Chapter 33: Invertebrates

This set of flashcards covers key vocabulary and concepts from the lecture on invertebrates, including various phyla, anatomical features, and developmental processes.

Invertebrates

Animals that lack a backbone and account for 95% of known animal species.

Sponges

Sedentary animals from the phyla Calcarea and Silicea with no true tissues or body symmetry

What type of feeders are sponges?

Suspension feeders

Suspension feeders

Capturing food particles suspended in the water that pass through their body

Ambeocytes

Found in the mesohyl and play roles in digestion and structure within a sponge

Hermaphrodites

The ability of an individual to function as both male and female

Cnidaria

An ancient phylum of eumetazoans characterized by a sac-like body plan with a central digestive cavity.

What are included in Cnidarians?

Jellies, corals, and hydras,

The two variations on the body plan of a cnidarian are:

The sessile polyp and motile medusa

Phylum Cnidaria is divided into four major classes:

Hydrozoa, Scyohozoa, Cubozoa, Anthozoa

Hydrozoa

Mostly marine, few freshwater, both polyp (often colonial) and medusa stages in most species

What are examples of Hydrozoans?

Portuguese man-of-wars, hydras, Obelia, some corals

Scyphozoa

All marine, polyp stage is absent or reduced, free-swimming, medusae up to 2 m in diameter

What are included in Scyphozaos?

Jellies (prevalent form of the life cycle), sea nettles

Cubozoa

All marine, box-shaped medusae, complex eyes, potent venom

What are examples of Cubozoa?

Box jellies, sea wasps

Anthozoa

All marine, medusa stage is completely absent, most sessile, many colonial

What are examples of Anthozoa?

Sea anemones, most corals, sea fans (only occurring as polyps)

Spongocoel

A central cavity in sponges through which water flows.

Choanocytes

Flagellated collar cells in sponges that generate a water current and capture food particles.

Osculum

The opening of a cavity

Ectoprocta

A phylum of lophophorates that comprises colonial animals resembling plants.

Lophophore

A horseshoe-shaped, suspension-feeding organ with ciliated tentacles found in lophophorates.

Lophophorates include two phyla:

Ectoprocta, Brachiopoda

What encases the colony of Lophophorates?

A hard exoskeleton and some are reef builders

Flatworms

Soft-bodied invertebrates (acelomates) that are flattened dorsoventrally and have a gastrovascular cavity

Where does gas exchange take place in Flatworms?

Across the surface

Protonephridia

Regulating the osmotic balance in a flatworm

Where do members of phylum Platyhelminthes (flatworms) live?

Marine, freshwater, and damp terrestrial habitats

Flatworms are divided into four classes:

Turbellaria, Monogenea, Trematoda, Cestoda

Turbellaria

Marine, mostly free-living flatworms

Planarians

Best-known turbellarians that have light-sensitive eye spots and centralized nerve nets

Planarians can reproduce:

Sexually or asexually through fission

Tapeworms

Parasites of vertebrates that lack a digestive system

Tapeworms absorb nutrients from:

The host’s intestine

What leaves the host’s body in feces from tapeworm?

Fertilized eggs produced by sexual reproduction

Rotifere (phylum Rotifera)

Tiny animals that inhabit fresh water, the ocean, and damp soil and are multicellular with specialized organ systems

Alimentary canal

A digestive tube with a separate mouth and anus that lies within a fluid-filled pseudocoelom in Rotifers

Rotifers reproduce by:

Parthenogenesis

Parthenogenesis

Females producing offspring from unfertilized eggs

Molluscs

Soft-bodied animals, most protected by a hard shell, are marine, inhabit freshwater, or are terrestrial

Which of the following is a typical characteristic of molluscs?

A rasping organ called the radula

Phylum Mollusca include:

Snails and slugs, oysters and clams, and octopuses and squids

All molluscs have a similar body plan with three main parts are:

Muscular foot, Visceral mass, Mantle (water-filled)

Four major classes of molluscs:

Polyplacophora, Gastropoda, Bivalvia, Cephalopoda

Polyplacophora

Chitons

Gastropods

Mostly marine, but many are fresh water and terrestrial species, most have a single, spiraled shell

Torsion

The most distinctive characteristic of gastropods that causes the animal’s anus and mantle to end up above its head

Hirudin

A chemical secreted by leeches that prevents blood from coagulating.

