Lesson 1 Syllabus Reference Outcomes A student Explains how biological understanding has advanced through scientific discoveries, technological developments and the needs of society. Content The theory of evolution by natural selection explains the diversity of living things and is supported by a range of scientific evidence. Students: a. Describe scientific evidence that present-day organisms have evolved from organisms in the past. b. Relate the fossil record to the age of the Earth and the time over which life has been evolving. c. Explain, using examples, how natural selection relates to changes in a population, eg in the development of resistance of bacteria to antibiotics and insects to pesticides. d. Outline the roles of genes and environmental factors in the survival of organisms in a population. Copyright MATRIX EDUCATION 2014 Page 2 of 31 Our Students Come First!
1. History of Evolution Quick review of evolution In a very broad sense, evolution simply means change over time. However, this is not a very good working definition for purposes of Biology. This is because many processes in nature involve change over time, yet we would not classify them as evolution. Can you think of any examples? 1 A better, but still very simple, definition of biological evolution is changes in a population of a species over a long period of time. This brings us to modern evolutionary theory which holds that all organisms descended from a single common ancestor. This means that all organisms are related, if very distantly in some cases. This concept is often referred to as the Tree of Life. Source: http://tbi.montana.edu/outreach/hotscience/materials/ Copyright MATRIX EDUCATION 2014 Page 3 of 31 Our Students Come First!
In the diagram on the previous page, where would the common ancestor be? Label it in the appropriate place on the tree. 2 The complex diagram below illustrates just how complicated the evolution history is! Can you identify which part of the diagram humans belong in? Label the earliest common ancestor in this diagram. http://www.randalolson.com/research/ Watch a VIDEO (Length 6:29) about the Tree of Life (David Attenborough). When is life first thought to have begun? 3 Copyright MATRIX EDUCATION 2014 Page 4 of 31 Our Students Come First!
Important scientists Jean Baptiste Lamarck Lamarck was a French naturalist who made important early contributions to evolutionary theory. He believed that adaptations were developed by individual organisms based on inner need, becoming acquired characteristics which were passed on to offspring directly. For example, Lamarck thought that giraffes necks became longer between generations if parent giraffes had to stretch their neck further to reach higher leaves on trees. Source: http://sabrinafair2.tripod.com/evolutionproject/id9.html Based on Lamarckian theory, describe what your offspring would look like if you went to the gym every day and became a bodybuilder. 4 Generally speaking, Lamarck s theory has been proven to be incorrect and has been largely replaced by Darwin s theory. Copyright MATRIX EDUCATION 2014 Page 5 of 31 Our Students Come First!
Charles Robert Darwin Darwin was an English naturalist with an intense passion for studying the natural world. Darwin developed his ideas and gathered evidence while aboard the H.M.S. Beagle on a British science expedition around the world. In South America, Darwin found fossils of extinct animals that were similar to modern species. On the Galapagos Islands he noticed many variations among plants and animals of the same general type as those in South America. His real legacy was not proposing the idea of evolution; that was old news. Darwin s real breakthrough came in proposing a mechanism for evolution: the process of natural selection. Source: http://beforeitsnews.com/science-and-technology/2012/03/darwins-h-index-1847177.html Copyright MATRIX EDUCATION 2014 Page 6 of 31 Our Students Come First!
Upon his return to London, Darwin theorised that: a) gradual change over time did occur b) evolutionary change was very slow, requiring thousands to millions of years c) variation in a species occurs randomly and can be due to mutation d) the survival of each organism is due to its ability to cope in a changing environment i.e. the primary mechanism for evolution was natural selection e) the millions of species alive today all arose from a single original life form through a branching process called speciation In 1859, Darwin wrote his famous book called On the Origin of Species. Watch a short VIDEO (Length 3:37) on Darwin. How do you think society and politics may have affected the development of the theory of evolution over time? 5 Source: http://www.mun.ca/biology/scarr/mans_place_in_nature.html Copyright MATRIX EDUCATION 2014 Page 7 of 31 Our Students Come First!
2. Darwinian Evolution Darwinian theory of evolution The Darwinian Theory of Evolution proposes that evolution occurs as a function of survival of the fittest. How do you think we measure fitness? What would be the single most important factor for scientists in determining if an organism is fit? 6 This theory states that: More offspring are produced than can survive in a population, and, as population size tends to remain relatively constant, many offspring must die. Source: http://evolution.berkeley.edu/evolibrary/article/evo_25 Thus, there is a struggle for existence where the individuals who are better adapted to their environment will survive so that they have the opportunity to reproduce and pass on their genes to their offspring. Source: http://evolution.berkeley.edu/evolibrary/article/evo_25 Copyright MATRIX EDUCATION 2014 Page 8 of 31 Our Students Come First!
