Evolutionary Patterns | Zoology Optional Notes for UPSC PDF Download

Introduction

• The evolutionary processes can rarely be observed directly in natural systems, albeit their accumulated effects result in different patterns that we can observe. The course Evolutionary Patterns turns the perspective from Evolutionary Processes around and focuses on how the evolutionary history is manifested in patterns that can be observed in and among organisms, and how these patterns can be detected and analysed to let us draw conclusions about the causes and the underlying processes.
• The course deals with evolutionary patterns in a broad perspective, patterns that are observed in different contexts such as in time and space (biogeography and fossils), between species (phylogenies), within populations (population genetics), in the individual organism (developmental biology) or in the genome (molecular evolution).
• The course will give you insight into questions and methods from different fields of evolutionary biology, and will be a good foundation for further advanced studies in any of the areas of evolutionary biology. The course is closely associated with the research at the Evolutionary Biology Centre.

Types of Evolution

Evolution over time can follow several different patterns. Factors such as environment and predation pressures can have different effects on the ways in which species exposed to them evolve. shows the three main types of evolution: divergent, convergent, and parallel evolution.

Divergent Evolution

When people hear the word "evolution," they most commonly think of divergent evolution, the evolutionary pattern in which two species gradually become increasingly different. This type of evolution often occurs when closely related species diversify to new habitats. On a large scale, divergent evolution is responsible for the creation of the current diversity of life on earth from the first living cells. On a smaller scale, it is responsible for the evolution of humans and apes from a common primate ancestor.

Convergent Evolution

Convergent evolution causes difficulties in fields of study such as comparative anatomy. Convergent evolution takes place when species of different ancestry begin to share analogous traits because of a shared environment or other selection pressure. For example, whales and fish have some similar characteristics since both had to evolve methods of moving through the same medium: water.

Parallel Evolution

Parallel evolution occurs when two species evolve independently of each other, maintaining the same level of similarity. Parallel evolution usually occurs between unrelated species that do not occupy the same or similar niches in a given habitat.