Animals 3: Protosomes

Coelom

fluid-filled body cavity that is completely lined with mesoderm derivatives

Functions of a Coelom

1. cushions internal organs

2. allows for growth of organs

3. allows for independent movement of internal organs

4. hydrostatic skeleton (some)

Coelomate organisms are grouped based on three developmental features:

1. cleavage pattern

2. fate of the blastopore

3. coelom formation

grouped as PROTOSTOMES or DEUTEROSTOMES

Cleavage Pattern

the pattern by which the zygote divides

Protostomes Characteristics:

spiral, determinate cleavage

Deuterostomes Characteristics:

radial, indeterminate cleavage

Fate of Blastopore:

blastopore - invagination of blastula

protostomes - forms mouth first

deuterostomes - forms anus first

Coelom Formation - How does the internal body cavity form?

protostomes: schizocoelous - splitting of mesoderm

deuterostomes: enterocoelous - outpockets of mesoderm

Phylum Mollusca - Mollusks, Snails, Slugs, Octopus, Clams

1. habitat: most are marine, some freshwater and terrestrial

2. body design: all have three body parts

foot, visceral mass, mantle

some have:

mantle cavity, radula

3. circulatory system (transport of gases) - open & closed

4. reproduction: sexual, most snails are hermaphroditic, many marine species have trocophore

Foot

muscular structure used for moving

Visceral Mass

internal organs

Mantle

layer of tissue that covers visceral mass

Mantle Cavity

fluid filled chamber formed by mantle

Radula

organ with “teeth”, used to scrape up food

Open Circulatory System

blood or fluid that transports gases is NOT completely contained within vessels

Closed Circulatory System

blood or fluid that transports gases is completely contained within vessels

Hemocoel

cavity around organs in which blood pools - bathes organs in blood

Hemolymph

fluid that transports gases; molecules, not cells

Trocophore

ciliated larval stage

Class Polyplacophora - chitons

1. habitat: marine

2. body design: oval shaped, eight dorsal plates, radula, strong foot

Class Gastropoda - Snails, Slugs, Nudibranchs

1. habitat: aquatic, terrestrial

2. nutrition: variable (herbivores, carnivores)

3. body design: exhibit torsion, snail - spiral shell, slugs & nudibranchs - no shell, gas exchange: aquatic - gills, terrestrial - mantle cavity, excretion - kidney

4. reproduction: sexual, some hermaphrodites

Torsion

digestive system twists anus near head, in mantle cavity

Class Bivalvia - Clams, Oysters, Mussels, Scallops

1. habitat: aquatic

2. nutrition: filter feeders (suspension feeders)

3. body design: shell, adductor muscles, gas exchange: gills, excretion: kidney, transport/circulatory system: open

Shell - Bivalvia

divided in two parts, hinged

Adductor Muscles - Bivalvia

keeps shell closed

Class Cephalopoda - Octopus, Chambered Nautilus, Cuttlefish, Squid

1. habitat: marine

2. nutrition: carnivores

3. body design: tentacles - modified foot, mantle covers visceral mass

shell - varying degrees

external: chambered nautilus

internal: cuttlebone-cuttlefish, pen-squid

no shell: octopus

gas exchange: gills

excretion: kidney

transport/circulatory system: closed

nervous system: well developed, complex brain; eye similar to humans

4. reproduction: sexual

Phylum Annelida - Segmented Worms

Class Oligochaetae - earthworms

Class Polychaetae - clam worms

Class Hirudinea - leeches

Phylum Annelida Characteristics:

1. metamerism - segmented body

2. paired setae often present

3. closed circulatory system

4. aquatic and terrestrial

Class Oligochaeta - Earthworms

1. habitat: aquatic, terrestrial

2. nutrition: detritovores - eat dead or decaying matter

3. body design: segmented, septum (septa) - partitions between segments, seta (setae) - bristles, or hair-like structures used for traction (movement)

digestive system: specialized

1. mouth

2. pharynx

3. esophagus

4. crop - storage

5. gizzard - muscular, grinding

6. intestine - absorption

gas exchange: through skin

excretion: nephridium - one per segment

transport/circulatory system: closed

aortic arches = “hearts” - muscularized blood vessels, 5 surround esophagus

4. reproduction: hermaphroditic, clitellum, mucus “ring” picks up eggs, then sperm; deposited in ground

Nephridium

“kidney”

Clitellum

structure that secretes mucus; “neck” of the earthworm

Class Polychaeta - Bristle Worms, Clam Worms

1. habitat: mostly marine

2. nutrition: variable (filter feeders, carnivores, detritovores)

3. body design:

gas exchange: parapodia

excretion: nephridia

transport/circulatory system: closed

4. reproduction: sexual, sexes separate

Parapodia

paddle-like structures on each segment

Class Hirudinea - Leeches

1. habitat: mostly freshwater

2. nutrition: carnivores, some parasites

3. body design: dorsoventrally flattened, hirudin - anticoagulant secreted during feeding

