Each phylum in the animal kingdom is separated from the others by different evolutionary milestones that took evolution in different directions.
Porifera
(Sponges)
All of the characteristics of the organisms in this phylum are present in higher animals. It is the simplest of all the animal phyla.
All of the characteristics of the organisms in this phylum are present in higher animals. It is the simplest of all the animal phyla.
Cnidaria
(Jellies, Anemones, and Corals)
In addition to the adaptations that sponges have, Cnidarians have specialized tissues, not just specialized cells, and radial symmetry.
In addition to the adaptations that sponges have, Cnidarians have specialized tissues, not just specialized cells, and radial symmetry.
Platyhelminthes
(Flatworms)
In addition to having specialized tissues like Cnidarians, flatworms have bilateral symmetry and cephalization. I like to remember them as "flatty helmets" so I can remember that they are flatworms and they have a head region.
In addition to having specialized tissues like Cnidarians, flatworms have bilateral symmetry and cephalization. I like to remember them as "flatty helmets" so I can remember that they are flatworms and they have a head region.
Nematoda
(Roundworms)
Round worms were the first animals to develop a body cavity or coelom in addition to everything the flatworms developed. Their body cavity is called a pseudocoelom because although it provides a space, it is not a true coelom. You can review body cavities on the animal characteristics page.
Round worms were the first animals to develop a body cavity or coelom in addition to everything the flatworms developed. Their body cavity is called a pseudocoelom because although it provides a space, it is not a true coelom. You can review body cavities on the animal characteristics page.
Mollusca
(clams, snails, slugs, octopi)
Mollusks are the first animals to have a true coelom, a true body cavity to support organs. They all have soft bodies, bilateral symmetry, and specialized tissues and organs.
Mollusks are the first animals to have a true coelom, a true body cavity to support organs. They all have soft bodies, bilateral symmetry, and specialized tissues and organs.
Annelida
(Segmented Worms)
Annelids are the first animals that display segmentation. This means that their body has repeating parts, some that are specialized. This means their body has repeating parts, some that are specialized. Check out the animal characteristics page to learn more about segmentation.
Annelids are the first animals that display segmentation. This means that their body has repeating parts, some that are specialized. This means their body has repeating parts, some that are specialized. Check out the animal characteristics page to learn more about segmentation.
Arthropoda
(Lobsters, Insects, Millipedes, Spiders)
Arthropod translates to "jointed foot." Think of arthritis as joint pain. These animals are the first to have appendages that have joints. Up until now, animals either had soft appendages that move freely and do not require joints, or have hard bristles. Each segment has appendages, some are more specialized than others.
Arthropod translates to "jointed foot." Think of arthritis as joint pain. These animals are the first to have appendages that have joints. Up until now, animals either had soft appendages that move freely and do not require joints, or have hard bristles. Each segment has appendages, some are more specialized than others.
Echinodermata
(Sea Stars, Sea Urchins, Sea Cucumbers, Sand Dollars)
Echinoderms all have rough bumpy skin and are the phylum most closely related to the phylum humans belong to due to their development. They are the first animals to develop as deuterostomes, meaning their blastopore becomes an anus and their mouth is the second hole that develops. Until now, animals with three tissue layers were protostomes, meaning their blastopore becomes their mouth.
Protostome = mouth first Deuterostome = mouth second
Echinoderms all have rough bumpy skin and are the phylum most closely related to the phylum humans belong to due to their development. They are the first animals to develop as deuterostomes, meaning their blastopore becomes an anus and their mouth is the second hole that develops. Until now, animals with three tissue layers were protostomes, meaning their blastopore becomes their mouth.
Protostome = mouth first Deuterostome = mouth second
Chordata
(Humans, Reptiles, Fish, Sharks, Lampreys)
At some point in their lives, all chordates, whether vertebrate or invertebrate have a notochord, dorsal nerve chord, pharyngeal slits, post-anal tail.
At some point in their lives, all chordates, whether vertebrate or invertebrate have a notochord, dorsal nerve chord, pharyngeal slits, post-anal tail.
Here are a couple quizlets to remember the differences between the phyla
with pictures without pictures
with pictures without pictures