Mammalia is named after the Latin word Mamma. The word Mammalia means mammals. They can range from the tiny Thai bat (1.5 grams) to the largest blue whale (130 metric tons). They have taken over the world. Humans are the greatest animals on earth. Their number of species is 6,000. 10 classes, 35 tribes and 138 species of mammals have been identified in Bangladesh. Dr. Siddiq Publications

Characteristics of mammals
1. Their skin is covered with hair.
2. The outer ear is attached to the pinna. The middle ear consists of malleus, incus and stapes. Cochlea exists in the inner ear. Dr. Siddiq Publications
3. Mature females have active mammary glands. Cubs drink mother’s milk.
4. Between the thorax and abdomen is a membrane called the diaphragm.
5. The crown of the head is connected to the spinal cord by two occipital condyles.
6. They have sweat glands and scent glands.
7. They are endothermic or warm-blooded animals. That is, their body temperature does not change with the rise and fall of the environment temperature.
8. Their red blood cells are without nucleus (exception – camel).
9. Their brains are developed and they have all the tantras.
10. They have 12 pairs or 24 cranial nerves.
11. They have teeth in both jaws.
12. The heart has four chambers. Two atria and two ventricles.
13. The circulatory system is advanced. Bi-cycle or double circulation. Systemic and pulmonary cycles are seen.
14. They have vocal cords in their larynxes. The glottis has a covering called the epiglottis.
15. Their poison is internal. They bear the uterus and give birth to babies.
[key words to remember features: hair, pinna, cochlea, cochlea, mammary gland, diaphragm, sweat gland, olfactory gland, endothermic, red blood cell, cranial nerve, tooth, heart, circulatory system, vocal card, uterus] Dr. Siddique Publications

Some animals of Mammalia
Human – Homo sapiens
Tiger – Panthera tigris
Lion – Panthera leo
Deer – Axis axis
Guinea pig- Cavia porcellus
Rabbit – Sylvilagus audubonii
Dolphin – Delphinus capensis
Bat- Pteropus giganteus
Kangaroo – Macropus giganteus
Platypus- Ornithorhynchus anatinus
Squirrel- Funambulus palmarium
Camels – Camelus dromedaries
Rhesus monkey- Macana mulatta
Cow – Bos indicus
Goat- Capra hircus
Sheep – Ovis aries
Buffalo – Bubalus bubalis
Hanuman- Trachypithecus phayrei
Rat- Bandicota indica
Dog – Canis lupus familiaris
Cat- Felis catus
Guinea pig- Cavia porcellus
Pig – Sus scrofa
Water elephant- Hippopotamus amphibius
Gorilla – Gorilla gorilla
Fox – Canis aureus
Elephant – Elephas maximus
Rhinoceros – Rhinoceros unicomis
Bear- Melarsus ursinus
Giraffe – Giraffa camelopardalis
Whales – Balaenoptera musculus

Classification of mammals
Class Mammalia is divided into three subclasses based on the nature of reproduction. These are Prototheria, Metatheria and Eutheria.
1. Prototheria: The word Prototheria is formed from the Greek word protos meaning first and ther meaning mammal. Mammals that lay eggs are called ovipositors or prototheria. They live in Australia and New Guinea. Dr. Siddique Publications
(i) They are primitive egg-laying mammals. They are not immortal.
(ii) They lay eggs with a leathery covering. A newborn is born from an egg.
(iii) Newborns suck the mother’s milk. Because their mammary glands do not have nipples.
(iv) They have sharp lips, no teeth and no external ears.
(v) There is only one mucous membrane for excretory, reproductive and digestive system. Hence they are called monotrims.
Examples: Goose-billed Platypus (Ornithorhynchus anatinus), Short-billed Echidna (Tachyglossus aculeatus)
2. Metatheria: The word Metatheria is formed from the Greek word meta meaning medium and ther meaning mammal. Mammals that have a pouch called a marsupium are called marsupials or metatheria. They live in Australia, Tasmania, New Guinea, Central and South America.
(i) They are simple immortal mammals.
(ii) They give birth to very immature neonates.
(iii) Female animals have pouch called marsupium. In this pouch the new-born attain fullness. Hence they are called marsupials.
(iv) Mammary glands including nipples are exposed in marsupium.
(v) They have two uteri and two vaginas.
Examples: Red kangaroo (Osphranter rufus/Macropus rufus), Virginia opossum (Didelphis virginiana), Koala (Phascolarctos cinereus).
3. Eutheria: The word Eutheria is formed from the Greek word eu meaning nature and ther meaning mammal. Mammals that possess true immortality are called immortalized mammals or eutheria. They are spread throughout the world. Dr. Siddique Publications
(i) They are true immortal mammals. Their embryo consists of chorion and allantois.
(ii) Immortals provide nutrients during their flowering. The gestation period is long lasting.
(iii) Their embryos remain in the uterus for some time and give birth to mature neonates.
(iv) Mammary glands of female animals are highly developed. It contains nipples.
(v) Their vagina is one. The testes are located in the scrotal sac.
Example: Human (Homo sapiens), Shushuk (Platanista gangetica), mouse (Mus musculus), Rusa deer (Rusa unicolor), tiger (Panthera tigris), fruit bat (Pteropus giganteus).

Diaphragm
The muscular membrane between the thoracic and abdominal cavities of mammals

Doyle – Copsychus saularis
Rooster – Galus galus
Owl – Bubo bubo
Eagle – Haliacetus leucogaster
Pigeon – Columba livia
Hummingbird – Mellisuga helenae
Dove – Streptopelia decaocto
Shalik – Lamprotornis hildebrandti
Cuckoo – Eudynamys scolopaceus
Buck – Nycticorax nycticorax
Passer domesticus
King vulture – Sarcogyps calvus
Black Pheasant – Francolinus francolinus
Quail – Coturnix coturnix
Moina – Gracula Religiosa
Tia – Psittacula krameri
Dahuk – Amaurornis phoenicurus
Crane – Grus antigone
Crow – Corvus splendens
Bulbul – Pycnonotus cafer
Ostrich – Struthio camelus
Peacock – Pavo cristatus
Babui bird – Ploceus philippinus
Pelican – Pelecanus philippensis

Birds evolved from reptiles during the Mesozoic Era. The ancestors of birds are reptiles. Reptiles have evolved into birds. In the early 20th century, the famous ornithologist Thomas Huxley called them birds as the majestic reptiles. Archeopteryx is a fossil link between reptiles and birds. That is, archeopteryx evolved from reptiles and birds evolved from archeopteryx. The characteristics of the creation of birds from reptiles are-
1. Reptiles are cold-blooded animals with low metabolic rates. Birds are high-blooded animals with high metabolic rate. Dr. Siddiq Publications
2. Reptiles are mobile animals. Birds can move faster due to the gain in flight ability.
3. Reptiles have dry fibrous bodies. Bird feathers have been created from the dung of reptiles. Dr. Siddiq Publications
4. The four-chambered heart of a bird has been created from the incomplete four-chambered heart of a reptile.
5. There are two systemic arches in the circulatory system of reptiles and one systemic arch of birds.
6. The renal portal system of reptiles is highly developed. It is decaying in birds.
7. The jaws of reptiles gave rise to the long beaks of birds.
The above discussion proves that birds have evolved from reptiles. That is, birds are majestic reptiles.

1. The body is covered with feathers and the forelegs are modified into two wings.
2. Their necks are elongated and S-shaped.
3. The jaws are toothless and have evolved into beaks.
4. Intraskeletal pores, bone hard, light and airy. Bones contain air-filled cavities.
5. Air sacs exist in the lungs. The sphincter consists of the syrinx, the organ that produces sound.
6. They are endothermic or warm-blooded animals. That is, their body temperature does not change with the rise and fall of the environment temperature.
7. The heart has four chambers, 2 atria and 2 ventricles.
8. Their digestive system consists of crop and gizzard. So able to digest energy food quickly. Dr. Siddiq Publications
9. The crown of the head is connected to the spinal cord by an occipital condyle. The sternum forms a boat-like keel.
10. They are bipedal and can fly.
11. Their feet have clawed toes.
12. They lay eggs. The egg hatches and the baby comes out.
13. Newborn babies are active and vigorous or naked and weak.
[key words to remember characteristics: feather, wing, neck, beak, air cavity, air sac, syrinx, endothermic, heart, digestive system, occipital condyle, keel, biped, toe, egg] Dr. Siddiqu Publications

