Intro to zoo Exam 3

Phylum Tardigrada (water bears)

In superphylum Ecdyzosoa: has an exoskeleton (chitin), molt to grow, cuticle is divided into plates

Body Plan: Bilateral

• Cylindrical body

• Four pairs of legs, 3 for locomotion, one is for clinging

• bands of muscle for leg movement

• pair of eye spots (light sensing)

• sensory papillae (light sensing)

Tissues: Triploblastic, eucoelomate (have a true hemocoel)

• Protostome

Simple Cephalization

Digestive system: Complete (well developed)

• prey enters mouth → pharynx → intestines →anus

• mouth with saliva

Exchange of gas: absorbed/ released through epidermis

Excretory system: malpighian tubules

• transport metabolic waste to digestive system

No circulatory system: bodily fluid + blood (hemolyph) contained within hemocoel

Nervous system: have a simple brain with ventral nerve cord

• ganglia along each leg with a nerve along each leg

Defining characteristics: Cryptobiosis (suspended metabolism), real legs, mouth with saliva

Reproduction: Dioecious, external fertilization (sexual)

• occurs when animals molt → eggs are attached to molted cuticle → will be fertilized by male →eggs will developed attached to exoskeleton

• young molt many times as they grow into adults

Phylum Arthropoda

In superphylum Ecdyzosoa: has an exoskeleton (chitin)

Molt to grow (dangerous and costly)→ controlled by hormones

• structure in brain releases neurohormone into blood

• hormone reaches epidermal cells, ecdysone is formed causing cells to divide and create new cuticle layers

• most only molt as juveniles

• most crusteceans molt as adults

Contains the greatest number of species

Terrestrial, aquatic, arieral species

Body Plan: Bilateral

• exoskeleton is (chitin + protein) → inside is softer than outside

  • Exoskeleton has modifications (sensilla) → receive chemical + mechanical stimuli from environment

• Compound eyes (composed of many light receiving units→ ommatidia)

  • have cornea and lens

  • Extremely sensitive to movement detection

Tissues: triploblastic, eucoelomate, protosome

• three main layers:

  • Epicuticle: outer hard layer

  • Exocuticle: inside epicuticle, hard, no wax lipids,

  • Endocuticle: innermost, soft,reabsorbed at molting

Digestive system: Complete

Exchange of gas: system varies

• terrestrial species have series of tubes (tracheae) through body, open to surface by spiracles

• Aquatic species have gills

Metabolic waste: system varies

• green gland in crustaceans

• Malpighian tubules in insects

Circulatory system: Open

• Hemocoel is main body cavity, coelom is greatly reduce in most arthropods (is divided into blood-filled spaces so that all tissues contact blood)

• Blood is moved through dorsal vessel by heart contraction + moved through hemocoel by muscular contraction

  • blood movement: enters heart through ostia → pumped from vessel into hemocoel → circulated through hemocoel → is oxygenated by respiratory organ → returns to heart/ dorsal vessel, enters through ostia

Nervous system: elaborate 3 lobed brain (initiates + controls behaviors)

• Ventral nerve cord down length of body

  • segmental ganglia extending throughout each segment and all appendages

• Neuromuscular system

  • striated muscles (fast movement)

  • Nerve control of muscle responds to signals from nerve endings along the segments + appendages

Defining characteristics:

• jointed leg appendages

  • sensing environment, capturing prey, walking, swimming, jumpung, digging

• striated appendage muscles attach inside of exoskeleton

  • Body segmentation, Cephalothorax + abdomen, Head + trunk

Arthropoda subphyla: Trilobita

• All extinct now (present 500MYA) → defining character

• Thought to be closely related to chelicerata

• Diverse when they were alive

Arthropod Subphyla: Chelicatera

Include: spiders, ticks, scorpions, horshoe crabs, etc.

