Evolution and Biodiversity

1. Evolution and Biodiversity G. Tyler Miller’s Living in the Environment 14th Edition Chapter 5

2. Chapter 5: Essential Questions / Objectives Briefly describe the evolution of life from chemical evolution to the development of eukaryotic cells. Briefly describe the theory of evolution, being sure to include the roles played by variation within the gene pool and natural selection, extinction, speciation, and adaptive radiation. Describe the tools available to researchers for learning the evolutionary history of life. (evidence for evolution) Define natural selection and the three conditions that are necessary for evolution of a population by natural selection.

3. Summarize and address two common misconceptions about evolution. Define coevolution. Distinguish between a specialist and a generalist. Evaluate the conditions that favor these two approaches. Define ecological niche. Distinguish between condition and resource; fundamental niche and realized niche. List the factors that determine the realized niche. Define speciation and compare allopatric speciation with sympatric speciation. Indicate which of these mechanisms is more common.

4. Define extinction and distinguish between background extinction and mass extinction. Discuss the role of humans on the rate of extinction at present. Discuss the pros and cons of artificial selection and genetic engineering. Consider the possible environmental impacts on resource use, pollution, and environmental degradation. Indicate what it is that has allowed humans to have such a profound influence

5. Origins and Early Evolution of Life Chemical evolutionof organic molecules, biopolymers, and systems of chemical reactions were needed to form the first cell. It took about 1 billion years. Biological evolutionfollowed, from single-celled prokaryotic bacteria to single-celled eukaryotic organisms to multicellular organisms. Is has been continuing for 3.7 billion years. Knowledge of past life comes from fossils, ice-core drilling, chemical analysis, and DNA analysis. These records are incomplete

6. The Theory of Evolution - Widely accepted scientific idea that all life forms developed from earlier life forms. Although this theory conflicts with the creation stories of many religions, it is the way biologists explain how life has changed over the past 3.6 - 3.8 billion years and why it is so diverse today. The Five Parts of Darwin’s Theory of Evolution Perpetual Change Common Descent Multiplication of Species Gradualism Natural Selection Galapagos Islands satellite view.

7. Darwin’s Observations and Inferences: Observation 1 – Organism have great potential fertility Observation 2 – Natural populations normally remain constant in size except for minor fluctuations Observation 3 – Natural resources are limited Inference 1 – There exists a continuing struggle for existence among members of a population Observation 4 – All organisms show variation Observation 5 – Some variation is heritable Inference 2 – There is differential survival and reproduction among varying organisms in a population

8. What Drives Evolution ? Variation Meiotic mix Population Dynamics Mutations Struggle for Existence Competition Predation Selective advantage

9. Natural Selection Process by which a particular beneficial gene (or set of genes) is reproduced in succeeding generations more than other genes. The result of natural selection is a population that contains a greater proportion of organisms better adapted to certain environmental conditions. Conditions for Natural Selection Included: There is genetic variation within the population Traits must heritable – past from one generation to the next The adaptation allows the organism to better survive under prevailing environmental conditions. Differential reproduction- Phenomenon in which individuals with adaptive genetic traits produce more living offspring than do individuals without such traits.

10. Differential Reproduction Misconceptions about Evolution Evolution is the change in a population's genetic makeup over time. Therefore, population evolve not individuals Evolution is concerned with leaving the most descendants, NOT the strongest ones. There is no master plan to achieve genetic perfection.

11. Evolution and Adaptation Macroevolution: long term , large scale evolutionary changes through which new species form from ancestral species and other species are lost through extinction. “speciation” Microevolution: small genetic changes that occur in a population. “variation within a species” Genes mutate Individuals are selected Populations evolve Gene pool: a collection of genes potentially available to members’ offspring in the next generation “ genetic variability in a population” Sexual reproduction leads to random recombination of alleles from individual to individual. Coevolution: Interacting species can engage in a back-and-forth genetic contest in which each gains a temporary genetic advantage over the other. Evolutionary Arms Race

12. Mutation: random changes structure or number of DNA molecules in a cell that can be inherited by offspring. Mutations occur in two ways: Gene DNA is exposed to external agents like X rays, chemicals (mutagens), or radioactivity Random mistakes that occur in coded genetic instructions Only mutations in reproductive cells are passed to offspring. Many mutations are neutral; some are deadly; and a few are beneficial. Fruit fly (Drosophila melangoaster) Vestigial Wing. Fruit fly (Drosophila) adult, dorsal view

13. Types Selection Stabilizing Directional– demonstrated by the peppered moths Stabilizing – tends to favor the average Disruptive– may lead to speciation Disruptive

14. What Limits Adaptation? A population's gene pool and its rate of reproduction limit the population's ability to adapt to new environmental conditions. The only genetic traits that can adapt are those already in the gene pool. A population's reproductive capacity limits those genes that can adapt. Genetically diverse species that reproduce quickly can often adapt quickly. Populations that reproduce slowly take a long time to adapt through natural selection. For a new favorable trait to predominate, most of an existing population would have to die prematurely.

