Animal diversity

Defining an Animal:

·       Multicellular cells adhere after mitotic cell division, cells communicate and support each other.

·       Heterotrophs, eat other organisms for energy, possess internal digestion (unlike fungi).

·       Motility, nerves, muscles, skeletons.

·       Vertebrates or Not?: Most animals are invertebrates

·       Ancient Phylogeny:

·       Note: Animals are monophyletic. The common ancestor of animals is thought to resemble the colonial choanoflagellates. Earliest and simplest animals are marine.

·       Ex: Sponges: lacking in tissues, their cells all act as one, with a cup-shaped form. Can collect nutrients from the water using its inner surface of the cup. This surface is composed of choanocytes, which use flagella to push water through pores like a hydroelectric dam.

Diploblastic Animals

·       2 Body Layers: Skin, gut. Possess a single opening for the gut, for intake and output.

·       Central gastrovascular cavity: Process and pump blood and gut items in the same cavity.

·       Tentacles: Ensnare smaller living things to pull into their mouths.

·       Jellyfish, corals

·       Noncentralized Nerve Net: No brain, but they do possess nerves.

·       Aquatic: body is supported by the water.

·       Cnidarians: Jellyfish, corals

·       Ctenophores: Comb jellies

·       Radial Symmetry: Rotate it 360 degrees, and if its appearance does not change at any point, it possesses radial symmetry.

Bilaterians (Triploblastic)

·       More complex animals have

·       3 Embryonic Layers

·       Bilateral Symmetry: Divides the animal into mirror-image halves. Also, most or all warning systems are near the front of the animal for efficient predation, or locomotion. Animals that move more are far more likely to have bilateral position.

Deuterostomes

·       Chordates

·       Central Nervous System: Dorsal, hollow nerve cord.

·       Postanal Tail: Used for locomotion. Called "postanal" because the tail extends beyond the end of the digestive tract.

·       Notochord: Flexible cartilage for the support of the spinal column, often as embryos, but some animals keep the notochord forever.

·       Pharyngeal slits: Like gills, for gas exchange. Like the notochord, only possess as embryos for some.

·       Lancelets: Notochord, pharyngeal slits

·       Tunicates: No notochord in adults

·       Vertebrates: You know what a vertebrate is, dumbass. But use fish as an example when possible.

·       Echinoderms

·       Radial Symmetry: Evolved from bilateral ancestors, but exhibit radial as adults (bilateral as youth). Not a derived trait, it was discovered that radial is more useful when the animal doesn’t move much.

·       Tube Feet: Useful for moving, grabbing, by creating suction.

·       Example: Sea stars.

Vertebrates (continued)

·       Chordates: Vertebrates are cordates.

·       Bilateral Symmetry: Anterior and posterior ends are completely different. The leading end possesses many sensory systems and the brain.

·       Innovations: These innovations made vertebrates with them more successful.

·       Internal skeleton of bone. Came from fishes that evolved to live on land and became amphibious.

·       Jointed fins. Eventually became limbs on land.

·       Nares. Became the nasal cavity and the nose for sensing and respirating.

·       Terrestrial limbs.

·       Amniotic eggs: Shell allows it to withstand dry conditions without dying (standard vertebrate egg) but also beginning gas exchange.

·       Fish: Half of all vertebrate species (27k) are ray-finned fish.

·       Jaws: Ray-finned fish gained a huge advantage by the innovation of jaws. Became largely successful by use of jaws.

·       Hagfishes and Lampreys do not have jaws. They are thus likely older than ray-finned fishes (diverged earlier).

·       Cartilaginous: Sharks, rays

·       Bones: Ray-finned, Lobe-fins

·       Lobe-finned Fish: The fins are tetrahedral, meaning that it is thought that the coelacanth is the early ancestor of the fish that walked on land.

·       Tetrapod: 4 Feet. 2 Front 2 back. Including amphibians.

·       Blastula: Hollow ball of cells in the early embryo develops into the anus (gastrula).

Protostomes

·       Arthropods and mollusks

·       Blastula: Differ from deuterostomes in that the blastula becomes the mouth.

Lophotrochozoans

·       Trochophore: Common larval form

·       Lophophore: Feeding apparatus

·       Mollusks: Have a "foot" for locomotion (such as the lower portion of a snail). Internal organs are visceral mass, and a mantle, an organ which secretes a shell.

·       Gastropods: Foot is close to stomach (snails)

·       Bivalves: Clams

·       Cephalopods: Octopi

·       Annelids: Worms, long, tubular, posterior and head look similar. Segmented bodies, unlike nematodes.

·       Flatworms: Some are parasites, live in digestive tracts. Some don't even have digestive tracts, they survive on their hosts'.

·       Rotifers: Asexual female eukaryotes. Ciliated corona as the lophophore to sweep food into mouth.

·       Bryozoans: Looks a bit like a moss, but is a colonial eukaryote.

Ecdysozoans

·       Shed exoskeleton to grow: Exoskeleton supports body, made of chitin, hard but flexible.

·       Nematodes: No limbs at all. Round worms. No segmentation. Scavengers, predators, or parasites (ex: Trichinella (swine parasite), Caenorhabditis elegans (lab animal)).

·       Arthropods: Arthropods are the most successful animals (most successful reproduction, most species-rich clade). They are also the most complex.

·       Possess a segmented body plan (metameric). Paired, jointed appendages

·       Metamerism: Specialization of repeated or similar body parts, such as the different uses of appendages in lobsters. For moving, predation, swimming, etc. Metamerism gives the groundwork for change to evolve. If limbs were not metameric, flight would not have evolved in arthropods.

·       Crustaceans: Marine, terrestrial (ex lobster)

·       Hexapods: terrestrial, aerial (grasshopper)

·       Myriapods: Repeating external units (millipedes)

·       Chelicerates: (horseshoe crab, spiders)

·       Tardigrades: Not jointed limbs, when too dry, shrink up. But when given water, come back up. They can live for a decade when dehydrated.

Amniotes

·       Possess amniotic egg. Common ancestor of all land mammals at one point had an amniotic egg.

·       Reptiles: Possess an amniotic egg as a "private pond" as well as scales. Not all scales in reptiles are the same, but they all are made of keratin. Fish scales are bone, however. 3 heart chambers.

·       Ex: Turtles, tuataras, squamates (snakes, lizards), crocodilians, dinos, birds.

·       Mammals: Possess mammary glands, maternal ability to feed offspring. Also possess sweat glands. 4 heart chambers, more elaborate heart in animals. Also have hair. Also have various different kinds of teeth for eating different kinds of food. 3 groups based on how offspring are born and reared.

·       Prototherians: Mammal that lays eggs.

·       The only known one is a platypus.

·       Marsupials: Newborns move to pouch as they are much more underdeveloped as youth. The pouch possesses mammary glands.

·       Ex: Possums, kangaroos.

·       Eutherians: Most developed at birth. Includes us. Largest of the 3 groups. Rodentia is the largest group of living eutherians.