27.

1 EVOLUTION OF NUTRITION •Micronutrients - are needed in small quantities

and include organic vitamins and inorganic
Nutrition - includes all of those processes by minerals
which an animal takes in, digests, absorbs,
stores, and uses food (nutrients) to meet its • Calorie (L. calor, heat) - is the amount of
metabolic needs. energy required to raise the temperature of 1 g
of water to 1°C.
Digestion- is the chemical and/or mechanical
breakdown of food into particles that the • calorie, with a small c, is also called a gram
individual cells of an animal can absorb. calorie.

•Autotrophs - synthesize all of their own •kilocalorie, also known as a Calorie or kilogram
complex molecules from simpler ones(Green calorie (kcal), is equal to 1,000 calories.
plants and photosynthetic protists)
•Carbohydrates - are a major carbon source for
• heterotrophs - are animals that consume incorporation into important organic
other animals for their nutrients compounds.

•herbivores-subsist entirely on plant material •Cellulose is sometimes called dietary fiber. It

assists in the passage of food through the
•carnivores - eat only meat (such as hawks and alimentary canal of mammals.
spiders)
•Neutral lipids (fats)\ triacylglycerols- are
•omnivores - eat plant and animal matter(such contained in fats
as humans bears, raccoons, and pigs)
and oils, meat and dairy products, nuts, and
• insectivores - eat arthropods. (such as bats) some fruits and
•Once an animal obtains complex organic vegetables high in fats, such as avocados.
molecules from its diet, it can lose the ability to
synthesize those molecules and expend less •Lipids - are the most concentrated source of
energy on biosynthetic processes. This is an food energy.
evolutionary advantage.
•Sterols -are also required for the synthesis of
steroid hormones.

•Cholesterol, which is incorporated into cell

membranes.

•Proteins- are needed for their amino acids,

27.2 THE METABOLIC FATES OF NUTRIENTS which heterotrophs use to build their own body
IN HETEROTROPHS proteins
• Macronutrients - are needed in large
quantities and include the carbohydrates, lipids,
and proteins.
•Micronutrients- are usually small ions, organic << VITAMIN CHARACTERISTICS>>
vitamins, inorganic minerals, and molecules
that are used repeatedly in enzymatic reactions Vitamin A (retinol)
or as parts of certain proteins. - synthesized from carotenes; stored in liver;
•Amino acids-Proteins the animal needs. stable in heat, acids, and alkalis.

• Essential minerals\ macrominerals- these are -Necessary for synthesis of visual pigments,
some minerals that are needed in relatively mucoproteins, and mucopolysaccharides; for
large amounts. normal development of bones and teeth; and
for maintenance of epithelial cells.
•sodium and potassium are vital to the
functioning of every nerve and muscle in an -Liver, fish, whole milk, butter, eggs, leafy green
animal’s body. vegetables, and yellow and orange vegetables
and fruits.
•Trace minerals, trace elements\
microminerals- are the minerals that an animals Vitamin D
need in only very small amounts for various - a group of sterols; resistant to heat, oxidation,
enzymatic functions. acids, and alkalis;
•Vitamin- is the general term for a number of - stored in liver, skin, brain, spleen, and bones
chemically unrelated, organic substances that
occur in many foods in small amounts and are - Promotes absorption of calcium and
necessary for normal metabolic functioning. phosphorus; promotes development of teeth
and bones
•Most water-soluble vitamins, such as the B
vitamins and vitamin C, are coenzymes needed - Produced in skin exposed to ultraviolet light;
in metabolism. in milk, egg yolk, fish-liver oils, fortified foods

•Sodium - is a good example and is needed for Vitamin E (tocopherol)

nerve and muscle functioning.
- a group of compounds; resistant to heat and
27.3 DIGESTION visible light; unstable in presence of oxygen and
ultraviolet light
•Intracellular (“within the cell”) digestion - are
strategy that some cells take in whole food - stored in muscles and adipose tissue
particles directly from the environment by
diffusion, active transport,and break them
down with enzymes to obtain nutrient - An antioxidant; prevents oxidation of vitamin
A and polyunsaturated fatty acids; may help
•Intracellular digestion circumvents the need
maintain stability of cell membranes
for the mechanical breakdown of food or for a
gut or other cavity in which to chemically digest - Oils from cereal seeds, salad oils, margarine,
food. shortenings, fruits, nuts, and vegetables
Vitamin K (phylloquinone) (2) removal of nutrients from the water, and

- Occurs in several forms; resistant to heat, but (3) transport of the nutrients to the mouth of
destroyed by acids, alkalis, and light the digestive system.

