Bio Exam 3 (Chaps 30,31,38, 39)

What are three things that describe Protosome Animals?

• Triploblastic

• Bilaterally Symmetrical

• The embryonic blastopore becomes the mouth

Two major derived traits of Proteosome animals

• Anterior brain that surrounds the entrance to the digestive tract

• Ventral nervous system with paired or fused longitudinal nerve cords

Lophotrochozoans

• Presence of crown of ciliated tentacles called lophophores

• Ciliated larvae called trochphores

• Many of them have a worklike body form (bilaterally symmetrical, legless, soft-bodied, and longer than they are wide) to burrow through marine sediment or soil.

Ecdysozoans

• 3 layered cuticle (organic matter) that is periodically molted or shedded

• exoskeletons, feathers, hair, skin, or shell

• A thin cuticle allows the exchange of gases, minerals, and water across the body surface, but it restricts the animal to moist habitats

• Many live in marine sediments where they extract organic material from ingested sediments or capture larger prey using a toothed pharynx

Trochophore

• The larval form of some lophotrochozoans that moves by beating a band of cilia

• found among many of the major groups of lophotrochozoans like mollusks, annelids, ribbon worms, entoprocts, and bryozoans

Molting

The process where the cuticle is shed and it is replaced with a new and larger cuticle

What is the strong, waterproof, polysaccharide that makes up the layers of an ecdysozoan exoskeleton?

Chitin

Arthopods

• A clade of ecdysozoan that has appendages which are manipulated by muscles

• Each segement of the exoskeleton has muscle that operate that segment and the appendages attached to it

What are some lophotrochozoans that exhibit spiral cleavage in early development?

• Flatworms

• Annelids

• Mollusks

• Ribbon Worms

Arrow Worms

• Hermaphroditic

• Has no distinct larval stage; mini-adults hatch from the egg

• gas exchange and waste secretion are done through diffusion through the body surface

Blind Gut

A gut with only one opening

Complete Gut

Separate entrance and exit openings

Bryozoans (“Moss Animals”)

• colonial animals that live in a “house” secreted by the external body wall

• They are sesile a majority of the time, but few solitary species can slowly move around in their environment

• Marine

• Colonies consist of many small (1-2mm) individuals connected by strands of tissue from which nutrients can be moved

• All of the individuals stem from the asexual reproduction of the colony’s founder

• Can reproduce sexually; sperm are released into the water and eggs are fertilized internally

• Anus is located outside the ring of tentacles that make up the lophophore

• Food particles are carried from the tips to the bases of the tentacles in the lophophore

• 3 part coelom

Entoprocts (meaning “anus inside”)

• Similar to Bryozoans, as they are marine colonial animals living in secreted homes

• Sesile

• Some species of entoprocts release unfertilized eggs into the water for fertilization, others brood their developing young as bryozoans do

• Anus is located in the center of the ring

• Food particles are taken from the bases to the tips of the lophophore tentacles in entroprocts

• Lack a coelom

Flatworms

• Dorsoventrally flattened body form that gives these animals their body name

• Lack Specialized organs for transporting oxygen to their internal tissues

• Digestive track comprises of a mouth opening into a blind gut(the mouth doubles as an anus)

• They glide over surfaces on a layer of mucus, powered by bands of cillia

• Most are parasites, with few being free-living

Parasitic Flatworms

• Has the characteristics of the typical flatworm

• Can be endoparasitic or feed externally on animal tissues (living or dead)

• They absorb digested food from the digestive tracts of their hosts, so many endoparasitic flatworms lack a digestive tract

Rotifers

• A complete gut passes from an anterior mouth to a posterior anus

• The body is a pseudocoel that acts as an hydrostatic skeleton

• They propel themselves through the water by rapidly beating cilia

• Their most distinctive organ is a conspicuous ciliated organ called the corona

• Coordinated beating of the cilia sweeps particles of organic matter into the animal’s math and into the mastax– a complex structure that grinds food into smaller pieces

