1. Phylum
    2. 1. Classification of Animals
    2. Protozoa
    3. Porifera
    4. Coelenterata
    5. Platyhelminthes
    6. Nemathelminthes
    7. Annelida
    8. Earthworm
    9. Arthropoda
    10. Cockroach
    11. Mosquito
    12. Honey bee and Silk moth
    13. Mollusca
    14. Echinodermata
    15. Hemichordata
    16. Chordata
    17. Pisces
    18. Amphibia
    19. Frog
    20. Reptile
    21. Aves
    22. Mammalia
    23. Rabbit bone
  2. Animal Behaviour and Adaptation
    3. 24. Animal behaviour
    25. Animal adaptation
    26. Migration
  3. Developmental Biology
    4. 27. Development of Animals
    28. Development of Frog
  4. Human Biology
    5. 29. Tissues
    30. Sense organs
    31. Digestive system
    32. Circulatory system
    33. Respiratory system
    34. Nervous system
    35. Endocrine system
    36. Reproductive system
    37. Excretory system
    38. Skeletal system
    39. Basic concept of Immunology
    40. Human diseases
  5. Evolutionary Biology
    6. 41. Origin of Life
    42. Organic Evolution
    43. Theories of Evolution
    44. Evolution of Human beings
    45. Horse Evolution
Phylum
20. Reptile
▢ Introduction:
❖ Study: Study of mammals is called Mammology.
❖ Origin: Mammals originated from the reptiles in the Triassic period of Mesozoic era.
❖ Dominance: Mammals are the dominated animals of Coenozoic, so this era is known as 'age of mammals'.
▢ General Characters:
❖ Body Covering: Mammals are hair-clad, mostly terrestrial tetrapod vertebrates.
❖ Hair Composition: Hairs of mammals are made up of α-keratin.
❖ Mammary Glands: Most important character of mammals is the presence of Mammary glands (Modified sweat glands).
❖ Diaphragm: Presence of a muscular diaphragm separating thoracic cavity from abdominal cavity.
❖ Body Division:
◉ Parts:
  1. Head
  2. Neck
  3. Trunk
  4. Tail
❖ Limbs:
◉ Number: 2 pairs
◉ Structure: Pentadactyl each with five or few digits.
◉ Adaptation: Limbs adapted for walking, running, climbing, burrowing, swimming or flying.
◉ Exception: Hindlimbs are absent in aquatic Cetaceans and Sirenians.
❖ Exoskeleton:
◉ Components:
  1. Hairs
  2. Spines
  3. Scales
  4. Claws
  5. Nails
  6. Hooves
  7. Horns
  8. Bony dermal plates
❖ Skull: Dicondylic with two occipital condyles (also in Amphibia).
❖ Lower Jaw: Each half with a single dentary bone.
❖ Vertebra: Flat centrum called amphiplatyan or acoelous.
❖ Cervical Vertebrae: Presence of seven cervical vertebrae.
❖ Pectoral Girdle: Coracoid is vestigial.
❖ Ribs: 12 pairs of ribs (also 12 pairs of cranial nerves).
❖ Cloaca: Absent (except in Monotremes).
❖ Skin Glands:
◉ Types:
  1. Sweat gland
  2. Sebaceous glands
❖ Digestive System:
◉ Teeth: Heterodont, thecodont and diphyodont.
❖ Respiration System:
◉ Lungs: Respiration by lungs (pulmonary), glottis protected by a fleshy and cartilaginous epiglottis.
◉ Larynx: With vocal cords.
❖ Circulation System:
◉ Heart: Completely 4-chambered (also in birds and crocodiles).
◉ Sinus Venosus: Absent.
◉ Aortic Arch: Only left aortic (systemic) arch persists in adult.
◉ Renal Portal System: Absent.
◉ Erythrocytes:
  1. Small
  2. Circular
  3. Non-nucleated
❖ Excretion System:
◉ Kidneys: Metanephric.
◉ Ureters: Open into a muscular urinary bladder.