Over long periods of time (remember, life is thought to be 3.5 billion years old!), the more suited adaptations or favourable traits of individuals will become prevalent in the population. Source: http://evolution.berkeley.edu/evolibrary/article/evo_25 Gradually, as new adaptations accumulate, the population will become very different maybe even with new species. How would you be able to tell if the changed population was a new species? 7 _ NOTE TO STUDENTS: Evolution is the theory which explains how species evolve over time. It is not a theory which explains the origins of life. This is a common misconception both among scientist and theologians in the ongoing debate of creation versus evolution. Copyright MATRIX EDUCATION 2014 Page 9 of 31 Our Students Come First!
The following flow-chart should be used when answering questions on evolution. VARIATION a in population SELECTION PRESSURE DEATH of poorly adapted organisms (with unfavourable characteristics) SURVIVAL of well-adapted organisms (with favourabe characteristics) REPRODUCTION - passing on the favourable characteristics to offspring DOMINANCE - majority of the population contains the favourable characteristics NOTE TO STUDENTS: Flow charts are a great way to organise and present processes in science. You may be asked to draw flow charts to outline different processes in your workbook questions and even in later on, in HSC questions! Copyright MATRIX EDUCATION 2014 Page 10 of 31 Our Students Come First!
3. Divergent and Convergent Evolution What is a species? The word species gets thrown around quite a lot, but surprisingly it is often misunderstood. See if you can write a definition for species below: 8 You need understand two important processes that are often discussed when mentioning species: (i) Divergent evolution and; (ii) Convergent evolution. In a very general sense, what does it mean for something to diverge? Draw a diagram of lines diverging. 9 What does it mean to converge? Draw a diagram of lines converging. 10 Copyright MATRIX EDUCATION 2014 Page 11 of 31 Our Students Come First!
Divergent evolution Divergent evolution is the process where two or more related species become less similar that is, they diverge. It can develop to the point where one species slowly evolves over time into two (or more) different species. If this process of divergent evolution continues to the extent of creating a number of distinct species from a single common ancestor, the process is referred to as adaptive radiation. The ancestral species have been subjected to divergent evolutionary mechanisms a number of times and each new species has adapted and radiated out to fill specific ecological niches (e.g. eating from specific food sources). Darwin s Galapagos finches are the prime example. Source: http://mayhewbiology.com/biology%20notes/speciation%20notes.htm Copyright MATRIX EDUCATION 2014 Page 12 of 31 Our Students Come First!
Convergent evolution Convergent evolution is the process by which unrelated (or only distantly related) organisms evolve to become more similar in some regard (e.g. body form, colour, behaviour, organs, etc.). This is caused by the unrelated organisms being subjected to similar environmental conditions or ecological niches. A classic example of convergent evolution is the presence of wings in bats, birds, and insects. Source: http://archive.peabody.yale.edu/exhibits/treeoflife/convergent.html These organisms are only very distantly related as their last common ancestor would have been a very simple multicellular organism from many hundreds of millions of years ago WITHOUT any wings. This means the wings have arisen independently in each group of organisms (bats, birds, and insects) due to environmental conditions, allowing them to exhibit similar behaviours (flying). Copyright MATRIX EDUCATION 2014 Page 13 of 31 Our Students Come First!
PLEASE NOTE: Convergent evolution does NOT state that the organisms are evolving into one another bats are not slowly becoming birds or even more bird-like. Convergent evolution simply states that birds and bats have developed a similar trait (wings) and behaviour (flying) as a response to similar environmental conditions and to fill specific ecological niches. Another good example of convergent evolution is the long list of similarities between various marsupial and placental mammals. See the table below. These mammals are similar in body form as well as habitat requirements. Source: http://www.tokresource.org/tok_classes/biobiobio/biomenu/evolution/page14.jpg Copyright MATRIX EDUCATION 2014 Page 14 of 31 Our Students Come First!
4. Evidence for Evolution Palaeontology Recall that paleontology refers to the study of fossils. Here is a fossil of some ammonites found in some limestone. Source: http://www.geocaching.com/geocache/gc4m7y5_limestone-fossils-rockwood What are fossils? And what are some examples? 11 Can you remember how fossils form? 12 Copyright MATRIX EDUCATION 2014 Page 15 of 31 Our Students Come First!
Unfortunately, the chances of fossilisation occurring are relatively low. Most plants and animals leave no trace of their existence, and those that do are rarely found. This means that we have an incomplete fossil record of the organisms that lived in the past. By studying the fossil record, the evolution of different species can be traced over time. The fossil record shows a change from simple organisms in the oldest rocks, to complex organisms in the youngest rocks. Source: http://www.dmp.wa.gov.au/11881.aspx Copyright MATRIX EDUCATION 2014 Page 16 of 31 Our Students Come First!
When tracing the evolution of organisms through time, scientists often search for transition fossils. What do you think a transition fossil is? 13 Archaeopteryx was the first real example of a transitional fossil, and is probably still the best known. It is half-way between birds and reptiles. It had fully formed feathers, but otherwise had reptilian/dinosaur-like characteristics. Source: http://www.adirondackwildlife.org/feathers_or_flight.html Explain why the Archaeopteryx is considered a transitional fossil. 14 _ Copyright MATRIX EDUCATION 2014 Page 17 of 31 Our Students Come First!