-stored in liver, Needed for synthesis of •Sponges, ascidians, branchiopods, ectoprocts,

prothrombin; needed for blood clotting entoprocts, phoronids, most bivalves, and many
crustaceans,polychaetes, gastropods, and some
- Leafy green vegetables, egg yolk, pork liver, nonvertebrate chordates are suspension
soy oil, tomatoes, cauliflower. feeders.

•Deposit feeding- involves primarily

• Extracellular digestion, the breakdown of omnivorous animals.
larger pieces of food into constituent molecules These animals obtain their nutrients from the
via enzymes usually occurs within a special sediments of soft-bottom habitats (muds and
organ or cavity. sands) or terrestrial soils.
27.4 ANIMAL STRATEGIES FOR GETTING AND •Direct deposit feeders- simply swallow large
USING FOOD quantities of sediment (mud, soil, sand, and
•Continuous feeders - are slow-moving or organic matter).
completely sessile animals (they remain •Herbivory- is the consumption of macroscopic
permanently in one place). plants. This common feeding strategy requires
For example, aquatic suspension feeders, such the ability to “bite and chew” large pieces of
as tube worms and clams, remain in one place plant matter (macroherbivory).
and continuously “strain” small food particles • Radula -is a muscularized, belt-like rasp armed
from the water. with chitinous teeth
•Discontinuous feeders- tend to be active, • Predation- is one of the most sophisticated
sometimes highly mobile, animals. Typically, feeding strategies, because it requires
discontinuous feeders have more digestive the capture of live prey.
specializations than continuous feeders because
discontinuous feeders take in large meals • Predators can be classified by how they
capture their prey:
•Suspension feeding - is the removal of
suspended food particles from the surrounding 1) Motile stalkers- actively pursue their prey
water by some sort of capture, trapping, or
filtration structure. 2) Lurking predators - sit and wait for their prey
to come within seizing distance.
This feeding strategy involves three steps:
3) Sessile opportunists -usually are not very
(1) transport of water past the feeding mobile. They can only capture prey when the
structure, prey organism comes into contact with them.
4) Grazing carnivores - move about the Function in extracellular digestion and
substrate picking up small organisms. absorption:

•Fluid feeding - is especially characteristic of 1)midgut

some parasites, such as the intestinal
nematodes that bite and rasp off host tissue or 2)hindgut
suck blood. 3) rectum
•Gastrovascular cavity- is the blind sac in the •Digestion is a coordination of three cycles: (1)
gut , It has only one opening that is both the feeding (2) extracellular digestion, and (3)
entrance and the exit intracellular digestion.
-it is an incomplete digestive tract. Some •Intracellular digestion - releases the nutrients
specialized cells in the cavity secrete digestive into the blood and produces the fragmentation
enzymes that begin the process of extracellular spherules that both excrete wastes and lower
digestion. the pH for optimal extracellular digestion.
•The development of the anus and complete •The grasshopper - is a representative insect
digestive tract (alimentary canal) in ancestral with a complete digestive tract and extracellular
animals was an evolutionary breakthrough. digestion.
Three examples further illustrate digestive •Midgut -secretes other enzymes
systems in protozoa and invertebrates: (carbohydrases, lipases, and proteases) that
(1) the incomplete digestive system of a ciliated enter the crop.
protozoan is an example of an intracellular •Insects have a complete digestive tract
digestive system because it contains a mouth, esophagus, crop,
(2) the bivalve mollusc is an example of an gastric seca, stomach, intestine, rectum, and
invertebrate that has both intracellular and anus.
extracellular digestion 27.6 DIVERSITY IN DIGESTIVE STRUCTURES:
(3) an insect is an example of an invertebrate VERTEBRATES
that has extracellular digestion and a complete •The complete vertebrate digestive tract (gut
digestive tract. tube)- is highly specialized in both structure
•The digestive tract has a short esophagus and function for the digestion of a wide variety
opening into a stomach, midgut, hindgut, and of foods.
rectum. •The basic structures of the gut tube: PESSOLRA
•The stomach contains a crystalline style, 1)the oral cavity (buccal cavity or mouth)
gastric shield, and diverticulated region. These
diverticulae are blind-ending sacs that increase 2)pharynx
the surface area for absorption and intracellular
3)esophagus
digestion.
4) stomach 1. Ingestion—eating

5)small intestine 2. Peristalsis—the involuntary, sequential

muscular contractions that move ingested
6)large intestine nutrients along the digestive tract
7)rectum 3. Segmentation—mixing the contents in the
8) anus/cloaca. digestive tract

