Topic-+Interdependence+in+Ecosystems

Topic: Interdependence in Ecosystems
Below is a list of key ideas related to Interdependence in Ecosystems. For each key idea, you will find a list of sub-ideas, a list of items, results from our field testing, and a list of student misconceptions. After clicking on a tab, click on it again to close the tab.

All organisms, both land-based and aquatic, are connected to other organisms by their need for food. This results in a global network of interconnections, which is referred to as a food web.
//Students are expected to know that:// //Boundaries//:
 * [|Sub-Ideas]
 * [|Items & Student Performance]
 * [|Misconceptions]
 * 1) When organisms eat or are eaten by other organisms, there is an effect on the two organisms involved and on the populations to which they belong.
 * 2) When organisms eat or are eaten by other organisms, there may be an effect on other populations that are not eating or being eaten by those organisms. This is because once an individual organism (or part of an organism) is eaten, it is no longer available as food for other populations of organisms and/or will no longer eat other organisms from other populations.
 * 3) Changes in the size of a population may result from changes in the size of the populations of organisms that it consumes, that consume it, or both. Specifically, if the size of a population increases (or is introduced), the size of a population of organisms that consumes it may increase because there will be more food available to that population, and if the size of a population increases (or is introduced), the size of a population of organisms that it consumes may decrease because more of them may be consumed. If the size of a population decreases (or the population disappears), the size of a population of organisms that consume it may decrease because less food is available to that population, and if the size of a population decreases (or the population disappears), the size of a population of organisms that it consumes may increase because there are fewer organisms to consume them.
 * 4) Changes to the size of populations of organisms due to changes in the size of populations it consumes or that consume it take time, and the relative sizes of the starting populations involved may affect the outcome.
 * 5) The network of populations of organisms being eaten by other populations can be thought of as a single global food web encompassing all populations, but food webs can also be described for populations in particular environments.
 * 6) Feeding interactions among selected populations of organisms in food webs can be represented by diagrams with arrows from populations being eaten to populations doing the eating. If an arrow is not present in a diagram, there is no feeding interaction between two populations, and if an arrow is present, there is a significant feeding interaction between the two populations.
 * 1) Students are not expected to know that microorganisms are part of food webs. This is addressed in a later idea.
 * 2) Students are not expected to know the terms producer, consumer, or trophic level.
 * 3) Students are not expected to know what any particular organism eats apart from what can be determined from food web diagrams they are given.
 * 4) Students are not expected to know that although a population may be connected by arrows to more than one population, organisms may rely on some organisms more than others for food.

