Angela's Tools · Chapter 20 · Resources in Living Systems Teacher answer key

Resource, Condition or Competitor? Sorting the Words of a Pond

Learning target: I can tell resources apart from conditions, sort resources as living or nonliving, and use the terms population, competition, limiting resource, carrying capacity, ecosystem and biosphere correctly in new situations.

Vocabulary in actionAbout 30 minIndividual MS-LS2-1 · supportsMS-LS2-2 · supports independent practicewriting

Standards connections

MS-LS2-1 (supports): Students cannot analyze data on resource availability until they can say precisely what a resource is and how a limiting resource differs from a carrying capacity. This sheet builds that language; it does not itself produce evidence toward the PE.

MS-LS2-2 (supports): Competition is one of the interaction patterns this PE asks students to predict across ecosystems. Here students only learn to recognize and name it.

Purpose: build · Time: about 30 minutes · Format: individual

Answers with reasoning

resource
Any material, energy or space a living thing takes in or uses in order to stay alive, grow and reproduce. Food, water, oxygen, light, soil nutrients and nesting space are all resources.
biotic resource
A resource that is, or comes from, a living thing: the grass a deer eats, the insects a frog eats, the dead leaves a snail scrapes up.
abiotic resource
A resource that is not alive: water, oxygen, carbon dioxide, sunlight, minerals in the soil, a space to nest.
condition
A feature of the environment that affects organisms but is not used up by them, such as temperature, how fast water flows, or how acidic the water is. Conditions decide where an organism can live, but they are not resources.
limiting resource
The resource that runs short first. When a population grows until there is not enough of one resource to go around, that resource sets the limit on how large the population can get.
carrying capacity
The largest number of members of one species that an area's resources can keep supporting over time. It changes when the supply of the limiting resource changes.
competition
An interaction in which two or more organisms need the same limited resource, so whatever one takes leaves less for the others. It happens within a species and between species.
organism
One individual living thing: a single heron, a single snail, a single cattail plant.
species
A group of similar organisms whose members can breed with one another and produce offspring that can also reproduce.
population
All the members of one species that live in the same area at the same time, such as all the bullfrogs in one pond.
ecosystem
All the populations in an area together with the nonliving things (water, soil, air, light) that they depend on and interact with.
biome
A very large region of Earth, on land or in water, with a particular set of conditions and resources and the kinds of living things those support, such as a tropical rainforest or a temperate grassland.
biosphere
Every part of Earth where life exists, from the deep ocean floor to the air above the highest peaks: all of Earth's ecosystems together.

Part A: Sort the pond

Twelve things from a farm pond are listed in the table. Decide whether each one is a biotic resource, an abiotic resource, or a condition (not a resource). Write a check mark in one column for each row. Then, in the last column, write the name of one pond organism that uses it (for resources) or is affected by it (for conditions).

1.Sort each item and name one organism that uses it or is affected by it.
Answer: Sunlight: abiotic resource (water plants, algae). Water temperature: condition (fish, frogs). Algae scraped by snails: biotic resource (snails). Dissolved oxygen: abiotic resource (fish, insect larvae). Nitrogen compounds in mud: abiotic resource (water plants, algae). Mosquito larvae: biotic resource (minnows). pH: condition (every organism; snails and amphibians are sensitive). Bank space for egg masses: abiotic resource (frogs). Minnows caught by a heron: biotic resource (heron). Dead leaves: biotic resource (shredder insects). Carbon dioxide: abiotic resource (water plants). Flow speed: condition (insect larvae, plants).
Why: Resources are taken in or occupied; conditions are experienced. Space is a resource because it can be filled. Dead leaves came from living plants, so they are biotic even though the leaves are dead; accept abiotic for dead leaves only if the student argues that the material is no longer alive, and then point out that the convention counts material of living origin as biotic.
Also acceptable: Any pond organism that plausibly uses the resource is acceptable in the last column.

Part B: Fill the levels

Levels of organization, smallest to largest (two levels are missing) Levels of organization, smallest to largest (two levels are missing) organism ? ecosystem ? many individuals of one species in one area add every other population plus the nonliving parts add every ecosystem on Earth
Each arrow says what gets added to move up a level.
2a.The second level (between organism and ecosystem) is called a ________. Write the word and then define it in one sentence using the pond.
Answer: Population. Example definition: all the bullfrogs that live and breed in this one pond make up the pond's bullfrog population.
Why: The arrow label 'many individuals of one species in one area' is the definition of a population.
Also acceptable: Any one-sentence definition that includes one species, one area.
2b.The largest level is called the ________. Write the word and then give one reason it must include the air above the pond.
Answer: Biosphere. The air above the pond must be included because organisms live in it and use it: dragonflies and herons fly through it, every organism takes oxygen from it, and plants take carbon dioxide from it.
Why: The biosphere is every place life exists, and the air is both a living space and a source of resources.
Also acceptable: Accept 'birds and insects live in the air' or 'the air holds the oxygen and carbon dioxide the pond organisms use.'
3.Many scientists add a level called a community between population and ecosystem. Using the definitions in the word list, what must a community include that a population does not, and what must an ecosystem include that a community does not?
Answer: A community includes all the different populations in the area (frogs, snails, minnows, cattails), while a population is only one species. An ecosystem adds the nonliving parts (water, mud, air, sunlight) that the community depends on; a community is only the living part.
Why: This repairs the textbook's four-level ladder, which skips the community level that most biology references include.
Also acceptable: A student who says 'a community is the living half of an ecosystem' has the idea.

