Learning Guide Unit 3
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ENVS 1301 UNIT 3
February 15-21
Unit 3: Evolution and Sustaining Biodiversity
Topics
Evolution
Conservation and Biodiversity
Learning Objectives
Research how biodiversity and sustainable development are used for projects by organizations.
Examine the economic value of protecting natural ecosystems and their services.
Tasks
Read the Learning Guide and the Reading Assignment
Participate in the Discussion Assignment (post, comment, and rate in the Discussion Forum)
Make entries to the Learning Journal
Take the Self-Quiz
Take the Graded Quiz
Introduction
1.
Discovering How Populations Change
Evolution by natural selection arises from three conditions: individuals within a species vary, some of those variations are heritable, and organisms have more offspring than resources can support. The consequence is that individuals with relatively advantageous variations will be more likely to survive and have higher reproductive rates than those individuals with different traits. The advantageous traits will be passed on to offspring in greater proportion. Thus, the trait will have
higher representation in the next and subsequent generations leading to genetic change in the population.
The modern synthesis of evolutionary theory grew out of the reconciliation of Darwin’s, Wallace’s, and Mendel’s thoughts on evolution and heredity. Population
genetics is a theoretical framework for describing evolutionary change in populations through the change in allele frequencies. Population genetics defines evolution as a change in allele frequency over generations. In the absence of evolutionary forces allele frequencies will not change in a population; this is known as Hardy-Weinberg equilibrium principle. However, in all populations, mutation, natural selection, genetic drift, and migration act to change allele frequencies
2.
Mechanisms of Evolution
There are four factors that can change the allele frequencies of a population. Natural selection works by selecting for alleles that confer beneficial traits or behaviors, while selecting against those for deleterious qualities.
Mutations introduce new alleles into a population. Genetic drift stems from the chance occurrence that some individuals have more offspring than others and results in changes in allele frequencies that are random in direction. When individuals leave or join the population, allele frequencies can change as a result of gene flow.
3.
Evidence of Evolution
The evidence for evolution is found at all levels of organization in living things and in the extinct species we know about through fossils.
Fossils provide evidence for the evolutionary change through now extinct forms that led to modern species. For example, there is a rich fossil record that shows the evolutionary transitions from horse ancestors to modern horses that document intermediate forms and a gradual adaptation of changing ecosystems. The anatomy of species and the embryological development of that anatomy reveal common structures in divergent lineages that have been modified over time by evolution.
The geographical distribution of living species reflects the origins of species in particular geographic locations and the history of continental movements. The structures of molecules, like anatomical structures, reflect the relationships of living species and match patterns of similarity expected from descent with modification
4.
Speciation
Speciation occurs along two main pathways: geographic separation (allopatric speciation) and through mechanisms that occur within a shared habitat (sympatric speciation). Both pathways force reproductive isolation between populations.
Sympatric speciation can occur through errors in meiosis that form gametes with extra chromosomes, called polyploidy.
Autopolyploidy occurs within a single species, whereas allopolyploidy occurs because of a mating between closely related species. Once the populations are isolated, evolutionary divergence can take place leading to the evolution of reproductive isolating traits that prevent interbreeding should the two populations come together again. The reduced viability of hybrid offspring after a period of isolation is expected to select for stronger inherent isolating mechanisms.
5.
Common Misconceptions about Evolution
The theory of evolution is a difficult concept and misconceptions abound
The factual nature of evolution is often challenged by wrongly associating the scientific meaning of a theory with the vernacular meaning. Evolution is sometimes mistakenly interpreted to mean that individuals evolve, when in fact only populations can evolve as their gene frequencies change over time.
Evolution is often assumed to explain the origin of life, which it does not speak to
It is often spoken in goal-directed terms by which organisms change through intention, and selection operates on mutations present in a population that have not arisen in response to a particular environmental stress.
Evolution is often characterized as being controversial among scientists; however,
it is accepted by the vast majority of working scientists
Critics of evolution often argue that alternative theories to evolution should be taught in public schools; however, there are no viable alternative scientific
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theories to evolution. The alternative religious beliefs should not be taught as science because it cannot be proven, and in the United States it is unconstitutional
6.
Importance of Biodiversity
Biodiversity exists at multiple levels of organization, and is measured in different ways depending on the goals of those taking the measurements. These include numbers of species, genetic diversity, chemical diversity, and ecosystem diversity.
The number of described species is estimated to be 1.5 million with about 17,000 new species being described each year. Estimates for the total number of eukaryotic species on Earth vary but are on the order of 10 million. Biodiversity is
negatively correlated with latitude for most taxa, meaning that biodiversity is higher in the tropics. The mechanism for this pattern is not known with certainty, but several plausible hypotheses have been advanced.
Humans use many compounds that were first discovered or derived from living organisms as medicines: secondary plant compounds, animal toxins, and antibiotics produced by bacteria and fungi. More medicines are expected to be discovered in nature. Loss of biodiversity will impact the number of pharmaceuticals available to humans.
Crop diversity is a requirement for food security, and it is being lost. The loss of wild relatives to crops also threatens breeders’ abilities to create new varieties. Ecosystems provide ecosystem services that support human agriculture: pollination, nutrient cycling, pest control, and soil development and maintenance.
Loss of biodiversity threatens these ecosystem services and risks making food production more expensive or impossible. Wild food sources are mainly aquatic, but few are being managed for sustainability. Fisheries’ ability to provide protein to human populations is threatened when extinction occurs
7.
