Animal Diversity: Form and Function

Kingdom Animalia - multicellular aerobic heterotrophs

Most form tissues (all except Porifera)
Most are diploid
Most are motile

Ways to organize animal diversity

No orgaized tissue vs organized tissue

Two Tissue Types (Diploblastic) vs Three Tissue Types (Triploblastic)
Radial Symmetry vs Bilateral Symmetry

Body Cavity Type: Acoelomate vs Psuedocoelomate vs Coelomate

Protostomes vs Deuterostomes

What is a tissue?

A tissue is a group of cells which work together for in a particular function

Tissue types

Endoderm - the innermost tissue - forms the digestive tract
Mesoderm - the middle tissue - forms the musculature, blood, bone, reproductive
Ectoderm - the outermost tissue - forms the skin, nervous tissue, sensory organs

Animal Diversity - The Kingdom Animalia

Phylum Porifera - sponges

sponges are animals with no tissues and no symmetry
There are different cell types in a sponge, each cell with different functions, but they are not a tightly integrated system like in other animals
- you could stick a sponge in a blender and the sponge would reform

Sponges are primarily filter feeders

Collar cells with flagella beat, pulling in water and food

Influx passes through the matrix, where amoebocytes and collar cells absorb food

Structure maintained by spicules

Phylum Cnidaria

Examples: corals, jellyfish, hydra


braincoral	jellyfish	hydra

radially symmetrical animals with only two tissue types

Endoderm - forms digestive tract

Ectoderm - forms epidermis

Mesoglea - jelly-like acellular substance between tissues (the "jelly" in jellyfish)

Not a true tissue

First organisms with a nervous system - not centralized (no brain)

Incomplete digestive tract

Possess nematocysts - stingers - unique character in group

Use to stun food for predaceous types

How do organisms arrange three tissue types?

The triploblastic organisms have three unique ways to organize their tissues - these are based upon the formation and arrangement of an internal, fluid-filled cavity. A fluid-filled cavity is very structurally diverse (for both flexibility and support) structure.
The fluid-filled cavity is known as a coelom (pronounced see-lom)
Allows for support (hydrostatic skeleton), protection from shock (important if an organism is going to become larger), movement (differential pressures create movement)

Phylum Platyhelminthes - the flatworms

Examples: planarians, flukes, tapeworms

acoelomate

usually internal parasites or free living organisms

incomplete digestive tract

flatworms are structurally limited by not having a fluid-filled cavity

Phylum Nematoda - the roundworms

	psuedocoelomate usually internal parasites complete digestive tract (possess both mouth and anus) separate sexes possess lateral muscles - can only move side to side (cannot manipulate coelomic fluid)
nematode

nematode anatomy

Phylum Molluska - mollusks

Examples: snails, clams, octopus

coelomates
Mantle tissue - secretes shell
radula (chitinous tongue - used like a rasp)
advanced sensor organs & nervous tissue

Three main classes (there are more, but we will only look at these three):

Class Gastropoda - snails & slugs

Usually have a coiled shell

Extremely diverse

Slugs = terrestrial gastropod which has lost shell

Octapus vulgaris Loligo forbesi Nautilus sp.
Class Cephalopoda - octopus, squid, Nautilus

Loss of shell (in all but Nautilus)
Most advanced nervous system and sensory organs of any invertebrate

Class Bivalva - clams, oysters

Two shells which can open and close

Aquatic

Phylum Annelida - segmented worms

Examples: earthworms, leeches, polychetes

coelomate

Ventral nerve cord

Two types of muscles - longitudinal & circular

Full utilization of coelom in movement, support

polychete worm

Phylum Arthropoda - arthropods

Examples: scorpions, spiders, insects

coelomate
Hardened chitinous exoskeleton
Specialized segmentation
Jointed appendages
Specialized respiratory organs (fully terrestrial)
Division of labor in life cycle

Subphylum Chelicerata - Chelicerates

specialized hollow mouth appendages
usually used for delivering venom or other toxins to prey

Examples: scorpions, spiders, horseshoe crabs, ticks

Tarantula sp. Scorpion

Subphylum Mandibulata - Mandibulates

have mandibles (solid mouth organs)

Examples: millipedes, centipedes, lobsters, insects

centipede

There are many groups of mandibulates. We will only be looking at two.

hermit crab shrimp

Class Crustacea - aquatic, all have gills
Examples: crabs, lobster, barnacles, pillbugs

aquatic
all have gills (even terrestrial ones like the rolly-polly)

sulfur moth honey bee

cockroach preying mantis

Class Insecta - most diverse group on the earth
Examples: ants, bees, butterflies, silverfish, roaches

Body parts in three segments
Most have wings & advanced sensory organs
Advanced communication, social structure

Note: insect images taken from The Virtual Insectary

The Deuterostomes

Phylum Echinodermata

Examples: sea urchins, starfish, sea cucumbers

sea cucumber starfish sea urchin

Water vascular system - system unique to this phylum

Functions in movement, support, respiration, digestion

Decentralized nervous system
Rapid regeneration
Secondary radial symmetry

Larvae are bilaterally symmetrical
Adults are radially symmetrical

A tube foot, an extension of the water vascular system of a starfish. The tube feet act like little suction cups which enable to starfish to grasp onto the sediment for movement or to break into bivalves for food. Note that since this is not a muscular system, they will not tire.

Phylum Chordata

Examples: Sea squirts, lancelets, vertebrates

Notochord
Pharyngeal Gill Slits
Dorsal Hollow Nerve Cord
Post Anal Tail

Subphylum Urochordata - the sea squirts

larval stage possesses all of the chordate characteristics
most of these characteristics are lost when the larvae undergo metamorphosis and emerge as adults
adult stage are primarily sessile filter-feeders

Subphylum Cephalochordata - the lancelets

possesses all of the chordate characteristics throughout life cycle
burrow into sand and use mucous-secreting organs to filter-feed
are feeble swimmers

Subphylum Vertebrata

BONE - reduction of notochord (vertebral disks)

lamprey Class Agnatha - the jawless fish (not monophyletic)
Examples: lamprey, hagfish

no jaws

most are parasitic fish
very diverse group in past. Now, only a few species are still hanging on

sand tiger shark stingray

Class Chondrichthyes - the cartilaginous fish (monophyletic ??)

Examples: sharks, rays, skates

endoskeleton is composed entirely of cartilage
heterocercal caudal fin
two-chambered heart
numerous rows of teeth
internal fertilization and separate sexes

Class Osteichthyes - bony fish (not monophyletic)

Examples: marlin, bass, catfish, anglefish, eels


scaley head	sea horse


wolf eel	stickleback

most diverse group of vertebrates
paired fins with fin rays of cartilage or bone.
Respiration by gills supported by bony gill arches and covered by a common operculum.
Swim bladder often present.
Two-chambered heart.
Sexes separate and fertilization is usually external.
- Ray-finned fish - most fish possess this fin structure
- Lobe-finned fish - lung fish, Coelacanth, etc.

coelocanth

Class Amphibia - amphibians (not monophyletic)
Examples: frogs, salamanders

Living skin - must be moist to breathe

Lay eggs in water

Outcompeted in water (fish) and land (reptiles)

Class Reptilia - reptiles (not monophyletic)
Examples: lizards, snakes, gators

first truly terrestrial animals

Amniotic egg

Scales (lungs now sole respiratory organ)

Modificatons of pectoral and pelvic girdles to facilitate movement on land