Part C: Which word fits?

4.Write the one vocabulary word that best names each description. Each word is used at most once.
Answer: 1 population; 2 competition; 3 limiting resource; 4 carrying capacity; 5 organism; 6 biosphere; 7 ecosystem; 8 biome.
Why: Row 3 describes a resource that ran short and stopped growth, which is a limiting resource (phosphorus). Row 4 is a number of individuals supported over time, the carrying capacity. Row 8 describes a tundra-like region, a biome.
Also acceptable: For row 3 accept 'abiotic resource' only with a note; the intended answer is limiting resource because the description says growth stopped when it ran out.

Part D: Use the words in a new place

5.Snails and tadpoles in the pond both scrape algae off rocks. Name the interaction between them, name the resource, and explain whether this is competition within a species or between species.
Answer: The interaction is competition; the resource is the algae on the rocks (a biotic resource). Because snails and tadpoles are different species, it is competition between species.
Why: Both organisms need the same limited resource, which is the definition of competition; the species distinction decides 'within' versus 'between.'
Also acceptable: A student who adds that two tadpoles scraping the same rock would be competition within a species has gone further.
6.A kelp forest off the California coast has kelp (a large seaweed), sea urchins that eat kelp, sea otters that eat urchins, sunlight, and nutrients in the seawater. Write three sentences about the kelp forest. Each sentence must use two vocabulary words correctly. Underline the vocabulary words.
Answer: Sample sentences: 'The sea urchin population and the sea otter population both belong to the same kelp forest ecosystem.' 'Kelp needs sunlight, an abiotic resource, and when urchins eat too much kelp, the kelp becomes a limiting resource for the urchins.' 'When otters are removed, urchin numbers can rise past the carrying capacity the kelp can support, and competition among urchins for the last kelp becomes intense.'
Why: Each sentence must use two listed terms in a way that matches the definitions. Check that 'population' is attached to one species and that 'competition' involves a shared limited resource.
Also acceptable: Terms may repeat across sentences as long as each sentence has two. A sentence using 'organism' for a single otter and 'biotic resource' for the urchins it eats is correct.
7.Explain the difference between a limiting resource and a carrying capacity using the pond's bullfrogs. Your answer must say which one is a thing and which one is a number.
Answer: A limiting resource is a thing: the specific resource that runs out first for the bullfrogs, for example the insects they eat or the bank space for egg masses. Carrying capacity is a number: the largest bullfrog population the pond's resources can keep supporting. The limiting resource sets the carrying capacity; if more insects are available, the carrying capacity goes up.
Why: Students often treat the two terms as synonyms. The thing-versus-number contrast and the 'sets' relationship are the targets.
Also acceptable: Accept any plausible pond resource as the example.
8.Bullfrogs live in thousands of ponds across North America. Explain why 'the bullfrogs in Miller's pond' is a population but 'bullfrogs' by itself is a species, not a population.
Answer: A population is all the members of one species in one area. 'The bullfrogs in Miller's pond' names one species in one place, so it is a population. 'Bullfrogs' alone names the whole species everywhere; it includes thousands of separate populations in different ponds that rarely meet, so it is a species, not a population.
Why: The distinction is the 'one area' part of the definition.
Also acceptable: Accept 'a species can be split into many populations.'

Teacher notes

Two accuracy points to hold firm on. First, temperature is a condition, not a resource: the textbook calls a biome's temperature range a 'limited resource,' but organisms do not use temperature up. Rainfall is different: it delivers water, which is a resource. Second, the species definition here says 'offspring that can also reproduce' because some different species can produce infertile hybrids; keep the definition at that level and do not test exceptions. The community level (q3) is standard in biology even though the textbook ladder omits it; students may use either the four-level or five-level ladder later as long as they order it correctly. In q1 the most common disagreements are dead leaves (biotic, because of living origin) and bank space (a resource, because it can be filled up).

Scaffold offered to students: The 'used up?' test and a word bank

For Part A ask two questions in order. (1) Can organisms use it up, so that there is less for others? If no, it is a condition. If yes, it is a resource. (2) Is it alive, or did it come from something alive? If yes, biotic; if no, abiotic. For Part C, the eight words you need are: organism, population, ecosystem, biome, biosphere, competition, limiting resource, carrying capacity. Cross each one out as you use it.

Extension: Your own resources and conditions

Make the same three-column sort for a human being living in a desert city: list at least four biotic resources, four abiotic resources, and three conditions. Then decide which single resource would most likely become the limiting resource for the city's population if the city kept growing, and write a paragraph defending your choice. Finish by explaining how the city's carrying capacity could rise without the resource itself increasing (for example, by using it more efficiently).

Angela's Tools · Chapter 20 · Resources in Living SystemsWorksheet 2 of 10 · Teacher answer key