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# Study Guide Exam 1 Biology 2335 BIO2335

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This 14 page Study Guide was uploaded by Ashley Alexander on Saturday September 24, 2016. The Study Guide belongs to BIO2335 at Georgia Institute of Technology - Main Campus taught by Dr. Lin Jung in Fall 2016. Since its upload, it has received 3 views.

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Date Created: 09/24/16

1 Study GuideExam1Biology 2335 Ecological systems: levels of integration Organism (the most fundamental unit of ecology) Population (individuals of the same species in a particular area) Community (many populations of different species in a particular area) Ecosystem (assemblages of organisms together with their physical environment) Biosphere (the global ecosystem, all organisms and environments on earth) Experiment Example: • Observation: – Male frogs sing more often on nights after rains than on nights following fair weather. – Singing by the males attracts females – Hypothesis (one of several possible ones) – Female frogs actively search for males only after rains. • Experiment test: – Step 1: record male frog songs – Step 2: play the songs on nights with rains versus nights without rains (experimental vs. control) – Step 3: tally the numbers of females attracted to the calls on different nights • Data analysis – Statistical tests Case Studies: California sea otter & sea urchin https://www.youtube.com/watch?v=jORLckfzD80 Nile perch in Lake Victoria https://www.youtube.com/watch?v=kQrAx84gfs0 2 Population and Distribution The distribution of maple trees in eastern North America Why is a species present in some places and absent from others? 1. Dispersal limitation 2. Interactions with biotic factors 3. Interactions with abiotic factors Examples of Dispersal limitation: Zebra Mussles https://www.youtube.com/watch?v=E4Y5ILzKgHg 3 Gypsy moths: https://www.youtube.com/watch?v=d43J__U5fVc Examples of Biotic interactions: Rat Kangaroos and Red Foxes: https://www.youtube.com/watch?v=IVZoMSThQ00 Two Fruit pigeons Diamond (1975) proposed that the distribution of birds in the Bismark Archipelago, and particularly the fact that some pairs of bird species did not co-occur on the same islands (producing a checkerboard pattern), was evidence that competition between species limited their distributions. 4 Examples of Abiotic Reactions: Lolbolly Pine: https://www.youtube.com/watch?v=5EFAROH5E-8 Determining the source of limitation on species distribution: transplant experiments • Three treatments of a transplant experiment: – Control: no cage – Full cage: to exclude potential predators or competitors – Cage control (partially caged): • Some sides of the cage are removed to allow the access of predators or competitors • Purpose: account for the pure cage effect (e.g., shading) • Three possible outcomes: – (1) All transplants in both the controls and cages survive. – (2) All transplants in both the controls and cages die. – (3) All transplants in the controls die, but those in cages live. Two main abiotic factors limiting species distribution -Temperature and Precipitation Biomes: • A system of classifying ecological communities based on dominant plant forms. • Geographic distributions of biomes correspond closely to major climate zones. 5 Population Ecology: Definition of population: • A group of organisms of the same species occupying a particular space at a particular time. • The basic characteristic of a population is its size. Primary Population Parameters: Birth + + - Immigration Population size Emigration - Death 6 Dispersion: Dispersion of individuals within a population describes their spacing with respect to one another. A variety of patterns is possible: • The even spacing of desert shrubs in Sonora, Mexico • Vegetative reproduction gives rise to clumped distributions of aspen trees in Coconino National Forest, Arizona 7 Assessing population size: • Mark-recapture method: – Often used with animal populations. An initial sample is collected and all individuals are distinctively marked. Marked animals are released into the population and allowed to mix a second sample is collected and marked and unmarked animals are tallied. – For an initial marked sample of size M, a second sample of size C, containing R marked individuals, the population size N is: N = (M×C)/R Life Tables: • A life table is a summary by age, size, or life history stage of the survivorship and fecundity of individuals in a population • Life tables summarize demographic information in a convenient format, including: - age (x) - number alive at age x (N ) x - survivorship (l x: proportion of individuals surviving from the start of the life table to age x - Number dying during the age interval x to x+1 (d ) x - Age-specific mortality rate (q )x proportion of individuals dying during the age interval x to x+1 - Age-specific fecundity (F ):xthe number of offspring produced per individual during the interval x to x+1 • Cohort