Animal Physiology

Phsiology

Describes the process and functions of an animal, similar to anatomy

Enviornment shapes animal form and function

Modifies shape-convergent evolution, as a response to shared environmental challenges

Example of how the environment shapes animal form and function

Marine predators, friction and drag issues, water 1000x denser than air, fusiform body, torpedo shape, limits friction, reduces drag, increases speed, maneuverability

Animal cells constrained by physical laws

usually similar sizes between animals, if a cell is too big diffusion gets too slow and metabolic processes slow down

smaller cells

higher surface area: volume, allows movement of more molecules and ions across the cell membrane per unit of cytoplasmic volume 

surface area of a cell 

Exchange of nutrient/waste products

Volume of a cell

relates to amount of chemical activity the cell carries out

As a cell increases in size…

volume grows proportionally more than its surface area

intestinal cells increase surface area by…

long skinny projections that increase surface area without significantly increasing volume, increased absorption of nutrients/diffusion 

Bioenergetics

overall flow and transformation of energy in an animal , determines nutritional needs impacts by animals size, activity and environment

Metabolism 

sum of an organisms chemical reactions

Catabolism

Energy-containing molecules from food use to make ATP, powers cellular work, breaks bonds for energy 

Anabolism 

after the needs of staying alive are met remaining food molecules are used in biosynthesis, energy builds bonds 

What does biosynthesis include…

body growth and repair, synthesis of storage material such as fat and production of gametes 

Why do we need energy

atoms of body in dynamic exchange with environment throughout life, molecular constituents are broken down and rebuilt, adults typically resynthesize 2-3% of body proteins each day 

cells organisation 

Molecular structure and spatial relationship are relatively constant over time, organisation requires energy, replacement of atoms is regulated and controlled 

Conformity 

Internal and external conditions are equal

Regulation

maintains internal consistency in the face of external variability

Metabolic rates

Total amounts of energy an animal uses in a unit of time, roughly proportional to body mass^(3/4)

What affects metabolic rates

Age, sex, activity, nutrition, health 

Basal Metabolic rate 

The metabolic rate of an animal at rest at a comfortable temperature

Standardized metabolic rates

Smaller animals have higher rates per gram, higher metabolic rate demands higher oxygen delivery rate

Metabolic rate is inversely…

rated to size

Endotherm

Generate Body heat from metabolism and maintain a relatively stable body temperature generally higher than ambient temperature

Ectotherm

Warms its body mainly by absorbing heat from the surroundings. Body heat is similar to ambient

Why is the metabolic rate higher in smaller endotherms?

Heat loss occurs more rapidly in smaller animals, have a larger Surface Area to Volume ratio, thus to compensate have higher metabolic rates to counter balance heat loss and maintain a constant body temperature

Small animals have…

a larger surface area to volume ratio

Small animals to supply a higher metabolic rate must…

have a higher breathing rate, higher blood volume, higher heart rate, eat more per body mass, greater rate of oxygen delivery to tissues

Ways to reduce metabolic rate 

torpor, hibernation, aestivation

Torpor

state of reduced activity and metabolism, adaptation to save energy

Hibernation/diapause

Adaptation to cold and food scarcity, body temperature decline, reduced metabolic rate/inactivity 

Avestivation 

Adaptation to prolonged high temperatures and scarce water supplies, reduced metabolic rate/inactivity 

Thermoregulation

Process by which animals maintain an internal temperature within a tolerable range 

Radiation 

Emission of electromagnetic waves 

Evaporation

Loss of heat from a liquids surface that is losing some molecules as gas

Conduction

Direct transfer of thermal heat

Convection 

Transfer of heat by the movement of air or liquid past a body surface 

Are endothermy and ectothermy exclusive

no, birds may bask, sharks can capture heat by swimming muscles, some insects can maintain heat generated by flying

Homeotherm

Has a relatively constant body temperature

Poikilotherms

Have a variable body temperature that fluctuates with the temperature of its environment

Endothermy vs ectothermy 

Endotherms can occupy thermal niches the exclude ectotherms as they have thermal independence from environmental temperatures, can maintain stable body temp even in fluctuations 

Endothermy vs ectothermy exercise 

Both capable of intense exercise in short spurts of a minute or less, endotherms can sustain intensity for longer periods and have a higher metabolic rate 

How to survive freezing temperature

Freeze avoiders, freeze tolerators

Why are ice crystals bad?