3 important glandular systems are associated 4. Secretion—the release of hormones,

with the digestive tract: enzymes, and specific ions and chemicals that
take part in digestion
(1) the salivary glands;
5. Digestion—the conversion of large nutrient
(2) the liver, gallbladder, and bile duct; particles or molecules into small particles or
molecules
(3) the pancreas and pancreatic duct
6. Absorption—the passage of usable nutrient
•Birds lack teeth, probably to reduce body
molecules from the small intestine into the
weight for flight. •Teeth are specialized,
bloodstream and lymphatic system for the final
depending on whether an animal feeds
passage to body cells
•Lampreys are an exception of salivary gland
7. Defecation—the elimination from the body of
because they have a pair of glands that secrete
undigested and unabsorbed material as waste.
an anticoagulant needed to keep their prey’s
blood flowing as they feed.

•The esophagus- is short in fishes and

amphibians, but much longer in amniotes due
to their longer necks. •The serosa forms a moist epithelial sheet
called the peritoneum. This peritoneum lines
•bird’s gizzard develops from the posterior part the entire abdominal cavity and covers all
of the stomach called the ventriculus. internal organs

• Bile - is a fluid containing bile salts and bile Two types of Smooth muscle layer
pigments.
•longitudinal smooth-muscle layer
- Bile salts play an important role in the
digestion of fats, although they are not • circular smooth-muscle layer
digestive enzymes. •Submucosa - contains connective
tissue, blood, and lymphatic vessels.

27.7 THE MAMMALIAN DIGESTIVE SYSTEM •The mucosa faces the central opening, which is
called a lumen.
•The process of digesting and absorbing
nutrients in a mammal includes:
•Peristalsis - is analogous to squeezing icing (1) it stores and mixes the food bolus received
from a pastry tube from the esophagus

•Segmentation-a movement mixes the food (2) secretes substances(enzymes, mucus, and
with digestive secretions and increases the hydrochloric acid [HCl]) that start the digestion
efficiency of absorption. of proteins

- an oscillating back-and-forth movement in (3) helps control the rate at which food moves
the same place where the small and large into the small intestine via the pyloric sphincter.
intestines have rings of smooth muscles that
repeatedly contract and relax. •Three types of cells are in gastric glands.

•Sphincters - are rings of smooth or skeletal 1) Parietal cells -secrete a solution containing
muscle at the beginning or ends of specific HCl
regions of the gut tract. 2) Chief cells- ecrete pepsinogen, the precursor
-also influence the flow of material through of the enzyme pepsin
the gastrointestinal tract and prevent backflow 3) Mucous cells- that secrete mucus that coats
• The lips- are highly vascularized, skeletal the surface of the stomach and protects it from
muscle tissue with an abundance of sensory the HCl and digestive enzymes.
nerve endings.

•Saliva - also contains bicarbonate ions

(HCO32), which buffer chemicals in the mouth,
and thiocyanate ions (SCN2). • Stomach contents have been sufficiently
mixed and are a semiliquid mass called chyme.

3 parts of small intestine

• Lysozyme -which kill microorganisms. It also
contributes an enzyme (amylase) necessary for 1) Duodenum -functions primarily in digestion
the initiation of carbohydrate digestion.
2) Jejenum
•Pharynx (Gr. “the throat”)- the common
3) Ileum
passageway for both the digestive and
respiratory tracts. • The jejunum and ileum function in nutrient
absorption.
•Epiglottis -temporarily seals off the opening
(glottis) to the trachea so that swallowed food • The duodenum contains many digestive
does not enter the trachea. enzymes that intestinal glands in the duodenal
mucosa secrete.
•Esophagus (Gr. oisophagos, to carry food) -
propel the bolus or liquid to the stomach •Villi - it is thousands of fingerlike projections ,
project from each square centimeter of mucosa
•The mammalian stomach- is a muscular,
distensible sac with three main functions.
•Large intestine has no circular folds, villi, or Some major metabolic functions of the liver
microvilli; thus, the surface area is much include:
smaller.
1. Removal of amino acids from organic
•The small intestine joins the large intestine compounds
near a blind-ended sac, the cecum (L. caecum,
blind gut). 2.Synthesis of nonessential amino acids.

• The human cecum and its extension, the 3. Conversion of galactose and fructose to
appendix (L. appendere, to hang upon), are glucose.
storage sites and possibly represent 4. Oxidation of fatty acids
evolutionary remains of a larger, functional
cecum, such as those found in herbivores. 5. Conversion of carbohydrates and proteins
into fat.
•Appendix -contains an abundance of lymphoid
tissue and may function as part of the immune 6.Modification of waste products, toxic drugs,
system. and poisons

(detoxification).