Mostly terrestrial, few aquatic

Body: divided into prosoma (cephalothorax) + opisthosoma (abdomen)

• no antennae

Defining Character: First set of appendages (chelicerae) are modified mouth parts from legs

• all but few have neurotoxin venom (comes from glands on chelicerae, pedipalps, posterior stinger, or a combination

• Most produce silk → for food capture/ storage and reproduction

Respiration:

• Aquatic: gill book appendages

• Terrestrial: book lungs

Metabolic waste:

• Aquatic: ammonia diffuses from gill books

• Terrestrial: Malpighian tubules

Reproduction:

• Aquatic: external fertilization by courtship spawning

  • Eggs develop in sand → hatch as larvae → molt through instar stages

• Terrestrial: internal fertilization

  • Males transfer sperm in spermatozoa → young hatch from eggs fully developed

Arthropoda Subphyla: Myriapoda

Includes: millipedes + centipedes

Terrestrial, found in humid environments

Defining character: Many legs

• Centipedes: one pair of legs per flattened body segment (projected laterally)

  • Carnivorous predators, venomous forcipules

• Millipedes: two pairs of legs per rounded body segment (projected ventrally)

  • Eat decomposing material and plants, no venom

Respiration: Internal tracheal system connects to spiracles on the outside of the body

• one spiracle on each side of a segment

Excretory: Malpighian tubes

Nervous: Brain w ventral nerve cord and peripheral ganglia into appendages

Circulatory: Open system

Reproduction: Internal fertilization

• Males transfer sperm in spermatozoa → females lay eggs in ground, young hatch fully developed

Athropoda Subphyla: Crustacea

Includes: crabs, lobsters, shrimp, + barnacles

Mostly aquatic, few terrestrial (isopods)

Defining Character: Two pairs of antennae, biramous appendages

• Exoskeleton of aquatic species has calcium in addition of chitin

• Body divided into cephalothorax (covered by carapace) + abdomen

Respiration: gills

Excretory: green glands → releases waste over gills

Circulatory: open system

Nervous: Brain w ventral nerve cord + segmented ganglia to appendages

Reproduction: mostly external fertilization,

• Males transfer sperm in spermatozoa → females uses sperm to fertilize eggs → she carries the eggs in modified appendages until the eggs hatch

  • Crustacean larva fall into one of two types: Nauplius (crabs, lobster), or Zoea (shrimp)

Antropoda Subphyla: Hexapoda

Include: True Insects (six legs)

Terrestrial

Defining characteristics:

• Body divided into head, thorax, + abdomen

  • Head has mouth, antennae, and compound eye

  • thorax has two pairs of legs + wings

  • Abdomen divided into 11 subsegments (has one pair of legs +external reproductive opening (s)

• Wings

  • Present in all but entognatha

  • Novel adaptation in hexapoda

  • for flight + Thermal regulation

Respiratory: Tracheal system connects to outside spiracles

Excretory system: Malpighian tubules→ regulate water loss during excretion of uric acid metabolic waste → uric acid is excreted into rectal area of digestive system → water is removed from fecal material to prevent desiccation of animal

Circulatory: Same as general arthropod

Nervous: same as general arthropod

Reproduction: internal fertilization, males transfer/ gift sperm in spermatozoa

• female lays eggs

• some exhibit complete metamorphosis ( larva stages look different from adult → stages called instars)

• Larva often have differnet food resources compared to adults (no competition)

Phylum Mollusca

Superphylum Lophotrochozoa

Includes: snails, cephalopods

Body Plan: Bilateral

• mouth contain an abrasive tongue (radula, not in class bivalvia)

Mantle: viceral mass (respiratory structures derived from this, produces calcium carbonate shell)

• Dorsal most organ (is epidermis in some species)

• Aquatic species have gills formed from the mantle lining

• Terrestrial species have “lungs” formed from the mantle lining

• Secretes calcium carbonate to create shell in species with a shell

Visceral Mass: internal body where organs are located

• Located ventral to mantle

• Contains major organs/ organ systems

Muscular Foot: For locomotion

• Most ventral organ

• Used for locomotion but varies in form + function depending on species

  • In species with shells, the foot is the same size as the shell + is extendable/ retractable

Classification is based on modifications of muscular foot and the mantle

Phylum Mollusca: Class Polyplacophora (Chitons)

All are marine

Body:

• shell is divided into 8 plates

• Large muscular foot

Minimal cephalization

Nervous: many ethetes (photoreceptors) in shell valves

• Two lateral nerves, one ventral nerve extending down length of body

Digestive: feed on mostly sessile organisms

• have a scraping radula with hard chiton teeth

Respiration: Gills along the mantle tissue

• Oxygen in water diffuses into gills

Open Circulatory system: with a heart and aorta

• Blood circulates through internal cavities

Metabolic waste: concentrated and excreted in/ by kidneys

Reproduction: Diecious

• Most exhibit broadcast spawning

• Sperm in water enter female body through respiration → eggs are fertilized internally → larvae are released from female body to complete development

