• Vascular system absent
• Gametophyte dominant
• Sporophyte attached to gametophyte
• Homosporous.

 Differentiation between Acoelomates, Pseudocoelomates and coelomates.

ACOELOMATES:

Ø  In phylum Platyhelminthes there is no body cavity or coelom, and the mesoderm form a loose, cellular tissue called mesenchyma or parenchyma which fills the space between the ectoderm and endoderm.

Ø  It forms a packing around the internal organs of the animals to support and protect them.

Ø  Such animals are called acoelomates

Ø  In acoelomates the gut is sac-type and there is no special transport system.

Ø  Only excretory system is developed for the transport of excretory products.

This system consists of flame cells, excretory ducts and excretory pores.

Ø  However the nervous system is well developed.

PSEUDOCOELOMATES:

Ø  In Aschelminthes the space between the body wall and the digestive tube is called pseudocoelom (false body cavity)

Ø  Pseudocoelom is not homologous to true coelom because.

Ø  It is not lined by coelomic epithelium.

Ø  It has no relation with the reproductive and excretory organs.

Ø  It develops from the blastocoel of the embryo and it is bonded externally by the muscles and internally by the cuticle of the intestine.

Ø  The animals having pseudocoelom are called pseudocoelomates.

COELOMATES:

Ø  Coelom is cavity present between the body wall and the alimentary canal and is lined by mesoderm.

Ø  The mesoderm splits into outer parietal layer (somatic) which under lines the body wall and the visceral layer (splanchnic) which covers the alimentary canal and the cavity between them is the true coelom.

Ø  It is filled with fluid called coelomic fluid.

Ø  The animals which posses coelom or true body cavity are called coelomates e.g. animals from annelids to chordates.

Ø  In coelomates gut attains more complexity and neuro-sensory system is well developed along with excretory system, circulatory system, respiratory and reproductive system.

 Test used to detect lipids?

Following tests are used to detect lipids:

(i)    Sudan-III Test: 

(ii)    Emulsion Test:

What are lipids ?

Lipids are the organic compounds made up of carbon, hydrogen and oxygen, are characterized by their solubility in organic solvents such as ether, alcohol and their insolubility in water.

What is the lymphatic system, write down its structure and function?

LYMPHATIC SYSTEM:

Definition:

(That system which consists of tissue fluid its transport and regulates the substances in body)

This system is responsible for the transport and returning of materials from the tissues of the body to the blood.

The system comprises of:

• Lymph capillaries,
• Lymph vessels,
• Lymph nodes, and
• Lymphoid masses,
• Lymph-the fluid which flows in the system.

(1) Lymph Capillaries:

Lymph capillaries end blindly in the body tissues, whore pressure from the accumulation of interstitial fluid or extracellular fluid forces the fluid into the lymph capillaries.

(2) Lymph and Lymph Vessels:

When this fluid enters the lymph capillaries, it is called lymph.

The lymph vessels empty in veins;

So lymph is a fluid in transit between interstitial fluid and the blood.

The intercellular spaces in the walls of lymph vessels are larger than those of the capillaries of blood vascular system.

So large molecules, from the interstitial fluid cal also enter the lymph capillaries.

Thoracic Lymph Vessel and Subclavin Vein:

Lymph capillaries join to form larger and larger lymph vessels; and ultimately from thoracic lymph duct-which opens into subclavian vein.

Direction of Flow:

The flow of lymph is always towards the thoracic duct.

Lacteals:

In the intestine, the branches of lymph capillaries, within villi, are called lacteals.

 The flow of lymph is maintained by:

(i) Activity of skeletal muscles,

(ii) Movement of viscera (internal organs)

(iii) Breathing movements.

(iv) Valves, which prevent back flow of lymph.

(3) Lymph Nodes:

Along the pathway, the lymph vessels, have, at certain points, masses of connective tissue where lymphocytes are present, these are lymph nodes. Several afferent lymph vessels enter a lymph node, which is drained by a single, efferent lymph vessel.

Location:

Lymph nodes are present in the:

(i) Neck Region.

(ii) Axilla (armpit) and.

(iii) Groin (genitalia) of humans.

(4) Lymphoid Masses:

In addition, several lymphoid masses are present in the:

(i) Walls of the digestive tract,

(ii) In the Mucosa and Sub-mucosa

The larger masses are:

(i) Spleen

(ii) Thymus

(iii) Tonsils (tissue mass in mouth) and

(iv) Adenoids (throat tissue) are all lymphoid masses.

