Name: ______________________Evidence for Evolution NoteTextbook: Section 8.2 (pages 332-228)

5 Key Evidences for Evolution:1. 2. 3. 4. 5.

1. Fossil Record– ______________________ (scientists who study fossils) have discovered

fossils of many ancestral life forms that link the past and present– Using microfossils, scientists have determined that life first evolved

approximately ___________________________– Fossils appear in _______________________________ in rock layers.– Fossils found in layers of rock closer to the surface (________________)

are much more ___________________ to species alive today than fossils found in deeper rock layers (_________________).

– Not all organisms appear in the fossil record at the same time. This shows that various organisms have evolved from other ancestral species

– See pg. 334 Figure 8.6– The “_________” process by which organisms are fossilized means that

the fossil record is not always as complete as scientists would like it to be.

– Fossil history suggests that the oldest vertebrates (back-boned animals) are fish. In recent layers of rock, you will find amphibians, reptiles, mammals and birds.

– ___________ ________________ _______________ _____________________

Transitional Fossils– These are fossils that ______________________________________– They show _____________________________ between ancient and more

recent fossils– Help scientists understand the evolutionary process and relationships

between groups of fossils

2. Biogeography– Biogeography is the study of the _____________________________ of past

and present (biological) organisms– Many of the observations Darwin and Wallace used to develop their

theories were based on biogeographical evidence

– Suggests that organisms evolve in _____________ and then spread out to other regions.

Biogeography: Example 1– Environments that are geographically _______ (ie; desert and forest in

South America) are _________________ to be populated by ___________ species than are locations that are geographically far apart but may be environmentally similar (ie; desert in Africa and desert in Australia)

– For example: cacti are only found in deserts in North, Central and South America, not in deserts in Africa or Australia

Biogeography: Example 2– Animals found on _________ often closely resemble animals found on

the nearest _______________ (mainland)– Suggests that animals on islands have evolved from mainland

migrants, with populations adjusting to the ______________________ of their new home over time

– Recall: Darwin’s Galapagos finches were more similar to finches found in South America than to those found in England

Biogeography: Example 3– Fossils of the ________________ can be found on the coastline of

__________________ _______________________

– The supercontinent Gondwana broke apart 150 million years ago, which explained how fossils of the same ancient reptile have been found in both Africa and South America.

3. Anatomical evidence: Homologous Structures– Homologous structures have _____________________, but may have

______________ _________________________ – Homologous structures are similar because they were inherited from a

______________ ______________________– All mammals have an almost identical number and arrangement of

bones– For example, the forelimbs of vertebrates contain the same set of

bones that are organized in similar ways.

Analogous Structures– Analogous structures evolve in organisms that live in similar

environments and perform ______________ ________________, but do not share a common ancestor

– For example, the wing of a bird and the wing of a butterfly have a common function but a very different internal anatomy

Analogous vs. homologous structures

Vestigial Structures– These are structures that serve __________________________ in a living

organism– They are reduced versions of structures that were functional in the

organism’s ancestors – Examples:

• Ear muscles and wisdom teeth in humans• Digits in dogs and horses• Hip bones in whales• Human appendix

4. Comparative Development: Embryology– Embryos have been studied to determine evolutionary relationships

between animals– In the development of an embryo, _________ traits appear before more

specialized traits– Embryos of many animals are similar in appearance during

____________________ of development due to similar genes at work– These similarities provide evidence of evolution from a common

ancestor– For example, vertebrate embryos show many similarities, such as the

gill slits, in the early stages of development. The most reasonable explanation for this is their _____________ ___________________.

– The gill slits in mammalian embryos mostly disappear later in development (except one which connects the pharynx at the back of the mouth to the middle ear), but their initial development provides evidence that mammals are descended from ______________________________ and that modifications have occurred in mammalian development through the course of evolution.

5. Molecular Evidence: DNA– Scientists can determine how closely organisms are related by

comparing the _______________________ in genes, and the sequence of amino acids and proteins

– 20 of104 amino acids occupy identical positions in all eukaryotic cells (19.2%) • Human vs. horse: differ in only 12 amino acids (88.5% similar) • Human vs. chimpanzee: identical

– ____________________ species have sequences that are ____________________ than distantly related species

– The greater the _______________________ from humans (yellow cladogram), the greater the number of amino acid differences in this sequence

– How might mutations in the DNA affect evolutionary processes….?