◉ Excretion Type: Ureotelic.
❖ Nervous System:
◉ Brain: Highly developed with corpus callosum connecting cerebral hemispheres.
◉ Cranial Nerves: 12 pairs.
❖ Ear:
◉ External Ear: With ear pinna.
◉ Middle Ear: With three ear ossicles: Malleus, Incus, and Stapes.
❖ Reproduction:
◉ Sexes: Separate
◉ Testes: Mostly in scrotal sacs for sperm development.
◉ Ovary: Contains Graafian follicles.
◉ Eggs:
  1. Small
  2. Microlecithal
  3. Homolecithal
  4. Acleidoic
◉ Reproductive Type: Viviparous, except egg-laying monotremes.
◉ Foetal Nourishment: Through placenta
◉ Extraembryonic Membranes: Amnion, chorion and allantois present (amniota).
◉ Parental Care: Greatly developed.
◉ Placenta Formation: By chorio-allantois.
❖ Intelligence: Mammals are the most intelligent animals among vertebrates.
❖ Body Temperature: Constant, warm-blooded (homoiothermous), average temperature 38°C.
▢ Classification:
❖ Sub-class: Protheria:
◉ Characteristics:
  1. Primitive mammals
  2. Egg-laying mammals (Oviparous)
  3. Reptile-like mammals (Cloaca present)
  4. Confined to Australian region
  5. Young fed on milk from mammary glands without nipples
  6. Body temperature low (25-28°C)
  7. Connecting link between reptiles and mammals
◉ Order: Monotremata:
◈ Features:
  1. Mammals with single opening or Cloaca
  2. No external ear pinna
  3. Testes abdominal
  4. Penis conducts only sperms
  5. Uterus and Vagina absent
◈ Examples:
■ Echidna (Tachyglossus)/ Spiny anteater:
■ Ornithorhynchus / Duckbilled platypus:
● Habitat: Aquatic, found in rivers.
● Mammary Glands: Functional in both male and female.
● Poisonous: Only poisonous mammal.
❖ Sub-class: Theria:
◉ Infra-class: Metatheria (Pouched mammals):
◈ Characteristics:
  1. Young born in very immature state
  2. Complete development in abdominal pouch or marsupium
  3. Corpus callosum absent
  4. Epipubic bone present
  5. No allantoic placenta
  6. Teeth one set, monophyodont
  7. Most primitive placental mammal is Shrew
◈ Order: Marsupials:
■ Examples:
● Macropus (Kangaroo):
⟣ Locomotion: Saltatorial
● Didelphis (Opossum):
⟣ Habitat: Tree-dwelling
◉ Infra-class: Eutheria:
◈ Orders:
    ● Order: Insectivora: Smallest and most primitive eutherians.
    ● Order: Dermaptera: Gliding mammals with patagium.
    ● Order: Chiroptera/ Bats:
    1. Nocturnal
    2. True flying mammals
    3. Capable of Echolocation, a type of radar system
    ● Order: Edentata: Teeth absent or reduced to molars, without enamel.
