Topic outline: Review: evolution and natural selection Evolution 1. Geologic processes 2. Climate change 3. Catastrophes Niche Speciation Extinction Biodiversity Genetic engineering
http://www.cengage.com/cgi-wadsworth/course_products_wp.pl?fid=m20b&product_isbn_issn=9780495015987&discipline_number=22 How do we know what organisms lived in the past? Fossils-record of evolutionary change in life forms over time. Ice-core drilling-examine kinds of life found at different layers Chemical/DNA analysis
Evolution (recap) Evolution = change in a population's genetic makeup over time. Mechanisms for evolution: Natural Selection (including coevolution) Mutation (some are neutral, negative, others beneficial) Migration Genetic drift (bottleneck and founder effect) Horizontal gene transfer *microorganisms
Sexual Reproduction is adaptive--maintains genetic diversity in a population Genetic diversity is important to be able to adapt to constantly changing and challenging environment. Remember traits are passed from parent to offspring (vertical gene transfer) Some microorganisms can exchange genes without sexual reproduction by horizontal gene transfer Adaptations can occur quickly--doesn't require generations. Confounds phylogenetic trees http://www.nature.com/nrmicro/journal/v4/n1/fig_tab/nrmicro1325_f2.html
Changes in the environment necessitates adaptation by natural selection. Geologic processes Climate change Catastrophes
Geologic Processes Tectonic plates Alfred Wegener The Earth's lithosphere is broken up into a series of giant solid plates. These plates sit on the asthenosphere (a layer of molten rock) and drift across the Earth's surface. http://www.rsc.org/education/teachers/resources/jesei/platerid/plates.htm
Geologic Processes Tectonic plates Effect on evolution: http://www.rsc.org/education/teachers/resources/jesei/platerid/plates.htm 1) Locations of continents and oceans influences earth's climate -->distribution of animals and plants. 2) Separation and joining of continents have allowed species to move, adapt to new environments, and form new species by natural selection. 3) Volcanic eruptions (at plate boundaries) destroys habitats and reduce or wipe out populations. Opens up habitat to be repopulated. Lava can yield fertile soil (rich in nutrients like phosphorous and other minerals) 4) Earthquakes can separate and isolate populations (leads to speciation)
Climate Change Repeated changes in earth's climate throughout history. Alternating periods of cooling and heating -Ice age and interglacial periods http://geology.utah.gov/surveynotes/gladasked/gladice_ages.htm
Climate Change Effects on evolution: 1) Determines where plants/animals can live (distribution) 2) Changes distribution of ecosystems--deserts, grasslands, forests, etc. 3) Some species become extinct when climate change occurs rapidly.
Catastrophes Asteroids and meteorites Asteroids and meteorites collide with earth. Impact causes destruction of ecosystems and extinction of species Effects on evolution: 1) Long period of environmental stress--wipe out species and habitat 2) Mass extinctions open up opportunities for new species
Ecological Niche Every species has a ecological niche, or a specific role in the ecosystem. > Where it lives/grows (habitat) > Where it reproduces and how > What it eats, how it eats. > How it interacts with other species and environment. > "How an organism makes a living"
Ecological Niche Fundamental niche - the full potential range of physical, chemical, and biological conditions and resources a species could theoretically use if it could avoid competition from other species. Realized niche - the actual niche a species occupies. Is only a part of the fundamental niche. Experiment by Joseph Connell \\ Figure 53.13, page 1117, Campbell's Biology, 5th Edition http://www.hammiverse.com/lectures/53/1.html
Ecological Niche Generalist species have broad niches. Can live in different places, eat many types of foods, tolerate wide range of environmental conditions. Better able to survive changing environment. Specialist species occupy narrow niches. Use only one/few types of food, tolerate narrow range of environmental conditions. More prone to extinction Low competition.
Specialist species can allow for resource partitioning. Resource partitioning reduces competition and allows sharing of limited resources. October 02, 2013
When different species compete for scarce resources, what is likely to happen due to natural selection? Increase in specialized species. Reduces competition and sharing of limited resources.
How do new species evolve? We just saw an example of how competition can lead to specialization of ecological niche. How does this lead to evolution of new species? What are the mechanisms of speciation?
