Invertebrate Flashcards

Invertebrates: Rotifers (Phylum Rotifera)

• Invertebrates: Animals without a backbone.

• Rotifers:

  • Small, often unseen.

  • Found in moist environments (mosses, damp soil, aquariums).

  • Size: Less than 5 mm.

  • Multicellular with a complete digestive tract and organ systems.

  • Possess a pseudo coelum.

  • Triploblastic (all animals discussed from here onward).

  • Ecological Importance:

    • Food for other animals.

    • Decomposers: Break down waste and recycle nutrients.

  • Tolerance to Harsh Conditions:

    • Can go dormant for up to nine years in unsuitable conditions.

  • Reproduction:

    • Mostly reproduce through parthenogenesis.

  • Growth:

    • Cells increase in size, rather than dividing, as they grow.

Tardigrades (Water Bears) - FYI

• Extremely resilient animals.

• Size: Less than 1 cm.

• Habitat: Moist environments.

• Tolerance:

  • Survived exposure to the vacuum of outer space (NASA experiment).

  • Withstand radiation (gamma rays, X-rays).

Lophophorates

• Not a formal classification, but a term for a group of animals.

• Defining Feature: Possession of a lophophore (ring-shaped tentacles) used for capturing food.

• Habitat: Marine.

• Three phyla:

  • Ectoprocts (Bryozoa):

    • Look like corals or plants.

  • Phoronids:

    • Resemble tube worms but possess a lophophore.

  • Brachiopods:

    • Superficially resemble mollusks (bivalves/clams), but differ in shell structure.

    • Shells are not mirror images (unlike bivalves).

    • Hinges are located in the middle and rear, not on the side like bivalves.

    • Brachiopods are sessile, whereas bivalves can move with their foot.

Nemertea (Ribbon Worms or Proboscis Worms)

• Marine animals with a unique feeding mechanism: a "mouth within a mouth."

• Possess a proboscis (a mouth part with a hook or harpoon) that shoots out to capture prey.

• Acoelomate.

• Possess a closed circulatory system (more advanced trait).

• Have a primitive brain and a complete digestive system.

Mollusks

• Habitat: Mostly marine, but some are terrestrial.

• Body Plan:

  • Foot: Used for movement.

  • Visceral Mass: Contains most of the organs.

  • Mantle: Tissue that secretes the shell; found underneath the shell.

• Triploblastic and have protostome development.

• Have a true coelum and complete digestive tract.

• Reproduction: Most are gonauchoristic (separate male and female individuals), some are hermaphroditic.

• Circulatory System: Open circulatory system, using hemolymph instead of blood.

  • Hemolymph leaves blood vessels and mixes with body tissues before returning to the vessels.

  • In a closed circulatory system, blood remains within blood vessels at all times.

Open vs. Closed Circulatory Systems

• Open Circulatory System:

  • Hemolymph pumped by heart into vessels.

  • Hemolymph exits vessels, mixes with body tissues, and returns to vessels.

  • Less efficient; common in smaller animals that don't require rapid oxygen/nutrient delivery.

  • Less susceptible to death by cuts

• Closed Circulatory System:

  • Blood remains within vessels.

  • More efficient for distributing nutrients and oxygen, allowing for larger body size and faster reaction times.

  • Blood pressure must be maintained for proper circulation; blood loss can be fatal.

• Radula: Teeth-like structure used by some mollusks (especially gastropods) to scrape food or algae from surfaces; moves back and forth like a saw.

Mollusk Classes:

• Polypolycophora (Chitons):

  • Marine animals with eight dorsal plates on their back.

  • Found in intertidal zones (where tides go in and out).

• Gastropoda (Snails and Slugs):

  • Most diverse group of mollusks (approximately three-quarters of all mollusks).

  • Examples: limpets, abalone, nudibranchs (sea slugs), conch.

  • Most have spiral shells, but some (like slugs) do not.

  • Aquatic gastropods have gills, while terrestrial gastropods may have lungs.

  • Developed nervous, circulatory, and reproductive systems.

• Gastropod Examples:

  • Limpets: Edible and found in intertidal zones.

  • Abalone: Expensive and valuable in Far East cuisine.

  • Torsion: Many gastropods undergo torsion, where their body is rearranged during development so that the anus ends up above the head.

• Bivalvia (Clams, Oysters, Mussels, and Scallops):

  • Shells consist of two halves (valves) that are mirror images of each other.

  • Gills are used for both feeding and gas exchange.

• Bivalve fact:

  • Teredo navalis: A type of clam that burrows into and eats wood in marine environments. Wooden ships are treated with creosote to prevent this; creosote is toxic and pollutes oceans.. Newer ships are made of metal to stop this problem from occurring.

• Cephalopoda (Octopus, Squid, and Nautilus):

  • Have a distinct head and tentacles.

  • Metaphor: Have cells called metaphors enable most to camouflage; change the texture of Skin to Camoflauge.

  • Developed eyes that can discern shape, size, and brightness, but may be color blind.

  • Considered intelligent, with the largest brain-to-body ratio among invertebrates.

  • Nautilus: The only cephalopod that has a shell.

    • Paper nautilus: Soft, papery shell.

  • Ink: Squid and octopus release ink, which contains melanin, as a defense mechanism.

    • Some squid inks create a pseudomorph (temporary shape) of the squid to confuse predators.

  • Squid Ink Pasta: Some cephalopods have ink that is added to pasta, to add a unique design, with no flavor added.

Annelids (Segmented Worms)

• Characteristics:

  • True coelum.

  • Protostome development.

  • Well-developed organ systems.

  • Closed circulatory system.

  • Segmented bodies (metamerism), with internal walls (septa) separating segments.

  • Each segment (metamere) has a ring like feature on the outside (annuli).

Annelid Structures:

• Clitellum: A structure that produces the cocoon for fertilized eggs.

  • Can be used to identify the anterior end of the worm (clitellum is closer to the head).

Annelid Classes:

• Oligochaeta (Earthworms):

  • Lack parapodia (leg-like structures).

  • Have hair-like structures (setae or keti) used for movement and chemosensing.

  • Breathe directly through their skin (no lungs).

• Polychaeta (Marine Tube Worms):

  • Have parapodia with setae, used for chemosensing and gas exchange.

  • Most build tubes to live in.

  • Can live in very high temperatures.

• Hirudinea (Leeches):

  • Bodies tend to be flatter with less obvious segments.

  • Mostly ectoparasites; some are scavengers.

Leech Information:

• Secrete water while feeding on blood.

• Used in medicine due to the presence of hirudin, an anticoagulant.

  • Used to treat circulatory and blood-clotting issues.

• Ticks also contain an anticoagulant in their saliva and have also been used for the same medical purposes.