Ecdysozoan Protostomes: Nematoda Overview
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Questions and Answers

What are the two major body regions in Chelicerata?

Cephalothorax and abdomen.

What are the functions of chelicerae and pedipalps in Chelicerata?

Chelicerae are fanglike structures for biting prey, while pedipalps can serve as grasping organs or sensory organs.

How do horseshoe crabs adapt their gills, and what is their primary habitat?

Horseshoe crabs have modified walking legs that function as gills, and they inhabit shallow coastal waters.

How many pairs of walking legs are found on the cephalothorax of Chelicerata?

<p>Four pairs.</p> Signup and view all the answers

What role do carnivorous bottom feeders, like horseshoe crabs, play in aquatic food webs?

<p>They serve as both predator and prey, contributing to the balance of the ecosystem.</p> Signup and view all the answers

What is a key characteristic of the body segmentation in the Phylum Arthropoda?

<p>Body segments show no internal separation and are often fused.</p> Signup and view all the answers

How does the circulatory system in Arthropoda function?

<p>Arthropods have an open circulatory system where the heart pumps haemolymph from the haemocoel.</p> Signup and view all the answers

What unique features are found in the respiratory systems of Arthropoda?

<p>Respiratory systems in Arthropoda vary by group, often including gills, tracheae, or book lungs.</p> Signup and view all the answers

Describe the digestive system in Arthropods.

<p>Arthropods possess a complete digestive system that allows for efficient processing of food.</p> Signup and view all the answers

What does cephalisation in Arthropods refer to?

<p>Cephalisation refers to the concentration of sensory organs and nerve tissues in the head region.</p> Signup and view all the answers

What distinguishes the class Trilobita within the Phylum Arthropoda?

<p>The class Trilobita is characterized as an extinct group of arthropods with a distinct body form.</p> Signup and view all the answers

List one characteristic feature of cirripedes.

<p>Cirripedes are characterized by their barnacle-like structure and are primarily sessile as adults.</p> Signup and view all the answers

How is the hexapod anatomy typically organized?

<p>Hexapods have a body divided into three segments: head, thorax, and abdomen.</p> Signup and view all the answers

What are the primary feeding appendages found in the Chelicerata group?

<p>The primary feeding appendages in Chelicerata are chelicerae and pedipalps.</p> Signup and view all the answers

Describe the significance of compound eyes in the Crustacea subphylum.

<p>Compound eyes in Crustacea provide a wide field of vision and are essential for detecting movement in aquatic environments.</p> Signup and view all the answers

What are the three main body regions of hexapods?

<p>The three main body regions of hexapods are the head, thorax, and abdomen.</p> Signup and view all the answers

How do the appendages on the abdomen of many crustaceans differ from those of other arthropod groups?

<p>Many crustaceans typically have no appendages on their abdomen, unlike other arthropod groups that may have them.</p> Signup and view all the answers

Explain the role of sensory appendages on the head of crustaceans.

<p>Sensory appendages on the head of crustaceans, such as antennae, are crucial for detecting environmental stimuli and facilitating communication.</p> Signup and view all the answers

What distinguishes hexapods from other arthropod groups in terms of leg structure?

<p>Hexapods have three pairs of walking legs, distinguishing them from other arthropod groups with different numbers and arrangements of legs.</p> Signup and view all the answers

How do aquatic food webs benefit from the diversity of organisms within the Crustacea subphylum?

<p>The diversity of Crustacea contributes significantly to aquatic food webs as they serve as both primary consumers and prey for larger organisms.</p> Signup and view all the answers

In what ways do the characteristics of Cirripedia contribute to their success in marine environments?

<p>Cirripedia, or barnacles, have adaptations like a calcareous shell for protection and filter feeding mechanisms that allow them to thrive in marine environments.</p> Signup and view all the answers

Study Notes

Ecdysozoan Protostomes

  • Ecdysozoans are protostomes that shed their protective external covering (ecdysis) regularly
  • They reproduce sexually, with separate sexes and internal fertilization
  • Three phyla: Nematoda, Onychophora, and Arthropoda

Phylum: Nematoda

  • Also known as roundworms
  • Extremely abundant and found everywhere
  • Representing a significant portion of the entire matter in the universe
  • Found in various ecosystems: mountains, hills, valleys, rivers, lakes, and oceans
  • Play a key ecological role in breaking down organic matter and recycling nutrients.
  • Can be agricultural pests, harming plant roots and infesting farm animals
  • Some nematodes are beneficial in ecological systems, helping with decomposition
  • Have medical importance, including causing diseases like hookworm and filariasis
  • Possess a cuticle as a protective layer against digestive enzymes
  • Have a simple body plan, with longitudinal muscles for movement
  • Lack a respiratory system, relying on diffusion for gas exchange
  • Possess a pseudocoelom, a fluid-filled body cavity