These produce lymphocytes.

(5) Functions:

These are several functions performed by the lymphatic system.

(i) Regulation of Blood Volume:

In an average person, about three litres more fluid leaves the blood capillaries than is reabsorbed by them each day.

It returns this excess fluid and its dissolved proteins and other substances to the blood.

(ii) Absorption of Lipids:

The lacteals of villi absorb large fat globules, which are released by interstitial cells after the products of digestion of fats are absorbed.

(iii) Defence Mechanism:

The lymphatic system helps defend the body against foreign invaders.

Lymph nodes have lymphocytes and macrophages that destroy the bacteria and viruses.

The painful swelling of lymph nodes in certain diseases (mumps is an extreme example) is largely a result of the accumulation of dead lymphocytes and macrophages.

(iv) Filtering Blood Destroyed aged RBC and Invaders:

Just as the lymph nodes filter lymph, the spleen filters blood, exposing it to macrophages and lymphocytes that destroy foreign particles and aged red blood cells.

 A short note on Chemiosmosis

CHEMIOSMOSIS:

In both cyclic and non-cyclic phosphorylation, the mechanism for ATP synthesis is chemiosmosis, the process that uses membranes to couple redox reactions to ATP production.

(1) Pumps Protons (H+):

Electron transport chain pumps protons (H+) across the membrane of thylakoids in case of photosynthesis into the thylakoids space.

They energy used for this pumping comes from the electrons moving through the electron transport chain.

(2) Potential Energy:

This energy is transformed into potential energy stored in the form of H+ gradient across the membrane.

(3) ATP Synthase:

Next the hydrogen ions move down their gradient through special complexes called ATP synthase which are built in the thylakoid membrane.

During this diffusion of electrons, the energy of electrons is used to make ATP

OPENING AND CLOSING OF STOMATA:

The guard cells function as multisensory hydraulic valves.

Environmental Factors:

Environmental factors such as:

(i) Light intensity and quality.

(ii) Temperature.

(iii) Relative humidity and

(iv) Intracellular CO2 concentration are sensed by guard cells and these signals are integrated (combine) into well-defined stomatal responses.

These are two hypothesis which may explain the opening and closing of stomata.

(1) Starch Sugar Hypothesis:

The German Botanist H. Van Mohl proposed that the guard cells are the only photosynthesising cells of epidermis of leaf.

Sugar are produced in the guard cells during day time when light is available.

(i) During Day Time:

When sugar level rises i.e. solute concentration increases or water potential decreases and the guard cells become turgid, and they separate from one another and stoma or pore opens.

(ii) During Night:

During night there is no photosynthesis the sugars are either converted into in soluble starch or are used in respiration, this decreases free sugars in cell.

So the osmotic pressure of guard cells is lowered, and water leaves the guard cells. They become flaccid and stoma or pore between them closes.

But these process are not fast enough to account for the rapid rise in turgor, of guard cells.

(2) Influx of Kᐩ Ions:

Potassium concentration in guard cells increases several folds,

Depending upon plant species.

(i) Stomata Open:

Stomata open due to active transport of potassium ions (Kᐩ) into the guard cells from the surrounding epidermis.

The accumulation of Kᐩ decreases the osmotic potential of guard cells.

Water enters the guard cells by osmosis, which become more turgid and stretched and stomata are opened.

(ii) Stoma Closes:

The stoma closes by reverse process; involving passive diffusion of K⁤ᐩ from guard cells followed by water moving out by osmosis.

What Controls the Movement of Kᐩ into and out of Guard Cells ?

• Level of carbon dioxide in the spaces inside the leaf end.
• Light, control this environment.

(i) Level of Carbon Dioxide:

A low level of carbon dioxide favors opening of the stomata, thus allowing an increased carbon dioxide level and increased rate of photosynthesis.

(ii) Light Quality and Intensity:

Exposure to blue light, which is also effective in photosynthesis has been shown to acidify the environment of the guard cells (i.e. pumps out protons) which enable the guard cells to take up Kᐩ followed by water uptakes resulting in increased turgidity of guard cells.

So in general stoma are open during day and closed at night.

This prevents needless loss of water by the plant when it is too dark for photosynthesis.

(iii) Actively Pumping Potassium:

The plant open their stomata by actively pumping potassium in guard cells causing water to follow by osmosis.

Guard cells become turgid and stoma or pore opens.

When Potassium leaves the guard cells (during night) water leaves the guard cells by exosmosis and guard cells become flaccid and stoma or pore between guard cells closes.