Exam 4

Crustaceans

  • General Body Structure:

    • head, thorax, abdomen

      • head has 5 segments, thorax has 8 segments, abdomen has 6 segments.

    • Anterior end has a nonsegmented rostrum

    • Posterior end includes telson and uropods, forming a tail fan in many crustacean’s.

    • Arthropods have a hemocoel derived from the blastocoel, with reduced coelomic spaces around gonads and excretory organs

  • Reproduction:

    • Most crustacea have separate sexes—-dioecious

    • Barnacles are monoecious, but they still cross-fertilize

    • Some ostracods reproduce via parthenogenesis, so males are rare

    • Crayfish have direct development.

    • Most others have indirect development with larval stages

  • Life Cycle:

    • Nauplius larva (uniramous antennules; biramous antennae)

    • Development proceeds through molts

    • Barnacles: nauplius → cyrpdi → sessile adult

  • Molting (Ecdysis)

    • Grow by molting

    • Epicuticle: thin, lipid-impregnated protein layer

    • Exocuticle: protein + calcium + chitin

    • Endocuticle: heavily calcified principal layer + a less calcified membranous layer

    • Hormonal control:

      • Molting triggered by environment

  • Feeding:

    • Crayfish stomach has a gastric mill for grinding food.

  • MAJOR GROUPS:

    • Ostracoda

      • “seed shrimp”

      • 6,000 species

    • Mystacocarida

      • Tiny interstitial marine sand dwellers.

    • Branchiopoda: Fairy shrimp, brine shrimp, tadpole shrimp, water fleas.

    • Isopoda: pill bug(terrestrial)

    • Amphipoda: Sand hoppers, Beach hoppers

    • Decapoda: crabs, lobsters, shrimp, crayfish.

      • Many have chelae, which are pincers

      • 5 pairs of walking legs, 3 pairs of maxillipeds.

Hexapods

  • 2 major groups:

    • Entognatha:

      • Mouthparts are enclosed in head

      • Protura, Diplura, Collembola (springtails)

      • Tiny, eyeless, soil dwellers

    • Insecta:

      • Mouthparts exposed

      • Most diverse animals on Earth; ~1.1 million described species

  • Insect Body Plan:

    • Head:

      • Compound eyes, 3 ocelli, antennae, mouthparts

    • Thorax:

      • Pro-, meso-, and metathorax

    • Abdomen:

      • Spiracles, reproductive organs

  • Malphigian Tubules removes waste

  • Gas Exchange:

    • Tracheal system with spiracles → trachae → tracheoles

    • Spiracles can close to reduce water loss

  • Vision:

  • Compound eyes with ommatidia → wide field of view but poor detail

  • Ocelli detect light intensity

  • Reproduction:

    • Most use sexual reproduction but some orders like Hemiptera and Hymenoptera may use parthenogenesis

    • Courtship by pheromones, light signals, sound or color.

    • Internal fertilization using spermatophores

  • Insect Growth and Metamorphosis:

    • Ametabolous:

      • No metamorphosis (silverfish)

    • Hemimetabolous:

      • Incomplete metamorphosis

      • Egg -→ Nymph → Adult

      • Grasshoppers, true bugs, dragonflies

    • Holometabolous:

      • Complete metamorphosis

      • Egg → Larva →Pupa→Adult

      • Butterflies, beetles, flies, bees

  • Feeding Strategies

    • Herbivores

      • majority of insects

    • Saprophagous: eat decaying matter

      • Many beetles

    • Predators:

      • Mantids, dragonflies, ladybugs

    • Parasitic:

      • lice, fleas

    • Parasitoids:

      • Wasps that kill their host; used in biocontrol

Echinoderms:

  • ~7,000 species

  • Larvae are bilateral, adults are radial

  • Water Vascular System → tube feet for locomotion and feeding

  • Endoskeleton of calcareous ossicles under epidermis

  • No parasitic forms

  • Major Group: Asteroidea:

    • Sea stars

    • Often predators, many live on rocky of soft substrates

    • Tube feet with suckers

    • Papulae = skin gills

    • Catch collagen: lets body stiffness change quickly

    • Able to regenerate arms, and sometimes can regrow an entire organism from a severed limb