Percent of students answering correctly (click on the item ID number to view the item and additional data)||~ Item ID Number ||~ Knowledge Being Assessed 6–8 ||~ Grades 9–12 ||~ Select This Item for My Item Bank ||
 * ~ Grades
 * [|IE029006] || [|Changes in a population of organisms in a food web (worms) can affect the population of its predator (robins).] || 84% || 80% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/1990"]] ||
 * [|IE032005] || [|Changes in the number of worms in an area can affect the number of foxes in that area even though foxes do not depend directly on worms for food.] || 73% || 79% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2105"]] ||
 * [|IE031007] || [|Changes in a population of organisms in a food web (worms) can affect other populations of organisms (foxes) even if they are not directly connected in a feeding relationship.] || 70% || 81% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/1992"]] ||
 * [|IE027005] || [|Changes in a population in a food web (grasshoppers) can affect the populations of both its predator (frogs) and its prey (grass).] || 66% || 78% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2101"]] ||
 * [|IE026005] || [|Changes in a population may affect populations that are not directly connected by a feeding relationship even if they are several steps away in a food web (no specific organisms indicated).] || 72% || 74% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2099"]] ||
 * [|IE026004] || [|Changes in a population may affect populations that are not directly connected by a feeding relationship even if they are several steps away in a food web (ocean ecosystem).] || 69% || 77% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2098"]] ||
 * [|IE014004] || [|Changes in a population in a food web (robins) can affect the population of its prey (caterpillars).] || 66% || 74% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2088"]] ||
 * [|IE029005] || [|Changes in a population in a food web can affect the population of its predator (no specific organisms identified).] || 63% || 74% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/1989"]] ||
 * [|IE031006] || [|Changes in a population in a food web can affect other populations of organisms even if they are not directly connected in a feeding relationship (no specific organisms identified).] || 63% || 72% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/1991"]] ||
 * [|IE019016] || [|Changes in a population in a food web (large fish) can affect the population of its prey (tadpoles).] || 61% || 69% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2080"]] ||
 * [|IE073004] || [|Changes in a population in a food web can affect the population of its prey (no specific organisms identified).] || 59% || 68% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2102"]] ||
 * [|IE032004] || [|Changes in a population in a food web can affect populations of other organisms even if they are not directly connected in a feeding relationship (no specific organisms identified).] || 56% || 68% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2104"]] ||
 * [|IE027004] || [|Changes in a population in a food web can affect the populations of both its predator and its prey (no specific organisms identified).] || 55% || 66% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2100"]] ||
 * [|IE012012] || [|Changes in a population in a food web (wolves) can affect populations of other organisms (grass) even if they are not directly connected in a feeding relationship (text only, no diagram).] || 55% || 58% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2093"]] ||
 * [|IE034005] || [|Changes in a population (rabbits) may affect populations that are not directly connected by a feeding relationship (crickets) even if they are several steps away and not within the same chain in a food web.] || 51% || 62% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2091"]] ||
 * [|IE012011] || [|Changes in a population in a food web (wolves) can affect populations of other organisms (grass) even if they are not directly connected in a feeding relationship.] || 53% || 57% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2092"]] ||
 * [|IE020004] || [|Changes in a population (fish in a pond) may affect populations that are not directly connected in a feeding relationship (large birds).] || 52% || 57% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2082"]] ||
 * [|IE025005] || [|Changes in a population may affect populations that are not directly connected by a feeding relationship even if they are several steps away in a food web (no specific organisms identified).] || 50% || 53% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2097"]] ||
 * [|IE025004] || [|Changes in a population may affect populations that are not directly connected by a feeding relationship even if they are several steps away in a food web (woodland ecosystem).] || 44% || 53% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2096"]] ||
 * [|IE019017] || [|Organisms that are not connected by an arrow in a food web diagram do not have a direct food relationship between them (pond ecosystem).] || 41% || 52% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2081"]] ||
 * [|IE028006] || [|Changes in a population (frogs) may affect populations that are not directly connected by a feeding relationship (mice) even if they are several steps away and not within the same chain in a food web.] || 34% || 45% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2085"]] ||
 * [|IE019014] || [|Changes in a population may affect populations that are not directly connected by a feeding relationship even if they are several steps away in a food web (pond ecosystem).] || 37% || 46% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2078"]] ||
 * [|IE016009] || [|Changes in a population of organisms (introduction of a new organism) can affect populations that are not directly connected by a feeding relationship (woodland ecosystem).] || 36% || 41% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2087"]] ||
 * [|IE028005] || [|Changes in a population may affect populations that are not directly connected by a feeding relationship even if they are several steps away and not within the same chain in a food web (no specific organisms identified).] || 35% || 42% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2084"]] ||
 * [|IE019015] || [|Changes in a population (fish in a pond) may affect populations that are not directly connected by a feeding relationship (insects) even if they are several steps away in a food web.] || 35% || 40% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2079"]] ||
 * [|IE017005] || [|Changes in a population (introduction of a new organism) may affect populations that are not directly connected by a feeding relationship even if they are several steps away in a food web (woodland ecosystem).] || 29% || 38% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2089"]] ||
 * [|IE018005] || [|It is NOT TRUE that top or apex predators (large fish) are not affected by changes in populations of organisms below them (frogs) in a food web (pond ecosystem).] || 27% || 34% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2083"]] ||
 * [|IE017006] || [|Changes in a population may affect populations that are not directly connected by a feeding relationship even if they are several steps away in a food web (woodland ecosystem).] || 20% || 28% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2090"]] ||
 * [|IE016008] || [|Changes in a population (introduction of a new species) may affect populations that are not directly connected by a feeding relationship (caterpillars) even if they are several steps away in a food web.] || 20% || 27% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2086"]] ||

Frequency of selecting a misconception||~ Misconception ID Number 6–8 ||~ Grades 9–12 || Frequency of selecting a misconception was calculated by dividing the total number of times a misconception was chosen by the number of times it could have been chosen, averaged over the number of students answering the questions within this particular idea.
 * ~ Student Misconception ||~ Grades
 * [|IEM022] || [|If a population in a food web is disturbed, there will be little or no effect on populations that are not within the linear sequence in the food web (Webb & Boltt, 1990).] || 31% || 30% ||
 * [|IEM065] || [|Varying the size of a population of organisms will affect only those populations of organisms that are directly connected to it in a feeding relationship, not organisms that are one or more steps removed/away from it (Griffiths & Grant, 1985; Webb & Boltt, 1990).] || 20% || 19% ||
 * [|IEM021] || [|If a population in a food web is disturbed, there will be little or no effect on populations below it in the food web (e.g. if a predator is removed, no effect on prey: Webb & Boltt, 1990; Leach, 1996).] || 18% || 15% ||
 * [|IEM006] || [|Organisms higher in a food web eat everything that is lower in the food web (Griffiths & Grant 1985).] || 15% || 12% ||
 * [|IEM030] || [|If the size of one population in a food web is altered, all other populations in the web will be altered in the same way (Griffiths & Grant, 1985).] || 12% || 8% ||
 * [|IEM029] || [|A change in the size of a prey population has no effect on its predator population (Griffiths & Grant, 1985).] || 10% || 8% ||
 * [|IEM061] || [|Changes in a population in a food web do not affect the populations of any other organism in the food web (AAAS Project 2061, n.d.).] || 10% || 8% ||
 * [|IEM047] || [|The top predator in a food web will never be significantly affected by changes in the populations of organisms below it in the food web (AAAS Project 2061, n.d.).] || 9% || 7% ||

