SLG-10.1 Properties of Population PDF
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Philippine Science High School System
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This document details a learning guide on population properties. It describes the relationship between species and populations, and discusses factors impacting dispersion and density. It includes examples and figures. The document appears to be a learning guide for high school students, likely in a biology course.
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INTERACTION BETWEEN LIVING AND NON-LIVING THINGS PROPERTIES OF POPULATION At the end of this module, you should be able to: 1. describe the relationship between population and species (C8.A.1), and 2. describe how external factors (environmental, social) relate to population...
INTERACTION BETWEEN LIVING AND NON-LIVING THINGS PROPERTIES OF POPULATION At the end of this module, you should be able to: 1. describe the relationship between population and species (C8.A.1), and 2. describe how external factors (environmental, social) relate to population dispersion and density (C8.B.1). If you happened to watch the movie, Finding Nemo, you would probably be able to recognize the organisms found in the picture below. Figure 1. This photo is The clownfish hanging out with sea anemones by Michael Arvedlund, 2007 in Public Domain Based on the picture, give an example of a species and a population. The picture shows two different species, Amphiprion ocellaris (clownfish) and Stichodactyla gigantea (sea anemone). It also illustrates two distinct populations: a population of clownfish and a population of sea anemones. Learning Guide 10.1 | page 1 of 7 As you continue to read this module, you will understand the relationship between species and population, and the external factors that affect the dispersion and density of a population. Relationship between Species and Population The term species has many different definitions, but we will define it simply as a unique type of organisms or an individual organism that can interbreed with its own kind. It can be a plant, an animal, a bacterium, a fungus, or any living organism. It is important to note that the term “species” always ends with an “s” even if you are referring to only one organism, a species. There is no such thing as a specie. Figure 2. This photo is Different species of Darwin’s Finches from Galapagos Archipelago by John Gould, 2012. In the public domain. On the other hand, a population refers to a group of the same species that live in a particular area at a particular time, which suggests that populations are geographically based and time-bound. For example, the population of field mice in the Philippines is different from the population of field mice in Indonesia. Learning Guide 10.1 | page 2 of 7 Population Size, Population Density, and Population Dispersion Population size refers to the number of organisms in a population. For example, a population of 100 individual birds. Population density (also known as ecological population density) is the amount or number of individuals in a population per unit area or volume. For example, the number of Cebu cinnamon (Cinnamomum cebuense) per square kilometer in the forest of Nug-as, er milliliter in a test tube. Alcoy, Cebu, or the number of Escherichia coli p Population dispersion is the pattern of spacing among individuals within the population boundary. Population boundary is the physical area that defines a population. In a population, the individuals may live in different patterns in an area reflecting the species’ characteristics and the environment. The patterns of dispersion within a population boundary are clumped, uniform, and random. o Clumped is the most common pattern in which individuals are clustered in groups. This reflects that their environment has a patchy distribution of resources. o Uniform is the pattern in which individuals are evenly spaced over the area they occupy. Organisms that exhibit uniform distribution have territoriality and intense competition over the available resources. o Random is the pattern in which individuals are in unpredictable spacing. This reflects that the individuals within the population boundary do not strongly interact. Figure 3. This photo Patterns of dispersion in populations by Boundless. Licensed under CC BY-NC-SA 3.0. How to measure population size and population density? To recall, population size is the number of individuals in a population, while population density is the number of individuals in a population per unit area or volume. Scientists study and understand the size and density of a population with the use of the most important methods: quadrat method, and mark-recapture method. These two sampling methods can be used depending on the type of organisms. Using these methods, scientists can model the change a population undergoes over time. Learning Guide 10.1 | page 3 of 7 Quadrat method is widely used to study the population size and density of immobile organisms, such as plants and immobile animals. A quadrat is a four-sided figure that encloses a sample area within a habitat (Figure 4). Figure 4. A scientist uses a quadrat to measure the size and density of plant population by LibreTexts, 2020 (https://bio.libretexts.org/). Licensed by CC BY-NC-SA 3.0. In measuring population density using the quadrat method, one has to identify the population size within the quadrat boundaries and the size (area) of the quadrat used. Population density has the formula: N D= A where o D is the population density, o N is the population size within the quadrat, and o A is the size of the quadrat. Learning Guide 10.1 | page 4 of 7 For example, you want to identify the population density of daffodils in the park, using your 2 m2 quadrat. Within the quadrat, there are 200 individual daffodils (population size). Using the formula, the population density of daffodils is 100/m2 (100 individual daffodils per 1 m2). 