Zoology Final Exam

Annelid: What is a worm?

• Animals that do not have legs, aren’t covered by a shell, are not deuterostomes, and do not have a lophophore

• Soft bodied

• They are longer than they are wide

• Can be flattened or round in cross section

In other words, an animal that is 2-15x longer than wide

Classes within annelids?

• They were traditionally 3 classes including Oligochaeta but now we only have 2 due to phylogenetic analysis. (polychaeta, Oligochaeta, hirudinea)

• Polychaeta: have parapodia, are marine worms

• Clitellate: have a clitellum

  • 2 subclasses are oligiochaeta (earthworms) and hirudinea (leeches)

Characteristic of Annelid

• 10,000 species

• Triploblastic

• paired epidermal setae

• Bilateral

• Metameric body (repeated segments)

• Closed circulatory

• Complete digestive tract

• They do possess a coelom

What is metamerism?

The segmentation of the body into repeated units called metameres or segments, which can contain repeated organs or structures. Found in annelids, arthropods, and chordates

What is tagmatization?

Specialization of body segments into distinct functional regions called tagmata. It is a result of metamerism.

Advantages of Metamerism?

• Segmented muscles allow for more precises and flexible movement

• Repetition of organs in segments means that if 1 is damaged, others can still function

• Segments can become specialized for different functions

• Aids in efficient growth and development

What is the septum in metamerism?

A thin internal wall of tissue that separates one body segment from another.

Annelid: Class Polychaeta

• 5,300 species

• Largest annelid class

• Marine

• Cephalization in most

• Parapodia

• Well developed setae

• Can be mono or dioecious

• 5-10cm long, can be much longer

• Predators, herbivores, deposit, filter feeders, and parasites

What is the parapodia?

Paired, fleshy, lateral appendages found on each segment of many polychaetae annelids. Helps the worm crawl or swim, acts as a sensory structure, can contain setae (bristles) for grip and traction. Often divided into 2 lobes.

Dorsal lobe: notopodium

Ventral lobe: Neuropodium

Polychaetae Cross Section

Polychaetae Anatomy

Annelid: Polychaetae Locomotion

They can swim, crawl, and burrow.

Crawling: via alternating movement of parapodia and body segments

Swimming: Rapid body movements with parapodia aiding propulsion

Burrowing: Using coordinated contraction and anchoring by pushing or eating away at substrate

Annelid: Polychaetae Feeding

They have a modified head region in order to feed

• Predators: use a proboscis (can be turned inside out) with jaws or teeth to capture prey

• Filter feeders: Use ciliated tentacles or palps to trap food particles from water, mucus helps trap them as well.

• Deposit feeders: Ingest sediment and extract organic material using tentacles or modified parapodia to gather food from substrate

• Herbivores: Graze on algae growing on sediment, uses rasping and scraping

Annelid: Polychaetae Digestion

Polychaetas have a complete, straight-tube gut that runs from mouth to anus, and they use extracellular digestion to break down food.

Annelid: Polychaetae Gas exchange and Circulatory

Gas exchange: Across body wall, parapodia, some have gills. Occurs primarily across the body wall and parapodia, which are well-vascularized and often thin enough for diffusion.

Circulatory: Closed system with dorsal & ventral aorta, segmental vessels, capillaries

Respiratory Pigments: Hemoglobin, hemerythrin, chlorocruorin aid oxygen transport

Annelid: Polychaetae Excretory

Excrete ammonia mainly by diffusion through their body surface. They regulate water and ion balance using excretory organs called metanephridia, with one pair per segment. Each metanephridium has a nephrostome that collects coelomic fluid, a tubule system for processing, and a nephridiopore for waste release.

Annelid: Polychaetae Nervous System

Paired suprapharyngeal (above the pharynx) and subpharyngeal (below the pharynx) ganglia. A double ventral nerve cord runs along the body with paired segmental ganglia in each segment.

They possess various sensory organs including simple to complex eyes, nuchal organs (chemosensory), statocysts (balance), and tactile sensors for environmental detection.

Annelid: Polychaetae Reproductive System

Sexual: Gonads form from the coelomic lining and gametes mature in the coelom. Gametes exit the body through nephridia or by body wall rupture. Fertilization is mostly external in the water. Many produce trochophore larvae, though direct development is also common.

Asexual: Some species reproduce asexually through epitoky. A specialized reproductive form (epitoke) is produced asexually. Epitokes swim to reproduce, while the original worm (atoke) stays safe. This ensures timing and location of egg and sperm for successful fertilization and avoids predators.