    • External fertilization

  • Ophiuroidea: Brittle Stars

    • Most active echinoderms

    • Move using arms

    • Slender arms

    • Tube feet lack suckers

    • Madreporite on ORAL SURFACE, unlike sea stars

    • No anus; waste is expelled through mouth

    • Respiration via bursae

  • Echinoidea: Sea Urchins, Sand Dollars

    • ~950 species

    • Body enclosed in rigid test

    • Tube feet emerge through pores

    • Regular urchins: radial, long spines → graze on algae

    • Irregular urchin(sand dollars): bilateral, short spines → deposit feeders

  • Holothuroidea: Sea Cucumbers

    • soft-bodied, ossicles reduced

    • Body elongated along oral-aboral axis

    • Oral tentacles are modified tube feet

    • Respiratory tree

    • Suspension or deposit feeders

  • Crinoidea: Sea Lillies & Feather Stars

    • ~625 species, common in fossils

    • Sea lillies: stalked, mostly sessile adults

    • Feather stars: free-living

Hemichordates

  • ~130 species

  • Formerly grouped with chordates due to gill slits and stomochord, but a stomochord is not a true notochord.

  • Bilateral, wormlike, fragile animals; most live in shallow burrows or tubes.

Chordates I: Lancelets, Tunicates, & Fishes

5 Chordate Characteristics:

  1. Notochord—flexible support rod

  2. Dorsal hollow nerve cord—forms CNS

  3. Pharyngeal slits/pouches—feeding or respiration

  4. Endostyle/Thyroid gland—feeding or iodine metabolism

  5. Postanal tail—propulsion

Cephalochordates (Lancelets/Amphioxus):

  • Retain ALL chordate traits as adults

  • No distinct head

  • Filter feeders, bury in sand

  • Muscles arranged in myomeres (zig-zag blocks)

  • resembles ancestral vertebrates

Tunicates(Urochordata):

  • ~3,000 species; most sessile adults, free-swimming larvae

  • Adults have a cellulose-like covering called a tunic

  • Adults retain only 2 chordate traits:

    • Pharyngeal slits

    • Endostyle

  • Larvae have all 5 traits, then lose them during dramatic metamorphosis

  • Hermaphroditic; external fertilization

Vertebrates:

  • Early forms: ostracoderms (jawless armored fishes)

  • Pikaia may represent earliest chordate-like fossil

  • Ammocoete larva (lamprey) resembles Amphioxus → model for ancestral vertebrate

  • The Evolution of Jaws:

    • Jaws evolved from the manidublar arch

    • Gill arch enlargmement improved respiration →repurposed into jaws

    • Derived from neural crest cells

Fishes

Agnathans:

  • Hagfishes

    • No vertebrae: scavengers; slime producing

    • Osmotic equilibrium with seawater

    • 3 accessory hearts

    • Reproduction poorly understood

  • Lampreys

    • Many parasitic; rasping keratinized teeth

    • Ammocoete larva →filter feeder for years → metamorphosis

Chondrichthyes (Cartilaginous Fishes):

  • Cartilaginous skeleton: no true bone

  • Powerful jaws, well-developed senses

  • Mostly marine

  • Sharks: heterocercal tail for lift; fusiform body

  • Shark Senses:

    • Olfaction: detect 1 part per 10 billion

    • Lateral line: detects low-frequency vibrations

    • Vision: excellent, even in dim light

  • Osmoregulation:

    • Use urea + TMAO to maintain osmotic balance

    • Rectal gland expels excess salt

  • Reproduction:

    • Oviparous — egg-laying

    • Ovoviviparous — eggs retained internally

    • Viviparous — placenta-like nourishment

Osteichthyes(Bony Fishes):

  • Endochondral bone

  • Swim bladder or lungs from gut

  • Huge diversity: 96% of all fish

  • Actinopterygii (Ray-finned fishes):

    • The majority of fishes

    • Teleosts:

      • Modern bony fishes

      • Incredibly diverse, 96% of all fish

      • Range from 7mm to 17m

      • Found from mountain streams to the deep sea to the Antarctic to hot spring

      • Have lighter cycloid/ctenoid scales

      • Highly mobile fins; specialized body forms

      • Operculum increases respiratory efficiency

  • Sarcopterygii(Lobe-finned Fishes):

    • Lungfishes:

      • South American & African species: true lungs, survive dry conditions

      • Australian species: relies mostly on gills

    • Coelacanths

      • Though extinct but rediscovered in 1938

      • Diphycercal tail (three lobed)

      • Fat-filled swim bladder (NOT for respiration)

Functional Biology of Fishes:

  • Swimming:

    • Myomeres (W-shaped blocks) provide power

    • Larger fish generally swim faster

  • Swim Bladder:

    • Control buoyancy

    • Absent in tunas, many deep-sea species

  • Hearing:

    • Weberian ossicles in ostariophysans enhance sound detection

  • Respiration:

    • Sharks → gill slits

    • Bony fish: operculum + continuous water flow

  • Osmoregulation in freshwater fish:

    • Hyperosmotic regulator → produce dilute urine, absorb salts via gills

Chordates II: Herps

  • Early Tetrapods:

    • Land invasion = most dramatic evolutionary transition

    • Devonian (~416 MYA): bony fish diversified into freshwater forms with features that pre-adapted them for land

      • Pre-adaptations:

        • Air-filled cavity + paired internal nares (primitive lungs)

        • Strengthened paired fins (primitive limbs)

  • Amphibians Overview

    • ~8,456 species across 3 orders

  • Gymnophiona(Caecilians)

    • ~214 species

    • limbless, burrowing creatures in tropics

    • Small eyes

    • Feed on underground invertebrates

    • Internal fertilization

  • Urodela/Caudata (Salamanders):

    • ~771 species, mostly in Northern Hemisphere

    • Many breath through external gills, lungs, skin, or all three

    • Plethodontids: fully lungless; rely on cutaneous respiration

****EVERYTHING BEYOND THIS POINT CAN BE BONUS QUESTIONS****

  • Anura (Frogs & Toads)

    • ~7,471 species; fossil record back 250 MYA

    • Adults tailless, larvae tailed

    • Must remain near water (reproduction & skin permeability)

    • Ectothermic, limiting range (no polar regions)

    • Skin & Coloration:

      • Chromatophores:

        • Xanthophores: yellow/orange/red

        • Iridophores: light-reflecting (mirror cells)

        • Melanophores: black/brown

      • Color change via cytoplasmic streaming

    • Circulation:

      • 3-chambered heart: 2 atria, 1 ventricle

      • Spiral valve helps separate oxygenated/deoxygenated blood

    • Brain:

      • Forebrain enlarged for olfaction

      • Midbrain → optic lobes

      • Cerebellum small (less complex movement)

  • Amniotes: Reptiles + Birds +Mammals

    • Transition from amphibians to amniotes marked by the amniotic egg

      • Amnion: cushions embryo

      • Allantois: stores waste

      • Yolk sac: nutrients

      • Chorion: respiration

      • Mineralized shell: reduces desiccation, allows gas exchange

  • Non-Avian Reptiles (Reptilia)

    • Amniotic egg

    • Desiccation-resistant skin (keratinized)

    • Rib ventilation

    • Stronger jaws

    • High-pressure cardiovascular system

      • 3 chambered heart with incomplete ventricular separation

      • Crocodilians, birds, and mammals have 4-chambered heart

      • Reptiles can bypass lungs during diving or estivation

    • Water-conserving nitrogen excretion

    • Expanded sensory systems

  •    

    • Testudines (Turtles):

      • Old lineage (240 MYA)

      • No teeth; keratinized beak

      • Shell = fused ribs + vertebrae + dermal bone

      • Oviparous; all bury eggs

      • Temperature-dependent sex determination:

        • low temp → males

        • high temp → females

    • Squamata (Lizards + Snakes):

      • Lizard traits:

        • Gekkos: toe pads, nocturnal.

        • Iguanas: crests, dewlap; marine iguana

        • Komodo dragon: largest lizard

        • Amphisbaenians: burrowing “worm lizards” with reinforced skull

        • Kinetic Skull:

          • Loss of certain bones → more flexible skull

          • Snakes: extreme version → they swallow large prey.

            • Lower jaws loosely joined.

            • Trachea extends forward while swallowing

        • Locomotion:

          • Lateral undulation

          • Concertina (good for climbing and narrow spaces)

        • Venomous Snake Families:

          • Elapidae: cobras, mambas, coral snakes (fixed fangs)

          • Viperidae: vipers, pit vipers (folding, tubular fangs)

            • Pit vipers can detect infrared

          • Colubridae: mostly nonvenomous; some rear-fanged venomous

          • Hydrophiidae: sea snakes

    • Crocodilia (Crocs, Gators, Gavials)

      • Archosaurs (with birds)

      • Very little change in 200 million years

      • Thecodont teeth (set in sockets)

      • Complete secondary palate → can breathe while mouth full of water/food.

      • 4-chambered heart

      • Adults have few predators; juveniles are vulnerable.