Biological Evolution Fossils present but rare Evolution and expansion of life Fossils become abundant Plants invade the land Age of reptiles Age of mammals Insects and amphibians invade the land Modern humans (Homo sapiens) appear about 2 seconds before midnight Recorded human history begins 1/4 second before midnight Origin of life (3.6–3.8 billion years ago)

Fossil Record Most of what we know of the history of life on earth comes from fossils (SJ Gould) Give us physical evidence of organisms Show us internal structure Uneven and incomplete record of species We have fossils for 1% of species believed to have lived on earth Some organisms left no fossils, others decomposed, others have yet to be found. Other info from ancient rocks, ice core, DNA The whale as an example Other evidence here

4 major mechanisms that drive evolution: Natural Selection Mutation Gene Flow Genetic Drift

Evidence of Evolution The Fossil Record Geographic Distribution of Living Things Homologous Body Structures Similarities in Early Development

Fossils The fossil record shows that: Things existed in the past that no longer exist today and Things exist today that did not exist in the past. The fossil record is a record of change in the composition of the biosphere over time.

What is a fossil?

Fossils are rare Most organisms are eaten or decay after death. Fossils only form in places where there is little erosion: lake bottoms, deep oceans, etc. We have little fossil record of beach organisms and alpine communities.

Some fossils show transition Because fossils are rare, and change can be rapid, there are few “missing links” in the fossil record. However, some fossil sequences of marine organisms do show good evidence of transition from one form to another.

Transitional Fossils Adaptations

What are transitional fossils? A transitional fossil may be defined as a fossil which exhibits traits common to both ancestral and derived groups. This is especially important when groups are sharply differentiated. They can show how a species might adapt to survive their new conditions.

Importance: Transitional fossils are often used to test theories of species development. These theories include broad shifts in habitat use (aquatic to terrestrial organisms) or shifts in physical characteristics within a species or group of species (development of hard shells in trilobites).

How can I see this now? Plants can adapt to change to the conditions of climate. We see this in drought resistant plants. Transitional fossils are more about the species natural ability to adapt instead of the act of genetic engineering (humans altering a species).

Fish compared to land animal The jaws of some fish might resemble animals that live on land, thus leading some scientists to believe that some fish adapted to live on land. Some scientists use the word evolve for the word adaptions.

Transitions from pre-mammal to mammal…

Human Adaptations Human skulls have increased in size Other ways in which humans have adapted include growth. Humans are now much taller today than they were a hundred years ago.

Comparative Anatomy Comparative Anatomy includes Homologous and Analogous structures as well as vestigial features. Comparisons of anatomical features in different organisms often provides evidence to support the theory of evolution. As Organisms are often classed together according to similarities in their structures. It was through comparing the anatomy of organisms that scientist discovered phylogeny, meaning the evolutionary history of a group of organisms. “What can be more curious than that the hand of a man, formed for grasping, that of a mole for digging, the leg of a horse, the paddle of the porpoise, and the wings of the bat, should all be constructed on the same pattern, and should include the same bones, in the same relative positions. -Darwin.

Homologous Structures Homologous structure are structures that share a common origin but may serve different functions in modern species. These structures are evidence that organisms with similar structure evolved from a common ancestor. Examples include the forelimbs of a variety of mammals. For example, human, cat, whale and bat.

Homologous Structures These species show the same skeletal elements. Is in the humorous, radius and ulna. However these skeletal elements have been modified over time to suit the different functions suitable for the type of mammal. Homologous structures result from divergent evolution meaning their ancestral lines started out fairly similar, but evolved along different paths, becoming more different over time.

Structures that are similar due to evolutionary origin, such as the forearm bones of humans, birds, porpoises, and elephants, are called homologous

Birds and Reptiles Both have scales Reptile fossils most common to modern birds 2017/12/24

Analogous Structures Analogous structures are a contrast to homologous structures. They serve the same function between organisms but are different in internal anatomy. Such as the wings of birds and butterflies or the eyes of lobsters and fish. These structures are of no use in classifying organisms or in working out their evolutionary relationships with each other. www.encarta.com Figure 4

Vestigial Structures Refers to an organ or part (for example, the human appendix) which is greatly reduced from the original ancestral form and is no longer functional or is of reduced or altered function Are often homologous to structures that are functioning normally in other species provide a clue to the evolutionary history of a species because they are remnants of structures found in the ancestral species.

Embryology  Different species often have very similar embryos, even if the adult forms are quite different.

Video http://www.youtube.com/watch?v=kfTbrHg8KGQ