Annelid: Subclass Sipuncula basic characteristics

Peanut worms

 320 sp.

 Triploblastic

 Organ level

 Bilaterally symmetrical

 2 mm to 72 cm

 Benthic marine

 Live in burrows

 Nonselective filter or deposit feeders

 Two coelomic cavities

Annelid: Subclass Sipuncula Systems

Digestive: Complete and J-shaped

Circulatory: No blood vascular system, the coelomic fluid performs circulatory functions, blood pigment is hemerythrin

Gas exchange: Diffusion

Excretory: Nephridial funnel is coelom

Nervous: Dorsal brain, ventral nerve cord, sensory cells in introvert

Skeletal: Hydrostatic

Muscular: Circular and longitudinal muscles

Reproductive: Dioecious, external fertilization, direct development

Annelid: Subclass Echiura Basic Characteristics

Spoon worms

 140 sp.

 Triploblastic

 Organ level

 Bilaterally symmetrical

 Benthic marine

 Filter feeder or deposit feeder

 1 cm - 50 cm

 Found shallow water and deep sea

Annelid: Subclass Echiura Systems

Digestive: Complete, long, and coiled. Intestine is where digestion occurs

Gas exchange: Across general body surface, water lung in urechis

Circulatory: Present in all but urechis, coelomic fluid serves as circulatory, hemoglobin present in urechis

Excretory: Anal sacs, may or may not have excretory functions

Nervous: Nerve ring around proboscis, no specialized sensory organs in adult, ventral nerve cord

Skeletal: Hydrostatic

Muscular: Circular and longitudinal muscles, locomotion by peristaltic waves

Reproductive: Dioecious, external fertilization, gametes mature in coelom, removed by genital sacs, trochophore larva

Annelid: Subclass Pogonophora Characteristics

Bearded tube worms

 80 Sp.

 Triploblastic

 Organ level

 Bilaterally symmetrical

 No digestive tract

 All marine

 5 cm to 2 m

 Tend to be deep sea

 Greater than 1000 meters in depth

Annelid: Subclass Pogonophora Systems

Digestive system: No digestive tract, mouth or anus

Circulatory system: Blood vascular system, Hemoglobin 30x larger than human, Coelomic fluid

Gas Exchange system: Plume acts as gill

Excretory system: Nephridia Function unsure

Nervous system: Ganglia at base of plume, ventral nerve cord Skeletal system: hydrostatic

Reproductive system: Dioecious, Gonads in trunk coelom, Trochophore larvae

Annelid: Class Clintellata Characteristics

• 3,000 species

• Earthworms and leeches

• Clitellum

• No parapodia

• New or not setae

• Monoecious

• Direct divelopment

Annelid: Class Clintellata Subclass Oligiochaeta

• 3,000 species

• Earthworms

• Primarily terrestrial or freshwater

• Few setae

• No distinct head

• Scavengers

• No sensory structures or prostomium

Annelid: Class Clintellata: Subclass Oligiochaeta locomotion

Move using peristaltic motion, a wave like movement produced by muscles and aided by bristles

The move by alternating contractions of circular and longitudinal muscles, using setae to grip the soil and propel themselves forward in a wave like motion.

Annelid: Class Clintellata: Subclass Oligiochaeta Digestion

Complete digestive tract specialized for processing soil and organic matter.

Mouth takes in soil—>Pharynx helps suck in food—>Esophagus transport food—>Crop stores food temporarily—>Gizzard grinds food—>intestine digests and absorbs nutrients—>Anus expels digested waste.

Calciferous gland is found in the esophagus, glands that help regulate calcium levels in the body

Annelid: Class Clintellata: Subclass Oligiochaeta Body systems

Gas Exchange: Diffusion Across body wall as they have no lungs or gills. Oxygen and co2 exits directly through moist body surface

Circulatory: Closed system with dorsal (pumps blood forward) & ventral vessels (carries blood backwards). Aortic arches (hearts) pump blood between vessels. Blood contains hemoglobin.

Nervous: Simple. Ganglia is connected to paired ventral nerve cord. Each segment has paired segmental ganglia for local control. Sensitive to light, touch, vibrations, and chemicals.

