2.5 Zonation, Succession & Change in Ecosystems (DP IB Environmental Systems & Societies (ESS): HL): Flashcards

The width of the kite shows the abundance of a species at each point along the transect.

In a kite diagram, the x-axis shows the distance along the transect.

Succession is the process by which an ecosystem changes over time, becoming more complex as new species colonise and modify the environment.

False.

Ecosystems are dynamic and constantly changing due to biotic and abiotic factors.

During succession, the biotic and abiotic conditions change over time.

Primary succession occurs on newly formed or exposed land with no species present, while secondary succession occurs on bare soil where a previous community existed.

Pioneer species are the first organisms to colonise newly exposed or formed land, such as mosses and lichens.

On coastal sand dunes, marram grasses are the pioneer species.

A seral community is a temporary and intermediate stage in the ecological succession of an ecosystem.

A climax community is the final, stable community formed at the end of succession, containing all the different plant and animal species that can be supported by the environment.

As small plants and shrubs die and decompose, the soil becomes deeper and more nutrient-rich.

During succession, species diversity is initially low but increases as more niches become available and more species colonise the ecosystem.

During the early stages of succession, energy flow, productivity, species diversity and nutrient cycling are all relatively low.

As succession progresses, more species with unique nutrient requirements and cycling processes colonise the ecosystem, making nutrient cycling more complex.

Ecosystem resilience is the ability of an ecosystem to recover after a disturbance.

Species redundancy is when multiple species perform similar ecological roles, so that if one species is lost, others can fill its function.

Greater diversity often means greater resilience because of species redundancy and genetic variation.

Greater diversity in an ecosystem typically leads to greater resilience, as there are more species and genetic variation to support recovery after disturbances.

False.

Low resilience means an ecosystem takes a long time to recover, or may not fully recover, after a disturbance.

More genetic diversity within a species allows populations to adapt to changing conditions, increasing the ecosystem's resilience.

An alternative stable state is a new equilibrium in an ecosystem that is permanently different from its original state due to severe disturbance.

Deforestation for agriculture can permanently alter succession by transforming a tropical rainforest into a savanna or grassland.

Mining can cause soil erosion and landslides, while also leading to pollution of water sources.

Greater biodiversity increases the likelihood that some species can compensate for losses or changes in the ecosystem, maintaining stability and function.

When an ecosystem is highly resilient, it can recover to its original state after mild disturbance, but a less resilient ecosystem may end up in a new stable state.

Succession is the gradual process by which ecosystems change and develop over time.

An abiotic factor is a non-living environmental factor, such as climate, soil, or water, that influences the process and direction of succession.

Areas with high rainfall and warm temperatures generally experience faster succession.

Wind and extreme temperatures in deserts slow down plant growth and allow only drought-tolerant species to thrive, thus shaping the community during succession.

Sandy soils drain quickly, favouring species that tolerate dry conditions. Clay-rich soils retain more water, favouring moisture-loving species.

False.

Acidic soils and alkaline soils support different plant species, as each type favours species adapted to its pH conditions.

Waterlogging leads to the development of wetland ecosystems with specialised plants like reeds, rushes, and mosses, because oxygen cannot reach plant roots.

Fires can clear away competing vegetation and create nutrient-rich ash in which new plants can sprout and thrive.

Keystone species have a disproportionate effect on their environment, often driving changes in succession and shaping the overall community structure.

Human activities like agriculture frequently disturb land, preventing natural succession and leading to the continuous planting of crops instead of ecosystem recovery.

Gross productivity is the total amount of energy captured by producers through photosynthesis in an ecosystem.

Net productivity is the energy remaining after respiration by producers, available for growth and consumption by other organisms.

The two types of productivity are gross productivity (GP) and net productivity (NP).

Gross productivity is the amount of energy captured by producers through photosynthesis.

False.

Net productivity is the energy left after respiration by producers, not the total energy captured.

Net productivity is calculated by subtracting respiration from gross productivity.

Gross productivity is low in early succession because of harsh environmental conditions, low nutrient availability, and low density of producers.

In early succession, pioneer species like mosses and lichens are the first to colonise bare areas.

Net productivity is relatively high and increases quickly in the early stages of succession because most energy is used for growth and there is less respiration.

In the climax community, gross productivity may remain high, but net productivity decreases and approaches zero because most energy produced is used up by cellular respiration.

As succession progresses, soil formation allows larger plants like shrubs and trees to establish.

Net productivity slows and approaches zero in a climax community because most energy produced by photosynthesis is used for cellular respiration by both producers and consumers.

In climax communities, nutrient cycling is more efficient and the system is more closed.

An r-strategist species is a species that produces large numbers of offspring rapidly, invests little energy in each, and thrives in unstable or recently disturbed environments where resources are temporary or unpredictable.

A K-strategist species is a species that produces few offspring, invests significant energy in their care, and is adapted to stable, long-established environments where competition for resources is high.

False.

r-strategists invest little energy into each individual offspring, which leads to low survival rates per offspring.

K-strategists are more likely to be found in climax communities, as they are adapted to stable, long-established ecosystems with high competition for resources.

r-strategists can rapidly colonise bare or disturbed ground and quickly exploit newly available resources, giving them an advantage in pioneer communities.

K-strategists produce fewer offspring and invest more energy in parental care than r-strategists.

r-strategists are typically found in pioneer communities, whereas K-strategists are successful in climax communities.

The populations of r-strategist species are controlled by density-independent factors, such as environmental disturbances.

A climax community is the final, stable stage in ecological succession, where the ecosystem has reached equilibrium and populations remain relatively stable.

When an ecosystem reaches equilibrium, its species diversity and population sizes remain relatively stable, and the ecosystem is in balance.

In a climax community, species are well-adapted to local conditions, and competition for resources is high.

Examples of climax communities include mature forests such as temperate rainforests or savannas dominated by large mammals.

False.

Ecosystems are dynamic and may have multiple stable states depending on conditions and random events.

An alternative stable state is when an ecosystem can reach different, stable community types depending on local conditions and random events.

The Vera wood-pasture hypothesis suggests that large herbivores like bison or wild cattle prevented forests from closing, creating a mosaic of grassland and woodland.

Without large herbivores acting as primary consumers, the natural mix of trees, shrubs, and grasses in climax communities would not form.

High deer populations eat young tree saplings, which can prevent forest regeneration and alter forest structure.

A plagioclimax is a semi-stable state in an ecosystem that is maintained by human activity, such as grazing or mowing, preventing natural succession.

True.

Without top carnivores, herbivore populations can increase unchecked, leading to overgrazing and reduced forest regeneration.