The Latin word Avis means bird. Vertebrate animals that have left water and land to take to the skies are called birds. Their bodies are adapted for flight and they have evolved as flying machines. The physical characteristics of the birds resemble those of archosaurs of the Mesozoic era. The total number of species is 10,000. 21 classes and 706 species of Avis class have been identified in Bangladesh. Dr. Siddiq Publications

The Latin word Avis means bird. Vertebrate animals that have left water and land to take to the skies are called birds. Their bodies are adapted for flight and they have evolved as flying machines. The physical characteristics of the birds resemble those of archosaurs of the Mesozoic era. The total number of species is 10,000. 21 classes and 706 species of Avis class have been identified in Bangladesh. Dr. Siddiq Publications

Features of Avis
1. The body is covered with feathers and the forelegs are modified into two wings.
2. Their necks are elongated and S-shaped.
3. The jaws are toothless and have evolved into beaks.
4. Intraskeletal pores, bone hard, light and airy. Bones contain air-filled cavities.
5. Air sacs exist in the lungs. The sphincter consists of the syrinx, the organ that produces sound.
6. They are endothermic or warm-blooded animals. That is, their body temperature does not change with the rise and fall of the environment temperature.
7. The heart has four chambers, 2 atria and 2 ventricles.
8. Their digestive system consists of crop and gizzard. So able to digest energy food quickly. Dr. Siddiq Publications
9. The crown of the head is connected to the spinal cord by an occipital condyle. The sternum forms a boat-like keel.
10. They are bipedal and can fly.
11. Their feet have clawed toes.
12. They lay eggs. The egg hatches and the baby comes out.
13. Newborn babies are active and vigorous or naked and weak.
[key words to remember characteristics: feather, wing, neck, beak, air cavity, air sac, syrinx, endothermic, heart, digestive system, occipital condyle, keel, biped, toe, egg] Dr. Siddiqu Publications

Adaptation for successful flight adaptation
1. Their bodies are covered with feathers. The body is light and the feathers help to float in the air.
2. Their necks are elongated and S-shaped. So can lean forward easily.
3. They are bipedal animals. The forelimbs have evolved into wings. Wings are their main flight organ. Dr. Siddiq Publications
4. Jaws have evolved into beaks. It helps in flight.
5. Their bones are hard, light and airy. It reduces body weight and can fly easily. Dr. Siddiq Publications
6. They have air sacs in their lungs. Air sacs contain air. The body is light and can fly easily.
7. The heart has four chambers, 2 atria and 2 ventricles. So pure blood supply is ensured. Dr. Siddiq Publications
8. The sternum has formed a boat-like keel which aids in flight

Birds are called majestic reptiles
Birds evolved from reptiles during the Mesozoic Era. The ancestors of birds are reptiles. Reptiles have evolved into birds. In the early 20th century, the famous ornithologist Thomas Huxley called them birds as the majestic reptiles. Archeopteryx is a fossil link between reptiles and birds. That is, archeopteryx evolved from reptiles and birds evolved from archeopteryx. The characteristics of the creation of birds from reptiles are-
1. Reptiles are cold-blooded animals with low metabolic rates. Birds are high-blooded animals with high metabolic rate. Dr. Siddiq Publications
2. Reptiles are mobile animals. Birds can move faster due to the gain in flight ability.
3. Reptiles have dry fibrous bodies. Bird feathers have been created from the dung of reptiles. Dr. Siddiq Publications
4. The four-chambered heart of a bird has been created from the incomplete four-chambered heart of a reptile.
5. There are two systemic arches in the circulatory system of reptiles and one systemic arch of birds.
6. The renal portal system of reptiles is highly developed. It is decaying in birds.
7. The jaws of reptiles gave rise to the long beaks of birds.
The above discussion proves that birds have evolved from reptiles. That is, birds are majestic reptiles.

