chordata. lectures from protochordata until mammles pptx

Chordata Lectures
Prepared by
Dr. Mervat El alfy
BIOLOGY DEPARTMENT
BISHA UNIVERSITY ,KSA
(2024-2025)

Animal kingdom is basically divided into two sub kingdoms:
(a) Non-chordata- including animals without notochord.
(b) Chordata- This comprising animals having notochord .
While the Chordata has a notochord at some stage during the life, it is not known to
exist in the Non-Chordata.
•The Chordata is the animal phylum with which everyone is most intimately familiar, since it
includes humans and other vertebrates However, not all chordates are vertebrates.
•All chordates have the following features at some stage in their life (in the case of humans
and many other vertebrates, these features may only be present in the embryos).
•Pharyngeal slits – a series of openings that connect the inside of the throat to the outside
of the “neck”. These are often, but not always, used as gills.
•Dorsal tubular nerve cord – A bundle of nerve fibers which runs down the “back”. It
connects the brain with the lateral muscles and other organs.
•Notochord – cartilaginous rod running underneath, and supporting, the nerve cord.
•Post-anal tail – an extension of the body post the anal opening.

PHYLUM: CHORDATA
Group ACRANIA (=PROTOCHORDATA) (Primitive
chordates without head and
vertebral column)
Subphylum HEMICHORDATA, Example Balanoglossus

GENERAL CHARACTERS OF HIMICHORDATA
•Bilaterally symmetrical and exclusively marine, worm- like and soft bodied animals.
•Body cavity a true coelom (enterocoel).
•Body divided into three sections, Proboscis, collar and trunk. Numerous paired gill-slits are present.
•Digestive tube complete, straight or U-shaped.
•Nervous system normally diffuses, but variable and partially open circulatory system.
•Possesses Glomerulus as an excretory organ and reproduction normally sexual, sexes usually
•separate but few acorn worms also exhibit asexual reproduction.
•Fertilization external in sea water .Development direct or indirect with a free swimming tornaria
•larva. Feeds on fine particles in the water.

The urochordates, sometimes known as the tunicates, are commonly known
as "sea squirts.
The body of an adult tunicate is quite simple, being essentially a sack with
two siphons through which water enters and exits.
Water is filtered inside the sack-shaped body.
Urochordates are small marine animals with larvae that swim freely and
adults that attach themselves to the ocean floor.

1. Atrial cavity surrounds the pharynx, into this cavity the gill slits, anus and genital ducts will
Open. It opens through atrial aperture.
2. Larva has notochord in the tail. It disappears during metamorphosis.
3. Respiratory system contains gills in the pharyngeal wall.
4. Open type of Circulatory system .
5. Nervous system is represented by a single dorsal ganglion in the adult.
6. Excretion is carried on by nephrocytes.
7. Asexual reproduction is by budding, Bisexual animal and Fertilization. is external

Urochordate’s-resemblance with Chordate. :-
Urochordates resemble the chorates owing to the following features-
• Presence of dorsal tubular nerve cord.
• Presence of notochord.
• Well developed pharynx with gill-slits.
• Presence of endostyle on the ventral side of the pharynx.
• Presence of atrium around the pharynx.
• Presence of post - anal tail with tail fin.
Because of these chordate features tunicates are included in chordate’s
group.

Cephalochordates : have all the typical chordate features.
The dorsal nerve cord is supported by a muscularized rod, or notochord.
The pharynx is perforated by over 100 pharyngeal slits or "gill slits", which
are used to strain food particles out of the water.
The musculature of the body is divided up into V- shaped blocks, or
myomeres, and there is a post-anal tail.
All of these features are shared with vertebrates. On the other hand,
cephalochordates lack features found in most or all true vertebrates: the
brain and the sense organs are very small and poorly developed, and there
are no true vertebrae.

Water passes from the mouth into the large pharynx, which is lined by numerous gill-slits. The
ventral surface of the pharynx contains a groove; called the endostyle. Which is connected to a
structure known as Hatschek's pit, produces a film of mucus. Ciliary action pushes the mucus
in a film over the surface of the gill slits, trapping suspended food particles as it does so. The
mucus is collected in a second, dorsal, groove, and passed back to the rest of the digestive tract.
Having passed through the gill slits, the water enters an atrium surrounding the pharynx, and
then exits the body via the Atri pore.

Nervous system
Amphioxus possesses a hollow nerve cord running along the anterior- posterior end of the body.
Unlike vertebrates, the dorsal nerve cord is not protected by bone but by a simple notochord made of a cylinder of cells, to form
a toughened rod.
REPRODUCTION IN AMPHIOXUS
Amphioxus is a unisexual animal. Amphioxus shows 26 pairs of Gonads. They are present from 25th myotomal
segments to 51. Gonads have no ducts.