==== In all environments, individual organisms that depend on the same resource may compete for that resource when it is limited. Resources that can be limited include food, space, water, shelter, and light. ==== //Students are expected to know that:// //Boundaries//:
 * [|Sub-Ideas]
 * [|Items & Student Performance]
 * [|Misconceptions]
 * 1) Organisms that depend on the same resource compete for that resource when it is limited.
 * 2) Resources that can be limited for animals include food, space, water, and shelter (including nesting sites).
 * 3) Resources that can be limited for plants include space, water, and light.
 * 4) Both plants and animals compete for resources.
 * 5) Competition may be between individuals of the same species or between individuals of different species.
 * 6) The scientific use of the term “competition” refers to the attempt of different organisms to obtain the same limited resource, whether or not the organisms interact with each other. In other words, competition for resources does not necessarily imply direct confrontation between organisms, and sometimes competition involves finding or using the resource first.
 * 1) Students are not expected to know which resources can be limited for other organisms besides animals and plants.
 * 2) Students are not expected to know that animals compete for light in some instances.

Percent of students answering correctly (click on the item ID number to view the item and additional data)||~ Item ID Number ||~ Knowledge Being Assessed 6–8 ||~ Grades 9–12 ||~ Select This Item for My Item Bank ||
 * ~ Grades
 * [|IE050004] || [|Animals compete for resources when they are limited.] || 80% || 87% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2117"]] ||
 * [|IE038008] || [|Organisms of the same species (wolves or bears) and animals of different species (wolves vs. bears) compete for resources.] || 67% || 77% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2111"]] ||
 * [|IE038009] || [|Organisms of the same species (owls or snakes) and organisms of different species (owls vs. snakes) compete for resources.] || 65% || 77% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2112"]] ||
 * [|IE038007] || [|Organisms of the same species (lions or cheetahs) and organisms of different species (lions vs. cheetahs) compete for resources.] || 65% || 72% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2110"]] ||
 * [|IE038010] || [|Organisms of the same species (sparrows or bluebirds) and organisms of different species (sparrows vs. bluebirds) compete for resources.] || 61% || 74% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2113"]] ||
 * [|IE058002] || [|Both plants and animals compete for resources when they are limited.] || 56% || 69% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2116"]] ||
 * [|IE074002] || [|Plants compete for water, space, and light when they are limited.] || 54% || 64% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2114"]] ||
 * [|IE038006] || [|Organisms of the same species (horses or cows) and of different species (horses vs. cows) compete for resources.] || 58% || 66% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2109"]] ||
 * [|IE075002] || [|Competition between animals does not always involve direct confrontation (fighting).] || 37% || 49% || [[image:http://assessment.aaas.org/img/star_16x16_grey.png link="http://assessment.aaas.org/users/itembank/add/2115"]] ||

Frequency of selecting a misconception||~ Misconception ID Number 6–8 ||~ Grades 9–12 || Frequency of selecting a misconception was calculated by dividing the total number of times a misconception was chosen by the number of times it could have been chosen, averaged over the number of students answering the questions within this particular idea.
 * ~ Student Misconception ||~ Grades
 * [|IEM053] || [|Competition between organisms always involves direct, aggressive interaction. Exploitative competition (e.g., getting to the resource before other organisms) is not competition (AAAS Project 2061, n.d.).] || 63% || 51% ||
 * [|IEM054] || [|Plants do not compete for resources (AAAS Project 2061, n.d.).] || 31% || 20% ||
 * [|IEM062] || [|Organisms of the same species do not compete with each other for resources (AAAS Pilot testing 2007).] || 15% || 11% ||
 * [|IEM052] || [|Plants do not compete for light (AAAS Project 2061, n.d.).] || 10% || 12% ||
 * [|IEM060] || [|Different kinds of organisms (species) do not compete for resources (AAAS Project 2061, n.d.).] || 10% || 8% ||
 * [|IEM055] || [|Animals do not compete for resources (AAAS Project 2061, n.d.).] || 11% || 7% ||
 * [|IEM049] || [|Animals do not compete for shelter (AAAS Project 2061, n.d.).] || 10% || 8% ||
 * [|IEM051] || [|Plants do not compete for space (AAAS Project 2061, n.d.).] || 7% || 4% ||
 * [|IEM048] || [|Animals do not compete for water (AAAS Project 2061, n.d.).] || 7% || 4% ||

Given adequate resources and an absence of disease or predators, populations of organisms in ecosystems can increase at rapid rates. Finite resources and other factors limit their growth.

 * [|Sub-Ideas]
 * [|Items & Student Performance]
 * [|Misconceptions]