans applied the selective pressure for traits like size, temperament, and coat length.
2. Convergent Evolution: Nature's Parallel Solutions
A fascinating phenomenon occurs when natural selection acts on completely different, unrelated species. Convergent evolution occurs when similar environmental selective pressures result in similar phenotypic adaptations in different populations or species.
Because these animals face the exact same environmental challenges, nature shapes them to look and function similarly, even though they do not share a recent common ancestor.
Analogous vs. Homologous
Convergent evolution produces Analogous Structures: features that share similar functions but evolved independently.
Example: The sleek, torpedo-shaped bodies and dorsal fins of a Shark (a fish) and a Dolphin (a mammal). They are very distantly related, but because both are active predators swimming in dense ocean water, natural selection favored the exact same hydrodynamic shape in both lineages. The fins are analogous.