Questions and Answers
Which of the following is a characteristic feature of animal multicellularity?
Unique intracellular communication
What is the main mode of reproduction in most animals?
Sexual reproduction
What type of life cycle do most animals exhibit?
Diplobiontic
Which developmental stage involves the formation of the blastula in animal embryos?
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What is the primary function of connective tissues in animals?
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Which tissue type is responsible for movement in animals?
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What is the role of Homeobox genes in animal development?
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Which type of animal symmetry is characterized by an arrangement around a central axis with parts radiating outward?
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What is the significance of germ layers in animal development?
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Which type of animal has a coelom that is derived from the mesoderm germ layer?
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Which group of animals has bilateral symmetry and cephalization enabling sense organs to be concentrated in the head region?
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What distinguishes coelomates from acoelomates in terms of body structure and function?
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Study Notes
Features of the Animal Kingdom
- Multicellularity and complex tissue structure are characteristics of the animal kingdom.
- Heterotrophy and motility are also features of animals.
- Animals have a diplontic life cycle, with 2n (diploid) multicellular organisms and 1n (haploid) gametes.
- Mainly, animals reproduce sexually, with a few species exhibiting asexual reproduction.
Animal Body Plan and Development
- Fixed body plan and embryonic developmental stages are characteristic of animals.
- Animal development involves cleavage, blastulation, and gastrulation, forming primary germ layers.
- Organogenesis gives rise to tissues, organs, and organ systems.
Germ Layers and Body Cavity
- Triploblastic animals have three primary germ layers: ectoderm, mesoderm, and endoderm.
- Diploblastic animals, like cnidarians and ctenophores, have two primary germ layers: ectoderm and endoderm.
- A coelom (body cavity) is present in most animals, derived from the mesoderm germ layer.
- Acoelomates, pseudocoelomates, and coelomates can be distinguished based on the presence and type of body cavity.
Homeobox Genes and Body Symmetry
- Homeotic (Hox) genes control embryonic development and determine body plan, segmentation, and appendage placement.
- Body symmetry is characterized as asymmetrical, radial, or bilateral, influencing the arrangement of body parts.
- Radial symmetry is suited for stationary or planktonic lifestyle, while bilateral symmetry allows for cephalization.
Classification of Animals
- Body plan, developmental pathway, number of tissue layers, and origin of mouth and anus are features used to classify animals.
- Animals can be characterized based on body symmetry, germ layers, and presence or absence of a coelom.
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