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BIOB50 (Eco) - Chapter Notes.docx

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BIOL 2050
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BIOB50 – Ecology STUDY NOTES Chapter 1 The Web of Life:  Henderson, Minnesota: Leopard frogs (Rana pipiens) 11 of the 22 frogs were deformed (missing or extra limbs etc.)  30-40% of frogs deformed at pond (figure 1.1)  USA 46 states with deformed amphibian species… world-wide issue  1993 over 500 frog populations decreasing  1980, 9 amphibian species extinct, another 113 species not seen/”possibly extinct from 2009 (figure 1.2)  Reason for concern in amphibians compared to other organisms also disappearing: 1. Decline started recently 2. Decline is in protected or pristine regions, far from effects of human activities 3. Amphibians are good “biological indicators” of environmental conditions… a. Permeable skin (pollutants and other molecules can pass) b. No hair c. Scales d. Feathers to protect them e. Eggs lack shells or other protective coverings f. Lives spent on water and land… therefore wide range of potential threats: i. Water and air pollution, temperature changes, UV light Introduction:  Humans have enormous impact on planet o Global climate changes:  Introduced new species  Ocean deterioration – declined fish stocks, `dead zones`  Many more…  Natural systems are driven by the ways in which organisms interact with one another and with their physical environment  Ecology: the scientific study of how organisms affect and are affect by other organism and their environment BIOB50 – Ecology STUDY NOTES Connections in the Nature  Events in the natural world can be linked or connected to one another o They occur as organisms interact with one another and with their environment  Two organisms may live in the same area but have little influence on each other  All organisms are connected to features of their environment o Organisms interact with other species and physical environment as they pursue what they need to live…  Ex. Food, space and other resources  Species that do not interact directly with each other can be connected indirectly by shared features of the environment Early observations suggest that parasites cause amphibian deformities  Stephen Ruth: o Northern California : Pacific Tree Frogs (Hyla regilla) and Long-ted salamanders (Amystoma macrodactylum) with deformities  Stanley Sessions (amphibian limb development expert) o Found that all deformed amphibians had parasite Ribeiroia ondatrae (trematode flatworm)  Hypothesis: Parasite caused the deformities  Testing done: Small glass beads near developing limb buds of tadpoles o The beads were to mimic effects of Ribeiroia, produces cysts o 1990 reported that beads caused deformities similar to parasite A laboratory experiment tests the role of the parasites  Ruth had assumed deformities were isolated, local phenomenon o Ruth and Sessions found indirect evidence that Ribeiroia causes deformities  Pieter Johnson 1996: Set out to find direct test of whether Ribeiroia parasites can cause deformities o Surveyed 35 ponds, Pacific tree frogs in 13 pounds of which, 4 ponds contained deformed frogs  Two of the four ponds had no other source of pollution ( pesticides, PCB`s, heavy metals)  Dissection of deformed frogs from these pounds revealed Rebeiroia o They four ponds with deformities were the only ponds that had both tree frogs and an aquatic snail (Planorbella tenius) o Controlled experiment: experimental group and control group  Experimental group – has the factor being tested BIOB50 – Ecology STUDY NOTES  Control group – lacks the factor being tested  Johnson et al. collected H. regilla eggs from regions with no parasites  Tadpoles assigned at random to one of four treatments  0 (control group), 16, 32, or 48 Ribeiroia parasites  Observed:  Greater the number of parasites, fewer the tadpoles survived and more of survivors had deformities  In control group, 88% of tadpoles survived with no deformities  Link made, Ribeiroia could cause frog deformities  Since exposure to RIberiroia killed up to 60% of tadpoles  Results suggestsed parasites could contribute to amphibian declines Figure 1.3: The life cycle of Ribeiroia  6 stages of life cycle, three hosts (snails, larval amphibians or fish, and birds 1. In the snail, the parasite undergoes asexual reproduction to produce free- swimming cercariae a. Planorbella tenuis (first intermediate host) 2. The cercariae infect tadpoles and form cysts around their developing limb buds a. Amphibian (second intermediate host) 3. The cysts (metacercariae cysts) interfere with normal limb development, causing limb deformities 4. The limb deformities make the amphibian more vulnerable to capture by predatory birds (definitive host) 5. The parasite matures to adulthood in the bird’s body and reproduces