Classification
Classification systems are used to separate organisms into groups based on similarities of both external and internal structure. Living things are first divided into five kingdoms.
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Kingdom |
Characteristics |
Examples |
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Monera |
These organisms are single-celled and do not have a nucleus or organelles |
Bacteria such as Streptococcus 4,800 species |
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Protista |
These organisms are single-celled or colonial and have a nucleus and organelles; Protista can be plant-like, animal-like, or fungus-like |
Algae, Euglena, Paramecia 57,700 species |
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Plantae |
These organisms are multicellular, complex, and make their own food by photosynthesis |
Mosses, Ferns, Gynnosperms, Angiosperms 248,400 species |
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Fungi |
These organisms are multicellular, complex, and digest food externally before absorbing nutrients |
Mushrooms, Slime Molds, Puff Balls 69,000 species |
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Animalia |
These organisms are multicellular, complex, and digest food internally to obtain nutrients |
Sponges, Starfish, Worms, Jellyfish, Chordates 1,023,000 species |
A simple classification key can be used to separate the organisms into the kingdoms.
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1. Does the organism have a nucleus? |
Yes, go to #2. |
No, the organism is a Moneran. |
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2. Is the organism multicellular? |
Yes, go to #3. |
No, the organism is a Protist. |
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3. Does the organism make its own food? |
Yes, the organism is a Plant. |
No, go to #4. |
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4. Does the organism digest food internally? |
Yes, the organism is an animal. |
No, the organism is a Fungus. |
Organisms can be further classified according to other characteristics.
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Kingdom |
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Phylum |
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Class |
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Order |
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Family |
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Genus |
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Species |
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Your complete classification is
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Kingdom |
Animalia |
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Phylum |
Chordata |
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Class |
Mammalia |
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Order |
Primata |
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Family |
Homonidae |
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Genus |
Homo |
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Species |
sapiens |
Darwin's Theory of Natural Selection
The kingdom has the greatest diversity of organisms. The species has the least diversity. Species are organisms that have enough genetic material in common to achieve successful reproduction. There may be variations among members of species. These slight differences are small mutations in the DNA of the genes. Over time, some variations may improve the survival of individuals. Individuals with a competitive advantage will likely survive and reproduce. If the variation that led to survival is genetic, it will be passed on the next generation. Over time, under certain conditions, variations may lead to new species. This is the basis of
Darwin's Theory of Natural Selection.
Phyla of the Animal Kingdom
|
Phylum |
Characteristics |
Example |
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Porifera |
These organisms are asymmetrical. They gather food by generating currents that flow through body pores. Food is digested by collar cells. |
Sponges 5,000 species |
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Coelenterata |
These organisms are simple with a digestive cavity and radial symmetry. |
Jellyfish, hydra 9,000 species |
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Echinodermata |
These organisms have spiny skin, pentaradial symmetry, and a water pressure endoskeleton |
Starfish, sanddollars, sea anemones 6,100 species |
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Mollusca |
A mantle protects these soft-bodies animals |
Clams, snails 50,000 species |
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Platyhelminthes |
These organisms are flat and have an incomplete digestive system with one opening |
Planaria 12,200 species |
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Nematoda |
These organisms are mostly parasitic, have a tubular body, and have a digestive system with 2 openings |
Trichina 12,000 species |
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Annelida |
These animals have segmented bodies, no appendages, and a complete digestive system |
Earthworm 12,000 species |
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Arthropoda |
These organisms have jointed appendages and an exoskeleton |
Lobster, insects, spiders, crabs, horseshoe crabs 874,000 species |
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Chordata |
These organisms are complex with a complete circulatory system, digestive system, and respiratory system, and a notochord or backbone |
Mammals, fish, reptiles, amphibians, birds 42,300 species |
Classes of the Animal Phylum Chordata
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Class |
Characteristics |
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Jawless Fish |
These chordates have gills and scales, but lack a mandible (jaw bone) |
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Cartilaginous Fish |
These chordates have gills, leathery skin, and cartilage |
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Boney Fish |
These chordates have gills, scales, and bones |
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Amphibians |
These chordates are adapted to live on land, but must return to water to reproduce |
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Reptiles |
These chordates have scaly skin, four legs, and lay leathery eggs |
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Birds |
These chordates have feathers, scales on their legs, and lay hard-shelled eggs |
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Mammals |
These chordates have body hair, three small bones in the ear, and feed their young milk |
Regulating Body Temperature
Warm-blooded animals maintain a constant body temperature regardless of environmental conditions. Cold-blooded animals are animals whose body temperature changes with environmental conditions. For example, butterflies will seek out shade to cool down in the summer or a frog may climb onto a rock to warm up in the sun.
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Cold-blooded |
Mostly Cold-blooded |
Warm-blooded |
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Jawless Fish |
Boney Fish |
Birds |
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Cartilaginous Fish |
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Mammals |
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Amphibians |
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Reptiles |
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Return to Second Marking Period Index
