This document discusses homeostasis in animals through osmoregulation. It describes two main classes of animals that maintain water and solute balance - osmoconformers and osmoregulators. Osmoconformers have body fluids that are isotonic to their external environment, while osmoregulators must adjust their internal osmotic state as their body fluids are hypertonic or hypotonic to the external environment. The document then discusses osmoregulation adaptations in marine, freshwater, and terrestrial animals. Marine animals face issues like passive water loss, while freshwater animals deal with flooding. Terrestrial animals have adaptations like specialized skin and kidneys to prevent dehydration.

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2. Homeostasis
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Prof. Sumaira Aslam
Lecturer Biology
Punjab College, Quaid Campus
Rawalpindi

3. REQUIRMENT:
Water continuously leave and enter the animal cell.
Animals require more critical baance of water and solutes as compared to plants.
This is bacause they can not survive a net gain or loss of water.
So they to maintain the balance of water and solutes.
CLASSIFICATION OF ANIMALS MAINAINING WATER AND
SOLUTES BALANCE
Two main classes of animals maintaining water and solutes balance are,
1: Osmoconformers
2: Osmoregulators
OSMOREGULATION IN ANIMALS
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4. OSMOCONFORMERS
 Their body fluids are isotonic
to their external environment
i.e. their internal body
conditions resemble or
matches with external
environment.
 They do not need to adjust
their internal osmotic state.
EXAMPLES:
 all marine invertebrates
 Some marine vertebrates e.g.
hag fishes ( jawless fishes),
cartiliginous fishes.
OSMOREGULATORS
 Their body fluids are either
hypertonic or hypotonic to the
external environmental state.
 They need to adjust their
internal osmotic state.
 EXAMPLES:
 All fresh water animals
 All terrestrial animals
 Some marine vertebrates e.g.
bony fishes and mammals.
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5. There are three classes of animals;
1) Marine animals
2) Fresh water animals
3) Terrestrial animals
OSMOREGULATION IN MARINE ANIMALS
Marine animals are either;
A: Osmoconformers
B: Osmoregulators
A: OSMOCONFORMERS
Their body fluids are isotonic to their external environment.
CLASSES OF ANIMALS
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6. ADAPTATIONS:
Outside environment is hypertonic, but to remain isotonic to the
environment, they have certain adaptations.
1: Retention Of Urea:
They become isotonic to their external environment by retaining
urea in their body.
Effect:
Urea in high amounts is damaging to these animals because it is an
alkaline material and it denatures the proteins. So in order to
A: OSMOCONFORMERS
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7. Prevent themselves from the harmful effects of urea, they retain
another chemical TRIMETHYLAMINE OXIDE. It is acidic in
nature so it regulate the pH.
Example: hag fishes and cartilaginous fishes.
B: OSMOREGULATORS
Their body fluids are hypotonic to their external environment i.e.
their external environment is hypertonic.
Examples: bony fishes ( descendents of fresh water ancestors but
later become marine).
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8. HARMS OF HYPERTONIC ENVIRONMENT:
These fishes face following harms;
• High amount of salts in their body
• Passive loss of water
Adaptations To Prevent High Amount Of Salts In Their Body:
These fishes are facing high amount of salts in their body, so they
have following adaptations to keep their body in balance.
• Their kidneys are specialized to secrete extra salts.
• Salts are also actively excreted through gills.
• they also posses salt secreting glands ( rectal glands). These are
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9.  Found on the wall of rectum. Rectal glands extract the salts from
the body fluids and throw them into the rectum.
PASSIVE LOSS OF WATER:
 These fishes also constantly lose water from their hypotonic body
fluids to hypertonic external environment. This continuous loss of
water from the body is called PASSIVE LOSS OF WATER.
ADAPTATIONS TO PREVENT PASSIVE LOSS OF WATER:
 These fishes have adapted themselves to drink large amount of sea
water.
 They secrete concentrated urine to release maximum salts and
ensure minimum water loss.
Conti…..
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10. ENVIRONMENT:
Body fluids of the fresh water animals are hypertonic to the external
environment i.e. external environment is hypotonic.
They all are osmoregulators.
EFFECTS:
Due to external hypotonic environment, they are constantly facing;
• Flooding of body fluids
• Loss of salts from the body
ADAPTATIONS:
To avoid loss of salts and flooding of body, they have certain adaptations;
OSMOREGULATION IN FRESH WATER ANIMALS
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11. FRESH WATER PROTOZOANS ( INVERTEBRATES):
Amoeba, paramecium pump out excess water from the body by contractile
vacuole.
FISHES ( VERTEBRATES):
These are also facing constant flooding, so they have following adaptations;
• These remove excess water by producing large volumes of very dilute
urine ( hypotonic urine).
Loss of salts is compensated by;
• Eating salt containing food
• By active uptake of salts by gills and skin
• These fishes do not drink water intentionally.
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12. Q: Why do marine fishes drink water unlike fresh water fishes?
Because marine fishes live in hypertonic environment in which they face
passive loss of water which leads to dehydration therefore they drink
water. On the other hand, fresh water fishes lives in hypotonic
environment which already causes flooding therefore these fishes do not
need to drink water.
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13. ENVIRONMENT:
These animals are mainly found in hypertonic environment.
EFFECTS OR PROBLEMS:
The major problem for terrestrial life is;
Evaporative loss of water leading to dehydration.
SUCCESSFULANIMALS:
Two groups of animals are most successful on terrestrial mode of life;
• Arthropods
• Mammals
OSMOREGULATION IN TERRESTRIAL ANIMALS
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14. ADAPTATIONS:
They have following adaptations;
• Prevention of the loss of water
• Gain / drinking of water
ADAPTATIONS IN THE SKIN SURFACE:
 Skin covers body surface so that water loss is prevented. This surface
is of two types.
 In insects a waxy exoskeleton called cuticle is present which prevent
the loss of water because cuticle is a hydrophobic compound.
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15.  In most terrestrial vertebrates a multilayered and dead keratinized skin
is present which prevent the loss of water.
 Hairs on the skin of mammals also prevent water loss.
Metabolic adaptations
 Metabolic adaptations are related to metabolism.
 Some desert mammals, kangro rat survives without drinking water. It
feeds on the seeds of desert plants containing more carbohydrates
which produce metabolic water.
 Terrestrial animals also produce concentrated urine in their kidneys
that reabsorbed most filtered water in the process of excretion.
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16. BEHAVIORALADAPTATIONS
 Some desert animals are nocturnal i.e. they remain hidden at day time
in shady places like under the rocks but comes out at night.
NUTRITIONALADAPTATIONS (Compensation of water)
 Loss of water is also compensated by drinking large amount of water
and eating moist food. Desert mammals also use metabolic water.
ANHYDROBIOSIS
 An ability to tolerate dehydration is called anhydrobiosis e.g.
Kangaroo rat survive without water.
 It comes from the metabolic and behavioral adaptation. It is
characteristic of terrestrial animals.
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