Phylum: Onychophora

  • Also known as velvet worms
  • Live under stones, logs, and forest litter, especially in tropical and moist temperate areas
  • Segmented bodies are characterized by multiple pairs of unjointed legs.
  • Segmented bodies with numerous pairs of excretory organs
  • Possess a flexible cuticle, an open circulatory system, and specialized respiratory systems
  • Characterized by large brains, jaws, and tiny claws on their feet
  • Many species reproduce by producing live young

Phylum: Arthropoda

  • 50% of animal species on Earth

  • Characterized by multiple jointed appendages and rigid chitinous exoskeletons
  • Exoskeleton advantages: protective, attachment site for muscles, waterproof
  • Exoskeleton disadvantage: cannot expand, limiting growth, requiring ecdysis (shedding)
  • Gas exchange occurs through a specialized respiratory system not through skin
  • Body is divided into segments (head, thorax, and abdomen)
  • Body segments can be fused, reducing the number of segments
  • Open circulatory system with a heart pumping haemolymph
  • Have a complete digestive system
  • Nervous system characterized by cephalization (brain, nerve cord, touch receptors), chemical sensors, and compound/simple eyes, hearing organs
  • Includes extinct group Trilobita
  • Further categorized into extant groups: Chelicerata, Myriapoda, Pancrustacea (with "Crustacea," Oligostraca, and Xenocarida), and Hexapoda

Class: Trilobita

  • Extinct since Permian period
  • Considered ancient arthropods
  • Body divided into three longitudinal lobes
  • Ovoid, dorsoventrally flattened, and heavily armored
  • Characterized by a head, thorax, and abdomen with walking legs
  • Possess a pair of chemosensory antennae and compound eyes

Subphylum: Chelicerata (Arachnida & Merostomata)

  • Two major body regions: cephalothorax and abdomen
  • Appendages on head/cephalothorax: Chelicerae (fang-like structures), Pedipalps (grasping/sensory organs) or walking legs.
  • Four pairs of walking legs on cephalothorax
  • Respiratory structures derived from ancestral appendages on abdomen
  • Merostomata (horseshoe crabs): carnivorous bottom feeders in coastal waters. Horseshoe-shaped shells with gills modified for walking legs.
  • Arachnida: highly modified chelicerae and pedipalps (predators). Spiders, scorpions, ticks, and mites.

Subphylum: Myriapoda

  • Centipedes and millipedes
  • All terrestrial
  • Two body regions: head (one pair antennae, simple eyes) and a trunk with many segments each having walking legs
  • Centipedes: one pair of legs per segment, predators with powerful toxins
  • Millipedes: two pairs of legs per segment, slow herbivores or scavengers

Subphylum: Crustacea

  • Mostly aquatic and extremely active animals in marine and freshwater environments
  • Have specialized appendages including chelipeds, walking legs, and swimmerets

Subphylum: Hexapoda

  • Also known as insects
  • Most diverse and successful animals on Earth
  • Characterized by three body regions (head, thorax, and abdomen), three pairs of legs, and usually two pairs of wings.
  • Have a diverse array of mouthparts for various feeding strategies
  • Undergo different developmental stages (no metamorphosis, incomplete metamorphosis, or complete metamorphosis)

Specialized Insect Mouthparts

  • Insects exhibit a diverse array of specialized mouthparts for feeding
  • These include mandibles, maxillae, labrum, and labium.

Insect Development

  • Three basic patterns: no metamorphosis, incomplete metamorphosis (nymphs), complete metamorphosis (egg-larva-pupa-adult)
  • This developmental pattern determines the progression of insects in their respective life stages

Importance of Arthropods

  • Agricultural Importance: beneficial (pollinators like bees, some decomposers, and other essential parts of food chains), some harmful (destroy crops, etc.).
  • Medical Importance: transmit diseases, clean wounds, forensics
  • Economic Importance: essential for various food chains, produce essential products for humans like honey and silk

Morphological Characteristics of Arthropods

  • The following morphological features can be characterized on the tree (plot them on the tree):
    • Presence of compound or simple eyes
    • Sensory appendages on the head
    • Number of appendages on the head
    • Presence of chelicerae and pedipalps
    • Presence of mandibles
    • Appendages on the abdomen
    • Number of walking legs per segment
    • Aquatic or terrestrial

Study Break Questions (Chapter 31.7)

  1. A nematode's cuticle protects it from the digestive enzymes of its host
  2. Onychophora shares similar characteristics with Annelida and Arthropoda.
  3. Arthropods grow by molting (ecdysis) their rigid exoskeleton
  4. The number of body regions and head appendages differ among the arthropod groups (chelicerates, myriapods, insects, crustaceans)
  5. Incomplete metamorphosis involves a gradual transformation from nymph to adult, whereas complete metamorphosis involves a dramatic change like egg-larva-pupa-adult stage

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Lecture 4: Ecdysozoan Protostomes PDF

Description

This quiz focuses on the Ecdysozoan protostomes, specifically the Nematoda phylum, commonly known as roundworms. Learn about their ecological roles, reproductive methods, and medical significance. Explore how they contribute to various ecosystems and the challenges they pose as agricultural pests.

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