Chapter 15 Pages DARWIN’S THEORY OF EVOLUTION

The Puzzle of Life’s Diversity Life includes organisms of varying size, shape and habitat – this variety of living things is called ______________. ___________, or change over time, is the process by which modern organisms have descended from _________________. What is a scientific theory? Charles Darwin’s contribution to science was his numerous _____________ and collected ___________ that led him to propose the _____________________. Darwin searched for a scientific explanation for the ________________ on this planet. He noted that plants and animals were well suited to the _____________ that they inhabited. Given the endless grasslands of Australia, why were there no rabbits? England had a very similar environment as that of Australia, yet, why were there no kangaroos in England?

The Puzzle of Life’s Diversity ________ are the preserved remains of ancient organisms. Some resembled organisms that were “extant” – or still alive. Others appeared completely different! But why did they disappear? Were they related to extant species? Darwin was most interested in the Galapagos Islands because although the islands were very close together, they had different ________. What did he notice about the birds on the various islands of Galapagos? An important observation was that the animals and plants _________________ among the different islands.

Ideas That Shaped Darwin’s Thinking Observations made by scientists and non-scientists lead many leading experts of Darwin’s time to include not one but _______ periods of creation. Each of these periods seemed to be preceded by a __________________ that killed off many forms of life. Certain geologists argued that the Earth is ________________ and the processes that changed Earth in the past are the same processes that operate in the present. While we aren’t concerned with Hutton or Lyell, we do need to understand that, as geologists, their observations were important to Darwin’s conclusions about the __________ of species. If the Earth could change over time, might life change as well? _______ would be needed for life to change in such a way. ____________ was the first scientist to recognize that living things have changed over time and that all species were descended from other species. He proposed that by _________________ or ________ of organs, organisms acquired or lost certain traits during a lifetime. These traits would be __________ to their offspring and over time, this led to change in a species. This is termed among biologists as Lamarckian evolution. But what do you think? If an organism changes over their lifetime, despite their genetic make up, will they pass these traits to their offspring?

Ideas That Shaped Darwin’s Thinking A scientist named ____________ argued that the human population may continue to grow unchecked and that at some point, there would be insufficient living space/food for all. This is Malthusian theory.

Darwin Presents His Case Darwin found that the birds he was studying on the Galapagos islands were all of the same ________! Darwin’s published work on his study of biodiversity is called ______________. The mechanism for evolution is called ______________________. In artificial selection (meaning that humans govern what traits are desired), nature provided the ____________, and humans selected those ______________ that they found useful. _________________ means that members of each species compete regularly to obtain food, water sources and living space. Predators and prey play an important role in this competition. Consider the local population of deer vs. hunters. What would happen if deer weren’t hunted? Prey that are faster or better camouflaged survive __________ than those that are not. Predators that are faster or more equipped to obtain prey survive ___________ than those that are not. _______ is the ability of an individual to survive and reproduce in its environment. Fitness is the result of ___________. But what is an adaptation?

Darwin Presents His Case What are some examples of adaptions observed among living organisms? Low levels of fitness usually means that an organism will _____________. A differential between survival and reproduction is known as ____________________. According to Darwin, survival of the fittest = ______________________. This occurs without human _________ or _________. Over time, natural selection results in changes in the _______________________________ of a population. These changes _____________ a species’ fitness in its environment. Can natural selection be seen directly? Why or why not? ________________________ is the idea that every living species has descended with changes from other species over time. Take a few moments and in your own words, explain Darwin’s principle of common descent. (top of page 382)

Darwin Presents His Case Darwin argued that living things have been evolving on Earth for ________________. Evidence of this can be found in the ________________ which is a geographical distribution of _______________, homologous structures of _____________________, and similarities in ___________________ AKA _____________. Darwin saw fossils as a record of the _________________ on Earth. Since Darwin’s time, has the number of known fossil forms increased or decreased? What are vestigial organs? What fact about dolphins causes biologists to classify them as mammals instead of fish? The early stages (embryos) of many vertebrates (animals with backbones) are very __________. Embryonic cells develop in the same order and in similar patterns to produce the ________ and _________ of all vertebrates. These common cells and tissues produce _____________________.

Darwin Presents His Case

Darwin’s Theory Summarized: 1.Individual organisms _________ and some of this variation is __________ (which means?). 2.Organisms produce more offspring than can survive, and many that survive do not ___________. 3.Because more organisms are produced than can _________, they compete for __________ resources. 4.Individual organisms best suited for their ___________ survive and reproduce most successfully and pass their heritable traits to their ___________. 5.Species alive today are descended with ____________ from ancestral species that lived in the distant past. - Evolutionary theory continues to change as new data are gathered and new ways of thinking arise. There is still uncertainty about ______________________.