Evolution 101 Understanding Evolution for the Layperson Jack Krebs April 6, 2006 Co-sponsored by The Shawnee Mission Universalist Unitarian Church And Kansas Citizens for Science
Introduction Jack Krebs President, Kansas Citizens for Science Member, Kansas Science Standards Writing Committee (High School Life Science sub-committee chairperson) Longtime public school educator as a teacher, technology director, and curriculum director. Undergraduate degree in anthropology Main Sources for this course The Understanding Evolution website at UCMP. The Writing Committee s Recommended Standards
Outline 1. Introduction 2. The nature and format of this class 3. The nature of science 4. Evolution - what has happened, when, and how? 5. Speciation and micro/macro-evolution The conclusion is that all life is related by common descent with modification back to the beginning of life. The theory of evolution describes what has happened and how it has happened. Next week (tentative): Types of evidence for evolution, misconceptions and concerns about evolution, more discussion
Resources at KCFS News http://www.kcfs.org/kcfsnews http://www.kcfs.org/kcfsnews/?page_id=26
The Recommended Standards http://www.kcfs.org/kcfsnews http://www.kcfs.org/kcfsnews/?page_id=5
Understanding Evolution http://evolution.berkeley.edu/evosite/evohome.html University of California Museum of Paleontology
Navigating Evolution 101
The format of this course Presentation: We will summarize important concepts and conclusions about evolution from mainstream science. We will not debate young-earth or Intelligent Design creationism. This course is not intended to convince the doubter who wants proof that evolution is true. Facilitated discussion Questions directly related to the presentation Other questions: religious issues, creationism, politics, etc, Take breaks as needed. We will go until 9:00 without an official break, but we will take a three minute break at 8:30 for those who may be ready to go. Discussion forum at KCFS website: KCFS Forums. Details are on your handout. I will expect civil, thoughtful, and on-topic participation from all of us.
The Nature of Science Seeks natural explanations about the natural world. Use observations, testable hypotheses and inferences, and ultimately theories to describe and explain the world. Balances open-ended tentativeness with a solid core of well-established knowledge. Is supported by huge amounts of technical data that has been critically evaluated by numerous scientists over many centuries. Reaches its conclusion through multiple threads of evidence.
The historical sciences Science makes testable inferences based on evidence. Science assumes that the laws and processes of nature are the same in other places in the universe and at other times as they are here and now, unless we have evidence that conditions were different. The theory of evolution is supported by evidence from what happens to living creatures now and from evidence about what has happened in the past. (See The Historical Sciences are Testable, by Keith Miller, at http://www.kcfs.org/kcfsnews/?p=25)
The Pyramid of Knowledge
Evolution: what has happened, and how? 1. What has happened? - a brief timeline 2. How has this happened? a. Genetic variation and genetic change b. Natural selection 3. The interrelated nature of evolutionary change 4. Speciation, and macro/micro evolution
4 billion to 550 million years ago From http://www.pbs.org/wgbh/nova/origins/life.html, from Nova
550 million years ago to the present There has been a succession of species, most of which are extinct now. A history of the development of a succession of different but related features has been left behind in the fossil record.
Changes in the earth over time Layers of rock have been created through both constructive and destructive geological processes (sedimentation, erosion, etc.) The continents have changed due to plate tectonics. The climate and composition of the atmosphere have changed.
Mechanisms of Evolution - Genetic variation 1 Genes control the basic structure and nature of organisms. (Organisms have a genotype and a phenotype.) Genetic material is passed on from parent to child organism through various means of reproduction. Genetic changes occur as part of the reproductive process, causing variation from one generation to the next. Sexual reproduction produces variation by the combining of genes from the parents. Study the section on genetics at http://evolution.berkeley.edu/evosite/evo101/iiicgeneticvariation.shtml
Mechanisms of Evolution - mutations Other changes occur when chromosomes don t make exact copies as they divide when the gametes (sex cells) are produced. These are all referred to as mutations, but there are a number of different types. Insertions and deletions Frameshifts CTG CTG AGT TGC TGA GTC Duplications and re-alignments Getting genetic material from viruses
Other facts about mutations Mutations can be harmful, neutral, or immediately useful. Many mutations are neutral and therefore stay in the gene pool until some later time when other mutations occur. The randomness of mutations: Mutations are random in the sense that whether a particular mutation happens or not is not related to how useful that mutation would be.
