Lect 04 The Evolution-Ecology Connection Some Plant and Animal Adaptations to Environmental Factors

Plant and Animal Adaptations to Environmental Conditions - Terrestrial Environments *Temperature Extremes *Water Issues – Desiccation Excesses Reproduction Competition for: – Light – Nutrients – Pollen transfer

Temperature and Thermoregulation: Warm- blooded vs. cold blooded Homotherms: constant body temperature Energetically expensive in cold temps Activity over broad range of temps Heterotherms: tend to maintain constant body temperature when active – but due to size may allow temp. to drop when inactive – Examples: daily temp. cycles assoc. with small mammals, birds – Seasonal – true hibernators Poikliotherms: body temperature varies Loss of activity with cold temps Tend to employ behavioral strategies to maintain temperature

Thermoregulation An animal must balance heat gain and loss to maintain its core body temperature –The core exchanges heat with the surface area by conduction –Influenced by thickness/conductivity of fat, movement of blood to surface –The surface layer exchanges heat with the environment via convection, conduction, radiation, and evaporation Terrestrial animals face more extreme (and dangerous) changes in thermal environment than aquatic animals Aquatic animals live in a more stable energy environment

H stored = H metabolism + H conduction + H convection + H radiation + H evaporation – The heat energy from metabolic processes (H metabolism ) is always positive – The heat energy from conduction, convection, radiation, and evaporation can be positive or negative Body heat = heat of metabolic activities +/- heat gained/lost from various sources

Endothermy: the process of generating body heat through metabolic processes assumes sufficient nutrients can be obtained to maintain body temperature Metabolically/energetically expensive Relied on heavily by homotherms/heterotherms Ectothermy: process of gathering heat energy from the environment Energetically inexpensive Major means of thermoregulation by poiklotherms

Acetylcholinesterase in a Poikilotherm: Rainbow Trout Degrades acetylcholine – neurotransmitter Two forms – 2 C - winter form – 17 C – summer form What allows some poikliotherms to function over a broad range of temperatures?

Counter-current heat exchange ~ Poikilotherm Thermo-regulation of swim muscle in Tuna and Sharks Warm blood leaving muscles warms blood entering

Homotherms and the Thermoneutral Zone: Temperature range over which metabolic rate does not change – basal metabolic rate maintained Outside of this range maintenance of body temperature comes with a metabolic cost

The thermoneutral zone is a range of environmental temperatures within which the metabolic rates are minimal Metabolic rate increases beyond the critical temperatures above and below the thermoneutral zone

Mechanisms/Adaptations impacting TMZ Behaviorial traits Insulation Countercurrent heat exchange mechanisms Vasoconstriction/vasodilation effects

Bird on Ice: thermal regulation via heat exchange Blood entering feet warms blood returning Other mechanisms – Cutaneous circulation reduced with cold temps

Raynaud’s syndrom – an example of a faulty thermoregulatory process

Cooling in homotherms: Perspiration Shading Panting Vasoconstriction/vasodilation Countercurrent circulatory mechanisms – redirecting of blood flow Behavior Radiating surfaces

Keeping heat out – The oryx cools the brain by cooling venous blood via evaporation in the sinus cavity

Heterotherms – regulate temp when active – but may allow temp to fall otherwise Hibernation: Period of reduced metabolic rate Fat reserves provide energy Torpor: esp in small creatures Enter torpor if food unavailable Torpor  low metabolic rate, even at high temps

Temperature optima Mesophiles: optimal growth 20-45C Thermophilic – adapted to high temperature Psychrophilic – adapted to cold environment Acclimation – physiologic adaptations – Physiological change

Decreasing Water Loss from Foliage – Different Approaches: Summer Deciduous: Loose leaves during warm/dry season Geophytes: retain food & water in subterranean bulb during dry months Annuals: complete life cycle before dry season begins – over-summer as seed

More Drought Evasion Strategies Low growth habit (reduced wind exposure) Hirsute leaves Leaf size/shape Leaf coloration

CO 2 necessary for photosynthesis enters passively stomata have to be open for long periods of time Water loss a serious problem in low RH climates

Strategies for decreasing water loss via leaves: Protect stomata: – Strategies: sunken in pits or grooves Obstructed by hairs, wax tubules More frequently found on undersides of leaves Develop small, thickened, wax coated leaves – sclerophyllous – Typically evergreen – most photosynthesis during spring/autumn – Tough/fibrous, poor nutritional quality, aromatic oils act as defense

Roots with different water seeking strategies in dry climates Dual root systems: – Thick taproot – – Mat of fine roots close to soil surface

Coast Redwood – Shallow root system Ca 6 ft. from surface – Reliance on summer fog drip limits range

Survival Following Fire: Sprouters and Seeders Sprouters: develop from burls or root crown (lignotuber) – May also develop from bud wood protected beneath bark (redwoods do this for example) Seeders: – Refractory seed survive prolonged fire – Germination stimulated by heat, volatile smoke related chemicals – Fire followers – Ashes of fire provide nutrients

Adaptations of Plants in CA Chaparral: Tiered root system with high root system: foliage ratio Sclerophyllous, small leaves Regeneration following fire

Too much water can stress plants as much as too little water – The symptoms of excess water are similar to symptoms of not enough water! Plants need sufficient water and rapid gas exchange with their environment – Much of this exchange occurs in the soil – When soil pores are filled with water, roots are essentially drowned as they switch to anaerobic respiration Wetland Environments Present Unique Constraints on Plant Adaptations

In the response to anaerobic or flooded conditions – Some plants accumulate ethylene in their roots –Stimulates cells to self-destruct and form gas-filled chambers called aerenchyma – Flooded roots die and adventitious roots emerge above where oxygen is available – Shallow root systems develop in poorly drained soils – Pneumatophores are specialized growths of the root systems of plants growing where the water table fluctuates

Salts Hyperosmotic or Hypertonic – more dissolved substances outside cell water leaves the cell  crenation (like a pickle) Hypoosmotic or Hypotonic – less dissolved substances outside water enters the cell  cell swells and bursts Isoosmotic or Isotonic – same concentration inside and out, the cell is at dynamic equilibrium

Halophytes are plants that take in water containing high levels of solutes For a halophyte to maintain a water potential gradient, they: – Accumulate high levels of ions within their cells (especially leaves) – Dilute solutes with stored water – Secrete salt onto the leaf surface to be washed away by rainwater The degree of salt tolerance varies greatly in different halophytes Wetland Environments Present Unique Constraints on Plant Adaptations

Pickle Weed: adaptations to salty environments Concentrates salt – thus water is absorbed from brackish waters