Animal Anatomy and Physiology

Diverse Forms, Common Challenges

• Anatomy refers to an organism's biological form.
• Physiology refers to an organism's biological functions.
• The comparative study of animals shows a close correlation between form and function.
• Structures are often specialized for particular functions.

Animal Form and Function Correlation

• The size and shape of an animal influences how it interacts with its environment.
• An animal's body plan is genetically determined and has evolved over millions of years.

Evolution of Animal Size and Shape

• Physical laws influence strength, diffusion, movement, and heat exchange in animals.
• Water properties limit the possible shapes for fast-swimming animals.
• Convergent evolution leads to similar adaptations, irrespective of the organism.
• Thicker skeletons are essential to support them as animals grow bigger.

Exchange with the Environment

• Animal cells' membranes must facilitate the exchange of materials like nutrients, waste, and gases.
• Surface area is proportional to the rate of exchange, while volume is proportional to the amount of material exchanged.

Adaptations for Exchange

• Single-celled organisms have sufficient surface area for all exchanges
• Multicellular organisms with a saclike body plan which have thin body walls to facilitate diffusion.
• Flat animals, tapeworms, directly expose most cells to the environment.
• Specialized evolutionary adaptations which include branched folds are structures for exchange.

Internal Environment

• Interstitial fluid resides in the space between cells and connects exchange surfaces to body cells.
• A complex body plan aids in maintaining a stable internal environment.

Hierarchical Organization of Body Plans

• Tissues with different functions constitute the cells of most animals.
• Organs comprise tissues, and organ systems comprise organs.
• The pancreas is an organ that belongs to more than one organ system.

Four Main Types of Animal Tissues

• Epithelial
• Connective
• Muscle
• Nervous

Epithelial Tissue

• Epithelial tissue lines the organs, and covers the body's exterior and interior cavities.
• The cells are closely packed.
• Epithelial cell shapes include cuboidal, columnar, and squamous.
• Epithelial cells arrangements include simple, stratified, and pseudostratified.

Connective Tissue

• Connective tissue supports and connects tissues.
• Cells are sparsely distributed within an extracellular matrix.
• The matrix comprises fibers with a liquid, solid, or jellylike basis.
• Collagenous fibers provide flexibility and strength
• Reticular fibers serve a joining role
• Elastic fibers can be stretched, and then snap back to their shape originally.

Connective Tissue Containing Cells

• Fibroblasts secrete extracellular fiber protein
• Macrophages are involved in the immune system

Vertebrate Connective Tissue

• Loose connective tissue connects epithelia to underlying tissues, and holds the organs into place.
• Tendons connect muscles to bones, and ligaments connect bones at joints; both are fibrous connective tissues.
• Bones are a mineralized tissue that makes up the skeleton.
• Adipose tissue stores fat for insulation and energy.
• Blood is composed of blood cells and cell fragments in blood plasma.
• Cartilage is strong, and provides flexible support.

Muscle Tissue

• Muscle tissue facilitates nearly all body movements.
• Interactions between actin and myosin protein filaments enable muscle contraction.

Three Types of Muscle Tissue in Vertebrates

• Skeletal muscle or striated muscle which is for voluntary movement
• Smooth muscle is for involuntary body activities.
• Cardiac muscle is for heart contraction.

Nervous Tissue

• Nervous tissue functions in information transmission, and processing.
• Neurons, or nerve cells, transmit nerve impulses.
• Glial cells, or glia, support the neurons.

Coordination and Control

• Control and coordination rely on the endocrine and nervous system.
• Hormones are signaling molecules released into the bloodstream by the endocrine system.
• Hormones coordinate gradual changes.
• The nervous system conveys signals through specific pathways.
• Nerve signal transmission is fast, and coordinate rapid responses.
• The endocrine and nervous systems often work together.

Feedback Control

• Animals manage internal environment while dealing with environmental fluctuations by conforming or regulating
• Regulators use internal control mechanisms to control internal changes.
• Conformers allow internal conditions to vary with outside changes.
• Animals can regulate some environmental variables and conform to others.

Homeostasis

• A "steady state" or internal balance is maintained by organisms using homeostasis.
• Body temperature, pH in blood, and glucose concentration, remain at a constant level due to homeostasis.

Mechanisms of Homeostasis

• Homeostasis regulates changes in environment in the body.
• A stimulus detected by a sensor occurs with shifts over/under set point, for any given variable.
• After detecting a stimulus, a control center responds.
• The response returns the variable back to set point.

Acclimatization

• Acclimatization is when homeostasis adjusts to external environment changes.
• Adjusting to low oxygen pressure at high altitudes is a temporary change during the animal’s lifetime.

Thermoregulation

• Thermoregulation is how animals maintain an internal temperature within a normal range.

