Stability and Change Study Guide

1.4 Stability and Change in Ecosystems (Bio.1.4)

Explore this Phenomenon

 These flowers are growing out of hardened lava! The lava flow destroyed all the plants it came in contact with, but after the lava hardened into a rock, these plants began growing out of it.

1. How do drastic changes, such as volcanoes, affect ecosystems?
2. What questions could you investigate to learn more about how the lava rock and plants affect the stability of the ecosystem?
3. What other factors could affect the number and types of organisms in an ecosystem?

Bio.1.4 Stable Ecosystems

Develop an argument from evidence for how ecosystems maintain relatively consistent numbers and types of organisms in stable conditions . Emphasize how changing conditions may result in changes to an ecosystem. Examples of changes in ecosystem conditions could include moderate biological or physical changes such as moderate hunting or a seasonal flood; and extreme changes, such as climate change, volcanic eruption, or sea level rise. (LS2.C)

The stability of factors in ecosystems affects the number and types of organisms in the ecosystem. As you read this chapter, look for evidence that you can use to show how the stability of ecosystems correlates with the number and types of organisms in the system.

Organisms Depend on the Environment and Each Other

What other species do you need to survive?

Species cannot live alone. All life needs other life to survive. The image shows a bluestreak cleaner wrasse eating algae and other small organisms off a giant moray eel. This is an example of a symbiotic relationship.

Interdependence of Living Things

All living things depend on their environment to supply them with what they need, including food, water, and shelter. Their environment consists of physical factors—such as soil, air, and temperature—and also of other organisms. An organism is an individual living thing. Many living things interact with other organisms in their environment. In fact, they may need other organisms in order to survive. This is known as interdependence. For example, living things that cannot make their own food must eat other organisms for food. Other interactions between living things include symbiotic relationships and competition for resources.

Since living things depend on their environment and other organisms, changes to the environment or one population can affect other populations. The numbers and types of organisms in an ecosystem are not usually static because ecosystems adjust to gradual changes. As conditions change, the numbers and types of species in the ecosystem gradually change over time. If conditions remain stable, what will happen to the number and types of organisms in the ecosystem?

Moderate Changes

Minor to moderate changes happen from season to season. Seasonal floods, hunting, climate change, and other factors can create changes to an ecosystem in a short period of time. The changes are typically not big enough to completely disrupt the ecosystem, but do affect the populations that inhabit the ecosystem. Ecosystems typically recover from this type of disturbance quickly.

Extreme Changes

A catastrophic event, such as a volcano, can destroy an existing ecosystem and also set the stage for a new ecosystem to be created. Primary succession occurs when an area has never been colonized; in other words, there are no living organisms or even soil in the area. Bacteria and lichens that can live on bare rock, along with wind and water, help weather the rock and form soil. Once soil begins to form, plants can move in. At first, the plants include grasses and other species that can grow in thin, poor soil. As more plants grow and die, organic matter is added to the soil. This improves the soil and helps it hold water. The improved soil allows shrubs and trees to move into the area.

Primary Succession. New land from a volcanic eruption is slowly being colonized by a pioneer species.

Secondary Succession occurs in a formerly inhabited area that was disturbed. The disturbance could be a fire, flood, or human action such as farming. This type of succession is faster because the soil is already in place. In this case, plants such as grasses, birch trees, and fireweed are the first plants to grow. Organic matter from the first plants improves the soil. This lets other plants move into the area.

Secondary Succession. Two months after a forest fire, new plants are already sprouting among the charred logs.

Putting It Together

These flowers are growing out of hardened lava! The lava flow destroyed all the plants it came in contact with, but after the lava hardened into a rock, these plants began growing out of it.

1. Explain this phenomenon. How are plants able to grow out of rock?
2. Predict if conditions in this ecosystem will remain stable or change, and use evidence about how organisms interact with each other and their environment to support your prediction.