Evolution by stages explanation
Answers
Answer:
The occurrence of different stages of evolution in a species is not because of a single DNA change. Evolution of eyes and feathers are classic examples to understand the process of evolution by stages.
Evolution of Eyes
The eye is an example of a complex homologous organ. It has been created in stages over generations.
The primitive organisms which existed on the Earth were slow moving and smaller in size. They did not require a specialised organ for observing any object.
Consider the example of flatworms. Flatworms are small invertebrates.
The eyes of flatworms are simple and exist in the form of eyespots. Eyespots are light-sensitive cells which can detect light.
As evolution progressed, comparatively larger and mobile organisms evolved. Most of them were predators and required better vision for predation.
Hence, from the basic design of eyes, more complex forms evolved.
Insects, octopuses and invertebrates have eyes. However, the structure of the eyes differs in each of these organisms. This suggests that they have a separate evolutionary origin.
Evolution of Feathers
Birds make use of their feathers for flying. However, feathers did not evolve for flight. They evolved as a means of providing insulation to the body in cold weather.
Scientists have discovered fossils of dinosaurs which had feathers for insulation against cold weather. Because the dinosaurs were reptiles, it implies that birds evolved from reptiles.
Answer:
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. Figure%: Types of evolution; a)divergent, b)convergent, and c)parallel.