Question: From NCERT 100% NCERT covered from Particular Keyword. NEET 2020 Explanations are 100% from NCERT | [Difficult level: Easy]
Which of the following statements are true for the phylum-Chordata?
(a) In Urochordata notochord extends from head to tail and it is present throughout their life
(b) In Vertebrata notochord is present during the embryonic period only
(c) Central nervous system is dorsal and hollow
(d) Chordata is divided into 3 subphyla : Hemichordata, Tunicata and Cephalochordata
1. (c) and (a)
2. (a) and (b)
3. (b) and (c)
4. (d) and (c)
Subtopic: Phylum Chordata |
Answer-3. (b) and (c)
👉Phylum
Classes comprising animals like fishes, amphibians, reptiles, birds
along with mammals(including humans) constitute the next higher category called
Phylum. All these, based on the common features like presence
of notochord and dorsal hollow neural system, are included in
phylum Chordata. In case of plants, classes with a few similar
characters are assigned to a higher category called Division.
👉Common name- Man
Biological Name- Homo sapiens
Genus- Homo
Family-Hominidae
order- Primata
Class- Mammalia
Phylum- Chordata
👉Phylum – Hemichordata
Hemichordata was earlier considered as a sub-phylum underphylum Chordata. But now it is placed as a separate phylum
under non-chordata. Hemichordates have a rudimentary
structure in the collar region called stomochord, a structure
similar to notochord.
This phylum consists of a small group of worm-like
marine animals with organ-system level of organisation. They
are bilaterally symmetrical, triploblastic and coelomate
animals. The body is cylindrical and is composed of an
anterior proboscis, a collar and a long trunk (Figure 4.15).
Circulatory system is of open type. Respiration takes place
through gills. Excretory organ is proboscis gland. Sexes are
separate. Fertilisation is external. Development is indirect.
Examples: Balanoglossus and Saccoglossus.
👉Phylum – Chordata
Animals belonging to phylum Chordata are fundamentally
characterised by the presence of a notochord, a dorsal hollow nerve cord and paired pharyngeal
gill slits (Figure 4.16). 
These are bilaterally
These are bilaterally
symmetrical, triploblastic, coelomate with
organ-system level of organisation. They
possess a post anal tail and a closed circulatory
system.Phylum Chordata is divided into three
subphyla: Urochordata or Tunicata,
Cephalochordata and Vertebrata.
Subphyla Urochordata and
Cephalochordata are often referred to as
protochordates (Figure 4.17) 
and are
and are
exclusively marine. In Urochordata, notochord
is present only in larval tail, while in
Cephalochordata, it extends from head to tail
region and is persistent throughout their life.
Examples: Urochordata – Ascidia, Salpa,
Doliolum; Cephalochordata – Branchiostoma
(Amphioxus or Lancelet).
The members of subphylum Vertebrata
possess notochord during the embryonic
period. The notochord is replaced by a
cartilaginous or bony vertebral column in the
adult. Thus all vertebrates are chordates but
all chordates are not vertebrates. Besides the
basic chordate characters, vertebrates have a
ventral muscular heart with two, three or four
chambers, kidneys for excretion and
osmoregulation and paired appendages which
may be fins or limbs.
👉Phyllum- chordata
organisation- organ system
symmetry- bilateral
coelom- coelomate
segmentation- present( present in Annelida, Arthropoda and chordata only)
Digestive system- (start from- Aschelminthes) Complete
Circulatory system- ( Start from - Annelida) Present
Respiratory system- ( start from Arthropoda) Present
Distinctive Feature- Notochord, dorsal hollow nerve cord,gill slits with limbs or fins.
👉Phylum Chordata includes animals which possess a notochord either
throughout or during early embryonic life. Other common features observed in
the chordates are the dorsal, hollow nerve cord and paired pharyngeal gill slits.
Some of the vertebrates do not possess jaws (Agnatha) whereas most of them possess
jaws (Gnathostomata). Agnatha is represented by the class, Cyclostomata. They
are the most primitive chordates and are ectoparasites on fishes. Gnathostomata
has two super classes, Pisces and Tetrapoda. Classes Chondrichthyes and
Osteichthyes bear fins for locomotion and are grouped under Pisces. The
Chondrichthyes are fishes with cartilaginous endoskeleton and are marine. Classes,
Amphibia, Reptilia, Aves and Mammalia have two pairs of limbs and are thus
grouped under Tetrapoda. The amphibians have adapted to live both on land and
water. Reptiles are characterised by the presence of dry and cornified skin. Limbs
are absent in snakes. Fishes, amphibians and reptiles are poikilothermous (coldblooded).
Aves are warm-blooded animals with feathers on their bodies and
forelimbs modified into wings for flying. Hind limbs are adapted for walking,
swimming, perching or clasping. The unique features of mammals are the presence
of mammary glands and hairs on the skin. They commonly exhibit viviparity.
👉Water vascular system is the characteristic of which group of the following:
(a) Porifera (b) Ctenophora (c) Echinodermata (d) Chordata
👉FROGS
Frogs can live both on land and in freshwater and belong to class
Amphibia of phylum Chordata. The most common species of frog found
in India is Rana tigrina.
They do not have constant body temperature i.e., their body
temperature varies with the temperature of the environment. Such animals
are called cold blooded or poikilotherms. You might have also noticed
changes in the colour of the frogs while they are in grasses and on dry
land. They have the ability to change the colour to hide them from their
enemies (camouflage). This protective coloration is called mimicry. You
may also know that frogs are not seen during peak summer and winter.
During this period they take shelter in deep burrows to protect them
from extreme heat and cold. This is known as summer sleep (aestivation)
and winter sleep (hibernation) respectively.
