Maharashtra Board Class 11 Biology Chapter 11 Study of Animal Type Cockroach PDF Download

Study Of Animal Type - Cockroach

Curiosity box:

1. Why do insects need moulting?

2. What is the difference between simple and compound eyes?

Can you recall?

1. How many different types of animals are present around us?

2. Can a person complete detailed study of each of those animals?

3. Which phylum is most diverse and populous?

11.1 Habit And Habitat

Cockroaches are omnipresent i.e. present everywhere, all over the world. It prefers damp and moist places, crevices to live. It is omnivorous, nocturnal and cursorial.

Periplaneta americana, Blatta orientalis and Blatta germanica are the three common species of cockroach found in India.

Teacher's Note

You can find cockroaches in dark, wet places like your kitchen sink or bathroom. They like to hide in cracks and eat any leftover food they find.

Exam Trick

Remember: Cockroaches = dark + wet + food scraps. They are like thieves that steal at night and hide during the day!

Points to Remember

Cockroaches live everywhere in the world.
They like damp and moist places.
They eat both plants and animals.
They are active at night.
Three common types are found in India.

11.2 Systematic Position

Kingdom: Animalia (Cell wall absent, heterotrophic nutrition.)

Phylum: Arthropoda (Jointed appendages are present, segmented body, chitinous exoskeleton.)

Class: Insecta (Two pairs of wings and three pairs of walking legs are present.)

Genus: Periplaneta (Nocturnal, straight wings.)

Species: americana (Origin is in Continent of America)

Teacher's Note

Systematic position is like a home address for animals. It helps us organize and find where they belong in the animal kingdom, just like your house has a street name and house number.

Exam Trick

Remember: Kingdom is biggest group, then Phylum, then Class, then Genus, then Species is smallest. It is like going from city to street to house number!

Points to Remember

Cockroach belongs to Kingdom Animalia.
It belongs to Phylum Arthropoda.
Its Class is Insecta.
Genus is Periplaneta.
Species is americana.

11.3 External Morphology

Shape And Size

Cockroach has an elongated, bilaterally symmetrical and dorso-ventrally flattened body. They are triploblastic, eucoelomate and truly segmented animals. Body cavity is called as haemocoel, filled with haemolymph.

Coloration

Cockroach is glistening brown or red brown in colour.

Exoskeleton

Body of cockroach is protected by hard, waxy, tough, non-living exoskeleton. Exoskeleton is formed by a nitrogenous polysaccharide-chitin that provides strength, elasticity and surface area for attachment of muscles. Each body segment of cockroach is covered by four chitinous plates (sclerites) namely, dorsal tergum, ventral sternum and two lateral pleurons.

Body Division

Body is divided into three regions namely head, thorax and abdomen. Head is attached at right angles to thorax by a thin, narrow, movable neck or cervix.

Head

It is formed by the fusion of six segments. It is triangular or ovate in shape. It is highly mobile due to flexible neck. It bears a pair of long antennae, a pair of compound eyes and mouth parts adapted for chewing and biting of food.

Teacher's Note

The cockroach's body is like a suit of armor made of chitin. This hard shell protects it just like your bones protect your body inside.

Exam Trick

Remember: Exo = outside, so exoskeleton = skeleton on the outside. Think of it like a knight's armor worn on the outside of the body!

Points to Remember

Cockroach has a flat, elongated body.
Its body is covered with hard chitin exoskeleton.
Body is divided into head, thorax and abdomen.
The neck is flexible and movable.
Head has antennae, eyes and mouth parts.

1. Antennae

Also called as feelers. There are filamentous, long, segmented structures that can be moved in all directions. They are lodged in membranous pits called antennal sockets. They are tactile (touch) as well as olfactory (smell) organs, useful in locating the food material in the vicinity.

2. Fenestrae

Also called as ocellar spots situated at the base of each antenna and they appear as white spots.

3. Compound Eyes

They are paired, dark, kidney shaped structures placed on lateral sides of the head and are made up of large number of ommatidia (singular ommatidium). Ommatidia are structural and functional units of compound eye, each forming an image of very small part of visual field. Collectively, compound eye produces a mosaic image.

4. Mouth Parts

Cockroach has pre-oral cavity in front of mouth in which foods is received. It is bounded by chewing and biting type of mouth parts. These are movable, segmented appendages which assist in ingestion of food. Mouth parts of cockroach comprise of....

i. Labrum (Upper lip): It is single flap-like movable part which covers the mouth from upper side. It forms an anterior wall of pre-oral cavity. It is useful in holding of the food during feeding.

ii. Mandibles (True jaws): These are two dark, hard, chitinous structures with serrated median margins. They are present on either side, behind the labrum. They perform coordinated sidewise movements to cut and crush the food. This movement is effected with the help of adductor and abductor muscles.

iii. Maxillae (Accessory jaws): These are also called as first pair of maxillae. These are situated on the either side of mouth behind the mandibles. Each maxilla consist of sclerites like cardo, stipes, galea, lacinia and maxillary palps. Maxillary palps act as tactile organs. The maxillae hold food, help the mandibles for mastication. Maxillae are also used for cleaning the antennae and front legs.

iv. Labium (Lower lip): It is also called as second maxilla which covers the pre-oral cavity from ventral side and is firmly attached to the posterior part of head. It has labial palps which is three jointed and sensory in function. It is useful in pushing the chewed food in the pre-oral cavity and also prevents the loss of food falling from the mandibles during the chewing.

v. Hypopharynx (Tongue): In front of the labium and between first maxillae, there is a some what cylindrical single structure called hypopharynx or lingua. A salivary duct opens at the base of this structure. Lingua bears comb-like plates called super-lingua on either side. It is useful in the process of feeding and mixing of saliva with food.

Teacher's Note

The antennae are like a cockroach's nose and fingers combined. They feel and smell food just like you use your nose to smell and your fingers to touch.

Exam Trick

Remember: Antennae = feelers, Eyes = see, Mouth parts = chew. Each body part has its own job to do!

Points to Remember

Antennae are feelers and smell organs.
Compound eyes make a picture by many small images.
Mandibles are the true jaws for chewing.
Labrum and labium are upper and lower lips.
Hypopharynx is like a tongue that helps in eating.

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