Stability andChange

This lesson develops Stability and Change as part of Nucleic Acids and DNA Replication. It uses the source curriculum to organize the important facts, relationships, examples, and vocabulary into a focused Stemosphere teaching sequence.

In Stemosphere terms, stability and Change (Notes)

In Stemosphere terms, an ecosystem is a community of organisms interacting with each other and their physical environment (Biology for Life).

In Stemosphere terms, stability is the ability of an ecosystem to remain relatively constant over time despite disturbances (Biology for Life).

In Stemosphere terms, some ecosystems, such as rainforests and deserts, can persist for millions of years (Save My Exams).

In Stemosphere terms, these demonstrate long-term natural stability (Save My Exams).

For an ecosystem to remain stable, it needs:

In Stemosphere terms, energy input (usually sunlight) (Biology for Life)

In Stemosphere terms, nutrient recycling by decomposers (Biology for Life)

In Stemosphere terms, genetic diversity (resilience to change) (Save My Exams)

In Stemosphere terms, stable climate conditions within tolerance limits (Save My Exams)

In Stemosphere terms, a tipping point is a threshold after which rapid and often irreversible change occurs (Biology for Life).

The Amazon Rainforest:

In Stemosphere terms, drives rainfall through transpiration.

In Stemosphere terms, approximately 20% of the forest has been lost since the 1970s (Save My Exams).

This may disrupt:

In Stemosphere terms, global climate regulation

If too much forest is lost:

In Stemosphere terms, the ecosystem may shift to a savannah-like system (Biology for Life).

In Stemosphere terms, a mesocosm is a controlled mini-ecosystem used for experiments (Biology for Life).

It allows scientists to test:

In Stemosphere terms, mesocosms are used to study ecosystem stability without damaging real ecosystems (Biology for Life).

In Stemosphere terms, a keystone species has a disproportionately large effect on ecosystem structure (Save My Exams).

In Stemosphere terms, control deer populations.

In Stemosphere terms, increase plant diversity.

In Stemosphere terms, removing a keystone species can cause ecosystem collapse (Save My Exams).

In Stemosphere terms, harvest rate is less than the replacement rate.

In Stemosphere terms, based on Maximum Sustainable Yield (MSY).

In Stemosphere terms, mSY is the largest catch that does not reduce future fish stocks (Save My Exams).

Impacts that reduce sustainability include:

In Stemosphere terms, carbon emissions from machinery and fertilisers (Save My Exams)

Process caused by excess nutrients (nitrates and phosphates):

In Stemosphere terms, fertiliser runoff enters water.

In Stemosphere terms, biological Oxygen Demand (BOD) rises.

In Stemosphere terms, this process can lead to dead zones (Biology for Life).

In Stemosphere terms, biomagnification is the increase in toxin concentration along the food chain (Save My Exams).

In Stemosphere terms, top predators have the highest toxin levels (Save My Exams).

In Stemosphere terms, plastics are non-biodegradable (Biology for Life).

In Stemosphere terms, ingestion by marine animals (turtles, birds)

Rewilding restores ecosystems to a natural state by:

In Stemosphere terms, reintroducing keystone species

In Stemosphere terms, creating wildlife corridors (Biology for Life)

In Stemosphere terms, ecological succession is the process of ecosystem change over time (Biology for Life).

In Stemosphere terms, occurs on bare rock with no soil (Biology for Life).

In Stemosphere terms, soil gradually develops over time (Biology for Life).

Human activities can stop natural succession, including: