Lecture 10 Animal Adaptations

Key processes common to all animals Animal adaptations: Key processes common to all animals Acquire and digest food Absorb oxygen Maintain body temperature and water balance Adapt to light and temperature variations

The ultimate source of most nutrients needed by animals is plants Plant quantity and quality affect herbivorous consumers Highest-quality plant food is high in nitrogen (protein)—growing tips, new leaves and buds As nitrogen content increases, assimilation of plant material improves Herbivores show some preference for the most nitrogen-rich plants The need for quality food differs among herbivores (ruminants versus nonruminants)

All animals are _______________ (in terms of energy acquisition). Carnivores Herbivores Omnivores

Carnivores have no problem digesting and assimilating nutrients from their prey A carnivore’s biggest issue is in obtaining enough food Carnivores have short intestines and simple stomachs

Herbivores: live on diets high in cellulose and low in protein Grazers and browsers These animals do not have the enzymes necessary to digest cellulose and so depend on specialized microbes living in their digestive tract to digest these Fermentation of cellulose by microbes releases inorganic acids and alcohols Foregut versus hindgut fermenters

Ruminants = foregut fermenters (cattle, deer) and have a four-compartment stomach Rumen: Digestion by microbes (fatty acids and methane) and churning by muscles Reticulum: Digestion by microbes and churning by muscles Omasum: Further digestion Abomasum (true glandular stomach): Microbial action breaks down carbohydrates and synthesizes B-complex vitamins and amino acids Foregut fermenters also regurgitate food and chew before it passes to the omasum

Figure 7.6b

Hindgut fermenters (rabbits, horses) have a long intestinal tract through which the food passes slowly and houses microbes in a caecum Coprophagy is the reingestion of fecal material for further extraction of nutrients

Aquatic animals live in a more stable energy environment 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

Hstored = Hmetabolism + Hconduction + Hconvection + Hradiation + Hevaporation The heat energy from metabolic processes (Hmetabolism) is always positive The heat energy from conduction, convection, radiation, and evaporation can be positive or negative heat gained/lost from various sources heat of metabolic activities Body heat = +/-

Thermoregulation: Regulation of Body Temperature Body heat = heat of metabolic activities +/- head gained/lost from various sources Poikilotherms = organisms whose body temp. varies with environmental temperatures Ectotherms: absorb heat from environment Homeotherms = maintain ~ constant body temperature Endotherms: internal energy/activities regulate Heterotherms are animals that regulate body temperature by both endothermy and ectothermy Bats, bees, and hummingbirds

Homeostasis depends on negative feedback Negative feedback counteracts the initial change and brings the level back within the accepted range

Poikilotherms have an upper and lower thermal limit that they can tolerate Can maintain a relatively constant daytime body temperature by behavioral means The operative temperature range is that at which poikilotherms carry out their daily activities Poikilotherms have a low metabolic rate and a high ability to exchange heat between body and environment

Aquatic poikilotherms are poorly insulated and heat is easily transferred from the animal (usually at the gill) and environment A rete, or blood circulation system, is found in sharks and tunas and allows them to keep internal temperatures higher than external ones Fish and aquatic invertebrates maintain a constant temperature because seasonal water temperatures are relatively stable Upper and lower limits of temperature tolerance vary among poikilotherm species

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

Countercurrent heat exchange can conserve heat in a cold environment or can cool vital parts of the body under heat stress Keeping heat in The porpoise maintains body core temperature by exchanging heat between arterial and venous blood A rete is a discrete vascular bundle that acts similar to the porpoise’s flippers

Figure 7.17

Figure 7.18

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

Acetylcholinesterase in a Poikilotherm: Rainbow Trout Degrades acetylcholine – neurotransmitter Two forms 2 C - winter form 17 C – summer form

Homeotherms: Metabolic activity provides heat energy Control via hypothalamus/pituitary – homeostasis Metabolically expensive! Strategies to prevent heat loss: High metabolic rate Insulation Countercurrent heat exchange Survival of food unavailability: Storage in body fat Torpor/hibernation Size The smaller the organisms (larger SA/V ), the greater the relative heat loss to the surrounding environment This heat loss must be offset by increased metabolic activity Large poikilotherms (e.g., alligators) are restricted to warmer environments

Figure 7.16

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

7.14 Some Animals Use Unique Physiological Means for Thermal Balance Supercooling of body fluids takes place when the body temperature falls below the freezing point without actually freezing The presence of solutes (e.g., glycerol) in body fluids functions to lower the freezing point of water Characteristic of arctic marine fish, some insects, reptiles, and amphibians

Animals in arid environments face a severe problem of water balance and deal with the problem in several ways Evade drought Leave the area during the dry season Enter a state of dormancy or diapause Develop a hardened (watertight) casing Evade the effects of drought Reduce respiratory water loss Nocturnal activity Utilize metabolic water Produce a concentrated (hypertonic) urine

Solutes – dissolved substances Solutions: Solutes – dissolved substances Osmosis: movement of water across cell membrane Osmotic potential: tendency of solution to attract water from high to low concentration due to dissolved substances – higher conc. dissolved substances – lower tendency to loose water  lower osmotic potential Semipermeable: the capacity (of a cell membrane) to restrict passage of certain substances – important in maintaining appropriate concentration of water/dissolved substances within a cell or organism DW: osmotic potential = 0 Osmotic potential is negative number – the higher the conc. of dissolved salts the lower the osmotic potential or more negative it becomes

In solutions 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

Aquatic organisms living in freshwater are hyperosmotic and gain water spontaneously from the surrounding water (which, by comparison, is hypoosmotic) Absorb and retain salt Produce copious amounts of dilute urine Marine organisms are hypoosmotic and lose water spontaneously to the surrounding water (which, by comparison, is hyperosmotic) Prevent accumulation of salts in the body—actively pumping salts across gill surfaces Inhibit water loss through the body wall and produce highly concentrated urine