• Most live in fresh water; some stay in a dried out state until it rains and they become mobile

Gastrotrichs ('“Hairy-backs”)

• live in marine sediments, fresh waters, and waterfilms that surronf grains of soil

• Have transparent bodies with a flat surfaces covered with cilia

• Hermaphrodites, but male organs have been greatly reduced or lost in some species that reproduce asexually

Ribbon Worms

• have simple nervous and excretory systems like that of a flatworm

• Unlike flatworms they have a closed circulatory system and a complete digestive tract with a mouth and an anus

• smaller ones move by slowly beating their cilia

• Larger ones employ waves of muscle contraction to move over the surface of sediments or burrow into them

• Almost all of them have a fluid filled cavity called the rhynchocoel, which has a hollow muscluar proboscis (a feeding organ) that extends the length of its body; contractions of the muscles surrounding the rhynchocoel pushes the proboscis out of an anterior pore

Brachiopods (“lampshells”)

• Solitary marine animals

• Have a rigid shell that is divided into two parts connected by a ligament

• The two halves of the brachiopod shell are dorsal and ventral rather than lateral as in bivalves

• Beating of cilia on the lophophore draws in water into the slightly opened shell; food is trapped in the lophophore and directed to a ridge, along which it is transferred to the mouth

Phoronids

• sessile worms that live in muddy or sandy sediments or attached to rocky substrates

• They secrete tubes made of chitin that they live in

• U-shaped gut with the anus located outside the lophophore

• Their cilia drive water into the top of the lophophore, and the water exits through the narrow spaces between the tentacles

• ciliary action moves trapped food into the mouth

Annelids

• Segmented Bodies

• The coelom in each segment is isolated from those in other segments

• a separate nerve center called a ganglion controls each segment; nerve cords that connect the ganglia coordinate their functioning

• Most of them lack a rigid external protective covering;they have a thin permeable body wall that allows for gas exchange

• Restriced to moist environments because they lose water rapidly in dry air

• Live in marine, freshwater, and moist terrestrial environments

Polychaetes (“Many Hairs”)

• More than half of all annelid species

• Marine, many live in burrows in soft sediments

• Have one or more pairs of eyes

• one or more pairs of tentacles used to capture prey or filter food from the surrounding water as the anterior end of the body

• In some species the body wall extends laterally as a series of thin outgrowths called parapodia( parapodia are used in gas exchange and some species used them to move)

• stiff bristles called setae protrude from each parapodium, forming temporary contact with the substrate prevent the animal from losing footing when its muscle contract

Pogonophorans

• Secrete tubes made of chitin and other substances that they live in

• Because they have lost their digestive tract, they take up dissolved organic matter directly from their environment

• Most of their nutrition comes from endosymbiotic bacteria that they house in a specialized organ known as the trophosome–Their bacteria oxideize hydrogen sulfide and other sulfur containing compounds, fixing carbon from methane in the process

• The uptake of the hydrogen sulfide, methane, and oxygen usedby the bacteria is aided by hemoglobin in the tentacles of the organism (giving it its red color)

• Many of them live in the deep-sea, and some have been reported to live by hydrothermal vents that provide sulfides.

What are the two clades of Clitellates?

Leeches and Oligochaetes

Oligochaetes (“Few Hairs”)

• No parapodia, eyes, or anterior tentacles, and they have four pairs of setae bundles per segment

• Hermaphroditic

• Earthworms are the most familiar in this clade of Clitellates– they burrow and ingest soil from which they extract food particles

• Eggs and sperm are deposited in a cocoon outside the adult’s body, and when the cocoon sheds the egg gets fertilized

Leeches

• Lack parapodia and tentacles

• The coelom of these is not compartmentalized; the coelomic space is largely fileld with undifferentiated tissue

• groups of segments at each end of the body are modified to form suckers, which act as temporary anchors that aid the leech in its movement.

