AE2001 Fundamentals of ecology / 8 Physical habitat

Liebig’s law of the minimum

Distribution & abundance of a species determined by environmental factor for which it has narrowest tolerance range.

Optimum range

Environmental conditions in which organism thrive, minimal stress & maximum growth, survival & reproduction.

Realised optimum range

Actual range a species occupies, narrower than physiological tolerance due to competition, predation, or other biotic interactions.

Competitive ability

Capacity of an organism to acquire resources & outcompete others in same ecological niche.

Low temperature effects

Reduces metabolic rates, slows enzymatic activity, limits growth & reproduction, frost stress in plants.

High temperature effects

Denatures proteins, disrupts cellular processes, increases evaporative water loss, induces heat stress.

Endothermic organisms

Organisms that generate internal body heat: maintain stable internal temperature & stay active in cold environments.

Example: mammals, birds

Ectothermic organisms

Organisms that rely on external heat sources & adjust activity levels based on ambient temperatures.

Example: reptiles, amphibians

Gigantothermic organisms

Retain heat due to low surface-area-to-volume ratio, can stay warmer than environment without actively regulating their temperature. (Not fully endothermic)

Example: elephants/ large turtles/ Great white shark

Mesothermic organisms

Partially regulate body temperature, not as consistently as true endotherms. Temperature somewhat internally regulated.

Example: Bluefin tuna, some fish.

Poikilothermic organisms

Have body temperature that fluctuates with environment & rely on external conditions to regulate their activity levels.

Example: Fish, amphibians, reptiles

Greenland shark

Cold-water species found in Arctic and North Atlantic oceans. Poikilothermic. Known for extreme longevity (400 years old) one of the longest-living vertebrates.

Coral bleaching

Corals expel symbiotic zooxanthellae due to thermal stress.

Leads to loss of colour, reduced energy supply, increased mortality.

Frost stress

Low temperatures cause water in plant cells to freeze, leads to cell rupture, tissue damage, restricted species distribution in colder regions.

Salinity effects

High salt concentrations reduce plant water uptake, alter osmotic balance, restrict species distribution in saline environments.

Calciphobe

Plant species that prefer acidic soils, struggle in calcareous (high pH) environments.

Example: Rhododendron

Calciphile

Plant species that thrive in alkaline (calcium-rich) soils, absent from acidic regions.

Example: Clematis

Neutrophile

Species that tolerate broad pH range, survive in both acidic and alkaline conditions.

pH limitations

Most organisms cannot survive below pH 4.5 or above pH 9 due to enzyme denaturation and ion imbalance.

Aquatic species are highly sensitive to pH changes.

Fire-dependent ecosystems

Some ecosystems rely on periodic fires to clear competition, recycle nutrients, trigger seed germination.

Example: grasslands, pine forests

Serotinous cones

Seed cones that require fire, to open & disperse seeds

Example: Pinus species

Evapotranspiration

Combined process of water loss from plants (transpiration) & soil (evaporation).

Influences climate and local water cycles.

Temperature extremes

More critical in limiting species distributions than mean temperatures.

Persistence hunting

Human hunting strategy relying on endurance running to overheat, exhaust prey over long distances in hot climates.

Thermophilic bacteria

Microorganisms that thrive in high-temperature environments.

Example: deep-sea hydrothermal vents

Climate envelope

Set of climatic conditions that define species' suitable habitat.

Dragonfly larval development

Depends on cumulative annual temperatures (degree days); larvae require a certain amount of heat accumulation to complete growth & metamorphosis, affects distribution in colder regions.