    ● Order: Pholidota:
    1. Body covered with large overlapping horny scales
    2. No teeth
    3. Tongue: Long and Protusible
    4. Eats ants
    ● Order: Rodentia:
    1. Largest order of mammals in number of species
    2. Small gnawing mammals
    3. Each jaw with one pair of long rootless chisel-like incisors growing throughout life
    4. No canines
    ● Order: Lagomorpha:
    1. Herbivorous with a second pair of upper incisors
    2. No canines
    3. Rabbit eats its own faeces
    ● Order: Carnivora:
    ⟣ Fissipedia (Terrestrial carnivores):
    1. Predatory flesh-eating mammals
    2. Examples: Dog, Cat, Lion, Tiger, Cheetah, Otter, Mongoose, Bear
    ⟣ Pinnipedia (Marine carnivores):
    1. Stream-lined body
    2. Reduced tail
    3. Limbs modified into flippers
    4. Examples: Walrus, Seal, Sea-lion
    ● Order: Cetacea:
    ⟣ Characteristics:
    1. Aquatic mammals
    2. Breathe by Lungs
    3. Blubber or Subcutaneous fat present for heat conservation
    4. Skin glands absent
    5. Forelimbs modified into paddle-like flippers
    6. No hindlimbs
    7. No external ears
    8. Testes abdominal
    9. Hairs only on snout
    10. Nostrils on the top of the head
    11. Teeth often lost
    12. Eyes very small
    13. Bones spongy
    14. Mostly gregarious and Carnivorous
    ⟣ Examples:
    ➢ Balaenoptera musculus (Blue Whale):
    1. Largest animal ever lived
    2. Length: 35 metres
    3. Weight: 150 ton
    4. Feeds on plankton in arctic and antarctic waters
    5. Milk squirted to baby by muscular contractions
    ➢ Others:
    1. Orcinus (Killer whale)
    2. Physeter (Sperm Whale)
    3. Delphinus (Common Dolphin)
    4. Platanista (Ganges Dolphin)
    5. Phocaena (Porpoise)
    ● Order: Sirenia:
    ⟣ Characteristics:
    1. Herbivorous aquatic mammals
    2. Paddle-like forelimbs
    3. No hindlimbs
    4. No external ears, no pinna
    5. Blubber present
    6. Testes abdominal
    ⟣ Examples:
    1. Rhytina - Sea cow
    2. Trichechus - Manatee
    3. Halicore - Dugong
    4. Manatus australis - Sea cow (has six cervical vertebrae)
    ● Order: Tubulidentata:
    ⟣ Characteristics:
    1. Tubular mouth
    2. Tongue slender protusible
    3. No incisor or canines
    4. Limbs clawed for digging ant and termite nests
    ⟣ Example: Orycteropus (Aardvark or Cape anteater of South Africa)
    ● Order: Proboscidea:
    ⟣ Characteristics:
    1. Largest land living animals
    2. Hairless skin (pachyderm)
    3. Nose and upper lip modified into proboscis
    4. Two upper incisors modified as tusks (Ivory obtained from tusks)
    5. Hairless skin is an adaptation for hot climate
    6. Mammoths and Mastodons were extinct elephants
    ● Order: Hyracoidea:
    ⟣ Characteristics:
    1. Small, guinea-pig like mammals distantly related to elephants
    2. Snout, ears and legs short
    3. 4 toes on front foot, 3 on hindfoot
    4. Commonly called 'African conies'
    ● Order: Perissodactyla:
    ⟣ Characteristics:
    1. Odd-toed hoofed animals, incisors present in both jaws
    2. Stomach simple
    3. Mule: Hybrid between male ass (jack) and female horse (mare)
    4. Hinny: Hybrid between male horse (stallion) and female ass
    ● Order: Artiodactyla:
    ⟣ Characteristics:
    1. Even-toed hoofed animals, incisors and canines in upper jaw usually absent
    2. Stomach 4-chambered
    3. All except pig ruminate or chew their cud
    4. Many with antlers or horns
    5. Term 'bovine' associated with Artiodactyla
    6. Hippopotamus: 'Horse of the river'
    7. Camels: 'Ships of the desert'
    ● Order: Primates:
    ⟣ Characteristics:
    1. Highest development of brain, most intelligent mammals
    2. Mostly arboreal
    3. First digit usually opposable for grasping
    4. Eyes typically large and turned forward
    5. Includes: Lemurs, Loris, Tarsiers, Monkeys, Apes, and Man
◉ Feet of Mammals:
◈ Plantigrade:
■ Description: With five digits (toes), entire sole rests on the ground.
■ Example: Man
◈ Digitigrade:
■ Description: With four digits, heel raised, walks on digits.
■ Example: Cat
◈ Unguligrade:
■ Description: Most specialized, with only one digit (third), walks on the hoof (homologous to toe nails).
■ Example: Horse