Threats to Biodiversity
The core threats to biodiversity are human population growth and unsustainable resource use.
To date, the most significant causes of extinction are habitat loss, introduction of exotic species, and overharvesting. Climate change is predicted to be a significant cause of extinction in the coming century.
Habitat loss occurs through deforestation, damming of rivers, and other activities.
Overharvesting is a threat particularly to aquatic species, but the taking of bush meat in the humid tropics threatens many species in Asia, Africa, and the Americas.
Exotic species have been the cause of a number of extinctions and are especially damaging to islands and lakes. Exotic species’ introductions are increasing because of the increased mobility of human populations and growing global trade and transportation.
Climate change is forcing range changes that may lead to extinction. It is also affecting adaptations to the timing of resource availability that negatively affects species in seasonal environments. The impacts of climate change are currently greatest in the arctic. Global warming will also raise sea levels, eliminating some islands and reducing the area of all others.
8.
Preserving Biodiversity
Five mass extinctions with losses of more than 50 percent of extant species are observable in the fossil record. Recent extinctions are recorded in written history and are the basis for one method of estimating contemporary extinction rates. The other method uses measures of habitat loss and species-area relationships. Estimates of contemporary extinction rates vary but are as high as 500 times the background rate, as determined from the fossil record, and are predicted to rise.
There is a legislative framework for biodiversity protection. International treaties such as CITES regulate the transportation of endangered species across international borders. Legislation within individual countries protecting species and agreements on global warming have had limited success; there is at present no international agreement on targets for greenhouse gas emissions
In the United States, the Endangered Species Act protects listed species but is hampered by procedural difficulties and a focus on individual species. The Migratory Bird Act is an agreement between Canada and the United States to protect migratory birds. The non-profit sector is also very active in conservation efforts in a variety of ways.
Conservation preserves are a major tool in biodiversity protection. Presently, 11 percent of Earth’s land surface is protected in some way. The science of island biogeography has informed the optimal design of preserves; however, preserves have limitations imposed by political and economic forces. In addition, climate change will limit the effectiveness of present preserves in the future. A downside of preserves is that they may lessen the pressure on human societies to function more sustainably outside the preserves
Habitat restoration has the potential to restore ecosystems to previous biodiversity
levels before species become extinct. Examples of restoration include reintroduction of keystone species and removal of dams on rivers
Zoos have attempted to take a more active role in conservation and can have a limited role in captive breeding programs. Zoos also have a useful role in education.
Reading Assignment
Read chapters 5, and 11 in the textbook and answer the 'End of Chapter Review Questions' in each chapter.
Discussion Assignment
This week I would like for you to find and review a project, organization or park related to protecting biodiversity through sustainable development. Preferably one that is near where you live. This could be a local group or non-profit organization that works to protect biodiversity. It could be a park, natural reserve, or conservation area. Or, it could be something else that is related.
To learn more about biodiversity and sustainable development read Why Biodiversity is Essential for Sustainable Development.
Study the information you have found, then answer the following questions:
1. What did you choose to cover? Please list the main link to the park/reserve/organization.
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2. Where is it located?
3. What is its mission?
4. Is there a sustainability development program in your local area that you are aware of? Describe the protected areas that are
covered in such programs if any.
5. How are human actions related to the problems they are working on?
6. In what ways could You participate in this project/reserve/organization you are reviewing?
Any materials cited should be referenced using the style guidelines established by the American Psychological Association (APA).
Learning Journal
Go to these weblinks and learn about ecosystem services, and also learn about the economic value of protecting natural ecosystems and their services.
The Ecological Society of America Costanza, R., et. al. (1997). The value of the world's ecosystem services and natural capital. Nature, 387, 253-260.
The United Nations: The Millennium Ecosystem Assessment & Humans
1. Of the different kinds of ecosystem services you learned about, discuss two that are important in your local area, village, forests
and/or nation.
2. How are these services endangered and what economic costs to society do you foresee with their loss?
For example, when people built homes and buildings over wetlands in Florida, then the wetlands
were destroyed. Normally, wetlands
are important to help control flooding, and without them, there were more floods and water damage in cities, which caused a lot of
economic costs to the citizens. So, now Florida is trying to restore many lost wetlands in order to
have the ecosystem service of flood
control returned.
3. What is one action that people could take to help protect these services?
4. One or two sentences or your own personal reflection on something you learned this week.
The Learning Journal entry should be a minimum of 400 words and not more than 750 words. Use APA citations and references if you
use ideas from the readings or other sources.
Self-Quiz
The Self-Quiz gives you an opportunity to self-assess your knowledge of what you have learned so far.
The results of the Self-Quiz do not count towards your final grade, but the quiz is an important part of the University’s learning process, and it is expected that you will take it to ensure understanding of the materials presented. Reviewing and analyzing your results will help you perform better on future Graded Quizzes and the Final Exam.
Please access the Self-Quiz on the main course homepage; it will be listed inside the Unit.
Graded Quiz
The Graded Quiz will test your knowledge of all the materials learned thus far. The results of the
quiz will count towards your final grade.
Please access the Graded Quiz on the main course homepage; it will be listed inside the Unit. After you click on it, the quiz’s introduction will inform you of any time or attempt limits in place.
Good luck!
Checklist
Read the Learning Guide and the Reading Assignment
Participate in the Discussion Assignment (post, comment, and rate in the Discussion Forum)
Make entries to the Learning Journal
Take the Self-Quiz
Take the Graded Quiz
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