Animal Development: Germ Layers and Body Plans
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Questions and Answers

What is one of the main advantages of the amniotic egg?

  • Ability to swim
  • Increased access to terrestrial environments (correct)
  • Increase in body size
  • Lower metabolic rates
  • Which group of animals is characterized by the presence of mammary glands and hair?

  • Reptiles
  • Amphibians
  • Mammals (correct)
  • Birds
  • What is a key characteristic of ectotherms?

  • Body heat comes primarily from the environment (correct)
  • Generate their own body heat
  • Depend on metabolic processes for heat
  • Maintain constant internal body temperature
  • Which of the following is NOT a group included under the class of reptiles?

    <p>Frogs</p> Signup and view all the answers

    What reproduction method involves the embryo developing in an egg sac attached to the mother?

    <p>Viviparous</p> Signup and view all the answers

    Which of these accurately describes monotremes?

    <p>They lay leathery eggs</p> Signup and view all the answers

    What is the primary distinguishing factor among the three major lineages of mammals?

    <p>Pregnancy and gestation methods</p> Signup and view all the answers

    Which group includes tuataras?

    <p>Sphenodontia</p> Signup and view all the answers

    What is the primary distinction between coelomates and acoelomates?

    <p>Coelomates have a true body cavity, while acoelomates do not.</p> Signup and view all the answers

    Which characteristic is NOT associated with the phylum Cnidaria?

    <p>Complete digestive system</p> Signup and view all the answers

    Which of the following statements correctly describes amphibians?

    <p>They undergo a complete metamorphosis.</p> Signup and view all the answers

    What defines a protostome during the early stages of development?

    <p>The mouth develops from the blastopore.</p> Signup and view all the answers

    Which class of Mollusca is characterized by a complete digestive system and bilateral symmetry?

    <p>Gastropoda</p> Signup and view all the answers

    Which characteristic is true for all members of Phylum Echinodermata during adulthood?

    <p>They display pentaradial symmetry.</p> Signup and view all the answers

    What is a defining feature of the Chordata phylum?

    <p>Development of a notochord.</p> Signup and view all the answers

    Which of the following statements is false about roundworms (Nematoda)?

    <p>They usually undergo complete metamorphosis.</p> Signup and view all the answers

    What type of symmetry is primarily exhibited by cnidarians?

    <p>Radial/Biradial</p> Signup and view all the answers

    Which group of animals is referred to as 'jawless fish'?

    <p>Agnathastomes</p> Signup and view all the answers

    Study Notes

    Diploblastic vs. Triploblastic

    • Diploblastic organisms have two primary germ layers: ectoderm and endoderm
    • Triploblastic organisms have three primary germ layers: ectoderm, endoderm, and mesoderm

    Body Plans of Animals

    • Asymmetrical animals lack any symmetry
    • Radially symmetrical animals have body parts arranged around a central axis
    • Bilaterally symmetrical animals have a distinct left and right side

    Acoelomates vs. Coelomates

    • Coelom refers to a body cavity derived from mesoderm tissue
    • Acoelomates are triploblastic animals without a coelom, with mesoderm filled with tissue
    • Coelomates (also known as eucoelomates) are triploblastic animals with a true coelom, surrounded by mesoderm tissue
    • Pseudocoelomates are triploblastic animals with a coelom partially lined by mesoderm and endoderm

    Protostomes vs. Deuterostomes

    • Protostomes develop the mouth from the blastopore, considered primitive
    • Deuterostomes develop the anus from the blastopore, considered novel

    Porifera

    • Sponges are asymmetrical and filter feeders
    • They reproduce both sexually and asexually
    • Adult sponges are immobile while larvae are motile
    • They are neither deuterostome nor protostome, nor triploblastic nor diploblastic
    • Sponges lack true tissue

    Cnidaria

    • Jellyfish display radial or biradial symmetry
    • They have an incomplete digestive system and are diploblastic
    • Neither protostome nor deuterostome
    • Exist in two forms: polyp (sessile) and medusa (motile)

    Platyhelminthes

    • Flatworms are bilaterally symmetrical, triploblastic, and protostomes
    • They are acoelomates with an incomplete digestive system
    • They reproduce both sexually and asexually

    Mollusca

    • Mollusks are bilaterally symmetrical, triploblastic, and protostomes
    • They have complete digestive systems and are divided into three classes:
      • Bivalvia: Clams, mussels, oysters
      • Gastropoda: Snails, slugs
      • Cephalopoda: Octopus, squid

    Annelida

    • Segmented worms are triploblastic, protostomes, and coelomates
    • They exhibit bilateral symmetry with simple cephalization and segmentation
    • They are motile with complete digestive systems

