Animals

Larva

sexually immature and morphologically distinct from the adult

How many living animal species are estimated

1.3 million

Choanoflagellates

a group of protists, are the closest living relatives to animals

Bilaterian traits

Bilaterally symmetric form, Complete digestive tract, One-way digestive system

body plan

a set of morphological and developmental traits

Ectoderm

covers the embryo’s surface, Develops into integumentary and nervous systems

Endoderm

lines the developing digestive tube, called the archenteron, Develops into digestive, respiratory, and some reproductive systems

Mesoderm

Develops into circulatory, reproductive, muscular, and skeletal systems

Diploblastic

animals have only ectoderm and endoderm, These include cnidarians and a few other groups

Triploblastic

animals also have a mesoderm, All bilaterally symmetrical animals are triploblastic

coelom (most triploblastic animals)

A true body cavity and derived from mesoderm

pseudocoelom

body cavity derived from the mesoderm and endoderm

acoelomates

Triploblastic animals that lack a body cavity are called

cleavage

leading to formation of a multicellular, hollow blastula

blastula

undergoes gastrulation, forming a gastrula with different layers of embryonic tissues

protostome development

cleavage is spiral and determinate, the splitting of solid masses of mesoderm forms the coelom

deuterostome development

cleavage is radial and indeterminate, the mesoderm buds from the wall of the archenteron to form the coelom

blastopore

forms during gastrulation and connects the archenteron to the exterior of the gastrula (becomes mouth in protostomes, becomes anus in deuterostomes

three major clades of bilaterian animals, all of which are invertebrates

Deuterostomia, Ecdysozoa, and Lophotrochozoa

Deuterostomia

includes hemichordates (acorn worms), echinoderms (sea stars and relatives), and chordates This clade includes both vertebrates and invertebrates

Ecdysozoa

secrete external skeletons, As they grow, they shed their exoskeletons through a process called ecdysis, all invertebrates

Lophotrochozoa

§another clade of bilaterian invertebrates, have a feeding structure called a lophophore, Others go through a distinct developmental stage called the trochophore larva, also invertebrates

Invertebraes

95% of animal life

Porifera

sponges, lacks tissues, is sedentary, and lives in marine or fresh waters

hermaphrodites

Each individual functions as both male and female (sponges)

Choanocytes

flagellated collar cells, generate the water current and ingest suspended food, type of sponge cell

amoebocytes

totipotent cells that play roles in digestion and manufacture of skeletal fibers, type of sponge cell

spongocoel

Water is drawn through pores into a cavity called the

osculum

Water is drawn out through an opening called the

Cnidarians

wide range of both sessile and motile forms including jellies, corals, and hydras, They exhibit a simple diploblastic, radial body plan

gastrovascular cavity (cnidarians)

a single opening that is both mouth and anus, acts as a hydrostatic skeleton for movement

Medusozoans

Cnidarian clade include all cnidarians that produce a medusa includes hydrozoans

Hydrozoans

alternate between polyp and medusa forms; however, Hydra, a freshwater cnidarian, exists only in polyp form and reproduces asexually by budding

Cubozoans

type of medusozoan, the medusa is box-shaped and highly toxic

Scyphozoans

type of medusozoan, regular jellies that vary in toxicity

§

Anthozoans

Cnidarian clade, the corals and sea anemones,  occur only as polyps

Corals

often form symbioses with algae and secrete a hard exoskeleton, Each generation grows on the skeletal remains of the previous generation, forming “rocks” that provide habitat for other species

Lophotrochozoans

includes the flatworms, molluscs, and annelids

Flatworms

Free-living members of phylum Platyhelminthes live in marine, freshwater, and damp terrestrial habitats, many are parasites

Proglottids

units that contain sex organs and form a ribbon behind the scolex

Mollusc

mostly soft-bodied animals protected by a calcium carbonate shell and includes snails and slugs, oysters and clams, and octopuses and squids some snails and slugs are terrestrial

mollusc body plan has 3 main parts

1) Muscular foot, 2) Visceral mass, 3) Mantle

Four of the major classes of molluscs

Polyplacophora (chitons), Gastropoda (snails and slugs), Bivalvia (clams, oysters, and other bivalves), §Cephalopoda (squids, octopuses, cuttlefish, and chambered nautiluses)

