Phylum Mollusca: Characteristics and Classification

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Which of the following molluscs has a highly developed brain and nervous system?


What is the primary function of the radula in molluscs?

To rasp and grind food

Which of the following arthropod subphyla is characterized by a side-to-side jaw movement?


What is the primary function of the spiracles in insects?

To exchange oxygen and carbon dioxide

Which of the following insects undergoes incomplete metamorphosis?


What is the primary function of the Malpighian tubules in arachnids?

To excrete waste products

What do honeybees use to relay vital information about death and food?

Chemical release of pheromones

Which of the following molluscs has a sessile lifestyle?


What is the primary function of the book lung in arachnids?

To exchange oxygen and carbon dioxide

What is the purpose of the Waggle Dance in honeybees?

To signal the need for food from a distant location

Which of the following characteristics is NOT unique to phylum Echinodermata?


Which of the following arthropod classes has a calcium chitin skeletal system?


What is the primary function of the pedipalps in arachnids?

To sense the environment

How do honeybees cool their nests?

By spreading water over the nest and fanning their wings

What is a characteristic of the digestive system in phylum Echinodermata?

It is a short, complete system that can be pushed outside of the body

Study Notes

Phylum Mollusca

  • Soft-bodied, mostly protected by a hard shell
  • Characterized by muscular foot, visceral mass, and mantle that secretes the shell
  • Protostomes, with a water-filled cavity and radula (rasping tongue)
  • Torsion, a unique body structure

Classifications of Mollusca

  • Gastropoda (snails and slugs)
    • Stomach foot
    • Have an opening, head, and nervous system
    • Simple brain, complete digestive system, and circulation
    • Gas exchange through gills or simple lungs
    • Hermaphroditic, with nephridia present
  • Bivalvia (clams and oysters)
    • Often marine, no head, and sessile filter feeders
    • Digestive system complete, gills trap food
    • Rudimentary nervous system, circulation pumped by two-chambered heart
    • Gas exchange through gills
  • Cephalopoda (squids, octopus, cuttlefish, and chambered nautiluses)
    • Head-foot, shell is internalized
    • Specialized foot as a tentacle, highly cephalized
    • Highly developed brain and nervous system
    • Closed circulatory system, gill gas exchange

Phylum Arthropoda

  • Protostomes, largest phylum
  • Important for pollination (economy and environmental)
  • Three body parts in insects (head, thorax, abdomen), two in spiders (cephalothorax and abdomen)
  • Jointed appendages from thorax, specialized for various functions
  • Chitin external skeleton, spiracles, metameric segmentation
  • Open blood system, sexes usually separate (females sting)
  • Highly motile, developed social behavior

Subphyla of Arthropoda

  • Chelicerates
    • Jaw moves side to side
  • Mandibulates
    • Have an up and down jaw

Classes of Arthropoda

  • Arachnida (spiders, scorpions, and ticks)
    • Cephalothorax and abdomen
    • Four pairs of walking legs, chelicera, pedipalps
    • Well-developed nervous system with sensory hairs and eyes
    • Book lung, open circulation, complete digestive system (bite/inject prey)
    • Malpighian tubule excretion
  • Insecta (butterflies, bees, dragonflies)
    • 30 orders of insects, first animals to fly
    • Live in almost every terrestrial habitat, rare in marine habitats
    • Segmented into head, thorax, and abdomen
    • Well-developed brain
  • Myriapoda (centipedes and millipedes)
    • Terrestrial, jaw like mandibles
    • Centipedes are carnivores, one pair of leg per segment
    • Millipedes feed on dead organic matter, two pairs of legs per segment
  • Crustacea (crabs, shrimp, lobster, crayfish)
    • Aquatic, mandible jaw
    • Branched appendages for feeding and locomotion
    • Many have gill appendages, open circulation
    • Green gland excretion, calcium chitin skeletal system
    • Complex nervous system

Life Cycle of Insects

  • Incomplete metamorphism: adult resembles young post-metamorphism (e.g., cockroaches)
  • Complete metamorphism: adult does not resemble young at all post-metamorphism (e.g., butterflies)

Social Behavior in Insects

  • Honeybees maintain nest temperature at 30°C, even in extreme climates
  • They cool the nest by spreading water and fanning their wings
  • They also vibrate their wings and bodies to heat up the nest
  • Communication in honeybees involves chemical release of pheromones to relay vital information
  • Two methods of communication: Round Dance and Waggle Dance

Phylum Echinodermata

  • Deuterostomes, with second opening as the mouth
  • Coelomates, with tube feet (suction cup)
  • Pentaradial symmetry, no head, short complete digestive system
  • Can push digestive system outside of their body
  • Simple circulation, endoskeleton

This quiz covers the characteristics and classification of Phylum Mollusca, including their soft bodied structure, shell, and unique features like radula and torsion. Learn about the different classes, such as Gastropoda, and their distinguishing features.

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