Speciation = formation of new species. Two species arises from one. For sexually reproducing species--when some members of a population can no longer breed with other members to produce fertile offspring. http://evolution.berkeley.edu/ evolibrary/article/0_0_0/evo_42
Mechanism of Speciation Reproductive isolation is the key to speciation-- barriers to gene flow allow genetic differences to accumulate and result in different species. Reproductive isolation may occur due to Different mating location, time, or rituals. Lack of "fit" between sexual organs. Offsprings not viable or fertile. These damselfly penises illustrate just how complex insect genitalia may be http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_44
Mechanism of Speciation Why does reproductive isolation occur? Reduced gene flow! 1) Allopatric speciation: Geographic Isolationmembers of the same population become physically isolated. Adapt to different environmental conditions > physical barriers (mountain range, stream, lake, road) > volcanic eruptions > earthquake > individuals taken away by wind or water http://evolution.berkeley.edu/evosite/evo101/vc1ballopatric.shtml
Mechanism of Speciation Why does reproductive isolation occur? Reduced gene flow! 2) Peripatric speciation A small number of individuals move into a new niche, and by chance (think genetic drift), have genes that are rare in the original population.
Mechanism of Speciation Why does reproductive isolation occur? Reduced gene flow! 3) Parapatric speciation No extrinsic barrier to random mating, but population mates non-randomly over a large geographic area. More likely to mate with others in same geographic location within population. Although continuously distributed, different flowering times have begun to reduce gene flow between metal-tolerant plants and metal-intolerant plants. http://evolution.berkeley.edu/evosite/evo101/vc1dparapatric.shtml
Mechanism of Speciation Why does reproductive isolation occur? Reduced gene flow! 4) Sympatric speciation Does not require large-scale geographic distance (physical isolation). Disruptive selection. http://evolution.berkeley.edu/evosite/evo101/vc1esympatric.shtml
Mechanism of Speciation These mechanisms of speciation occur very slowly-- over many years. There are other mechanisms of evolution that can happen quickly (in one generaiton) 1) Hybridization Two individuals of different species are able to mate and produce viable offspring. (often happens in plants by polyploidy). 2) Horizontal gene transfer
Extinction Also affects number of species on earth. Extinction = entire species ceases to exist. Why might a species become extinct? Populations cannot adapt to changing environmental conditions. What kinds of species are more likely or more vulnerable to extinction? Endemic species = species that are only found in one area. (Islands, small unique areas, highly specialized)
All species eventually become extinct. background extinction = ongoing extinction of species dues to changes in environmental conditions. Estimated to be about 1-5 species for each million species on earth. mass extinction = widespread event of high extinction rate. Large groups of existing species (25-70%) are wiped out. Estimated there have been 5 mass extinctions during past 500 million years. mass depletion = extinction rates higher than normal but not high enough to be considered mass extinction.
When a mass extinction or mass depletion occurs, what generally occurs afterwards? Gives other species opportunity to fill previously occupied niches or newly created ones!
Biodiversity = speciation - extinction Why is biodiversity important for the ecosystem?
Human Effects on Earth's Biodiversity Human activities are decreasing earth's biodiversity. Why?
Predictions by Stuart Primm and Edward O. Wilson (2005 Millenium Ecosystem Assessment) Extinction rates have increased 100-1,000 times natural background extinction rates. by 2030: premature extinction of 1/5 earth's species. Can we recover from these major losses? Species formed over millions of years. Humans are depleting and destroying habitats with in years.
Artificial Selection and Genetic Engineering Artificial selection = selective breeding. Humans breed certain animals or plants for certain traits. http://en.wikipedia.org/wiki/selective_breeding http://en.wikipedia.org/wiki/file:cornselection.jpg
Artificial Selection and Genetic Engineering Genetic engineering = alteration of an organism's genetic material through adding, deleting, or changing segments of its DNA to produce desirable traits or eliminate negative ones.
Artificial Selection and Genetic Engineering recombinant DNA = DNA that has been altered or contain gees or portions of genes from organisms of different species. GMOs or transgenic organisms = organisms that have been genetically engineered using recombinant DNA Synthetic biology = use fundamental components of other organisms to build new organisms.
For Homework: Please look up 3 examples or uses of genetic engineering that is relevant to environmental science. Then identify 1) What is the genetically modified organism? 2) What is the goal or purpose of developing the GMO? 3) What is the origin of the recombinant DNA? 4) What are some opinions or evidence that supports or refutes the use of these GMO's? 5) What are your opinions about the GMO? 6) Cite your sources.
Some ideas to get you started: Various crops (tomatoes, corn, strawberries, wheat, rice, potatoes, plums...) Mosquitoes Bacteria (many many different products) Algae Salmon Livestock (pigs, cows, goats).