Give a brief account of parasitic adaptations in Platyhelminthes

Parasitic adaptation in Platyhelminthes

Adaptation

•      Fitness of an organism to its environment

•      It is the characteristic which results in suitable & convenient morphological & functional correlation between an organism & its environment

Parasitic adaptation

•      Platyhelminthes have undergone profound adaptation to suit their parasitic modes of life

•      These adaptations- parasitic adaptations

•      Are of morphological & physiological nature

1. Morphological adaptations

A. Body covering

B. Organs of adhesion

C. Organs of locomotion

D. Organs of nutrition (Trophic organs)

E. Neurosensory system

F. Reproductive system

A. Body covering

Thick tegument frequently provided with scales affords suitable protection to the parasite

This thick protoplasmic layer is continually renewed by mesenchymal cells forming it

B. Organs of adhesion

•      For a firm grip on/in the host’s body, some special organs of adhesion are needed

•      Flatworms are variously armed with suckers, hooks & spines

•      Suckers may be with/without hooks/spines

C. Organs of locomotion

•      Locomotion is actually an effort of procuring food

•      But parasites habitually inhabit such places in host’s body, where sufficient food is available without effort

•      Thus, organs of locomotion such as cilia of turbellarians- absent in parasitic forms

•      Locomotory organs present in free living larvae of parasitic forms

•      Miracidium possess cilia & cercaria bears a tail for locomotion

      

D. Organs of nutrition (Trophic organs)

•      Food of parasite comprises readily available & digested/ semi digested food of the host

•      Elaborate organs of nutrition not needed

•      Trematodes have an incomplete gut & in most cases a suctorial pharynx for sucking food

•      An eversible pharynx is present in free living turbellarians

•      In cestodes, parasite freely bathes in digested food of host which is absorbed directly

      Thus, total absence of alimentation in tapeworms

E. Neurosensory system

•      Need for quick & efficient “response to stimuli” is associated with free active life & not with a quiet parasitic life in a safe environment

•      In parasites therefore, there is preferred reduction of nervous system & a total absence of sense organs

•      But the free living miracidium possesses eye spots

F. Reproductive system

•      Best developed system in helminth parasites, designed & preferred to meet the need for tremendous egg production

•      Parasitic flatworms with a few exceptions like Schistosoma, are monoecious (hermaphrodite)

•      Hermaphroditism is of distinct advantage to the parasite because:

1. It ensures copulation even when a few individuals are present

2. After copulation both individuals lay eggs, doubling the rate of production

3. In absence of companion parasite can reproduce offspring

•      In cestodes reproductive system is much more elaborate & each mature proglottid possesses 1 or2 complete sets of male & female genitalia

•      In gravid proglottid all other organs of the system degenerate to make room for the uterus which becomes highly enlarged & branched to accommodate large number of eggs

2. Physiological adaptations

A. Protective mechanism

B. Anaerobic respiration

C. Osmoregulation

D. High fertility

                                      

A.  Protective mechanism

•      Inside the alimentary canal the parasites have to protect  themselves from the action of digestive juices of host

•      Tapeworms accomplish this:

1. By stimulating walls of gut to secrete mucus, which then forms a protective clothing around parasite

2. By secreting antienzymes to neutralize the digestive enzymes of host

3. By probably continually renewing their protective body covering i.e., tegument

B. Anaerobic respiration

•      Environment in gut & bile ducts is devoid of free oxygen

•      Flatworms inhabiting these places, therefore, respire anaerobically by breaking down glycogen

C. Osmoregulation

•      Osmotic pressure of endoparasite’s body fluids, especially in case of trematodes is almost the same as that of host

•      This renders osmoregulation unnecessary

•      But in intestinal tapeworms, osmotic pressure is little higher

•      This permits ready absorption of host’s digested food by tapeworms

D. High fertility

•      Eggs produced by a parasitic flatworm face a very uncertain future while passing through the complex life cycle, these potential offsprings face several hazards as a result of which a very small percentage of total eggs produced reaches adulthood

•      This threat to the very existence of species is suitably met by parasite which in its life time may produce eggs in millions

•      Reproductive organs of flatworms are accordingly developed

Show that for an ideal gas, Cp - Cv= R

From the definitions , it is clear that two heat capacities are not equal and C_P is greater than C_V by a factor which is related to the work done. At a constant pressure part of heat absorbed by the system is used up in increasing the internal energy of the system and the other for doing work by the system. While at constant volume the whole of heat absorbed is utilized in increasing the temperature of the system as there is no work done by the system. Thus increase in temperature of the system would be lesser at constant pressure than at constant volume. Thus C_P is greater than C_v.

We know             C_p = dH/dT                               …(1)

And                      C_v = dE/dT                               ….(2)

By definition,  H = E + PV for 1 mole of an ideal gas

Or                           H = E + RT                        (PV= RT)

Differentiating w.r.t. temperature, T, we get

                                dH/dT = dE/dT + R

or                            C_p = C_v+ R                            By using (1) and (2)

or                            C_p – C_v = R

                                                                (Shown)

What is the difference between Reversible and Irreversible process?

Ans: The difference between Reversible and Irreversible process is given bilow.

Reversible Process	Irreversible Process
1. It takes place in infinite number of infinitesimally small steps and it would take finite time to occur.	1. It takes place infinite time.
2. It is imaginary as it assumes the presence of frictionless and weight less piston.	2. It is real and can be performed actually.
3. It is in equilibrium state at all stage of the operation.	It is in equilibrium state only at the initial and final stage of the operation.
4. All changes are reversed when the process is carried out in reversible direction.	4. After this type of process has occurred all changes do not return to the initial stage by themselves.
5. It is extremely slow.	5. It proceeds at measureable speed.
6. Work done by a reversible process is greater than the corresponding irreversible process.	6. Work done by a irreversible process is smaller than the corresponding reversible process.

What Is a Hernia?

A hernia occurs when an organ or fatty tissue squeezes through a  weak spot in a surrounding muscle or connective tissue called fascia. The most common types are inguinal (inner groin), incisional (resulting from an incision), femoral (outer groin), umbilical (belly button), and hiatal (upper stomach).

In an inguinal hernia, the intestine or the bladder protrudes through the abdominal wall or into the inguinal canal in the groin. About 80% of all hernias are inguinal, and most occur in men because of a natural weakness in this area.
In an incisional hernia, the intestine pushes through the abdominal wall at the site of previous abdominal surgery. This type is most common in elderly or overweight people who are inactive after abdominal surgery.
A femoral hernia occurs when the intestine enters the canal carrying the femoral artery into the upper thigh. Femoral hernias are most common in women, especially those who are pregnant or obese.
In an umbilical hernia, part of the small intestine passes through the abdominal wall near the navel. Common in newborns, it also commonly afflicts obese women or those who have had many children.
A hiatal hernia happens when the upper stomach squeezes through the hiatus, an opening in the diaphragm through which the esophagus passes.

What Causes Hernias?

Ultimately, all hernias are caused by a combination of pressure and an opening or weakness of muscle or fascia; the pressure pushes an organ or tissue through the opening or weak spot. Sometimes the muscle weakness is present at birth; more often, it occurs later in life. Poor nutrition, smoking, and overexertion all can weaken muscles and make hernias more likely. Anything that causes an increase in pressure in the abdomen can then cause a hernia, including obesity, lifting heavy objects, diarrhea or constipation, or persistent coughing or sneezing.