Chapter 17, Problem 41A

Summary Introduction

To describe:

The three lines of evidences that support evolution.

Introduction:

The inheritable changes that occurs in biological populations over time is known as evolution. Evolution helps an organisms to better suit to its existing environments. It is a continuous occurring process.

Explanation of Solution

According to the theory of evolution, it states that all organisms have descended from a common ancestors.

The following lines of evidences support the theory of evolution are:-

1. Fossil record.

2. Comparative anatomy.

3. Comparative embryology.

1. Fossil record.

Fossils records provide an essential and informative sources for determination of ancestry and pattern of evolution. Fossils provide record of ancient species that share similarities with present day species. However, not all ancient fossilized form have recent counterparts, for example, the horseshoe crab. Fossils also contain features that are shared by different species and are known as transitional fossils. Two major classes of traits are shown by transitional fossils, are derived traits and ancestral traits. Derived traits are newly evolved features and ancestral traits are primitive in nature.

Archaeopteryx fossils provide essential evidence of characteristics that show that birds retained several characters of dinosaurs.

2. Comparative anatomy.

According to comparative anatomy, organisms inherit anatomically similar structures from their ancestors. It is predicted that an organism’s body parts are more likely to be modified from ancestral body parts. For example, wings of bird and limb of reptiles are similar in shape and construction, which means they are inherited from a common ancestors though birds use their wings to fly and reptiles use their limbs to walk.

3. Comparative embryology.

The embryo of vertebrate provides an important insight about the evolutionary trends. The vertebrate embryos exhibit homologous characters during specific phases of development which suggest that vertebrates share a common ancestry. However, the adult forms differ from one another. For example, all vertebrates’ embryos have a tail and paired structure known as pharyngeal pouches. These pouches develop into gills in fishes and in reptiles, birds and mammals, it becomes structures of ears, jaws and throats.

Conclusion

The different lines of evidence of evolution helps to understand the basic link or connection between different groups of organisms. It is a scientific way of evaluating the ancestry of both the extinct and present organisms.