• They live in freshwater or terrestrial habitats

• They are ectoparasites that feed by making an incision in a host, where they will suck the host’s blood

• They can ingest so much blood in a single feeding that its body might swell several times its original size

• It secretes an anticoagulant into the woud that keeps the host’s blood flowing

• One species, Hirudo medicinalis is used today to reduce fluid pressure and prevent blood clotting in damaged tissues to eliminate pools of coagulated blood, and to prevent scarring

Mollusks

• The most diverse group of lophotrochozoans, both in the number of species and the environments they occupy

• They all share the same body components: a foot, a visceral mass, and a mantle

• Many use their gills as filter-feeding devices

• Others feed using a rasping structure known as a radula to scrape algae from rocks

• In some, the radula has been modified into a drill or a poison dart

• In all mollusks except cephalopods, the blood vessels do not form a closed circulatory system; the rest form an open circulatory system

Body Components of a Mollusk: Foot

• A large muscular structure that originally was used as an organ of locomotion and a support for internal organs

• In squid and octopueses, the foot has been modified to form arms and tentacles born on a head with complex sensory organs

• In groups like clams, the foot is a burrowing organ

Body Components of a Mollusk: Visceral mass

The heart and the digestive, excretory, and reproductive organs are concentrated in a centralized, internal visceral mass

Body Components of a Mollusk: Mantle

• A fold of tissue that covers the organs of the visceral mass

• The it secretes the hard, calcareous shell that you see in many mollusks

• In most mollusks, the mantle extends beyond the visercal mass to form a cavity that contains gills used for gas exhcnage

• When cilia on the gills beat, they create a current of water that passes through vascularized tissue that takes up oxygen from the water and released carbon dioxide

Mollusk Clade: Chitons

• Eight overlapping calcereous plates, surrounded by a structure known as the girdle, protect the internal organs and muscular foot of this group

• Bilaterally symmetrical and have simple internal organs

• Omnivorus

• Spends most of its adult life clinging tightly to rock surfaces with its large, musclar, mucus-covered foot

• Moves slowly by ripping waves of muscular contraction in the foot

Mollusk Clade: Gastropods

• Snails, whelks, limpets, slugs, nudibranchs, and abalones all belong to this clade

• most of them move by gliding on the muscular foot, but in a few species, the foot is a swimming organ

• Shelled gastropods have one-piece shells

• The only mollusks that live in terrestrial environments are gastropods

• In these terrestrial species, the mantle tissue is modified into a vascularized lung

Mollusk Clade: Bivalves

• Clams, oysters, scallops, and mussels belong to this clade

• Found in both marine and freshwater environments

• Have a hinged, two-part shell that extends over the sides of the body as well as the top

• They feed by taking in water through an opening called an incurrent siphon and filtering food from the water with their large gills (also the main sites of gas exchange).

Mollusk Clade: Cephalopods

• Squid, cuttlefishes, octopuses, and nautiluses all belong to this clade

• In these mollusks the excurrent siphon is modified to allow the animal to control the volume of the mantle cavity and thereby bring in or expel water; this allows for these animal to move quickly through “jet propulstion”

• This enchanced mobility allowed them to become highly efficient predators

• They have a head with complex sensory organs (their eyes are similar to vertebrates in their ability to resolve images)

• The head has a large branched foot that bears arms and/or tentacles and a siphon; arms have suckers along most of their length while tentacles only have suckers near the tips, or none at all

• Octopuses have eight arms and no tentacles typically

• Squid and cuttlefishes have eight arms plus two tentacles

• This clade uses their arms and tentacles to capture and subdue prey

• Nautiluses are the only surviving cephalopods with an external chambered shell divided by partitions; its chambers are connected by a strand of tissue that runs through ducts in the partitions

Toothed Pharynx

A muscular organ at the anterior end of the digestive tract used by ecydozoans to catch large prey.