Question

The main features of chordates. How can they be described according to examples of representative species, basic morphology, type of symmetry, germ layers and coelom, digestive system, respiratory system, circulatory system, excretory system, nervous system and types of reproduction?

Answer 1

The main features of the chordate system.

1)Level of organization--organ system.

2)symmetry of body--bilateral.

3)coelomic cavity.

4)respiratory system circulatory system, excretory and nervous system are present.

The main feature and characterization of the chordates--These organisms have a vertebral column, bones in the skeleton and a spinal cord for supporting the posture and balance of the body.

• body is triploblastic composed of ectoderm, mesoderm and the endoderm layer.
• they have a notochord which runs along the axis of the body.
• presence of the dorsal hollow nerve chord present along the notochord.
• pharnygeal gill slits are there for breathing.
• presence of a tail from the embryonic stage.

The phylum chordata is divided into three subtypes called as the urochrodata, cephalochordata and the vertebrates.

The vertebrates include chondrichthyes--sharks,skates and rays, actinopterygii-bony fishes, amphibia--frogs ,salamanders, reptilia--snakes,lizards and crocodiles,aves--birds, and mammals-pigs.

Digestive system-in rats-It consists of the organs used for the digestion of the food like mouth, food pipe, esophagus, pharnyx, larynx, stomach, intestine. The small intetsine consists of the duodenum, jejunum and ileum. The large intestine consists of the caecum, colon and rectum. The undigested food passes from the anus and the rectum.

Respiratory system in the fishes--The external gills are present for breathing the gas and for the intake of the oxygen from the water. Lungs are present in other vertebrates for breathing. Ribs are present for the protection of the organs and for supporting the balance, structure and the posture of the body. The gills increase the surface area of the exchange of the gases in the body, help in the efficient exchange of the gases in the respiratory system, and the establishment of the concentration gradient of the gases in the system. The gills in the fishes consist of the operculum, opercular cavity and the gill slits for the exchange of the gases. The flow of the water is opposite to the flow of the blood in the fishes which creates a concentration gradient for the movement of the gases. Primary lamellae and the secondary lamellae are present for the exchage of the gases in the system. The lungs in the amphibians consist of the alveoli, bronchi, bronchioles,pulmonary arterioles, trachea and the alveolar ducts.

The circulatory system consists of the heart, the bicuspid, tricuspid valves, the aorta , superior vena cava, inferior vena cava, left auricles and ventricles, right auricles and ventricles. The blood flows into the heart for the oxygenation process to take place.

Excretory system--it consists of the nephrons for the excretion of the metabolic wastes from the body of the vertebrates. The excretion takes place with the help of of the nephrons made up of the affrerent and efferent arterioles, proximal and distal convoluted tubules, loop of henle and the collecting duct for the filtration of the metabolites and ions in the body of the organism. The other organs include the ureter, urinary bladder for storing the urine and the urethra pipe for the excretion of the fluid waste from the body.

nervous system--It consists of the brain with the cerebral hemispheres, cerebral cortex, cerebellum, pons, thalamus, medulla oblongata and the white and the gray matter in the brain.

Reproductive organs--consists of the prostrate gland, vas deferens, epididymus, seminal vesicles and the testis in the males and the presence of the ovary, ovules, fallopian tubes, and the egg in the female for reproduction.