Cyclostomata is a group of chordates that comprises the living jawless
fishes:
• the lampreys and hagfishes.
• Both groups have round mouths that lack jaws but have retractable
horny teeth.
• The name Cyclostomata means "round mouths".
• Their mouths cannot close due to the lack of a jaw, so they have to
constantly cycle water through the mouth.
1. The body is long, eel like. It has a trunk and a compressed tail.
2. Paired fins are absent. Median fin is supported by cartilaginous fin-rays.
3. The skin i.e soft and smooth. It is slimy. It is scale less.
4. Z- shaped myomeres are present in the trunk and tail Protractor and retractors muscles .
5. These vertebrates do not have jaws, hence called Agnetha.
6. The mouth is circular. It works like a sucker and is surrounded by tentacles.
7. Tongue bears teeth.
8. 10. Stomach is absent and esophagus leads into the intestine.

lampreys can be flesh-feeders or blood-feeders, depending primarily on the structure of
their teeth.
Feeding behavior is characterized by rhythmic rasping, negative pressure pulses in the
sucker, and swallowing of fluid into the gut.

The Digestive System
The digestive system consists of the alimentary canal, which runs from the mouth to the anus. Food
enters the food enters the mouth and moves through the pharynx into the esophagus. The adult
lamprey is an ectoparasite and its food is in the form of fish blood. A lamprey does not have a
stomach.
Circulatory System:
Blood flows through a series of vessels to supply oxygen and nutrients to the body and to remove
carbon dioxide and other wastes.–Arteries and arterioles carry blood away from the heart–Veins
and venules carry blood back towards the heart–Capillaries are the smallest vessels where the
gases are exchanged with the cells of the body

Nervous system
Lampreys have a primitive nervous system, the brain structure is fairly
simple compared to other vertebrate animals. System consists of the brain
and a hollow spinal cord–Situated above the alimentary canal.

Respiratory Systems:
A lamprey “breathes” by extracting the oxygen present in the water in which it lives. Within the
respiratory tube are seven gill pouches, each containing the finer feather-like gill lamellae.

A fish is a group of organisms that consist of all gill- bearing aquatic craniate animals that lack
limbs with digits.
Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish.
Most fish are ectothermic ("cold-blooded"), allowing their body temperature to vary as ambient
temperature changes though some of the large active swimmers .
Fishes
Chondrichthyes:-
The members of the Chondrichthyes are cartilaginous fishes possess’ true bone and also posses
a skeleton made up of cartilage.
Only the teeth of this species and rarely the vertebrae are calcified. Sharks, Skates, and Rays
make up the group of Chondrichthyes.
Osteichthyes:-
About 30000 species of bony fish are found in this class. Skins are protected by protective scales.
Some fishes of this category have actual lungs to breathe and also have sharp eyesight.

Bony fish are again classified into ray finned and lobe finned fish.
Ray finned fish have thin, flexible skeleton rays. Lobe finned fish have muscular fins supported by
bones.
Chondrichthyes:- (dog fish)
Scoliodon is widely distributed in India, Pacific West India and eastern coasts of South America and
Atlantic Oceans.
The common Indian dogfish ,which means “Black Shark

Placoid scales:
Placoid scales are found in the cartilaginous fishes.
They are also called dermal denticles.
The scales are supported by spines, which feel rough when stroked in
a backward direction but, when flattened by the forward movement
of water.

Digestive system:
Digestive system consists of alimentary canal and
associated glands.
Alimentary canal:
It is complete and is divided into buccal cavity, pharynx,
esophagus, stomach, intestine and rectum.

Respiratory System:
In Scoliodon respiration takes place through 5 pairs of gill slits or gill pouches.
They are present in a series on the wall of pharynx on either lateral side .

Circulatory system :
1- Thin-walled, flat called sinus veno Circulatory system consists of Four chambers.
2- Second chamber called auricles, in which the sinus venosus is open
3- Muscular chamber, thick walled chamber called ventricle
4- conus arteriosus

Digestive System:
stomach, intestine, pancreas, liver, pyloric caecae
• Pyloric caecae - slender tubes that secrete digestive enzymes
• Plant eaters = long intestine, Meat eaters = short intestines

Urinogenital system:
Excretory system
❖consists of two elongated kidney,
❖two short mesonephric duct (the two ducts unite after leaving the kidney to form a
common mesonephric duct),
❖small urinary bladder and urogenital papilla.
*Reproduction system
The male reproductive system in bony fish consists of two testes, vas deference and open
on urogenital papilla,
The female reproductive system consists of two ovaries, oviduct and open on genital
papilla.

Circulatory system
Circulatory system consists of three chambers
1- Sinus venosus
2- second chamber called auricles, in which the sinus venosus is
open
3- Muscular chamber, thick walled chamber called ventricle
Conus Arteriosus is absent in bony fishes

The nervous system of a fish: is similar to that of other vertebrates.
They contain a central nervous system containing a brain and spinal cord and a peripheral
nervous system
containing the various nerves throughout the body.

Respiratory system:
Most amphibians breathe through lungs and their skin. Their skin has to stay wet
in order for them to absorb oxygen so they secrete mucous to keep their skin
moist (If they get too dry, they cannot breathe and will die).