•The major functions of the large intestine •Gallbladder - is a small organ near the liver.
include the reabsorption of water and minerals
- it stores the greenish fluid called
and the formation and storage of feces.
bile that the liver cells continuously produce.
•Feces - a mixture of bacteria, fungi, undigested
•Bile is very alkaline and contains pigments,
plant fiber, sloughed-off intestinal cells, and
cholesterol, lecithin, mucin, bilirubin.
other waste products.
• bile salts that act as detergents to emulsify
•Pancreas - is an organ that lies just ventral to
fats (form them into droplets suspended in
the stomach and has both endocrine and
water) and aid in fat digestion and absorption.
exocrine functions.
(Recall that fats are insoluble in water.)
•Liver- the largest internal organ in the
• Micelles are lipid aggregates (fatty acids and
mammalian
glycerol) with a surface coat of bile salts.
•Hepatocytes- millions of specialized cells in
28.1 HOMEOSTASIS AND TEMPERATURE
the liver that take up nutrients absorbed from
the intestines and release them into the REGULATION
bloodstream.
• Thermoregulation- ability to control the
- it also manufacture the blood temperature of the body and involves the
proteins prothrombin and albumin body.
nervous, endocrine, respiratory, and circulatory (3) they can generate and trap heat internally to
systems in animals. maintain a constant body temperature, despite
fluctuations in the temperature of the external
• The total body temperature- is a result of an environment.
interaction of these factors and can be
expressed as: •Ectotherm - derive most of their body heat
from the environment rather than from their
Body temperature = heat produced own metabolism
metabolically +heat gained from the
environment- heat lost to the environment •Most birds and mammals are called
endotherms because they obtain their body
•Animals use four physical processes to heat from cellular processes.
exchange heat with the environment:;
conduction, convection, evaporation, and
radiation.

•Endothermy -allows animals to stabilize their

core temperature so that biochemical processes
and nervous system functions can proceed at
•Conduction - is the direct transfer of thermal steady, high levels.
motion (heat) between molecules of the
environment and those on the body surface of •Homeotherms-maintain a relatively constant
an animal. body temperature.

•Convection -is the movement of air (or a • most ectotherms are heterotherms (have a
liquid) over the surface of a body variable body temperature)

•Evaporation - is loss of heat from a surface as • Many invertebrates have relatively low
water molecules escape in the form of a gas. metabolic rates and have no thermoregulatory
mechanisms; thus, they passively conform to
•Radiation- is the emission of electromagnetic the temperature of their external environment.
waves that objects, such as another animal’s These invertebrates are termed
body or the sun, produce. thermoconformers.
•Animals cope with temperature fluctuations in • Rete mirabile (“miraculous net”) - where
one of three basic ways. smaller vessels are arranged in a countercurrent
(1) They can occupy a place in the environment heat exchanger.
where the temperature remains constant and • Gular pouch- a highly vascularized pouch in
compatible with their physiological processes; species throat that they can flutter (a process
(2) their physiological processes may have called gular flutter) to increase evaporation
adapted to the range of temperatures in which from the respiratory system
the animals are capable of living;
• Blubber - thick pelts and a thick layer of •Negative feedback mechanisms (with the
insulating fat under the skin help marine hypothalamus acting as a thermostat) trigger
animals, such as seals and whales, to maintain a either the heating or cooling of the body and
body temperature of around 36 to 38°C (97– thereby control body temperature.
100°F)
• Hibernation (L. hiberna, winter) - resting state,
• Birds and mammals can generate heat During hibernation, the metabolic rate slows, as
(thermogenesis) by muscle contraction, ATPase do the heart and breathing rates.
pump enzymes, oxidation of fatty acids in
brown fat, and other metabolic processes. • Estivation (L. aestivus, summer). In this state,
both breathing rates and metabolism decrease
• Shivering thermogenesis- Heat generation by when environmental temperatures are high,
shivering food is scarce, or when dehydration is a
problem.

• Thyroxine -increases the permeability of many

cells to sodium (Na1) ions, which leak into the 28.2 CONTROL OF WATER AND SOLUTES
cells. (OSMOREGULATION AND EXCRETION)

• Nonshivering thermogenesis- is the hormonal

triggering of heat production.
•Excretion (to eliminate) - can be defined
•Brown fat - is a specialized type of fat found in broadly as the elimination of metabolic waste
newborn mammals, in mammals that live in products from an animal’s body.
cold climates, and in mammals that hibernate.
These products:
<The two hypothalamic thermoregulatory
areas> 1) carbon dioxide

•heating center 2) water (which cellular respiration primarily

produces); 3) 3) 3) excess nitrogen (which is
• cooling center. produced from the deamination of amino acids)