15. The Fossil Record as Evidence for Evolution FossilsSkeletons, bones, shells, body parts, leaves, seeds, or impressions of such items that provide recognizable evidence of organisms that lived long ago. Fossil of algae, Gunflint chert, 2.1 billion years old. Brightfield X400. Burgess Shale arthropod fossils, 530 years old, Middle Cambrian Period. Trilobite fossil from the Silurian period 405mya.

16. Comparative anatomy Darwin recognized the major source of evidence for common descent was found in the concept of homology. Homology is the name given to similarity of organs or structures due to common embryonic or evolutionary origin. Forelimbs of five vertebrates show skeletal homologies: Yellow --- Humerus Blue ---- radius and ulna Pink ---- wrist White ---- phalanges Clear homologies of bones and patterns of connection are evident despite evolutionary modifications for particular functions

17. Phylogenetic Reconstruction The phylogenetic pattern specified by 15 homologous structures in the skeletons of ratite (flightless) birds. The homologous features are numbered 1-15 and are marked both on the branches of the tree on which they arose and on the birds that them Simplified phylogenetic reconstruction of vertebrates

18. Transitional Species Whale evolution - the movement of the nostrils from the front of the skull to the top of the skull Why is having the nostrils at the top of the skull an advantage? Environmental changes require adaptations also. Organisms must be able to adapt to the new conditions, migrate to an area with a more favorable environment, or become extinct.

19. DNA Evidence for Evolution http://www.pbs.org/wgbh/evolution/library/03/4/quicktime/l_034_04.html

20. Ice cores unlock climate secrets Gases and particles trapped in the layers of an ice core provide information about the Earth's climate and atmosphere. Oxygen and hydrogen isotopes reveal the temperature when the ice formed, for example, while high carbon dioxide and methane levels indicate periods of global warming.

21. Geological Time and Major Evolutionary Events Modern humans (Homo sapiens) appear about 2 seconds before midnight Photosynthesis and Oxygen Origins of the Eukaryotic Cells The Cambrian Explosion Movement on to land Recorded human history begins 1/4 second before midnight Age of mammals Age of reptiles midnight Insects and amphibians invade the land Origin of life (3.6–3.8 billion years ago) First fossil record of animals Plants begin invading land noon Evolution and expansion of life

22. Ecological Niches and Adaptation An ecological niche is a species' way of life in an ecosystem, everything that affects its survival and reproduction. The niche includes the member's adaptations, its range of tolerance for physical and chemical conditions, its interactions with other components of the ecosystem, and its role in energy flow and matter recycling. This is NOT the same as the organism's habitat. The habitat is the physical location where a species lives. The fundamental niche is the full potential range of conditions and resources a species could use. Its realized niche is the part of the potential niche that allows a species to survive and avoid competition with other species for the same resources

23. Ecological Niches and Adaptation Fig. 5-4 p. 91

24. Broad and Narrow Niches Generalists Some species have broad ecological roles and are termed generalist species. Their living range is broad and includes many different places. They can eat a variety of foods and tolerate a wide range of environments. If the environment is changeable, the generalist will survive better than the specialist. Specialists Some species have narrow ecological roles and are termed specialist species. Specialist species can live only in very specific environments. This makes them more prone to extinction when environmental conditions change. If the environment is constant, specialists have fewer competitors. Intense competition may lead to evolutionary divergence of a single species into a variety ofsimilar species with specialized niches.

25. Speciation: A new species arises when members of a population are isolated from other members so long that changes in their genetic makeup prevent them from producing fertile offspring if they get together again. Fig. 5-7 p. 94

26. Speciation Natural selection can lead to development of an entirely new species. In speciation, two species arise from one when some members of a population cannot breed with other members to produce fertile offspring. Allopatric Speciation is the most common mechanism and occurs in two phases: Geographic isolation: physical separation for long time periods Reproductive isolation: the gene pools are so changed that members become so different ingenetic makeup that they cannot produce fertile offspring

27. Allopatric Speciation Exactly how speciation occurs is not well understood. Most biologists believe in Allopatric (“other place”) Speciation: A small population becomes geographically isolated in some way. Breeding only among themselves, its members evolve away from the ancestral Humans and chimpanzees diverged, it is believe, because the ancestral species was divided by Africa’s Great Rift Valley

28. Sympatric Speciation Sympatric Speciation is less common. It occurs when two species live close together but can't interbreed due to a mutation or subtle changes in behavior. Sympatric speciation can involve seasonal or habitat isolation- potential mates aren’t in the same place at the same time- or behavioral isolation, for example when a courtship ritual develops that appeals to some but not all. Northern Fence Lizard (Sceloporus undulatus hyacinthinus) male and female, showing sexual dimorphism.