The digestive system of amphibians has two major
components, a digestive tract, and digestive glands.
The digestive tract starts from the mouth and ends as the anus,
emptying into the cloaca.

In amphibians, the urogenital system consists
of the testicles attached to fat bodies and
accessory ducts .
They are located above the testicles and are
whitish, yellowish, or orange in color.
The testicles are located in the ventral region
of the kidney in the abdominal cavity.

The nervous system is basically the same as in other vertebrates, with a
central brain, a spinal cord, and nerves throughout the body

The front limbs consist of a humerus and a radio-ulna, and the frog's
wrist bones, or carpals, articulate with the radio-ulna.
The hind limbs, two tarsal bones (tibiale and fibulare) have elongated to
form a third leg segment that adds approximately two body-lengths to
frogs' maximum jumping distance.

The scales of reptiles prevent them from absorbing oxygen through their skin, as amphibians
can. Instead, reptiles breathe air only through their lungs. However, their lungs are more efficient
than the lungs of amphibians, with more surface area for gas exchange

The digestive system of modern reptiles is similar in general
plan to that of all higher vertebrates.
It includes the mouth and its salivary glands, the esophagus,
the stomach, and the intestine and ends in a cloaca.

Most reptiles reproduce sexually and have internal fertilization.
Males have one or two penises that pass sperm from their cloaca to the cloaca of a
female. Fertilization occurs within the cloaca, and fertilized eggs leave the female's body
through the opening in the cloaca

They are called pneumatic bones and
include the skull, humerus, clavicle, keel
(sternum), pelvic girdle, and the lumbar
and sacral vertebrate.
Another important type of bone in the
avian skeleton is medullary bones. These
include the tibia, femur, pubic bone, ribs,
ulna, toes and scapula.

Like mammals, birds have nares, a larynx, trachea and
lungs. In addition, they have nine air sacs and a syrinx
(vocal center). Unlike mammals, they have no
diaphragm and there is a unidirectional air flow that
requires two full inspiratory and expiratory cycles to
complete.
Birds have air sacs located in front of and behind the
lungs, while mammals have air sacs within the lungs.
Birds inhale and exhale twice for every respiration,
whereas mammals inhale and exhale once per
respiration. Mammalian respiratory systems also

The digestive order is as follows:
bill, mouth, tongue, pharynx, esophagus,
crop, proventriculus, gizzard, small intestine, caeca,
rectum, cloaca.

The avian nervous system can be divided into the
central nervous system which comprises the brain and
spinal cord and the peripheral nervous system which
includes the cranial and spinal nerves, their ganglia
and plexi and the peripheral portions of the autonomic
nervous system.

The avian reproductive system is heterosexual
and requires both a male and a female, each to
contribute half of the genetic constitution of the
offspring. The male contributes his half by way of
the sperm produced by the testes and carried in
the semen.

There are 46 bones that make up the spinal
column alone, 7 cervical (the neck), 12
thoracic (the chest), 7 lumbar (the lower
back), 4 sacral (the pelvis) and 16 (the tail). A
rabbit's bones have extremely thin cortices
and are easily shattered.

In mammals, air is warmed and humidified
in the nasal cavity. Air then travels down the
pharynx, through the trachea, and into the
lungs. In the lungs, air passes through the
branching bronchi, reaching the respiratory
bronchioles, which house the first site of gas
exchange.
Internal respiration: It involves the exchange of
gases between tissue fluids and the blood.
External respiration: It involves a gas
exchange between inhaled air and the
pulmonary blood. Cellular respiration: It
involves aerobic and anaerobic respiration.

The heart is divided into four
chambers consisting of two atria and
two ventricles; the atria receive blood,
while the ventricles pump blood.
The right atrium receives blood from
the superior and inferior vena caves
and the coronary sinus; blood then
moves to the right ventricle where it
is pumped to the lungs

In mammals, the digestive tract is
made up of multiple organs such as
the stomach, pancreas, and
intestines. These all work together to
form the alimentary canal we use to
digest food.

The nervous system of rabbit consists of three
divisions:
1. The central nervous system including brain
and spinal cord.
2. The peripheral nervous system including
nerves coming out from the brain and spinal
cord, i.e., cranial nerves and spinal nerves.

The rabbit's male reproductive system consists of a pair of ovoid-shaped testes. Scrotal sacs
in the abdominal cavity contain the testes. Seminiferous tubules are a type of tiny tubule found in
each testis. These network of tubules leads to the epididymis, a coiled tubule that leads to the vas
deferens, the sperm duct.
The female reproductive system in rabbit consists of a pair of ovaries which are small ovoid
structures. A pair of oviducts opens into the body cavity by a funnel shaped opening from each side of
the ovary. The anterior part of the oviduct is the fallopian tube. It leads into a wider tube called
uterus.

chordata. lectures from protochordata until mammles pptx

More Related Content

What's hot (20)

Similar to chordata. lectures from protochordata until mammles pptx (20)

Recently uploaded (20)

chordata. lectures from protochordata until mammles pptx