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Different Ways to Divide the Animal Kingdom (Invertebrate (Molluscs…
Different Ways to Divide the Animal Kingdom
Invertebrate
Worms
Flatworms (Phylum Platyhelminthes)
Least complex worms
Are acoelomates with three layers of cells
This group includes parasitic tapeworms, flukes, and the free-living planarians
Have a simple nervous system with a brain-like concentration of cells, including an eyespot
A different body plan
Segmented worms (Phylum Annelida)
Have long tube-like bodies that are divided into a series of ringed segments
Have a distinct head end and several organ systems
Digestive system
Excretory system
Nervous system
Circulatory system
Example: Earthworm
Are coelomates that are segmented on the inside and on the outside
Echinoderms (Phylum Echinodermata)
Include sear stars, sea urchins, sea cucumbers, and sand dollars
A sea star uses its tube feet to open the two shells of a clam
Are marine animals
Have radial symmetry
Have spiny endoskeletons
An endoskeleton is an internal skeleton that protects organs and provides support for muscle attachment
Endoskeletons in echinoderms are made of calcium carbonate plates, often with spines attached
Is covered by a thin layer of skin
Have tube feet
Are small muscular, fluid-filled tubes that end in structures that are similar to suction cups
Have a water-vascular system
Is a system of closed tubes that includes the tube feet
Sponges and Cnidarians
Sponges (Phylum Porifera)
An asymmetrical body plan
Have no tissues, no organs
Two layers of cell
Sessile as adults
Cnidarians (Phylum Cnidaria)
One of the oldest animal groups
Include freshwater hydras (Class Hydrozoa), marine jellyfish (Class Scyphozoa), and sea anemones and corals (Class Anthozoa)
Corals are cnidarians that can form reef environments
Have two layers of cell
Have tissues, including muscle tissue; Have a simple nervous system
This allows them to swim and capture prey by using stinging tentacles around their mouth opening
Food is then digested in the body cavity (
gastrovascular cavity
)
Have two basic body forms
Polyp
Medusa
Have radial body symmetry
Molluscs (Phylum Mollusca)
Are the second-most diverse animal phylum, with about 100,000 species
Have bilateral symmetry
Have three layers of cells
Have a coelom
Have two body openings
Have a soft body
Is protected by a hard shell (in many species)
Three of the main classes of molluscs
Bivalves (Class Bivalvia)
Example: File clam
Are marine and freshwater species that are protected by a hinged shell
Gastropods (Class: Gastropoda)
Example: Land snail
Shelled snails and non-shelled slugs
Are found in terrestrial, freshwater, and marine ecosystems
When the shell is present, it is usually coiled
Cephalopods (Class: Cephalopoda)
Example: Octopus
Has a relatively large brain and is capable of learning complex tasks
Octopuses and squids
Are marine organisms with grasping tentacles
Can propel themselves with great bursts of speed by drawing in water and then forcefully releasing it
All molluscs have a similar body plan
A mantle surrounds the internal organs and secretes calcium carbonate for the shell
Have organ systems
Digestive system
Circulatory system
Respiratory system
Excretory system
Reproductive system
Nervous system
Have a muscular foot, which is used for movement
Some species have well-developed eyes and other sense organs
Arthropods (Phylum Arthropoda)
The majority of animal species are arthropods, making up the largest animal phylum
Include spiders, scorpions, crustaceans (such as lobsters), and insects
The term
arthropod
means jointed foot
Arthropods are characterized by having legs made up of movable sections connected by joints
Have a body divided into segments and a hard exoskeleton
Exoskeleton is an external skeleton that protects organs, provides support for muscle attachment, and protects against water loss and predation
The exoskeleton is constructed of proteins and chitin, is periodically shed or moulted as the animal grows
Its rigidity protects the animal, and it provides points of attachment for the muscles that move the legs
The exoskeleton resists drying out
The exoskeleton enabled arthropods to colonize terrestrial ecosystem several hundred million years go
Characteristics of Arthropod Groups
Chelicerates: spiders, mites, and scorpions
Have two body segments
A cephalothorax
An abdomen
Have six pairs of jointed appendages
Have no antennae
Have special appendages for feeding
Some are poisonous
Myriapods: millipedes and centipedes
Each segment has one or two pairs of legs
Have a single pair of antennae and, in most cases, simple eyes
Live in moist habitats, under logs or stones
Centipedes are poisonous
Millipedes are not poisonous
Crustaceans: crabs, lobsters, shrimp, and barnacles
Five pairs of jointed appendages
Two pairs of antennae
Have fewer body segments, with a tendency for segments in the head and thorax regions to fuse and become specialized
