ORIGIN OF CHORDATES (FIRST CHORDATE, PROBABLE ANCESTOR, TIME OF ORIGIN, ERA OF ORIGIN, PLACE OF ORIGIN).

ORIGIN OF CHORDATES:

• Chordates is a group of animals having three important (salient) features.

• Presence of Notochord,

• Dorsal hollow nerve chord,

• Presents of pharyngeal gill slits.

• Basically they are identified by the primitive stick or notochord.

• Among 30 phylum the chordate is the last phylum and also well developed in animal kingdom.

• The chordates are comprised about 49,000 species approximately founded.

• These includes the Amphioxus (Cephalochordates) ,Balanoglossus, Hemichordata, Ascidian , tunicates (urochordata)also developed animals such as fish (pisces), Frog (Amphibian), Lizard(Reptiles), Aves (Birds).

TIME OF ORIGIN:

• It is believed that the first chordates are originate in the sea( PLACE  OF ORIGIN).

• The fossils of vertebrates animal from the chordates have been collected from the cambrian beds of paleozoic era.Hence it is believed that the chordate originate prior to the cambrian period which is around 600 million years ago.

FIRST CHORDATE: 

• It is believed that the ''Fixed Ascidians'' are the first chordates in the earth .The larvae of ascidians are developed ino amphioxus and fishes through Neoteny.

• Neoteny refers to that maturity of adult animal features are present in juvenile stage itself.

PROBABLE ANCESTOR: 

• Though there is a several theories of ancestor of chordates, the commonly believed that the Lophophorata animals or arm feeding animals is an ancestor of chordates which is invertebrate deutrosome.

• The deutrosome animals have developed anus before the growth of mouth in embryonic stage.

[PUBLISHED AND CREATED BY : S.V. AVINASH, M.Sc. ZOOLOGY] 

#zoology for life #chordates #invertebrate #chordates #first chordates # zoologyforlife.blogspot.com # ZOOLOGYFORLIFE #Zoology for life #chordates.

Skin and it's Derivatives in Invertebrates - Skin layers, structure and functions.

                                                                   THE SKIN

• The skin is an external protective layer of an organism. The skin spread all over the surface of the body such as Nostrils, Eyelids, Genitals. Outer membrane of Eardrum is also skin, conjunctiva of eyelids also skin.
• The evolution of skin in vertebrate is transition from the aquatic to the terrestrial are correlated.

STRUCTURE OF SKIN AND FUNCTION OF SKIN;

• The vertebrate skin can be derived into three strata, They are Epidermis, Dermis and Hypodermis.
• The Epidermis is made up of Ectoderm and the dermis or corium are made of mesoderm.

EPIDERMIS;

• Epidermis is the thin outer most layer of the skin, which is made up of four different cell types in five layers.
• The epidermis is made up of four different cell types in five layers, They are
• The deepest layer ''Stratum Basale''
• Stratum Spinosum,
• Stratum granulosum,
• Stratum lucidum
• Stratum corneum

THE DEEPEST LAYER STRATUM BASALE,

• Stratum Basale is the outermost layer attached to the dermis , this deepest layer stratum basale which is base layer contains single row of keratinocytes.
• The keratinocytes are rapidly dividing all the time and pushing the new cell to form the layer above.
• These continuous pushing of keratinocytes help in regenerating the dead cells or injured area as the Name suggests the keratinocytes are made of enormous keratin.
• In aquatic fishes the Keratinized layer forms the cuticle.
•  The Stratum Basale not only contains the keratinocytes, But its also contain Melanocytes which produce melanin and tactile cells which act as a sensory receptor for touch.

STRATUM SPINOSUM,

• The stratum spinosum is an pricky layer, because the cells looks spiky.
• Stratum spinosum is a thick layer formed by full of cells , Which looks likes a web like system full of intermediate filament attach the other cells and forms tight junction called desmosomes.
• The cell stratum spinosum also contains dendritic cells which ingest foreign substances and activates immune system.