Endothermy and Ectothermy

• Endothermy involves generating heat through metabolism; an example is seen in mammals and birds.
• Ectothermy involves gaining heat from external sources; an example is seen in most invertebrates, amphibians, or nonavian reptiles.

Stable Body Temperature

• Endotherms maintain stable body temperature despite environmental fluctuations.
• Ectothermy is less energetically expensive than endothermy.
• Ectotherms tolerate greater internal temperature variation.

Variation in Body Temperature

• Poikilotherm's body temp is as same as that of it's surrounding
• Homeotherm's body temp is constant.
• Heat source and body temperature is not fixed.
• Hibernating mammals have fluctuating body temperatures whereas some marine fish have stable temperatures.

Heat Exchange

• Organisms exchange heat by radiation, evaporation, convection, and conduction.

Thermoregulation in Mammals

• Heat regulation in mammals are made possible by skin, hair and nails
• Thermoregulation is aided by insulation, circulatory adaptations, evaporative heat loss, behavioral responses, and adjusting metabolic heat production.

Insulation

• Insulation, an adaptation for thermoregulation, is reduced by skin, feathers, fur, and blubber.
• Marine mammals use insulation.

Circulatory Adaptations

• Animals alter the amount of blood flowing thus regulating heat.
• Vasodilation increases blood flow leading to greater heat loss.
• Vasoconstriction decreases blood flow leading to lower heat loss.
• Birds and mammals use blood vessels arranged for countercurrent exchange.
• Countercurrent heat exchangers facilitate heat transfer between fluids flowing in opposing directions and thereby minimizes heat loss.

Cooling by Evaporative Heat Loss

• Heat loss is done through evaporation of water from the skin.
• Sweating or bathing cools the animal.
• Birds/mammals use panting to increase the cooling effect.

Behavioral Responses

• Both ectotherms and endotherms regulate body temperature using behavior.
• They seek warm places or heat sources when feeling cold.
• Bathing, moving to cooler areas, huddling, or changing orientation can help when hot.

Adjusting Metabolic Heat Production

• Thermogenesis maintains body temperature through metabolic heat adjustment.
• Muscle activity like shivering raises body temperature.
• Some birds/nonavian reptiles shiver to generate heat.
• Metabolic activity is increased by nonshivering thermogenesis.
• Some mammals use brown fat tissue production.

Acclimatization in Thermoregulation

• Birds/mammals adjust insulation to changing season temperatures.
• To maintain their fluidity at low temperatures, membranes change their lipid composition.
• To prevent ice from forming at subzero temps, ectotherms produce antifreeze compounds.

Physiological Thermostats and Fever

• Thermoregulation in mammals is controlled by hypothalamus.
• Heat loss heat-generating by the hypothalamus
• Fever increases in body temperature which is a biological thermostat.
• To combat infections, some ectotherms move to warmer environments to increase temp.

Energy Requirements

• Bioenergetics describes the flow and transformation of energy in an animal.
• An animal's nutritional requirements relate to its size, activity, and environment.

Energy Allocation and Use

• Organisms can be classified according to their energy source.
• Autotrophs rely on light and heterotrophs harvest chemical energy.
• ATP fuels cellular work with food molecules.
• Biosynthesis, such as body growth, repair, and fat storage, can use remaining food molecules after sustenance needs are met.

Quantifying Energy Use

• Metabolic rate is the sum of energy used by an animal per unit of time.
• Metabolic rate can be determined by heat loss or the amount of O2 consumed or CO2 products.

Basal Metabolic Rate and Standard Metabolic Rate

• Basal metabolic rate (BMR) measures the metabolic rate of resting endotherms at a comfortable temperature.
• Standard metabolic rate (SMR) measures the metabolic rate of resting ectotherms at a specific temperature.
• SMR is at a specific temperature
• Both rates assume animals that are non-growing, fasting, non-stressed.
• Endotherms have much larger metabolic rate compared to that of ectotherms
• Adult male BMR is 1600–1800 kcal/day and female = 1300–1500 kcal/day.
• Alligator SMR is 60 kcal/day at 20°C.

Influences on Metabolic Rate

• Metabolic rate depends on factors besides endothermy or ectothermy.
• Some factors are age, sex, size, activity, temperature, and nutrition.

Size and Metabolic Rate

• Body mass determines the metabolic rate.
• Smaller animals have higher metabolic rates than larger ones.
• Leads to higher oxygen delivery and breathing rate is by smaller animals.

Activity and Metabolic Rate

• Both ectotherm and endotherm activity greatly affects the metabolic rate.
• The maximum metabolic rate is inversely proportional to the duration of the exercise.
• For most terrestrial animals, the rate of energy consumption is around 2 to 4 times the BMR or SMR.
• The animal's size, behavior, and environment determine how much energy for it's activities.

Torpor and Energy Conservation

• Decreased activity and metabolism defines torpor.
• Torpor enables the animal to survive in tough conditions.
• Hibernation is winter adaptation.