Insects: beetles, bees, butterflies, moths, ants, and flies
Three body segments
Head, thorax, and abdomen
Three pairs of legs
One or two pairs of wings, or no wings
Mouthparts specialized for siphoning, piercing, sucking, and chewing
Vertebrate (Phylum Chordata)
Are the most familiar group of animals
There are about 50,000 species in this phylum
Are divided into five major classes
Fish
About half of all vertebrate species are fish
Occupy freshwater and saltwater habitats
Fish range in size from the 12m whale shark to a dwarf carp, less than a centimetre long, which is found in Asian forest swamps
Lampreys
Are the oldest living vertebrates
Jawless and lack paired fins and bony skeleton
Rely on a suction mouth for holding on to food and penetrate the bodies of prey
The sea lamprey has managed to invade the Great Lakes using the lock system made for shipping
This has caused devastation to native fish populations, including lake trout
Have a cartilaginous skeleton
Have gills to obtain dissolved oxygen from water
The major two groups of fish developed around 400 million year ago
Have paired fins and jaws
The sharks and rays (Class Chondrichthyes)
Have a skeleton of cartilage rather than bone
Cartilage: the flexible, non-bony, tough material found in vertebrate endoskeletons
Example: manta
The bony fish (Class Osteichthyes)
A group contains guppies, tuna, and salmon
Have a skeleton made of bone
Most bony fish have an air sac called a
swim bladder
By filling the swim bladder with oxygen and then emptying it, a fish is able to rise and sink in the water column
Example: Ontario's pumpkinseed sunfish
Amphibians (Class Amphibia)
The first tetrapods to appear and live a portion of their life cycle on land were the amphibians
Frogs and toads (Order Anura)
Salamanders (Order Urodela)
Have lungs, most amphibians use moist skin to assist in gas exchange
Most species reproduce using external fertilization
Dramatic declines in amphibian populations have been taken place
Costa Rica's golden toads have disappeared completely
In Ontario, there are representatives of the two major amphibians orders
The bullfrog is an anuran (Frogs and toads)
The spotted salamander is a urodelan (salamanders and newts)
Reptiles (Class Reptilia)
The first members of Class Reptilia appear in the fossil record about 300 million years ago
Lizards and snakes (Order Squamata)
Turtles (Order Testudines)
Crocodilians (Order Crocodilia)
Have body scales that create a waterproof barrier that helps prevent dehydration in dry air
Lack of moist skin
Use only their lungs for gas exchange
Have shelled eggs
Resist drying out
Have a land-based existence
Amniotic egg
Are ectothermic and have a three-chambered heart
Birds (Class Aves)
Are related to at least one group of dinosaurs
Are endothermic and have a four-chambered heart
Have a high body temperature like mammals
Have a unique respiratory system
Promotes one-way movement of air through the use of air sacs that connect to the lungs
There are about 9000 species of birds on Earth
Have great structural diversity
Small black-capped chickadee
Giant running ostrich
Most birds can fly
Most have weight-saving adaptions for flight
Most have feathered wings
Bones that are lightweight and hollow, a toothless skull, and a compact body all help keep body weight low
More than a half of birds have distinctive song-like voices and calls
Are known as songbirds
Mammals (Class Mammalia)
Female mammals have mammary glands
Produce and secrete milk to nourish developing young
Have hair
Insulation, camouflage, waterproofing, and communication
Specialized hairs can be used in defence
Such as the quills of porcupines
Eyelashes are used for sensory detection
In some species, the hair is greatly reduced
Such as in naked mole rats, elephants, marine mammals, and humans
Are endothermic, have four-chambered hearts
Is divided into three main groups
Momotremes
Egg-laying mammals
Only living examples are the duck-billed platypus and the echidna
Found only in Australia and New Guinea
Marsupials
Pouched mammals
Have a short gestation period
Mostly found in Australia
Examples include koala bears and kangaroos
Opossum is the only North American marsupial
Placental mammals
Have a placenta
Have great diversity in species and structure
Include bears, bats, whales, primates, and humans
Animals in this phylum have several important features in common
A notochord
A rod-shaped structure that extends the length of the body
Used for the attachment of movement muscles
The notochord forms in the embryo
A dorsal nerve cord
A tube-shaped cord that extends along the back of the body
During the development, the nerve cord becomes the brain and spinal cord, which are eventually enclosed in the skull and spine respectively
Some of the bony fish changed over time into limbs, these organisms include modern amphibians, reptiles, birds, and mammals, are known as tetrapods