Biomes, zonation, succession

Mainly using abiotic climate factors, especially temperature and precipitation.

Weather is the short-term atmospheric conditions at a specific time and place (e.g., temperature, rainfall, wind, cloud cover).

Because Earth is spherical and tilted, sunlight hits different latitudes at different angles and day length varies by season.

Weather is short-term; climate is long-term average patterns over decades.

By salinity: freshwater (low salinity) versus marine (high salinity).

Freshwater, marine, forest, grassland, desert, and tundra biomes.

Warm air rises (less dense) and cool air sinks (more dense), creating convection that redistributes heat.

Temperature and precipitation.

Light penetration and oxygen availability (also nutrients and temperature variation).

Climate is the long-term average pattern of atmospheric conditions in an area, usually measured over decades.

Moderate rainfall with seasonal growth, often maintained by grazing and periodic fires.

Hadley cell, Ferrel cell, and Polar cell (in each hemisphere).

Wind (wind-driven movement in the upper ocean).

Salinity (freshwater vs marine).

A biome is a large group of ecosystems with similar climate, vegetation and organisms, which can occur on different continents.

Salinity, tidal inundation, anaerobic soils, and warm temperatures in tropical/subtropical coasts.

Around 30° latitude where air sinks, warms, and dries, reducing cloud formation and rainfall.

Temperature and precipitation.

Density differences caused by temperature and salinity: colder, saltier water is denser and sinks.

Rising air cools and condenses, forming clouds and increasing rainfall.

Biomes can shift poleward or to higher altitudes as temperature and precipitation patterns change and species track their tolerance ranges.

Because air often sinks around 30° latitude, warming and drying as it descends, which reduces cloud formation and rainfall.

Because similar long-term climate conditions lead to similar vegetation, which supports similar animal communities.

They redistribute heat, moderating temperatures and influencing regional climate patterns.

They redistribute heat around the planet, moderating regional temperatures and influencing rainfall patterns.

Zonation is a change in species composition across space along an environmental gradient.

Altitude, latitude, tidal level, and soil depth.

A change in species composition across space along an environmental gradient.

Abiotic conditions change, species have tolerance limits, and competition affects where species survive.

Biodiversity generally decreases as altitude increases because conditions become colder, windier, and growing seasons shorten.

A gradual change in an abiotic factor across space (e.g., tidal exposure, altitude, moisture, light).

Tidal level on a rocky shore (high tide zone → mid tide → low tide).

Transects (often with quadrats at intervals) to record changes across a gradient.

The low tide zone, because it is submerged most of the time and conditions are more stable.

Abundance (number of organisms).

A transect is a straight line laid across an environmental gradient along which observations are made at intervals.

Because abiotic conditions change across space, species have tolerance limits, and competition excludes less adapted species from some zones.

The range of abiotic conditions a species can survive and reproduce in; outside the range it cannot persist.

Local scale (e.g., rocky shores, forests) and global scale (e.g., climate zones and biomes).

Species distribution and abundance along a transect; kite width indicates abundance and position shows where the species occurs.

Seral stages progressing toward a climax community.

Succession is the process of change in species composition and community structure over time.

Succession that starts on bare rock/land with no soil present.

Resilience is the ability of an ecosystem to resist disturbance or recover and return to a stable state after disturbance.

Biodiversity, biomass, and soil depth/nutrients (also food web complexity).

By keeping ecosystems at early stages through farming, grazing, or urban development.

Primary starts with no soil (bare rock). Secondary starts with soil present after disturbance.

Pioneer species are the first organisms to colonise a barren environment; they tolerate harsh conditions and start soil formation.

Recovery. Resilience describes how well an ecosystem bounces back after disturbance, not whether disturbance happens.

Succession that starts after disturbance where soil already exists (e.g., after fire or farming).

Biomass increases, biodiversity increases, soil depth/nutrients increase, and food webs become more complex.

Because soil, nutrients, and often seeds/roots are already present, so recovery can start immediately.

A climax community is the final, stable community in equilibrium with the environment, with maximum biodiversity for that area.

Large storages (e.g., biomass, soil nutrients) act as buffers, allowing the system to keep functioning if inputs are temporarily disrupted.

It helps plan ecosystem restoration by predicting which stage comes next and estimating recovery time after disturbance.

Succession is change over time; zonation is change over space.

More species and interactions create complex food webs with multiple pathways, so loss of one species is less damaging.

Lichens and mosses (also algae).

Resilience is the ability to resist disturbance or recover and return to a stable state after disturbance.

Species change the environment over time (e.g., soil and shade), making conditions suitable for different species to replace them.

Redundancy is when multiple species perform similar roles; it increases resilience because another species can replace a lost function.

Deforestation and urbanisation (also intensive agriculture or repeated grazing).

After a volcanic eruption or retreating glacier, succession can start on bare rock with lichens and mosses.

Primary = from scratch (bare rock, no soil). Secondary = soil already there (just disrupted).

Biodiversity and large storages (also redundancy and negative feedback).