Hirudin

keeps blood from clotting

Phylum Onychophora - Peripatus - Velvet Worm

1. same respiratory and circulatory system as arthropod characters

2. cuticle made of chitin

annelid characters:

3. unjointed legs

4. segmented nephridia

Phylum Arthropoda

1. habitat: all habitats (aquatic & terrestrial)

2. body design:

   1. segmentation - body divided into parts, parts show specialization of function

   2. exoskeleton - outer protection called a cuticle - outer covering made of chitin and protein

   3. jointed appendages - legs, claws, jaws modified for different functions

   4. extensive cephalization - well defined head region where most of the senses occur

   5. circulatory system - open

   6. gas exchange: aquatic - gills, terrestrial - tracheal system

   7. dorsal brain with ventral nerve cord

Subphylum Trilobita - Trilobites (extinct)

1. inhabited shallow seas

2. showed segmentation, but little variation between segments

Subphylum Chelicerata - Spiders, Ticks, Scorpions

1. habitat: aquatic and terrestrial

2. body design:

   1. two body segments: cephalothorax and abdomen

   2. chelicerae - pincers - feeding appendages

   3. ocellus (ocelli) - simple eyes (one lens)

   4. no antennae

Class Merostomata - Horseshoe Crabs

1. habitat: marine

2. nutrition: carnivores

3. body design:

   1. ocellus

   2. gas exchange: book gills

4. reproduction: sexes separate

Class Arachnida - Spiders, Scorpions, Ticks, Mites

1. habitat: mostly terrestrial

2. body design:

   1. ocellus - simples eye - one lens

   2. cephalothorax with six pairs of appendages

1 pair chelicerae - feeding structures (fangs)

1 pair pedipalps - sensory/feeding structures

4 pairs walking legs

3. feeding: use chelicerae to attack prey, masticate (chew up) food, emit digestive juices on prey, grind with chelicerae, then suck up juices

4. spiders:

   1. silk - liquid protein that becomes solid upon contact with air - immobilize prey

   2. spinnerets - structures that emit silk

5. circulatory system: open

6. gas exchange: book lungs

7. reproduction: sexual, males smaller than female, female may store sperm in sperm receptacle

Book Lungs

look like pages of a book, highly folded structure to increase surface area in a small space

Subphylum Uniramia

1. habitat: all

2. body design:

   1. three body parts: head, thorax, abdomen

   2. mandibles - modified appendages jaw-like, moves side to side

   3. one pair of antennae

   4. one pair of compound eyes made of multiple units called ommatidium (ommatidia)

   5. uniramous - one branch, or joint to leg

Class Diplopoda - Millipedes

1. body design: two pair of walking legs per segment

2. nutrition: feed on detritus, plants

Class Chilopoda - Centipedes

1. body design: one pair of walking legs per segment

2. nutrition: carnivores

anterior - most trunk segment has poison

claws - defense, immobilize prey

Class Insecta - Insects

1. habitat: all

2. body design:

   1. circulatory system: open

   2. excretory system: Malpighian tubules

   3. gas exchange: tracheal system - branched tubes lined with chitin - carry oxygen directly to the cells, spiracles - openings on outside of abdomen

   4. nervous system - two ventral nerve cords with ganglia, dorsal brain - capable of complex behavior

   5. only invertebrates capable of flight

   6. undergo metamorphosis

   7. reproduction: separate sexes, fertilization usually internal

      1. spermatophore - packet of sperm

      2. spermatheca - internal female structure that stores sperm

advantages to flight:

1. dispersal

2. find food or mates

3. escape predators

wings: structure varies depending on order of insects

Metamorphosis

distinct stages in development where individuals changed from an immature larva to a sexually mature adult

Gradual Metamorphosis

young resembles adult; has different body proportions, molts - exoskeleton is shed as juvenile grows

Complete Metamorphosis

distinct larval and adult stages

larva - grubs, maggots, caterpillars

worm-like appearance, designed to eat and grow

pupa - stage of transformation

adult - beetles, flies, butterflies, moths designed to repoduce and die

Subphylum Crustacea - True Crabs, Lobster, Crayfish, Shrimp

1. habitat: mostly aquatic

2. body design:

   1. two body parts: cephalothorax and abdomen

   2. multiple, highly-specialized appendages

   3. two pair of antennae

   4. carapace - covers head and thorax

   5. lost appendages can be regenerated

   6. gas exchange: small crustaceans - diffusion across cuticle, large crustaceans - gills

   7. circulatory system - open

   8. excretion: green glands = labyrinth eliminated in head region

   9. reproduction: sexes separate

Class Malacostraca - Ten Walking Legs

lobster, crayfish, crab, shrimp, isopods

Class Branchiopoda - Daphnia

water flea

Class Cirripedia

barnacles