4) in the form of either ammonia, urea, or uric

acid;
•Heating center - controls vaso-constriction of
superficial blood vessels, erection of hair and 5) solutes (various ions).
fur, and shivering or nonshivering
thermogenesis. • Osmoregulation- a physiological process in the
excretion of nitrogenous wastes which is usually
• Cooling center controls vasodilation of blood associated with the regulation of water and
vessels, sweating, and panting. solute (ionic) balance.
• Osmolarity - is a measure of the osmotic •Metanephridium - more common type of
pressure (strength) of a solution measured in excretory structure among invertebrates.
osmoles and is related to the molar
concentration of solutes in a solution. •Protonephridia and metanephridia have
critical structural differences. Both open to the
• If the osmolarity of the body fluids of an outside, but metanephridia (1) also open
animal varies with that of the environment, the internally to the body fluids and (2) are
animal is an osmoconformer and the animal is multicellular.
isosmotic to its medium.
•Nephridia-are tubular (saccular) structures in
• Osmoregulator- condition when an animal the renal organs of adult molluscs.
that maintains its body fluids at a different
osmolarity from that of its surrounding •The excretory organs in some crustaceans
environment. (crayfish and crabs) are called antennal glands
or green glands because of their location near
the antennae and their green color.

28.3 INVERTEBRATE EXCRETORY SYSTEMS •Maxillary glands - fluid collects within the
tubules from the surrounding blood of the
•Freshwater invertebrates are strong hemocoel, and this primary urine is modified
osmoregulators substantially by selective reabsorption and
because it is impossible to be isosmotic with secretion as it moves through the excretory
dilute media. system and rectum.

•Contractile vacuoles- are energy-requiring •Malpighian tubules - remove nitrogenous

devices that expel excess water from individual wastes (uric acid) from the hemocoel.
cells exposed to hypoosmotic environments. •Coxal glands - are common among arachnids
• Nephridia - that serve for excretion, (spiders, scorpions, ticks, and mites).
osmoregulation, or both. 28.4 VERTEBRATE EXCRETORY SYSTEMS
•Protonephridium - Probably the earliest type <How Vertebrates Achieve Osmoregulation>
of nephridium to appear in the evolution of
animals. 1. Filtration- in which blood passes through a
filter that retains blood cells, proteins, and
•Protonephridial excretory system - is other large solutes but lets small molecules,
composed of a network of excretory canals that ions, and urea pass through
open to the outside of the body through
excretory pores. 2. Reabsorption, in which selective ions and
molecules are taken back into the bloodstream
•Flame-cell systems - function primarily in from the filtrate
eliminating excess water.
3. Secretion, whereby selective ions and end
•Nitrogenous waste simply diffuses across the products of metabolism (e.g., K1, H1, and NH3)
body surface into the surrounding water.
that are in the blood are added to the filtrate pressure, and do not interfere with enzymes or
for removal from the body proteins. This reciprocity is termed the
counteracting osmolyte strategy.
•Renal capsule -are coat of connective tissue in
each kidney.

•Medulla-inner portion of the kidney. •Nephrons- is the functional unit of the

metanephric kidney consists of over 1 million
•Cortex -the region between the capsule and individual filtration, secretion, and absorption
the medulla. structures.
there are three kinds of vertebrate kidneys: •Glomerular capsule-filtration apparatus at the
1) pronephros beginning of the nephron , which looks rather
like a tennis ball that has been punched in on
2) mesonephros one side.

3) metanephros. •Glomerulus- fine network of capillaries.

•Pronephros - is the first osmoregulatory and • Afferent (“going to”) - arteriole enters and
excretory organ of the embryo. branchesinto the glomerulus

•Mesonephros- gives way during embryonic • The walls of these glomerular capillaries
development to the metanephros. contain small perforations called filtration slits
that act as filters.
•Rectal gland- it secretes a highly
concentrated salt (NaCl) solution. To reduce • Ureter-continuous with a tube where in the
water loss, they use two organic molecules— renal pelvis of the mammalian kidney that
(1)urea and (2) trimethylamine oxide carries urine to a storage organ called the
urinary bladder .
(TMAO)—in their body fluids to raise the
osmolarity to a level equal to or higher than -Urine from two ureters (one from each
that of the seawater. kidney) accumulates in the urinary bladder. The
urine leaves the body through a single tube, the
•Urea denatures proteins and inhibits enzymes,
urethra, which opens at the body surface at the
whereas TMAO stabilizes proteins and activates
end of the penis (in human males) or just in
enzymes. Together in the proper ratio, they
front of the vaginal entrance.
counteract each other, raise the osmotic