200 daf f odils D= 2 m2 D = 100 daf f odils/m2 Mark-recapture (capture-recapture) method is used to study the population size of mobile organisms. This method involves taking a sample from the population, marking those individuals in the sample with bands, tags, or other body markings; and releasing them back into the population where they mix with the unmarked individuals. Later, a new sample is taken from the same population, which now includes some marked individuals (recaptures) and some unmarked individuals. The ratio between marked and unmarked individuals allows scientists to calculate the number of individuals in the population as an estimate of the total population size. In mark-recapture method, population size can be determined using the formula: Mn N= m where o N - the population size to be estimated, o M - the number of individuals in the population that are captured initially and tagged (first sample), o n - the number of individuals in the second sample (recaptured), and o m - the number of individuals in the second sample that were already marked. For example, if 100 Philippine deer (Rusa marianna) are captured, marked, and released back into the forest, and later 200 Philippine deer are captured with 50 of them already tagged, then the estimated population size of Philippine deer is 400. (100 deer)(200 deer) N= 50 deer N = 400 deer Learning Guide 10.1 | page 5 of 7 GRADED FORMATIVE ASSESSMENT I. Read each item carefully and choose the best answer. 1 point each 1. Which of the following describes a population? A. It is a group of one species living in an area. B. It is a group of multiple species living in an area. C. It refers to all living organisms living in an area. D. It refers to all living and nonliving things in an area. 2. Which pattern of dispersion is described when organisms are spaced out equally? A. uniform B. random C. clumped D. none of these 3. Which dispersion pattern is a result of resources that are not evenly spread out in an area? A. uniform B. random C. clumped D. none of these II. Write TRUE if the statement is correct. If otherwise, change the underline word/s to make the statement correct. 2 points each 4. Population size refers to the average number of individuals in a population per unit of area or volume. 5. A species with a random dispersion pattern probably competes for a sparse resource. 6. A species with a very large population is more likely to be at risk of extinction. III. Solve for the population size and density using the methods that were discussed. 2 points each 7. The side of a square quadrat is 1 m long and there are 200 individual dandelions within the quadrat. Identify the population size and population density of dandelions. 8. In the forest, 50 Cebu warty pigs (Sus cebifrons cebifrons) are captured, tagged, and released back into the wild. Later, 50 Cebu warty pigs are captured and 25 of them are already tagged. What is the estimated population size of Cebu warty pigs? Learning Guide 10.1 | page 6 of 7 In Summary o Species is a unique individual organism that can interbreed with its own kind. o Population is a group of individuals of the same species that is geographically based. o Population size is the number of individuals in a population. o Population density is the number of individuals in a population per unit area or volume. o Population dispersion is the pattern of spacing among individuals in a population. o Quadrat method is widely used to study the population size and density of plants and sessile animals. o Mark-recapture method is used to study the population size of mobile organisms. Biology LibreTexts (2020). Population Size and Density. bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_Gene ral_Biology_(Boundless)/45%3A_Population_and_Community_Ecology/45.1%3A_ Population_Demography/45.1B%3A_Population_Size_and_Density CK-12: Biology Concepts (2020). Population Size, Density, and Distribution. https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A _Introductory_Biology_(CK-12)/06%3A_Ecology/6.17%3A_Population_Size%2C_ Density%2C_and_Distribution Edwards, W.J. & Edwards, C.T. (2011). Population Limiting Factors. Nature Education Knowledge 3( 10):1. Khan Academy (2020). Ecological levels: from individuals to ecosystems. Khan Academy. https://www.khanacademy.org/science/high-school-biology/hs-ecology/hs-introducti on-to-ecology/a/ecological-levels-from-individuals-to-ecosystems Reece, J.B., Urry, L.A., Cain, M.L., Wasserman, S.A., Minorsky, P.V. & Jackson, R.B. (2011). Campbell Biology. Pearson © 2020 Philippine Science High School System. All rights reserved. This document may contain proprietary information and may only be released to third parties with approval of management. Document is uncontrolled unless otherwise marked; uncontrolled documents are not subject. Learning Guide 10.1 | page 7 of 7