29. Extinction When population members cannot adapt to changing environmental conditions, the species becomesextinct. A species manages to survive one to ten million years before extinction occurs. Life has had to cope with many major natural disasters that may reduce or eliminate species. Introduction of new species into an area has also led to reduction in number or elimination of species. When local environmental conditions change, some species will disappear at a low rate; this is called background extinction. Mass extinction is a significant rise in extinction rates above the background extinction level. Usually, from 25-70% of species are lost. Recent evidence suggests that there have been two mass extinctions on Earth. There appear to have been three mass depletions on Earth. Mass depletions are periods of extinction are higher than normal , but not high enough to classify as a mass extinction

30. Mass Extinction Adaptive radiations are recovery periods after mass extinction when numerous new species evolve to fill niches in changed environments. It takes one to ten million years to rebuild biological diversity after a mass extinction/depletion. Terrestrialorganisms 1600 Silurian Triassic Permian Jurassic Devonian Cambrian Ordovician Cretaceous Marineorganisms 1200 Carboniferous Pre-cambrain 800 Number of families Tertiary Quaternary 400 0 3500 545 500 440 410 355 290 250 205 145 65 1.8 0 Millions of years ago

31. Continental drift plays a role in speciation and extinction by isolating populations both geographically and reproductively LAURASIA LAURASIA PANGAEA PANGAEA GONDWANALAND GONDWANALAND MADA- GASCAR MADA- GASCAR AUSTRALIA AUSTRALIA ANTARCTICA ANTARCTICA 120° 80° 40° 80° 120° 120° 80° 80° 120° 135 million years ago 225 million years ago EURASIA NORTH AMERICA AFRICA 120° 80° 120° 120° 0° 40° 120° INDIA SOUTH AMERICA 65 million years ago Present

32. Evolutionary tree models Evolutionary tree diagrams interaction. Click to view animation.

33. Human Impact on Extinction The Earth's biodiversity is decreasing because of human activities. Biodiversity equals speciation minus extinction. Humans are causing the premature extinction of species, estimated to be 100 to 1,000 species per million species. It has been predicted that by the end of the 21st century we may see the extinction of half of the present species now on Earth. Humans and their activities are also destroying/degrading ecosystems that might be centers for future speciation.

34. Human Impacts on Evolution Artificial Selection Genetic Engineering Concerns about Genetic Engineering

35. What is the Future of Evolution? Man has used artificial selection to change the genetic characteristics of populations. We use selective breeding to obtain specific desired traits. Traditional crossbreeding is a slow process; it takes many generations of selection for the desired trait. Wild and cultivated roses illustrating artificial selection.

36. What is the Future of Evolution? Genetic engineering/gene splicing are techniques that isolate, modify, multiply, and recombine genes from different organisms. Genes from different species that would never interbreed in nature are being transferred to each other. Genetically modified organisms (GMOs)/transgenic organisms are the results of this gene splicing. Gene splicing takes half as much time to develop a new crop/animal, as does traditional crossbreeding. Cloningproduces a genetically identical version of an individual. Biopharming is a new field where genetically engineered animals act as biofactories to produce drugs, vaccines, antibodies, hormones, etc.

37. Phase 2 Make Transgenic Cell Phase 1 Make Modified Gene cell Identify and extract gene with desired trait gene Transfer plasmid copies to a carrier agrobacterium A. tumefaciens (agrobacterium) DNA Identify and remove portion of DNA with desired trait plasmid Agrobacterium inserts foreign DNA into plant cell to yield transgenic cell Plant cell Remove plasmid from DNA of E. coli Nucleus E. coli Host DNA DNA Foreign DNA Genetically modified plasmid Insert extracted DNA (step 2) into plasmid (step3) Transfer plasmid to surface microscopic metal particle plasmid Insert modified plasmid into E. coli Use gene gun to inject DNA into plant cell Grow in tissue culture to make copies

38. Genetic engineering is an unpredictable process and raises privacy, ethical, legal, and environmental issues. It is a trial and error process. The average success rate of genetic engineering experiments is about 1%. There are many questions about gene therapy: Who will be helped with genetic knowledge — only those who can pay for it? If one has a defect, will he or she be able to get health insurance, or a job? Should we clone spare parts for people's bodies? Phase 3 Grow Genetically Engineered Plant Transgenic cell from Phase 2 Cell division of transgenic cells Culture cells to form plantlets Transfer to soil Transgenic plants with new traits

39. Genetic Engineering A backlash developed in the 1990s against increased use of genetically modified food plants and animals. Proponents of more careful control of genetic engineering point out that most new technologies have had unintended, harmful consequences, so caution should be practiced regarding geneticengineering. What is the Future of Evolution? Humans have become such a powerful species so quickly due to two evolutionary adaptations: a complex brain and strong opposable thumbs. Humans have quickly developed powerful technologies to meet our needs and wants. Humans need to change our ways in order not to be called Homo ignoramusinstead of Homo sapiens sapiens, the doubly wise.

40. Resources: http://www.pbs.org/wgbh/evolution/