STRATUM LUCIDUM;

• The stratum lucidum is otherwise called clear layer. It is 2-3 cell layers thick. 
• The flattend keratinizationed cells form the below layer caller stratum granulosum and now completely keratinized or dead cells and completly flattened and clear layer.
• These keratinocyte cell are aggregatedinto arrays called tonofilaments.

STRATUM CORNEUM: 

• The stratum corneum is also known as horny layer. It is a  outermost layer thick upto 20-30 cell layers which is full of dead and no nucleus in it.
• In stratum corneum the cells are dead in different manner that is the cell plasma membrane with the thick keratin protein give protection to organism.
• In aquatic fishes the keratinized layer forms the cuticle , but in amniotic animals the stratum corneum is cuticle these are also called cornified cells.

             DERMIS

• In skin integument the dermis is situated below the epidermis layer and above the hypodermis layer.
• The dermis packed with outer loose layer and inner dense layer the dermis is full of connective tissue muscles, capillaries. blood vessels, collagen fiber, Nerves and glands and etc,
• In amphibian and reptiles the collagen fibre which store energy and dissipate energy and transmits forces, are arranged regularly and in aves and mammals the collagen fibre arranged irregularly.
• In some parts of animals such as comb of cock and face and buttocks of monkeys are looks bright red blood circulatory area..

            HYPODERMIS

• The hypodermis is the deepest layer of skin in this layer also contains the , muscle fibre, blood vesseles, Nerves collagen etc.
• An the hypodermis refion under the skin is purpose of storing the fat under the Adipose tissues( helps store fat).

SOME IMPORTANT FUNCTIONS OF SKIN INCLUDES:-

• PROTECTION -   Against entry of foreign bodies and mechanical injuries, forms protective                                        derivatives such as Nail, Hair, Scales, Bony plates, feather and in organisms,.

• TEMPERATURE CONTROL-  Protection from loss of water and maintain homeostasis.

• FOOD STORAGE- stores the food under the skin and also used to fat from the food to control body heat.

• SECRETION- Sweat glands, oily glands from the skin helps kills the bacteria in the skin, and stop cell dehydration,

• EXCRETION-  Some animals excrete the waste though their skins they excrete the salt, nitrogenous wastes through sweet.

and Respiration in some animals such as frog skin as cuticle respiration, Locomotion in fishes through the fins, the fins are modifications of skin and Sexual attraction in Aves skin provides feathers which has amazing colours helps the bird to attract their opposite sex, these help them to selects their potential mates.

Respiratory Pigments, Respiratory Pigments in Invertebrates , Vertebrates.

 RESPIRATORY PIGMENTS :

•  The respiratory pigments are colored  substance protein in blood and transporting O2 and CO2.

SALIENT FEATURES OF RESPIRATORY PIGMENTS;

• They are colored pigment, distributed in blood and body fluid. 
• They are chromoprotein, which contains a metallic iron.
• They play an important role in the transport of oxygen and carbon di oxide.

TYPES OF RESPIRATORY PIGMENTS;

• Hemoglobin,
• Hemocyanin,
• Hemerythrin,
• Chlorocruorin,
• Pinnaglobin,
• Vanadium,
• Echinochrome.

HEMOGLOBIN;

• The red color.
• These respiratory pigment is present in blood cells mostly in vertebrates (RBC).
• Also found in Chironomus Insects (larva) and Annelids.
• Hemoglobin found in muscle cells of birds and mammals are called Myoglobin.
• The myoglobin stores the oxygen in muscle cells temporarily.
• The molecular weight of Hemoglobin is 68,000 Dalton.
• Hemoglobin made up of two components they are
• Protein- globin.
• Non - Protein- heme

• Globin is made up of Polypeptide chain, there are two chains are present in hemoglobin they are 
• Alpha chain
• Beta chain,
• Hemoglobin HB+ Oxygen O2 ----------> HbO2 oxyhemoglobin.
• Hemoglobin= transfer of oxygen from lungs to cells and transfer of carbon di oxide from cells to lungs.