Sensory: Organs reduced, no developed eyes, sensory structures over body surface

Reproduction: Monoecious, sperm exchange during copulation, clitellum forms mucus for cocoon for eggs, direct development

Annelid: Class Clintellata: Subclass Hirudinea

• 500 species

• Leeches

• Freshwater, marine terrestrial

• 34 body segments

• Setae reduced or absent

• Dorso ventrally flattened

• Feed on small invertebrates or body fluids of vertebrates

Leech locomotion

Move by inching itself forward, worm style of movement

Annelid: Class Clintellata: Subclass Hirudinea Body System

Gas exchange: Diffusion

Circulation: Sinus replace vessels, coelomic fluid takes on blood function, no respiratory pigments

Nervous: 10-17 pair of highly modified metanephridia. simple brain (ganglia) a ventral nerve cord along the body, nerve cord has segmental ganglia.

Reproduction: Monoecious, clitellum, sperm exchange during copulation, clitellum forms mucus for cocoon for eggs, direct development

What is a chordata?

Subphylum Craniata

Infraphylum Vertebrata

Group derived from cephalochordate lineage, they have a skull, 3 part brain, includes all vertebrate groups (fish, bird, mammals)

Vertebrate Origins

Derived from a cephalochordate-like ancestor, the earliest possible were conodonts which are jawless creatures considered among the first craniates. Oldest craniate fossil dates back to 530 MYA. Adaptive radiation of fish is the rapid diversification into many forms began around 500-750 MYA. Bone first appeared around 500 mya, contributing to vertebrate complexity.

Phylum Chordata Characteristics

• 45,000 species

• Vertebrae made of cartilage or bone

• Endoskeleton

• Brain in protective chamber cartilage or bone

• Closed circulatory system

• High degree of cephalization (brains)

• Sexual reproduction

Vertebrate Advantage

Fast reaction time and movement

Nervous system structure and neuron structure

High pressure closed circulatory system, high o2 delivery

Jointed endoskeleton and segmented muscles

Phylum Chordata: Superclass Gnathostomata (jaws)

Evolutionary group within chordata.

• Chondrichthyes: sharks, rays, cartilaginous fish

• Bony fish (Actinopterygii) ray finned, and (Sarcopterygii) lobe finned fish and tetrapod

• Tetrapod: amphibians, reptiles, birds, mammal

Jaws evolved from gill arches which allows animals to bite, grasp, chew (expand feeding options)

Paired appendages, fins or limbs that appeared in pairs which improve movement and balance

Enhanced sensory system: well developed eyes, olfactory organs, and inner ears. In aquatic species they have a lateral line

Vertebral column: backbone made of vertebrae protecting the spinal cord

Mineralized tissues (bones and teeth) offer structural support and defense

What are placoid scales in cartilaginous fishes (chondrithyes)

Small tooth like scales found on skin of cartilaginous fish

Provide protection from predators and parasites

Phylum Chordata: Class Chondrichthyes

• 820 species

• Shark, skates, rays

• Skeleton made of cartilage

• Placoid scales

• Scavengers and predators

• Ancient lineage

Shark teeth and jaw structure

• Teeth are modified placoid scales

• Conveyor belt arrangement

• Jaw made of cartilage covered tesserae

Bony fish characteristics

• Most abundant and diverse group

• Bony skeleton

• Lungs or swim bladder

• operculum cover

• Two chambered heart

Class Actinopterygii

Ray finned fish

• swim bladderes

• gas filled bladder that regulates buoyancy

• chondrostean ancestor

Class Sarcopterygii

Lobe finned fish: fin bases are thick, muscular with bone supports

Lung: breath air

tetrapods

Class actinopterygii infraclass teleostei

Teleosts are so successful because they have an effiicient gas exchange system, locomotion system, sensory system, lateral line system, reproductive system.

Actinopterygii Digestive system

Actinopterygii have a complete digestive system with mouth, stomach, intestine, and pyloric caeca for efficient digestion adapted to diverse diets.

actinopterygii circulation system

Ray-finned fish have a closed circulatory system with a two-chambered heart and single blood circuit passing through gills for oxygenation before reaching the body.

Heart→Gill→Body→back to heart

actinopterygii gas exchange system

Ray-finned fish breathe by passing water over gills where oxygen diffuses into the blood via a counter-current system, making gas exchange very efficient.

actinopterygii nervous system

Ray-finned fish have a complex nervous system with a well-developed brain, sensory organs like lateral line, eyes, and olfactory organs, allowing them to sense and respond to their environment effectively.

Actinopterygii reproduction system

Ray-finned fish typically reproduce sexually with external fertilization, producing many eggs, though some have internal fertilization and parental care. They are dioecious

Actinopterygii excretion/osmoregulation system

Ray-finned fish excrete ammonia and regulate water and salt balance differently depending on their habitat—freshwater species dilute urine to remove excess water, while marine species conserve water and excrete salts.