Natural selection In any population of organisms, there is a spectrum of genetic variation, and thus variation in phenotypes. Organisms must work to survive, seeking water, food, shelter, mates, and so on, as well as avoiding becoming food for others. Organisms must reproduce in order to pass their genetic material on to the next generation. Survival is difficult: many more organisms are born than survive to reproduce Therefore, on average the organisms with qualities best suited to the environment survive to reproduce and raise their young. This differential reproduction rate changes the overall distribution of genes in the population: the average organism is different, and evolution has occurred.
Interrelated factors in evolution The environment changes sometimes slowly and sometimes quickly. Properties of organisms which are welladapted to one environment might be less so when the environment changes. Environmental changes will stimulate changes in populations of organisms. Organisms compete against other kinds of organisms for the same resources. In fact, sometimes organisms are in fact the resources other organisms are seeking. Therefore, other organisms are part of the environment that is constantly changing, because as one type of organism changes to be more adaptable, that becomes a factor in the evolution of other organisms. Organisms co-evolve, and in fact whole ecosystems evolve, not just species individually.
Classifying organisms and taxonomy Taxonomy is the human activity of naming and classifying organisms according to their characteristics and their evolutionary history. The basic unit of taxonomy is the species. In living sexually reproducing animals, species are roughly defined as populations of organisms that can interbreed. In asexual or extinct organisms, and in plants, determining species is much more difficult and can be somewhat arbitrary.
Family Trees from shared characteristics We classify organisms by shared characteristics. These characteristics exhibit nested hierarchies.
Family Trees from evolutionary history
Speciation Populations evolve over long periods of time and over many generations. There is no magic moment (no single generation or single birth) when species A becomes species B.
Transitional form and missing links
How does speciation happen?
Microevolution and macroevolution Microevolution is evolution on a small scale within a single population. (Within a population of a species.) Macroevolution generally refers to evolution above the species level. Macroevolution encompasses the grandest trends and transformations in evolution, such as the origin of mammals and the radiation of flowering plants. Macroevolution is evolution on a grand scale what we see when we look at the over-arching history of life: stability, change, lineages arising, and extinction. Macroevolution Microevolution
Common misconception about macroevolution Anti-evolutionists use macroevolution as a synonym for evolution of species. They claim this is fundamentally different than microevolution. Their denial of macroevolution is a denial of the fundamental conclusion of common descent. Evolutionary biologists use "macroevolution" to refer to a range of issues having to do with the pattern of evolutionary change: how groups are related to one another above the level of the species, and issues such as rates of change, the behavior of lineages over time, and so forth. But in the [Alabama] disclaimer, the term "macroevolution" means merely the general principle of evolution: that living things have descended with modification from common ancestors. This is not what macroevolution means in science, and it misleads and confuses students to use the term as a synonym for evolution. Biologist and textbook author Ken Miller
Primate family tree Human beings, like all animals, have evolved from ancestor species. We are related by common descent to all the rest of life on earth.
Human Evolution
Facilitated Discussion Session First half directly related to the material presented. Second half more open: religious and philosophical issues, youngearth and Intelligent Design creationism, state and national political issues, etc. There will be a short break at 8:30 to give you the opportunity to leave if you re ready to go. Civil, thoughtful, and on-topic behavior is expected. Keep your questions and comments short. Please respect my right and responsibility to manage the discussion. Hand in your questions at the end. Hand in your forum discussion information sheet if you wish.