Unit 7 · Segment 3: The Distribution of Earth's Resources · printed p. 260 (PDF p. 296)
Resources in Ecosystems
When various species of cichlid fish are combined in aquariums, some stop eating to the point of dying.
Anchoring phenomenon
Chapters
- 20 Resources in Living Systems
What do living things need from their surroundings, and what happens to organisms and populations when a needed resource runs short?
1 presentation10 worksheets3 labs - 21 Interactions Among Organisms
Why do the same kinds of relationships between species appear in ecosystems that share no species at all, and how can knowing those patterns let us predict what happens when one population changes?
1 presentation10 worksheets3 labs - 22 Changing Ecosystems
How do ecosystems change over time, and how can we use evidence to argue that a change to one part of an ecosystem affects the populations living there?
1 presentation10 worksheets3 labs
Standards in this unit
Unit vocabulary
resourceAny material or energy a living thing must take in from its surroundings to stay alive, grow and reproduce, such as food, water, oxygen, sunlight, soil nutrients or space. A resource can be used up.Chapter 20
biotic and abioticBiotic means living or coming from living things; abiotic means nonliving. Grass is a biotic resource for a horse; water, oxygen and sunlight are abiotic resources.Chapter 20
conditionA feature of the environment, such as temperature, that affects which organisms can live somewhere but is not consumed by them. Conditions are not resources, even though both set limits.Chapter 20
organismOne individual living thing: one frog, one horse, one grass plant, one bacterium.Chapter 20
speciesA group of similar organisms whose members can mate with one another and produce offspring that can also reproduce. (A few different species can form hybrids, but those are usually infertile.)Chapter 20
populationAll the organisms of one species that live in the same area at the same time and can breed with one another.Chapter 20
competitionAn interaction in which two or more organisms need the same resource that is in short supply, so what one takes, the other cannot have. It happens within a species and between species.Chapter 20
limiting resourceThe resource that is in shortest supply compared with how much organisms need, so it sets the limit on growth even when every other resource is plentiful.Chapter 20
carrying capacityThe largest population of a species that an area's resources can support over time. A real population drifts above and below it, and it rises or falls when the resources change.Chapter 20
communityAll the populations of different species that live and interact in one area; the living part of an ecosystem.Chapter 20
ecosystemA community of living things together with the nonliving parts of its surroundings, such as water, soil, air and light, that it depends on.Chapter 20
biomeA very large region of Earth defined by its climate and by the kinds of plants and animals that climate supports, such as a temperate grassland, a boreal forest or a coral reef.Chapter 20
predationAn interaction where a predator gets food by eating all or part of another living thing, its prey. In this lesson the word covers plant eaters as well as hunters.Chapter 21
predatorThe organism that does the eating in predation. Hunters such as owls count, and so do grazers such as deer, because both take resources from another living thing.Chapter 21
preyThe organism that gets eaten in predation, whether it is an animal, a plant or a microbe.Chapter 21
carnivoreA predator whose food is mostly other animals.Chapter 21
herbivoreA predator whose food is mostly plants or plant parts, such as leaves, seeds or nectar.Chapter 21
omnivoreA predator that regularly eats both plants and animals. The mix does not have to be equal: black bears eat mostly plant food and are still omnivores.Chapter 21
competitionAn interaction in which two species need the same limited resource, so each one gets less than it would alone. Both are harmed.Chapter 21
mutualismAn interaction between two species in which each partner gains something that helps it survive, grow or reproduce. Each partner is acting for itself, not out of kindness.Chapter 21
commensalismAn interaction that helps one species while the other shows no measurable gain or loss, as far as scientists can tell.Chapter 21
parasitismAn interaction in which one species, the parasite, lives on or inside another living species, the host, and takes resources from it. The host is weakened but usually not killed.Chapter 21
hostThe living organism that a parasite lives on or inside and feeds from.Chapter 21
criteria and constraintsCriteria are the requirements a design must meet to count as a success; constraints are the limits, such as cost, size, time or effects on living things, that narrow down which designs are allowed.Chapter 21
dynamic systemA system whose parts are always changing, whether the change is slow or fast, small or large. Every ecosystem is one, because its living things, water, soil and climate never stay fixed.Chapter 22
disturbanceAn event that damages or removes living things from part of an ecosystem and changes the resources there. Fires, floods, eruptions, storms, logging and land clearing are disturbances.Chapter 22
ecological successionThe gradual replacement of one community of organisms by another as living things change the conditions of a place. Early arrivals make soil, shade and shelter that let later arrivals move in.Chapter 22
primary successionSuccession that starts on brand-new ground with no soil, such as cooled lava, fresh pumice, or gravel left behind by a melting glacier.Chapter 22
secondary successionSuccession that starts after a disturbance that leaves soil behind, often with roots, seeds and buried animals still alive. It is usually much faster than primary succession.Chapter 22
pioneer speciesA hardy organism, such as a lichen, moss, lupine or fireweed, that can settle bare or damaged ground first and begin to improve conditions for the species that follow.Chapter 22
biological legacyLiving things or their remains that survive a disturbance in place, such as buried seeds, roots, fungi, logs, or animals in burrows, and give recovery a head start.Chapter 22
keystone speciesA species whose presence shapes the ecosystem far more than its numbers suggest, because many other species depend on what it does. Removing it can change the whole community.Chapter 22
cascading changeA chain of effects in which a change to one population alters resources for a second population, which then alters a third, and so on through the food web.Chapter 22
resilienceThe ability of an ecosystem to absorb a disturbance and recover its main populations and functions, rather than switching permanently to a different kind of ecosystem.Chapter 22
invasive speciesA species that people moved, on purpose or by accident, into a region where it did not live before, and that spreads there and harms native populations or the way the ecosystem works.Chapter 22
empirical evidenceInformation gathered by observing or measuring the real world, such as population counts, photographs taken over time, or comparisons between similar places that differ in one way.Chapter 22