    Nematoda

    • Roundworms are triploblastic, protostomes, and pseudocoelomates
    • They are bilaterally symmetrical with primitive cephalization
    • They are motile with complete digestive systems and molt an exoskeleton
    • They reproduce both sexually and asexually

    Arthropoda

    • Insects are triploblastic, bilaterally symmetrical, and coelomates
    • They have complete digestive systems and are protostomes with jointed appendages and body segmentation

    Arthropoda (Largest Phylum)

    • They are divided into multiple classes:
      • Crustacea: Mostly aquatic
      • Myriapoda: Terrestrial
      • Chelicerata: First set of appendages are distinct
      • Trilobita: All extinct
      • Hexapoda: True insects

    Echinodermata

    • Starfish are bilaterally symmetrical in larval stage and radial or pentaradial in adult stage
    • They are triploblastic, coelomates, and deuterostomes
    • They are invertebrates with complete digestive systems

    Chordata

    • Chordates are bilaterally symmetrical, deuterostomes, and triploblastic coelomates
    • They possess novel adaptations:
      • Notochord
      • Dorsal hollow nerve cord
      • Pharyngeal slits
      • Post-anal tail
      • Endostyle/thyroid gland

    Chordata Invertebrates

    • Cephalochordata (lancelets): possess notochord, dorsal hollow nerve cord, pharyngeal slits, post-anal tail, and endostyle
    • Urochordata (tunicates): possess pharyngeal slits and endostyle

    Fishes

    • Agnathans (jawless fish): possess a cranium, includes Hagfish (Myxini) and Lamprey (Petromyzontidae)
    • Gnathostomes (jawed fish):
      • Osteichthyes (bony jawed fish): marine and freshwater, possess swim bladder for buoyancy, vertically flattened
      • Chondrichthyes (sharks, rays, skates): mostly marine, cartilaginous, well-developed sensory system
    • All fish have a two-chambered heart and a circulatory system

    Amphibians

    • Include frogs, salamanders, and caecilians
    • They exhibit a dual life transitioning between aquatic and terrestrial environments
    • They are water-dependent for reproduction
    • First tetrapods to evolve
    • Undergo complete metamorphosis
    • Divided into three orders:
      • Urodela (salamanders): Lungless
      • Anura (frogs and toads): capable of vocalization, have lungs and an eardrum
      • Apoda (caecilians): lack limbs, a derived trait

    Reptiles

    • Lizards, snakes, alligators, turtles, and others
    • Novel adaptation of the amniotic egg
    • Respiration in lungs
    • Shedding of skin
    • Divided into four orders:
      • Sphenodontia: Tuataras
      • Squamata: Lizards and snakes
      • Testudines: Turtles
      • Crocodilia: Alligators, crocodiles, etc.
    • Ectotherms: Body heat comes from the environment

    Amniotic Egg

    • Advantages:
      • Increased access to terrestrial environments
      • Less competition for pools
      • Decreased predation
    • Examples:
      • Reptiles
      • Birds
      • Mammals

    Amniotic Egg & Evolution

    • The evolution of the amniotic egg allowed organisms to reproduce without standing water, allowing for greater terrestrial expansion

    Birds

    • Novel trait of feathers
    • Endotherms: regulate body temperature internally
    • Complex sensory system
    • Sexual reproduction
    • Low body weight for flight
    • Possess a cloaca: a body cavity connected to the digestive, urinary, and reproductive systems, eliminating the need for solid waste

    Mammals

    • Hair and mammary glands are novel adaptations for mammary glands
    • Endotherms: regulate body temperature internally
    • Secretory skin
    • Adductor muscles in the jaw: facilitate up-down and side-to-side movement
    • Four-chambered heart
    • Kidneys
    • External ears
    • Brain with cerebral cortex

    Three Major Lineages of Mammals

    • Distinguished primarily by pregnancy and gestation:
      • Monotremes: Lay leathery eggs
      • Marsupials: Short placental gestation, born fetal and complete development occurs in a pouch
      • Placentals: Placenta connects fetus to mother

    Offspring Production

    • Viviparous: Egg sac remains attached to mother, embryo obtains nutrients from the mother, live births (most mammals)
    • Oviparous: Fertilized eggs are laid outside the mother and obtain nutrients from the yolk (fish, reptiles, birds)
    • Ovoviviparous: Fertilized egg develops inside the mother, embryo relies on the yolk for nutrients and hatches inside the mother, young are fully developed at birth (sharks, snakes, lizards)

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    Description

    This quiz covers the differences between diploblastic and triploblastic organisms, various body plans of animals, and the distinctions between acoelomates and coelomates. Additionally, it examines the developmental pathways of protostomes and deuterostomes, emphasizing their key features. Test your understanding of these fundamental concepts in animal biology.

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