sexually 6. Eggs in the bird’s feces are released into water, where they hatch into free-swimming miracidia that infect the snail Figure 1.4: Parasites can cause amphibian deformities  A graph that shows the relationship between the number of Ribeiroia parasites that tadpoles were exposed to and their rates of survival an deformity o Control group – 0 parasites, 88 % survival o Experimental groups:  16 parasites, 70% survival  32 parasites, 42% survival  48 parasites, 40% survival BIOB50 – Ecology STUDY NOTES A field experiment suggests that multiple factors influence frog deformities  Researches suspected other factors played role in deformities/decline o There were also pesticides in ponds found with deformed frogs  Joseph Kiesecker – Conducted experiment to examine possible joint effects of parasites and pesticides o Conducted field experiments in six ponds  All contained Ribeiroia, three ponds with pesticide, and three without  6 cages were placed in each pond  Three cages had a mesh which Ribeiroia could pass, while the other three had a mesh too small for parasites  Results:  No deformities found in frogs with small mesh size, in all ponds  Deformities found in some frogs with large mesh size  Every frog with deformity was infected by Ribeiroia o Ponds with pesticides had more deformities versus ponds with no pesticides (29% vs 4%)  Exposure to Ribeiroia was necessary for deformities to occur  When frogs exposed to Ribeiroia, deformities were common in ponds with pesticides than in ponds without pesticide o Hypothesized that pesticides might decrease the ability of frogs to resist infection by parasites  Testing done:  Reared frog tadpoles in environment with pesticide and other without pesticide and exposing all of them to Ribeiroia  Results showed tadpoles exposed to pesticides had fewer white blood cells (suppressed immune system) and higher rate of Ribeiroia cyst formation Figure 1.5: Do Ribeiroia and pesticides interact in nature?  To test effects of RIbeiroia and pesticides on frog deformities in field, screened cages placed in six ponds – three ponds contained pesticides, other three did not o Three cages in each pond had 75 µm mesh, too small for Ribeiroia  No tadpole deformities developed o Three cages in each pond had 500 µm mesh, Ribeiroia can go through  4% deformities developed in ponds with no pesticide  29% deformities developed in ponds with pesticide BIOB50 – Ecology STUDY NOTES Figure 1.6: Pesticides may weaken tadpole immune systems  Wood frog tadpoles exposed to low or high concentrations of pesticide esfenvalerate, then exposed to 50 RIbeiroia parasites o Two controls:  First with only parasites added to tadpoles container (control)  Both parasites and solvent used to dissolve the pesticide were added (solvent control) a) Numbers of eosinophils (type of white blood cell for immune response) 1. Tadpoles exposed to pesticides had fewer white blood cells b) Number of Riberioia cysts 1. Tadpoles exposed to pesticides had more RIberoia cysts than the controls A field experiment suggests that multiple factors influence frog deformities  Events in nature are interconnected o When people alter one aspect of the environment, we can cause other changes that we do not intend or anticipate  Increased our use of pesticides and fertilizers, we did not intend to increase the frequency of deformities in frogs  Indirect effects of humas o Local and global environment change, increased human health risks o Damming of rivers in Africa made habitat for snails with trematode parasites, increasing spread of infection that can weaken or kill people  Human actions are either direct or indirect o Direct – by urban or agricultural development o Indirect – Result of climate change Figure 1.7: Rapid spread of a deadly disease  Within 7 years, West Nile virus had spread from New York City to all but one of the 48 states of United States (Maine).  Birds are primary hosts, which explained the rapid spread  Mosquitoes transmit the disease from birds and other animal hosts to people Ecology:  Ecology – Scientific study of interactions between organisms and their environment o The interactions of organisms with one another, because organisms are an important part of one another’s environment o Other definitions:  Scientific study of interactions that determine the distribution (geographic location) and abundance of organisms BIOB50 – Ecology STUDY NOTES  Environmental science – interdisciplinary field that incorporates concepts from natural sciences (including ecology) and the social sciences (e.g., politics, economics, ethics) o Environmental scientists focus on how people affect the environment and how we can address environmental problems o Ecologists would examine pollution as one of several factors that influence reproductive success of wetland plants, while environmental scientists would focus on how economic and political systems could be bused to reduce pollution Public and professional ides about ecology often differ  There is a “balance of nature” o Natural systems are stable and tend to return to an original, preferred state after a disturbance  Each species in nature has a distinct role to play in maintaining that balance o Thus bringing morals and ethics into ecological systems  Eddenberg et al. 1995 states quote:  “There is a certain balance in nature, and there is a place for all species. There is a reason for their existence and we are not free to exterminate them.” Table 1.1: Some Ecological Maxims 1. You can never do just one thing a. Events in nature are connected and what affects one organism or place can affect others as well 2. Everything goes somewhere a. There is no away into which waste materials disappear 3. No population can increase in size forever a. There are limits to growth and resource use of every population 4. There is no free lunch a. An organisms energy and resources are finite, and increasing inputs into one function (reproduction) results in trade-off which is a loss for other functions (growth) 5. Evolution Matters a. Organisms evolve or change over time. Organisms adapt change in environments 6. Time matters a. Ecosystems change over time. Past affects present, and present affects future 7. Space matters a. Abiotic and biotic environment conditions change from one place to another. Organisms influenced by multiple spatial scales (local to regional to global) 8. Life would be impossible without species interactions a. Species depend on one another for energy, nutrients and habitat BIOB50 – Ecology STUDY NOTES The scale of an ecological study affects what can be learned from it  Ecologists draw boundaries around what they observe  Ecologists have appropriate scales for collections observations, including both time and space  Spatial scale: small or large o Centimeter to meter scales, or the entire Earth’s atmosphere  Time scale: short or long o Seconds to hours or centuries to millennia or longer Ecology is broad in scope  Ecologists study interactions in nature across many levels of biological organization o Some ecologists interested in molecules to organ systems o Ecological studies usually emphasize the following levels:  Individuals, populations, communities, ecosystems, landscapes, or biosphere  Population - group of individuals of a single species that live in a particular area and interact with one another  Community - association of interacting populations of different species that live in the same area o Many questions – how and why locations and abundances of populations change over time o Cover large or small areas, differ in numbers and types of species found within  Biotic – living components of a natural systems  Abiotic – physical environment o Temperature, precipitation, nutrients  Ecosystem – community of organisms plus the physical environment in which they live o Ex: Rate at which chemical enters particular community as well as how species living there affect what happens to chemical (Amphibian deformities)  Landscapes – areas that vary from one place to another, multiple ecosystems  Biosphere – All living organisms on Earth plus the environment which they live o Use satellite data to answer questions such as how do different ecosystems contribute to ongoing changes in global concentration of CO2in atmosphere Figure 1.8: An ecological Hierarchy  Individual – ex. Mexican gold poppy  Population – ex. Many Mexican gold poppy  Community – Interacting populations of different species  Ecosystem – interactions populations and environment  Landscape – multiple ecosystems, including steam ecosystem and desert ecosystem  Biosphere – All of Earths ecosystems BIOB50 – Ecology STUDY NOTES Figure 1.9: A few of Earths many communities a) Savanna in Kenya, male topi antelope stand on ant mound attracting mate b) Rainforest on Saint Lucia c) Dune in Namib Desert, Namibia, dry (2-85 mm precipitation per year) d) Shallow-water marine community off cost of Indonesia Some key terms are helpful for studying connections in nature Table 1.2: Key terms for studying connections in nature  Adaption – Feature of an organism that improves its ability to survive or reproduce in its environment  Natural selections – Evolutionary process in which individuals possess particular characteristics survive or reproduce at higher rate than other individuals because of those characteristics  Consumer – Organism that obtains energy be eating other organism or their remains  Producer – Organism that uses energy from external source (sun) to produce its own food without eating other organisms or remains  Net primary production (NPP) – Amount of energy (per unit of time) that producers fix by photosynthesis or
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