Table of Contents Link Unit 8 Ecology Student Notes Page 1 AP Biology Unit 8 Student Notes Table of Contents Link Unit 8 Ecology Student Notes Page 2 Unit 8 Student Notes Table of Contents A. Ecology Basics —Pages 3-4 B. Population Ecology—Page 5-17 C. Measuring Population Size—Pages 5-6 D. Patterns of Dispersion—Pages 6-7 E. Survivorship Curves—Page 9 F. Age-Sex Structures—Pages 10-11 G. Life History Strategies—Pages 11-12 H. Population Dynamics—Pages 12-18 I. Community Ecology—Pages 17-22 J. Interspecific/Interpopulation Interactions—Pages 17-21 K. Communication Between Organisms—Pages 21-22 L. Community Structure—Pages 22-25 M. Simpson’s Diversity Index—Pages 23-24 N. Ecological Succession—Pages 26-27 O. Ecosystem Ecology—Pages 27-40 P. Responses to the Environment—Pages 29-30 Q. Energy and Matter in Ecosystems—Pages 30-40 R. Energy Flow and Primary Productivity—Pages 36 S. Thermoregulation—Pages 36-39 T. Biogeochemical Cycles--Pages 39-44 U. Carbon Cycle—Pages 39-40 V. Nitrogen Cycle—Pages 41-42 W. Phosphorus Cycle—Pages 42-43 X. Water Cycle—Page 44 Y. Movement of Water Through a Plant—Pages 45-46 Z. Biological Magnification—Pages 46-47 AA. Ecology and Evolution—Page 47 Table of Contents Link Unit 8 Ecology Student Notes Page 3 Important Ideas/Enduring Understandings for This Unit Timing and coordination of biological mechanisms involved in growth, reproduction, and homeostasis depend on organisms responding to environmental cues. Transmission of information results in changes within and between biological systems. The highly complex organization of living systems requires constant input of energy and the exchange of macromolecules. Living systems are organized in a hierarchy of structural levels that interact. Communities and ecosystems change on the basis of interactions among populations and disruptions to the environment. Naturally occurring diversity among and between components within biological systems affects interactions with the environment. Evolution is characterized by change in the genetic make-up of a population over time and is supported by multiple lines of evidence. Competition and cooperation are important aspects of biological systems. Ecology Basics Ecology – Is the study of the interactions that occur between organisms and their environment. Ecologists also study how the distribution and abundance of organisms across the planet is affected by both abiotic and biotic factors. Abiotic factors –environmental factors that are not living. Abiotic factors include: temperature, light, water, nutrients, soil, and wind. Biotic factors – environmental factors that are living or are related to living things. Biotic factors include: bacteria, protists, fungi, plants, animals, competition, and symbiosis. Ecologists study the field of Ecology at five different levels: the organism level, the population level, the community level, the ecosystem level, and the biosphere level. At the organism level, ecologists study the adaptations that allow individual living things to live in specific environments. At the population level, ecologists study the size, density, and structure of groups of the same species that live in the same place at the same time. Table of Contents Link Unit 8 Ecology Student Notes Page 4 At the community level, ecologists study the interactions between different populations that live in the same area. At the ecosystem level, ecologists study the flow of energy and the recycling of nutrients in an area and how communities interact with the environment. At the biosphere level, ecologists study the interactions between ecosystems and how these interactions affect the entire Earth. Table of Contents Link Unit 8 Ecology Student Notes Page 5 The five levels of ecology (discussed above) were introduced from small to large. The levels build progressively— populations are made up of individual organisms; communities are made up of populations; ecosystems are made up of a community plus its environment; and so forth. Each level of organization has emergent properties, new properties that are not present in the level's component parts but emerge from the parts' interactions and relationships. Population Ecology A population includes all of the organisms of the same species that live in the same area at the same time and show signs of reproduction with each other. Demography is the statistical study of populations and how they change over time. Population Ecologists focus on the population size (N) (the number of individuals in a population) and population density (the number of individuals per unit of area or volume). These measures are both important for describing the status of a population and for making predictions about future changes that may occur. Measuring Population Size It typically isn’t possible or cost effective to count each member of a population. Scientists usually estimate the size of the population by taking samples from the population