Polyplacophora: Chitons

are marine animals with oval-shaped bodies and a shell made of eight dorsal plates, §The foot is used to grip and creep slowly along rock The radula is used to scrape algae off the surface

Gastropods

move slowly by a rippling motion of the foot or by cilia and most have a single, spiraled shell that functions in protection from injury, dehydration, and predation

Bivalves

aquatic and include many species of clams, oysters, mussels, and scallops, They have a shell divided into two halves drawn together by adductor muscles and some have eyes and sensory tentacles along the edge of their mantle

Cephalopods

active marine predators with beak-like jaws surrounded by tentacles They can immobilize prey with a venom present in their saliva The foot is modified into a muscular excurrent siphon and part of the tentacles The shell is reduced and internal or missing in most species, except the chambered nautiluses

Annelids

coelomates with bodies composed of a series of fused rings, segmented worms that live in marine, freshwater, and damp soil habitats

Errantians - Polychaeta

is mostly marine clade of mobile swimmers, crawlers, or burrowers and immobile tube-dwellers, Many have well-developed jaws used for predation or grazing on multicellular algae

Annelids: Sedentarians - Oligochaeta

Cross-fertilizing hermaphrodites that eat through soil, extracting nutrients as the soil moves through the alimentary canal, Some reproduce asexually by fragmentation

Sedentarians - Leeches

Leeches include predators of invertebrates and parasites that suck blood Most species of leeches live in fresh water; some are marine or terrestrial

Ecdysozoans

the most species-rich animal group with the two largest phyla being nematodes and arthropods They are covered by a tough coat called a cuticle that is shed or molted through a process called ecdysis

Nematodes

round worms, have an alimentary canal, but lack a circulatory system Body wall muscles are all longitudinal, and their contraction produces a thrashing motion

Arthropods

body plan consists of a segmented body, hard exoskeleton, and jointed appendages, evolution is characterized by segments becoming functionally united into “body regions” specialized for feeding, walking, or swimming

Clades of Arthropods

Chelicerates, Myriapods, and Pancrustaceans

Chelicerates

named for clawlike feeding appendages called chelicerae, clade of arthropods

Arachnids

include spiders, scorpions, ticks, and mites, Arachnids have six pairs of appendages: the chelicerae, the pedipalps, and four pairs of walking legs, clade of arthropods

Myriapods

entirely terrestrial and includes millipedes and centipedes, clade of arthropods

Pancrustaceans

insects and crustaceans form the clade (also part of the arthropod clade)

Decapods

relatively large crustaceans and include lobsters, crabs, crayfish, and shrimp, cuticle is hardened by calcium carbonate

Hexapoda

enormous clade including insects and their relatives

Coleopterans, (Beetles) Dipterans, (Flies) Lepidopterans, (Butterflies) Hymenopterans (Bees)

Winged insects with complete metamorphosis

Hemipterans (True bugs) Orthopterans (Grasshoppers)

Winged insects with incomplete metamorphosis

Deuterostomia

Radial cleavage, Formation of the anus from the blastopore, Echinoderms and chordates make up the clade

Echinodermata

part of Deuterostomia, sessile marine animals that have thin epidermis covers an endoskeleton of hard calcareous plates, have a unique water vascular system, a network of hydraulic canals branching into tube feet that function in locomotion and feeding

Echinoderms

larvae have bilateral symmetry , but most adult echinoderms appear to have radial symmetry with multiples of five. part of Deuterostomia

Crinoidea

Sea lilies live attached to the substrate by a stalk Feather stars can crawl using long, flexible arms Both use their arms in suspension feeding part of echidnoderm

Holothuroidea

Sea cucumbers lack spines and have a very reduced endoskeleton Sea cucumbers have five rows of tube feet; some of these are developed as feeding tentacles part of echinoderm

Asteroidea

Sea stars have multiple arms radiating from a central disk and can regrow lost arms The undersurface of each arm bears tube feet, which grip a substrate with adhesive chemicals part of echinoderm

Ophiuroidea

Brittle stars have a distinct central disk and long, flexible arms that they use for movement part of echinoderm

Echinoidea

Sea urchins and sand dollars have no arms but have five rows of tube feet part of echinoderm