• eggs develop into trochophore larvae

Phylum Mollusca: Class Bivalia

Includes: Musscles, oysters, clams

Body: enclosed in a two part shell (fused on dorsal side)

• Adductor muscles close shell, abductor muscles open shell

Mantle: fused to inside of shell

• produces pearl by encasing foreign material in calcareous material

Muscular foot: allows for burrowing + movement

No cephalization, some have eye spots

Digestive: filter feeders

• intake and expel water

• food captured by gills and movement to mouth by cilia (no radula)

Open Circulatory system: heart + aorta

Metabolic waste: excreted by a pair of nephridia/ kidneys

Reproduction: Most are dioecious, broadcast spawning

• trochophore larvae develop into various types of veliger larvae (eventually settle on substrate, as spat, to finish development)

• Some species are brooding with sperm entering the female body in water → eggs are fertilized in female body → larvae are released from female to develop in water column → eventually settle on substrate

Phylum Mollusca: Class Gastropoda

Marine, freshwater, and terrestrial

Body: diverse in size, body, shell morphology (some do not have shells)

Muscular foot: for locomotion

True caphalization: head, eyes, tentacles

Digestive: Predators, herbivores, scavengers, suspension feeders

• have radula for scraping, grinding, boring, etc.

Defining characteristic of shell species: Embryonic torsion

• Mantle and visceral mass are rotated and twisted back over the perpendicular

  • Anus is now above and slightly behind the head

  • left-sided organs are now on the right sight, right-sided organs on the left

  • This allows for space for the head to be tucked into the shell

Respiration:

• Aquatic: gills

• Terrestrial: thin blood vessels in the mantle uptake oxygen by diffusion (some have a modified lung of tissue derived from the mantle)

Circulatory: Heart with blood vessels to head/ foor and to visceral mass

Metabolic Waste: concentrated in nephridia/ kidney

Nervous: Brain is typically three pairs of cerebral ganglia

• those branch into nerve cords that run the length of body

Reproduction:

• Marine: all but one are dioecious, broadcast spawning (external fertilization/ some do internal)

  • larvae develop first into trochophore larvae → velinger larvae → they settle and develop into adults

• terrestrial: Monoecious, internal fertilization

  • eggs are laid underground → young hatch as miniature versions of adults

Phylum Mollusca: Class Cephalopoda

Includes: Squid, octopuses, etc.

All are marine ( some can tolerate freshwater for short periods)

Body: Only nautilus has shell (others is reduced to internal calcium “pen”

Muscular foot: modified into funnel, tentacles, and arms

True Cephalization (highly inteligent)

Digestive: carnivorous predators (beaked jaw)

Defining character: color and texture changing camouflage

• pigments are in the skin, in chromatophore cells

• Chromatophore cells can make black, yellow, brown, and black pigments

• Have iridophores and leucophores that reflect light to make blue, green, and white

Respiration: well developed gills

Circulatory: Closed Circulatory system (systemic heart and gill hearts)

Metabolic waste: managed by well developed kidney

Nervous system:

• Largest, most well developed brain of all invertebrates

  • Greater brain to body weight ratio than fish and most reptiles

  • central brain in head is the “command center”

  • Each arm has a mini brain that controls that arm and receives sensory info

• Optical lobes process visual sensory input

• Vertical lobe for arms, tentacles, suckers (serve as sensory receptors), gravity

• Extremely sophisticated eyes, comparable vertebrate eyes

• Extremely inteligent

Buoyancy control: achieved by movement of water and gas within the chanbers of the Nautilus’ shell (cuttle fish use cuttlebone for the same purpose)

• Sodium and chloride ions are actively pumped out of the chanbers. Water follows through osmosis ( causes the chambers to fill with gas = animal is lighter)

• Pumping Sodium and chloride into the chambers causes water to follow through osmosis (causes the chambers to filll w water = animal is heavier)

Ink defense: all but nautilus use ink for defense

• ink sac is modified portion of the digestive tract, it empties into the anus (animal uses water expulsed from funnel to eject the ink)

• Ink can be compromised of mixture of melanin protein, mucus, and (in some animals) dopamine

  • melanine protein = ink cloud

  • melanine + mucus = blob of ink

  • dopamine = disorientation

Reproduction: Dioecious, courtship mating, internal fetilization

• sperm transferred in packets (spermatophores)→ transferred into female mantle through male penis or modifies arm (hectocotylus)→ females lay eggs ( most gueard eggs)→ embryo development takes place within the egg ( young are mobile at hatching, no larval stage)