Download Chapter 25

Chapter 25
Control of the Internal
Environment
PowerPoint Lectures for
Biology: Concepts and Connections, Fifth Edition
– Campbell, Reece, Taylor, and Simon
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Let Sleeping Bears Lie
• Bears do not actually hibernate but are dormant
during the winter
• Animals have internal homeostatic mechanisms
to compensate for fluctuations in the external
environment
–
Thermoregulation: maintenance of internal
temperature
• Endothermy: body heat derived largely
from metabolism
• Ectothermy: heat absorbed from
surroundings
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
– Excretion: Disposal of nitrogen-containing
wastes
– Osmoregulation: Control of gain and loss of
water and solutes
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
THERMOREGULATION
25.1 Heat is gained or lost in four ways
• An animal exchanges heat with the environment
by four physical processes
–
Conduction: transfer of heat between
molecules of objects in direct contact
–
Convection: transfer of heat by movement
of air or water past a surface
–
Radiation: emission of electromagnetic
waves
–
Evaporation: loss of heat from the surface
of a liquid transforming to a gas
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
LE 25-01
Radiation
Convection
Evaporation
Conduction
25.2 Thermoregulation involves adaptations that
balance heat gain and loss
• Each species has an optimal internal
temperature range
• Endotherms and many ectotherms maintain a
fairly constant internal temperature through five
types of adaptation
–
Metabolic heat production
• Hormonal changes, movement,
clustering
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
–
Insulation
• Hair, feathers, fat
–
Circulatory adaptations
• Dilation or constriction of blood
vessels
• Countercurrent heat exchange: warm
and cold blood flow in opposite
directions in adjacent vessels
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
LE 25-02b
Blood from
body core
in artery
35
Blood
returning to
body core
in vein
Blood from
body core
in artery
33C
30
27
20
18
10
9
Blood
returning
to body core
in vein
– Evaporative cooling
• Panting, sweating, spreading saliva
– Behavioral responses
• Migration, basking, burrowing, bathing
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
25.3 Reducing metabolic rate and body
temperature saves energy
• Some ectotherms can spend the winter “frozen”
• Endotherms have various adaptations to adjust
to temperature extremes
–
Torpor: state of reduced activity in which
metabolic rate and body temperature
decrease
–
Hibernation: long-term torpor in cold
weather
–
Estivation: summer torpor
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
OSMOREGULATION AND EXCRETION
25.4 Osmoregulation: Animals balance the gain
and loss of water and solutes
• Animal cells cannot survive net water gain or
loss
• Osmoregulation is based largely on regulating
solutes
–
Water follows the movement of solutes
by osmosis
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Osmoconformers have the same internal solute
concentration as seawater
–
Only marine animals
–
Expend some energy to maintain ion
concentrations
• Osmoregulators have different solute concentration in
body fluid than environment
–
Use energy to regulate water gain or loss
–
Freshwater and saltwater fishes have different
adaptations
–
Fishes that change habitat use freshwater or
saltwater strategies as necessary
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
LE 25-04a
Osmotic water gain through gills
and other parts of body surface
Uptake of
some ions
in food
Uptake of
salt by
gills
Excretion of
large amounts of
water in dilute
urine from kidneys
LE 25-04b
Gain of water and
salt from food
and by drinking
seawater
Osmotic water loss
through gills and other
parts of body surface
Excretion of salt
from gills
Excretion of excess ions
and small amounts of
water in scanty urine
from kidneys
• Land animals are osmoregulators
–
Cannot exchange water directly with
environment
–
Like marine fishes, their primary problem
is losing water and becoming dehydrated
• Arthropods and vertebrates have
adaptations that have made them the
most successful land colonizers
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
CONNECTION
25.5 Do we need to drink eight glasses of water
each day?
