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Lecture 1 & chapter 1

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Biology 2483A
Hugh Henry

Lecture 1 Chapter 1: The Web of Life Ecology 1. the scientific study of interactions between organisms and their environment 2. the scientific study of interactions that determine the distribution (geographic location) and abundance of organisms a. mechanisms of why  other meanings in public usage  differs from environmental activism and environmental science (solutions to environmental problems) o ecology is understanding how these systems work o environmental activism or environmental science apply this knowledge looking at solutions for our environmental problems general misconceptions: 1. balance of nature - return to original preferred state after disturbance i. some truth, but ecosystems are always dynamic, it’s always changing (climate, species) – humans can affect it beyond ability of return too 2. each species has a distinct role to play in maintaining that balance i. that and ecosystem functions as a organism – each species is an important organ - yes, some species are very important, but not all ii. it’s a beneficial to have a diversity of species, but it’s also redundant to have different species that are very similar (ex. Some trees in the rainforest almost exactly the same) – if one species is removed it does not change the function of the ecosystem Ecological Maxims (guiding principles): 1. Organisms interact and are interconnected a. you cannot fully observe all interactions, and you remove an organism from these interactions when doing a controlled lab study 2. Everything goes somewhere a. Pollution; Flow of nutrients and energy 3. No population can increase in size forever a. Why do they grow? & we know they will stop growing b. we understand the mechanisms that control the pop growth 4. Finite energy and resources result in TRADEOFFS a. Organisms have diff strategies – ex. Avoid being eaten --Physical defenses (spines) or behavioral adaptations. b. Tradeoff b/c when you invest energy & resources invested into any strategy, you take that energy away from somewhere else. c. IE. – no ideal strategy – all context dependent d. tradeoff is what we look at when we study the functions of organisms within their environment 5. Organisms evolve a. The key mechanisms driving a lot of patterns we see are based on the adaptations that the organisms developed over time b. Adaptations is a characteristic that improves survival or reproduction. (physiology, behaviours) – (mutation) c. Natural selection: Individuals with certain adaptations tend to survive and reproduce at a higher rate than other individuals. i. a process that favors CERTAIN adaptations based on who well suited they are to their environment. ii. ***If the adaptation is heritable, the frequency of the characteristic may increase in a population over time. iii. Mutation -> selection pressure -> change % in pop iv. These processes occur at the population scale, some unadaptive traits make it through to the next generation, but we look at the relative change/success of each adaption v. Relative change in the representation in the pop overtime is what drives natural selection. 6. Communities and ecosystems change over time d. This can occur quickly in microorganisms e. Forest trees (live 100-1000 yrs) – we’re less sensitive to these changes over time (harder to track) f. We’re biased in our perception of ecological change because of our short live spans & time we have to study things. 7. Spatial scale matters g. Micro to macro effects of interactions Ecological Hierarchy 1. Organism: Individuals 2. Population: Group of individuals of a single species, living & interacting in a particular area 3. Community: Clusters/associations of populations of different species, living & interacting in the same area a. Example: Savvanah, rainforest, sanddune communites i. group them off based on locations b/c certain communities associate with specific environments 4. Ecosystems: Community of organisms plus the physical environment a. The biotic part (the organisms, living components) added to the abiotic part (physical components) of natural systems. b. Looking at a single community, but now looking at nutrients, water, and all the aboitic commonents c. NOT simply a collection of communities  Landscapes = Collections of Ecosystems o Areas with substantial differences, typically including multiple ecosystems 5. Biosphere: ALL the world’s ecosytems a. living organisms on Earth, plus the environments they live in. i. ―Super ecosystem‖ *Complexity increases a lot as you move up through these different levels & take diff approaches Ecosystem processes  when looking at ecosystems, focus less on individual species, and we classify them in terms of their functions: plants & animals  producers & consumers  Producers: capture energy from an external source (e.g. the sun) and use it to produce food. o Net primary productivity (NPP): Energy captured by producers, minus the amount lost as heat in cellular respiration (the costs).  how much plant material you’re producing in a given time in a given area  the currency that we describe ecosystems & how much they’re producing  Consumers: get energy by eating other organisms or their remains How Ecosystems Work  Comparing the flow of energy (orange arrows) & nutrient cycle (green arrows)  Energy moves through ecosystems in a single direction only—it cannot be recycled. – it just passes through the system o sun -> translated by plants -> consumers  eventually lost to the system (ex. heat)  Nutrient cycle: nutrients are continuously recycled from the physical environment to organisms and back again o Taken up by plants, then eaten by other organisms, these organisms die and the nutrients make it back into the organic material in the environment, which is then taken up by plants again.  Energy & nutrients are both critical for organisms, but they work in the ecosystem is very different wants o We will look at how organisms have adapted to capture these Ecological Experiments:  Ecologists use experiments, observations, and models to answer ecological questions Experiments can be done at different scales: 1. Laboratory experiements: test for microbial activity in response to a particular stressor, temperature, ect. a. Good because you can control a lot, but you’re loosing realism 2. Small-scale field experiments: Mesoplasism study: take an artificial unit and put it into the field (intermediate study) 3. Large-scale field experiments: in a realistic environment & incorporating all the ecological complexity in it. -- Problem is you’re in control of so much less Design and Analysis 1. Assignments of treatments and control 2. Replication – # of treatments & controls a. Eliminates the possibility of other variables due to differences in each individual. 3. Random assignment of treatments a. Some cases you can’t do this – in preexisting differences/treatments i. Cannot use already polluted vs. unpolluted ponds 1. Must find unpolluted ponds and randomly pollute some 4. Statistical Analyses (statistical vs. biological significance) a. Even if there is a treatment effect of significant difference, is this even biologically important? - Examples: Insects have controls over plant community contribution because they feed dispropor
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