life tables - based on data collected from a group of individuals born at the same time and followed throughout their lives: - difficult to apply to mobile and/or long-lived animals • Static life tables - consider survival of individuals of known age during a single time interval: - require some means of determining ages of individuals 8 Construction of static life tables for the Dall mountain sheep in Denali National Park, Alaska • Olaus Murie used the distribution of ages at death to construct a static life table in the 1930s. • A total of 608 remains were recovered. • The size of the horns provided an estimate of age at death. Age in years Observed no. Proportion No. dying (x) alive (Nx) surviving at within interval start of age x to x+1 (x ) interval xx(l ) 0 608 1.000 121 1 487 0.801 7 2 480 0.789 8 3 472 0.776 7 4 465 0.764 18 5 447 0.734 28 6 419 0.688 29 7 390 0.640 42 8 348 0.571 80 9 268 0.439 114 10 154 0.252 95 11 59 0.096 55 12 4 0.006 2 13 2 0.003 2 14 0 0.000 0 9 Survivorship: Three types: Textbook page 230 Growth Rate calculations: The net reproductive rate, R , i0 the expected total number of offspring of an individual over the course of her life span. R = Σ(l F ) across all age classes. 0 x x R 0 1 represents the replacement rate R 0 1 represents a declining population R 0 1 represents an increasing population The generation time for the population is calculated as G = Σ(xl F ) x xl F )x x The intrinsic rate of increase is the exponential rate of increase (r) assumed by a population with a stable age distribution. Computation of r is based on R an0 G as follows: r = loge 0/G 10 When a population grows with constant schedules of survival and fecundity, the population eventually reaches a stable age distribution (each age class represents a constant percentage of the total population). Under a stable age distribution: - all age classes grow or decline at the same rate r - the population also grows or declines at this constant rate r Large values of R a0d small values of G lead to the most rapid population growth Intrinsic rate of increase (r): • r is a per capita rate • r = 0 represents a constant population size • r > 0 represents an increasing population • r < 0 represents a declining population • r is environment-specific: • Changes in environmental conditions may affect l and F xnd hencx r. Examples: Age structures of the human population influence population growth rates: Life table analysis helps to save the loggerhead sea turtle (Caretta caretta) making it clear to scientists that efforts to preserve juvenile seaturtles are much more beneficial to the specie’s intrinsic growth rate than efforts to increase the amount of hatchlings that make it to the sea. https://www.youtube.com/watch?v=t-KmQ6pGxg4 11 Population Growth: Two Models Exponential Growth: Appropriate when young individuals are added to the population continuously Geometric Growth: Appropriate when young individuals are added to the population at one particular time of the year or some other discrete intervals Experimental Population Growth: The equation describing exponential growth is: - dN/dt = rN This equation encompasses two principles: - The intrinsic rate of increase (r) expresses population increase on a “per individual basis” - The rate of increase (dN/dt) varies in direct proportion to N Exponential growth results in a continuously accelerating curve of increase. Population size over time: - N(t) = N(0)e rt - where: N(t) = number of individuals after t time units and N(0) = initial population size 12 Geometric Population Growth: The equation describing geometric growth is: N(t + 1) = N(t) where: N(t) = population size at time t N(t + 1) = number of individuals after 1 time unit = ratio of population at any time to that 1 time unit earlier, such that λ = N(t + 1)/N(t); geometric growth rate. To calculate the growth of a population over many time intervals, we multiply the original population size by the geometric growth rate for the appropriate number of intervals t: t N(t) = N(0) For a population growing at a geometric rate of 50% per year ( = 1.50), an initial population of N(0) = 100 would grow to ____________ in 10 years. Comparing Geometric and Exponential Growth Models: These models are related by: = e And log e= r 13 Exponential and geometric growth can describe increasing or decreasing populations Doubling Time: log e 0.693 tdoubling r r When Exponential Growth stops: The modified differential equation for population growth is the logistic equation: dN/dt = rN(1 - N/K) in which K is the carrying capacity of the environment for the population. 14 The logistic equation describes a population that stabilizes at its carrying capacity, K: populations below K grow populations above K decrease a population at K remains constant A small population growing according to the logistic equation exhibits sigmoid growth. An inflection point at K/2 separates the accelerating and decelerating phases of population growth.

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