Intracellular organelles torn apart, salt concentration increases dehydrating cell, punctures cell membrane

Freeze avoiders

Antifreeze proteins bind to the surface of developing ice crystals impeding growth, sugars in haemolymph lower the freezing point

Freeze tolerators 

Controls ice formation by allowing it to form at high sub-zero temps and promoting growth of multiple small crystals, promotes growth outside of cells

Endotherm adaptations to ice 

Insulation, circulatory responses, kleptothermy, changes in body size, metabolic heat production 

Insulation

Reduce heat flow between an animal and the environment, raised fur or feather trap air increasing efficiency of insulation 

Ciculatory adaptations

regulation of blood flow near the body surface significantly affecting thermoregulation

Vasoconstriction 

Blood vessels constrict reducing blood flow to skin decreasing heat loss

Vasodilation

Blood vessels expand increasing blood flow to skin increasing heat loss

counter current heat exchange

Transfer heat between fluids flowing in opposite direction, heat from warmer artery to cooler vein, reduces heat loss 

Thermogenesis

Increased skeletal muscle activity, hormonal control of mitochondria to increase metabolic activity, some have brown fat, specialized tissue for rapid heat production

Kleptothermy

Animal shares metabolic heat of another

Bergmann Rule 

Warm-blooded animals increase in size in response to decreasing mean temperature gradients 

Allens rule

Endotherms in colder climates have shorter appendages

Body shape

Individuals in colder environments are larger, have shorter and thicker limbs and body appendages

Cooling by evaporative heat loss 

lose heat through evaporation of water from their skin, sweating, panting increase the cooling effect as it increases evaporation from respiratory system and convective heat loss, behavioural adaptations

Circulatory adaptations to heat loss

Fennec fox, large ears with lots of blood vessels, loses heat to the environment by convection, vasodilation

Heterotrophs

Obtain energy from organic molecules manufactured by other organisms

What do animals obtain from eating other organisms

energy source, carbon source, essential nutrients

Herbivores 

eat plants or algae 

Carnivores

eat other animals

Omnivores

Regularly consume animals as well as plants or algae

An animal diet must provide…

Chemical energy for cellular processes, organic building blocks for macromolecules

Macromolecules

Proteins, carbohydrates, lipids, nucleic acids 

Essentail nutrients 

Required materials that an animal cannot assemble from simpler organic molecules 

Essential nutrient classes

Amino acids, fatty acids, vitamins, minerals

Four strategies of feeding

Bulk feeding, Filter feeding, Fluid feeding, Substrate feeding

Bulk feeding

Animals that eat pieces of other organisms or them whole

Filter feeding 

Strain small organisms/food particles from medium, need structures that can capture or trap materials 

Fluid feeding

Suck nutrient-rich fluid from living host, may have long tongue or sharp puncturing mouthpieces

Substrate feeding

Animals that live on or in their food source

Sponge digestive system

Food particles get trapped in collar, brought in by phagocytosis and pinocytosis, broken down intracellularly by lysosomes

Gastrovascular cavity 

Two way gut, food and waste moves through mouth, stores food 

Gastrovascular cavity process

Digestive enzymes are released from a gland cell, enzymes break food down into small particles, particles are engulfed and digested in vacuoles

Alimentary canal

Forms one way gut, food comes in mouth, waste out anus, can ingest food while digesting food 

Dental adaptations 

Structural variation reflecting diet, mammals are specialised for different diets, non mammals are less specialised with more uniform teeth 

Mammalian dentition 

Incisors for biting and cutting, Canines for piercing and tearing, Molars for crushing and grinding 

Non-mammalian denture 

Tearing teeth but not grinding, stomachs to help progression of food to stomach 

Dogfish papillae 

Finger like projections that help movement of food in oesophagus to stomach and secrete mucus

Digestion

use mechanical processes, chemical processes, break down molecules into smaller components, used to build macromolecules

Stomach and intestinal adaptations for carnivores 

Many carnivores have large expandable stomachs, eat alot in one sitting, protein easy to digest so shorter intestines, shorter alimentary canals 

Stomach and intestinal adaptations for herbivores and omnivores

Longer alimentary canal, need longer to digest vegetation and absorb nutrient molecules

Stomach

Low pH, churning action, activity of enzymes, Activity on stomach converts food to chyme, churning moves chyme into small intestine

Cellulose degrading bacteria

Found in stomach of ruminants and caecum, mutualistic relationship with many herbivores, benefit by having stable host environment and supply of nutrients, can extract energy from cellulose rich diet 

Gut bacteria 

Can benefit an animals nutrition, immunity or gut development, produce vitamins, modulate the innate immune system, prevent pathogen growth, regulate the development of the intestinal cells 

Digestion in intestine

Smeel intestine where most digestion happens, long, narrow compartment, pH of chyme neutralized by bicarbonate

Large intestine

More involved with passage of waste and recovery of water

Absorption in small intestine

Digested food pushed through lumen of small intestine, nutrient absorption occurs via villi, huge surface area

Carbohydrates are digested by..

Enzymes in mouth, enzymes from pancreas and intestines in small intestine 

Protein digestion…

Enzymes from gastric juice in stomach, from pancreas and intestine in small intestine

Nucleic acid digestion of nutrients

enzymes from pancreas and intestines in small intestine

Fats digestion by…

Bile salts and enzymes from pancreas in small intestine

Digestion of all basic nutrients 

Chewing, grinding, tongue movement and saliva, low pH and churning in the stomach 

Faeces is made up from…

Water, undigested food material, bacteria, cells, mucus, metabolic waste products 

Osmosis

Diffusion of water across a semi permeable membrane

Osmolarity

solute concentration of a solution, determines movement of water across a selectively permeable membrane

If two solutions differ in osmolarity…

net flow is from the hypoosmotic (less concentrated) to the hyperosmotic (more concentrated) 

Isoosmotic 

Similar to sea water in total salt concentration