HEMOCYANIN;

• Blue in color.
• Copper and protein are found in blood.
• One copper atom and one peptide chain.
• 200 amino acid present in hemocyanin.
• The molecular weight of hemocyanin is 6,600,000 Dalton.
• This kind of Hemocyanin pigment observe UV Rays.
• Hemocyanin = involves in gaseous exchange, Pigment present in Plasma of blood.
• Example; Arthropods, Molluscans such as octopus.

HEMERYTHRIN;

• Reddish violet in color .
• Iron and protein are found in blood.
• One iron atom and one peptide chain.
• Molecular Weight is 66,000 Dalton.
• Hemerythrin is present small amount in blood and large amount in Plasma.
• Example ;unsegmented marine animals, marine worms.
• Low oxygen caring capacity comparing other pigments.

CHLOROCRUORIN;

• Green in color.
• This respiratory pigment contains Iron.
• Chlorocruorin pigment present in Plasma.
• Example ; Polychaete animals..

PINNAGLOBIN;

• Brown in color.
• Present in body fluid of molluscans. 
• Pinnaglobin pigment contain Manganese and protein.

VANADIUM;

• Silvery grey in color
• It contains chemical elements
• Example; Ascidian (urochordate).

ECHINOCHROME;

• Red in color.
• Present in Coelomic fluid.

Origin of Biological Membrane , Biological membrane composition, Lipid, Protein, Oligosaccharides.

                   ORIGIN OF BIOLOGICAL MEMBRANE

ORIGIN:

• The new phospholipid bilayer is made by the enzymes, which bound the (ER) Endoplasmic Reticulum. faces the cytosol of the membrane..

• Now , the phospholipid bilayer is deposited half of the biological membrane, which is now. The other half (outer half) is renovated by the process of flippases (flip-flop).
• The phospholipid bilayer also consist of
• Lipids..
• Protein
• Oligosaccharides..

Lipids:

• The phospholipid  bilayer is made up of lipids with hydrophobic polar head and non polar tails.
• The lipid are not in standard position they moves like a wave.
• The bilayer also comprises of cholesterol basically in RBC(erythrocyte).. 

PROTIEN:

• The phospholipid bilayer has different types of protein they are Integral protein, this protein involves in transportation . Which food required by cells to produce ATP. 
• Peripheral protein this protein involves or act as a catalyst , enzymes, signaling and much more process, by creating asymmetrical. 

OLIGOSACCHARIDES:

• The oligosaccharides are sugar and lipid molecule know as Glycolipids.
• The oligosaccharides plays important role in immune system and responsible for protection of cells and also vast Number of function and makes extremely asymmetrical.

Biological Membrane or Plasma Membrane or Biomembrane (Zoology students Edition)UG,PG

Biological Membrane or Plasma membrane or Biological Membrane:

 

• Bio-Membrane (or Cell Membrane or Biological Membrane or Plasma Membrane) is a selectively permeable membrane which separates the cell internals from the external environment.  
• The Biological membrane also creates the compartment with in the cell organelles from damaging itself. Which acts as a boundary between each organelles of the cells.
  
• In eukaryotic cells, the cell membrane or Biological Membrane is made up of 'Phospholipid Bilayer' ,Whereas the biological membrane in prokaryotic cell is made up of protein and carbohydrate. The compound is peptidoglycan or Mucopeptide.

• In eukaryotic cell the Biological Membrane are made up of Phospholipid bilayer which is selectively permeable membrane.
• The phospholipid bilayer is a polar membrane consists of two layers, There are  
• Inner lipid layer and 
• Outer lipid layer.

• The phospholipid are comprise the polar head and Non polar tail like structure embed inside.
• The Biological membrane or phospholipid bilayer contains proteins with them they are
• Integral proteins and 
• peripheral protein.

INTEGRAL PROTEIN;

• The integral protein are the type of protein which is permanently attached to the biological membrane and responsible for transfer of macro molecules. (Eg; Glucose)
• The integral protein is cannot be breakdown by any food molecules or enzymes unless the cell goes to apoptosis.

PERIPHERAL PROTEIN;

• The peripheral proteins are temporary protein attached to the phospholipid bilayer and creates asymmetry in layer. These asymmetry helps for cell signaling . 
• These peripheral protein acts as a catalysts , enzymes, etc.