• The Institute of Medicine has found that most
people get sufficient water in their daily food
and beverages
–
Men need an average of 3.8 liters daily
–
Women need about 2.6 liters
–
Caffeinated beverages do not remove
water from the body
• Athletes or people living in hot climates may
need more water
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
25.6 Animals must dispose of nitrogenous wastes
• Metabolism produces nitrogenous wastes from
the breakdown of proteins and nucleic acids
• Most aquatic animals dispose of their
nitrogenous wastes as ammonia
–
Highly soluble in water
–
Diffuses rapidly across cell membranes
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Land animals convert ammonia to less toxic
compounds
–
Can be safely stored and transported in
the body
–
Released periodically by the excretory
system
–
Requires energy for conversion
–
Different adaptations and type of
reproduction determine excretion as urea
or uric acid
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
–
Urea
• Excreted by mammals, most
amphibians, sharks, and some bony
fishes
• Can be stored in concentrated solution
but requires water for disposal
–
Uric acid
• Excreted by birds, reptiles, insects,
some amphibians
• Excreted as solid paste
• Uses more energy for excretion
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
LE 25-06
Proteins
Nucleic acids
Amino acids
Nitrogenous bases
NH2
Amino groups
Most aquatic animals,
including most fishes
Ammonia
Mammals, amphibians,
sharks, some bony
fishes
Urea
Birds and many other
reptiles, insects, land
snails
Uric acid
25.7 The liver performs many functions, including
the production of urea
• The liver performs more functions than any other
organ in the body
–
Breaks down amino acids for energy or
recycling
–
Produces urea
–
Breaks down toxins
–
Produces bile, plasma proteins, and
lipoproteins
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
–
Plays a key role in regulating body
metabolism
• Converts glucose to glycogen
• Balances stored glycogen and
released glucose
• The hepatic portal vein transports nutrients
absorbed by the intestines directly to the liver
–
Substances detoxified before going to
the heart for distribution
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
LE 25-07
Kidneys
Liver
Hepatic
portal
vein
Intestines
25.8 Alcohol consumption can damage the liver
• Some breakdown products of alcohol
detoxification can cause liver cell damage
• Heavy, frequent exposure to alcohol can
produce cirrhosis, abnormal liver scarring
–
Impairs liver functioning
–
Cannot be reversed, but treatment can
stop or delay progression
–
Also caused by hepatitis
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
25.9 The excretory system plays several major
roles in homeostasis
• The excretory system expels wastes and
regulates water and ion balance
• Kidneys are the main processing centers of the
excretory system
–
Filled with tubules and intricate network
of blood capillaries
–
Filter blood, which circulates through
repeatedly
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Nephrons are the functional units of the kidneys
–
Extract filtrate, consisting of water, urea,
and solutes, from the blood
–
Refine filtrate into small quantity of urine
–
Return most water and solutes to blood
• Urine leaves the kidneys via ureters
–
Is stored in the urinary bladder and
expelled through the urethra
–
About 1.5 L of urine are excreted each
day
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
LE 25-09a
Aorta
Inferior
vena cava
Renal artery and vein
Kidney
Ureter
Urinary bladder
Urethra
The excretory system
Animation: Nephron Introduction
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
25.10 Overview: The key processes of the
excretory system are filtration, reabsorption,
secretion, and excretion
• Filtration
–
Blood pressure forces water and many
small solutes into the nephron through
the glomerulus
• Reabsorption
–
Valuable solutes are returned to the
blood from the filtrate
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Secretion
–
+
Substances such as excess H and
toxins are transported into the filtrate
• Excretion
–
Urine, the product of the earlier
processes, passes from the kidneys to
the outside
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
LE 25-10
Filtration
Nephron tubule
H2O, other small molecules
Capillary
Reabsorption
Secretion
Excretion
Urine
Interstitial fluid
25.11 From blood to filtrate to urine: A closer look
• The nephron returns much of the water that
filters into it from the blood
–
Nutrients, salt, and water are reabsorbed
into capillaries from the proximal and
distal tubules
–
Secretion of excess H , toxins, and K
–
and reabsorption of HCO3 also occur in
the tubules
–
High NaCl concentration in the medulla
promotes reabsorption of water through
the loop of Henle
+
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
+
–
Final refining of the filtrate occurs in the
collecting duct, where NaCl is
reabsorbed
–
As filtrate moves through the medulla,
more water is reabsorbed before the
urine passes into the renal pelvis
–
Antidiuretic hormone (ADH) regulates the
amount of water the kidneys excrete
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
LE 25-11
Blood
Filtrate composition
H2O
NaCI
HCO3–
H+
Urea
Glucose
Amino acids
Some drugs
Proximal tubule
Bowman’s
capsule Nutrients H2O
HCO3–
NaCI
Some
H+
drugs
and poisons
Distal tubule
NaCI
H2O
HCO3–
K+
H+
Cortex
Collecting
duct
Medulla
Loop of
Henle
NaCI
NaCI
H2O
Reabsorption
Urea
Secretion
NaCI
H2O
Urine (to renal pelvis)
Animation: Bowman's Capsule and Proximal Tubule
Animation: Loop of Henle and Distal Tubule
Animation: Collecting Duct
Animation: Effect of ADH
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
CONNECTION
25.12 Kidney dialysis can be a lifesaver
• Failure of both kidneys will lead to death if
untreated
• A dialysis machine is a type of artificial kidney
–
Blood is pumped from an artery through
tubes made of selectively permeable
membrane
–
As blood circulates, urea and excess
ions diffuse out
–
Needed substances diffuse from the
dialyzing solution into the blood
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings