Further classification of Kingdom
Animalia:
The vertebrates
Within each of the five kingdoms of living things there are further
groupings. These form a hierarchy of groups from the largest category
(Phylum) where the groups contain the most individuals and show the
most diversity, to the bottom category (species) with a small number
of similar types. Carolus Linnaeus, in the late 1700's, devised a
classification system based on similar structural features. Under
this system humans are classified as:
Kingdom: |
Animalia |
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increasing diversity more types in group
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Phylum: |
Chordata
(sub-phylum Vertebrata) |
Class: |
Mammalia |
Order: |
Primates |
fewer types in group increasing similarity
|
Family: |
Hominidae |
Genus: |
Homo |
Species: |
sapiens |
All vertebrates have a backbone and a dorsal
nerve chord (i.e. along the back) enlarged into a brain at the
head end.
Vertebrate
classes
The vertebrates are divided into seven main
classes:
- Class
Agnatha:Jawless fish. Skeleton is made of cartilage,
two-chambered heart, no paired fins, e.g. lamprey.
-
Class Chondrichthyes: Cartilagenous fish. Paired fins,
skeleton made of cartilage, gills, e.g. shark, stingray.
-
Class Osteichthyes: Bony fish. Skeleton of bone, two-chambered
heart, gills, e.g. eel, salmon, seahorse.
-
Class Amphibia: Frogs, newts. Young are aquatic, but
adults also terrestrial (land-dwelling) with lungs, three-chambered
heart, moist skin, no scales, e.g. cane toad, salamander,
frogs.
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- Class
Reptilia: Reptiles. Terrestrial
and aquatic, but all have lungs and breathe air. Dry, scaly skin,
three-chambered heart, eggs with soft shells or young born alive,
e.g. tortoise, crocodile, snakes, lizards, goannas.
- Class
Aves: Birds. Mostly terrestrial, scales modified as feathers,
hard-shell eggs, front limbs modified as wings, four-chambered heart,
endothermic (warm-blooded), e.g. kiwi, emu, all birds.
-
Class Mammalia: Mostly terrestrial, mammary glands of females
produce milk, scales modified as hairs or fur, four-chambered heart,
endothermic (warm-blooded). Mammals survive successfully in most
habitats because they are endothermic and show a wide range of adaptations.
Orders of mammals
All classes are further sub-divided into Orders.
We will investigate Class Mammalia further.
- Order Monotremata:
Egg laying mammals. Mammary glands lack nipples. There are only
two monotremes in the world, both of which are only found in Australia
- the platypus and the echidna.
- Order Marsupialia:
Pouched mammals. Young born undeveloped, then grow further on a
nipple in the pouch, e.g. kangaroo, possum.
- Order Primates:
Internal development of young with placenta, eyes usually directed
forward, nails instead of claws, e.g. monkey, chimp, ape, human.
- Other separate orders group together:
- Rats, mice, porcupines - Rodentia
- Rabbits, hares - Lagomorpha
- Dolphins, whales - Cetacea
- Tigers, dogs, cats, foxes - Carnivora
- Seals, walruses - Pinnipedia
- Elephants - Proboscidea
- Dugongs, manatees - Sirenia
- Horses, rhinoceroses - Perissodactyla
- Herbivores such as sheep, pigs, camels,
deer, giraffes - Artiodactyla
These groups are distinguished by different characteristics.
However, the distinctions are man-made, which means that differing
opinions will result in minor variations in classification systems.
Not all biologists agree!
Each order is then further divided into Families,
Genera (sing. Genus) and Species (sing. Species).
The binomial (two names) scientific name tells
the Genus (with a capital letter) and the species (always written
in lower case). The binomial name is always in italics or underlined.
Most names are derived from Latin or Greek, e.g. Homo sapiens
is the binomial scientific name for humans.
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