Download 8.2: Evidence for Evolution: Fossils and Biogeography

8.2: Evidence for Evolution: Fossils and Biogeography
Fossil Record: shows the kinds of organisms that were alive in the past, where they lived, when they
became extinct, and the order that they appeared in history.
Fossils are the preserved remains or traces of animals, plants, and other organisms from the remote
past.
Fossils are found in sedimentary rock, older fossils are found in the deeper rock and younger fossils are
closer to the surface. Different fossil are found at different levels in the sedimentary rock. This is
evidence that not all life forms were in existence at the same time.
Transitional Fossils: show organisms with similarities to two groups. They provide evidence that the two
groups are related.
Vestigial Structures: in fossils also provide evidence for evolution. Scientist believe that vestigial
structures once functional in a common ancestor.
The fossils found within the sedimentary rock are only a fraction of what once occupied Earth. Many of
the species’ remains were simply destroyed
Biogeography: is the study of how organisms are distributed throughout the world.
Biogeography supports the idea that species evolved in one location and then spread out to other
locations that are now geographically separate but similar in environment. For example;
- Geographically close environments are more likely to be populated by related species than
are locations that are geographically separate but environmentally similar.
- Animals found on islands often closely resemble animals bound on the nearest continent
- Fossils of the same species can be found on the coastlines of neighbouring continents.
- Closely related species are almost never found in exactly the same location or habitat.
Learning Check:
1. Explain these two apparently contradictory statements:
Statement 1: Evidence from the fossil record is unique, because it provides a time perspective for
understanding the evolution of life on Earth.
Statement 2: The fossil record is incomplete and working with it is like trying to put together a jigsaw
puzzle with missing pieces.
2. The human appendix is the small organ that represents the caecum. In most vertebrates, the caecum
is a large, complex organ of the digestive system. In herbivorous mammals such as mice, the caecum is
the largest part of the large intestine and functions in the storage and digestion of plant material.
a) In evolutionary terms, what is the human appendix?
b) How can the appendix provide evidence of human evolution?
3. The plains of North and South America and the plains of Africa have similar environmental conditions
but different mammals. Use what is written in this study guide and your textbook, as well as what you
know about geology and the movements of the continents; to infer why there are zebras in Africa but
not in North and South America.