Ecdysis

The process of molting the outer cuticle in ecdysozoans as they grow.

Metamorphosis

A developmental process in insects where they undergo changes in body form, including larval and adult stages.

Nematodes

Roundworms that are typically found in various habitats

Where are nematodes found in?

Most aquatic habitats, in the soil, moist tissues of plants, body fluids, and tissues of animals

Nematodes have a:

An alimentary canal but no circulatory system.

How do Nematodes reproduce?

Through sexual reproduction by internal fertilization

Where are the parasitic nematode Trichinella spiralis located?

Usually encysted in human muscle tissue

Arthropoda

The largest phylum in the animal kingdom, found in nearly all habitats of the biosphere

What are Arthropods characterized by?

A segmented body, hard exoskeleton, and jointed appendages, early arthropods show little variation

What type of system do Arthropods have?

An open circulatory system

Hemolymph

A fluid circulated into spaces surrounding the tissues and organs

What are the four major lineages of arthropods?

Cheliceriforms, Myriapods, Hexapod, Crustaceans

What do most chelicerforms include?

Spiders, scorpions, ticks, and mites

Arachnids are composed of:

An abdomen and a cephalothorax, six pairs of appendages, and the chelicerae (the most anterior)

Where does gas exchange in spiders occur?

Book lungs (respiratory organs)

What do many spiders produce?

A liquid protein silk from specialized abdominal glands

Myripods

Terrestrial, and have jaw-like mandibles

Subphylum Myriapoda includes:

Millipedes and centipedes

Millipedes (class Diplopoda)

Contain trunk segments that have two pairs of legs

Centipedes (class Chilopoda)

Carnivores with one part of legs per trunk segment

What are included in the Subphylum Hexapoda?

Insects and relatives

Where do the insects live?

In almost every terrestrial habitat and in fresh water

What does the internal anatomy of an insect include?

Several complex organ systems

Insect diversification of evolution:

Flight, adaptation to feeding on gymnosperms, and the expansion of angiosperms

Incomplete metamorphosis

Nymphs (young) that resemble adults but are slightly smaller and go through series of molts until reaching full size

Complete metamorphosis

Insects with larval stages known by such names as maggot, grub, or caterpillar and look different from adult stage

How do insects reproduce?

Through sexual reproduction of separate males and females

How do individual insects recognize members of their own species?

Bright colors, sound, or odors

How are insects beneficial?

As pollinators

How are insects harmful?

As carriers of diseases, or pests of crops

Where do Crustaceans usually live?

In marine and freshwater environments

What do Crustaceans (subphylum Crustacea) typically contain?

Branched appendages specialized for feeding and locomotion

Isopods

Terrestrial, freshwater, and marine species

Decapods

Relatively large crustaceans that include lobsters, crabs, crayfish, and shrimp

Tube feet

Hydraulic structures in echinoderms used for locomotion, feeding, and gas exchange.

Bivalvia

A class of molluscs that includes clams and oysters, characterized by a two-part shell.

The mantle cavity of a bivalve contains:

Gills that are used for feeding, gas exchange

Cephalopoda

Carnivores with beak-like jaws surrounded by tentacles of their modified foot

What are included in Cephalopods?

Squids, octopuses

Where do most octopuses search for their prey?

Along the sea floor

What allows squids to swim quickly?

Their siphon to fire a jet of water

Which group of cephalopods survive today?

Nautiluses

What type of system do Cephalopods have?

A closed circulatory system, well-developed sense organs, and a complex brain

Ammonites

Common shelled cephalopods before the end of Cretaceous

Cnidocytes

Specialized cells in cnidarians used for defense and capturing prey, containing stinging nematocysts.

Annelida

A phylum of segmented worms that have bodies composed of a series of fused rings

The phylum Annelida is divided into three classes:

Oligochaeta, Polychaeta, Hirudinea

Olgiochaetes

A class of earth worms that are named for relatively sparse chaetae, bristles made of chitin

What do Oligochaetes include?

Earthworms and a variety of aquatic species

How do earthworms obtain their nutrients?

Through soil as it moves through the alimentary canal

Earthworms are:

Hermaphrodites but cross-fertilize