Some birds of Avis
Doyle – Copsychus saularis
Rooster – Galus galus
Owl – Bubo bubo
Eagle – Haliacetus leucogaster
Pigeon – Columba livia
Hummingbird – Mellisuga helenae
Dove – Streptopelia decaocto
Shalik – Lamprotornis hildebrandti
Cuckoo – Eudynamys scolopaceus
Buck – Nycticorax nycticorax
Passer domesticus
King vulture – Sarcogyps calvus
Black Pheasant – Francolinus francolinus
Quail – Coturnix coturnix
Moina – Gracula Religiosa
Tia – Psittacula krameri
Dahuk – Amaurornis phoenicurus
Crane – Grus antigone
Crow – Corvus splendens
Bulbul – Pycnonotus cafer
Ostrich – Struthio camelus
Peacock – Pavo cristatus
Babui bird – Ploceus philippinus
Pelican – Pelecanus philippensis

Lizard- Hemidactylus frenatus
Flying lizard – Chameleon vulgaris
Tortoise – Trionyx gangeticus
Sea turtle – Caretta caretta
Takshak – Gekko gecko
Gharial – Gavialis gangeticus
Gokhra snake – Naja naja
Guisap – Varanus komodoensis
Chameleon – Calotes versicolor
Crocodile – Crocodylus porosus
Fresh water crocodile – Crocodylus palustris

1. The body is dry and composed of scales or hard plates arising from the epidermis.
2. Each foot has 5 clawed toes.
3. Their body is divided into three parts. Head, neck and body.
4. The ventricles of their heart are incompletely bifurcated (except in crocodiles).
5. They are ectothermic land animals. That is, their body temperature changes with the rise and fall of the environment temperature.
6. They are cold blooded animals. So it goes into hibernation in winter.
7. They walk on the chest.
8. Their number of carotid nerves is 12 pairs or 24.
9. They lay eggs. ie Oviporous. Eggs are covered with a leathery calcareous shell.
10. The crown of the head is connected to the spinal cord by an occipital condyle.
11. Retractable holes are located transversely.
12. Four extra-embryonic membranes (amnion, chorion, yolk sac, allantois) are formed during the development of the embryo.
13. They are unisexual animals. Fertilization occurs. Muscular male sexual organs exist. Dr. Siddique Publications
14. They have no larval stage.
[key words to remember characteristics: epidermis, hard plate, finger, heart, ectothermic, hibernation, thoracic mass, cranial nerve, ovipore, occipital condyle, excretory pore, copulatory organ, larva]

The class Reptilia is named after the Greek word rep meaning chest walking. Reptilia means reptiles. They walk with their chest full. The Mesozoic era of 16 and a half million years ago is called the Age of Reptiles. Their number of species is 9,831. 3 classes, 25 tribes and 167 species have been identified in Bangladesh.

The class Reptilia is named after the Greek word rep meaning chest walking. Reptilia means reptiles. They walk with their chest full. The Mesozoic era of 16 and a half million years ago is called the Age of Reptiles. Their number of species is 9,831. 3 classes, 25 tribes and 167 species have been identified in Bangladesh.
Features of Reptilia
1. The body is dry and composed of scales or hard plates arising from the epidermis.
2. Each foot has 5 clawed toes.
3. Their body is divided into three parts. Head, neck and body.
4. The ventricles of their heart are incompletely bifurcated (except in crocodiles).
5. They are ectothermic land animals. That is, their body temperature changes with the rise and fall of the environment temperature.
6. They are cold blooded animals. So it goes into hibernation in winter.
7. They walk on the chest.
8. Their number of carotid nerves is 12 pairs or 24.
9. They lay eggs. ie Oviporous. Eggs are covered with a leathery calcareous shell.
10. The crown of the head is connected to the spinal cord by an occipital condyle.
11. Retractable holes are located transversely.
12. Four extra-embryonic membranes (amnion, chorion, yolk sac, allantois) are formed during the development of the embryo.
13. They are unisexual animals. Fertilization occurs. Muscular male sexual organs exist. Dr. Siddique Publications
14. They have no larval stage.
[key words to remember characteristics: epidermis, hard plate, finger, heart, ectothermic, hibernation, thoracic mass, cranial nerve, ovipore, occipital condyle, excretory pore, copulatory organ, larva]

Some animals of the class Reptilia
Lizard- Hemidactylus frenatus
Flying lizard – Chameleon vulgaris
Tortoise – Trionyx gangeticus
Sea turtle – Caretta caretta
Takshak – Gekko gecko
Gharial – Gavialis gangeticus
Gokhra snake – Naja naja
Guisap – Varanus komodoensis
Chameleon – Calotes versicolor
Crocodile – Crocodylus porosus
Fresh water crocodile – Crocodylus palustris