and using the samples to make inferences about the size of the actual population. The two most important sampling methods used in Ecology are the quadrat method and the mark-recapture method. Quadrat Method The quadrat method works best for immobile or slow-moving organisms. As part of the quadrant method, multiple small plots/quadrats of a habitat are staked off. All of the individuals within each quadrant are counted and the counts are used to estimate the population size or density for the entire habitat. Mark-Recapture Method The Mark-Recapture Method works best for mobile organisms. The process involves capturing a sample of the organisms and marking them with tags, paint, bands, etc… The marked organisms are then released back into the original environment. At a later time, a new sample is collected from the same environment. The new sample should include some of the marked individuals from the initial sample and some individuals that were never marked/captured. The ratio of the marked to unmarked individuals in the sample can be used to estimate the population size. Table of Contents Link Unit 8 Ecology Student Notes Page 6 Patterns of Dispersion Ecologists are also often interested in species dispersion patterns or distribution patterns. These patterns refer to how the individuals in a population are distributed in space at a given time. Types of Dispersion/Distribution Patterns A. Clumped/Aggregated/Clustered – In this pattern, individuals are clustered together in groups. This pattern is common in plants that drop their seeds on the ground and in animals that live in schools or herds. B. Uniform (evenly) – In this pattern, individuals are spaced evenly throughout a habitat. This pattern is common in animals that stake out and defend their territories. C. Random – In this pattern, individuals are distributed with no regular or predictable pattern. This pattern is common in plants that have wind dispersed seeds. Table of Contents Link Unit 8 Ecology Student Notes Page 7 Life Tables Life Tables summarize the birth and death rates for organisms at different stages of their lives. The data from these tables can be used to predict how a population is likely to grow or shrink in the future. The life table included below illustrates the life pattern of the Dall mountain sheep. Table of Contents Link Unit 8 Ecology Student Notes Page 8 Note: The age-specific mortality rate for each age interval was calculated by dividing the number of organisms who died in the interval by the number surviving at the beginning of the age interval. Table of Contents Link Unit 8 Ecology Student Notes Page 9 Survivorship Curves A survivorship curve is a graph showing the number or proportion of individuals surviving to each age for a given species or group (e.g. males or females). Survivorship curves are constructed for a given cohort (a group of individuals of roughly the same age) based on the data from a life table. There are three common types of survivorship curves: Type I individuals survive well early in life and generally live many years. At an advanced age, the death rate increases dramatically. Examples include large mammals. Type II individuals have a death rate that is relatively constant at any age. Examples include lizards, hydra, and some small mammals. Type III individuals initially have a rather low chance of survival. Those that do survive may live to an advanced age. Examples include many insects and fish. Table of Contents Link Unit 8 Ecology Student Notes Page 10 Age-Sex Structures The most important demographic characteristic of a population is its age-sex structure. Age-sex pyramids (also known as population pyramids) graphically display this information to improve understanding and ease of comparison. How to Read an Age-Sex Pyramid Graph An age-sex pyramid breaks down a population into male and female genders and age ranges. Usually, you'll find the left side of the pyramid graphing the male population and the right side of the pyramid displaying the female population. Along the horizontal axis (x-axis) of a population pyramid, the graph displays either the number of individuals of that age or a percentage of the population at that age. The center of the pyramid starts at zero population and extends out to the left for male and right for female in increasing size or proportion of the population. Along the vertical axis (y-axis), age-sex pyramids display five-year age increments, from birth at the bottom to old age at the top. Example Age-Sex Pyramid Table of Contents Link Unit 8 Ecology Student Notes Page 11 Countries with rapid population growth have a sharp pyramid shape in their age structure diagrams. That is, they have a large fraction of younger people, many of whom are of reproductive age or will be soon. This pattern often shows up for countries that are economically less developed, where lifespan is limited by access to medical care and other resources.