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Bio1B-MT3-review - Bio 1B Section 120 Review for...

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N ( t + 1) = N ( t ) + r N ( t ) K - N ( t ) K Bio 1B Section 120 May 11, 2005 Review for Midterm #3 (Ecology) Topic Points # questions Ecology (Midterm #3) 100 40 Ecology (final) 50 20 Evolution (final) 50 17 Plants (final) 50 17 Logistics: There will be no clear distinction between Midterm #3 and the final; you will get one single packet of test questions and one Scantron sheet. You will have slightly more time on this exam (1.5 points per minute) than on the previous exams (2 points per minute). Scope of the exam: All of Dr. Resh’s lectures will be covered on this exam. If he didn’t mention it in class , it won’t be on the test . You do not specifically need to focus on material from the textbook, lab manual, or PDF lecture handouts; use these only as an aid to understand the lectures. Note, the handouts do not always match what Dr. Resh covered in lecture. His sample exam questions are not representative of the topics on the midterm, except to indicate his writing style. For question topics, see the Section 106 practice exam. General themes - Ecology (definition): Study of how organisms interact with each other and with their environment. - There are many connections between ecology, plant biology, and evolution. - Ecology deals with the most complex systems of any of the biological sciences. Population growth - A population is a group of individuals (of one species) that are located in a given area and are interbreeding. E.g. bacteria in Petri dish; humans on Earth. - With no limits, population growth would be exponential, but in reality it is logistic: - Logistic growth equation: where: N(t) = number of individuals now (at time t ) N(t+1) = number of individuals in the future (at time t +1 ) r = net reproductive rate (i.e. birth rate - death rate) K = carrying capacity (determined by resources in the environment) Damselfly nymph and adult. Source: www.epa.gov/owow/nps 1 time pop time pop EXPONENTIAL LOGISTIC
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- This can also be expressed as: - Be sure you understand all the terms above, especially r and K . r sometimes includes immigration and emigration as well as birth/death. When r = 0, there is no population growth. K is the maximum number of individuals the environment can support. It’s hard to figure out K except by direct observation. - Theoretically, a population will eventually reach K and fluctuate slightly around it. - Birth rate and death rate are affected by some factors that are density-independent (i.e. it does not matter how crowded the individuals get) and some that are density- dependent. For example: Death due to drought = density-independent Death due to disease = density-dependent - The population levels off at K because of density-dependent factors. -
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Bio1B-MT3-review - Bio 1B Section 120 Review for...

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