body plan

Examples of body plan in the following topics:

• Body Plans

  • Animal body plans can have varying degrees of symmetry and can be described as asymmetrical, bilateral, or radial.
  • Animal body plans follow set patterns related to symmetry.
  • In order to describe structures in the body of an animal it is necessary to have a system for describing the position of parts of the body in relation to other parts .
  • Animals exhibit different types of body symmetry.
  • The table illustrates common directional terms that are used to describe the position of body parts in relation to other body parts.

• Characteristics of the Animal Body

  • Every animal has a distinct body plan, adapted in response to environmental pressures, that limits its size and shape.
  • From a sponge to a worm to a goat, an organism has a distinct body plan that limits its size and shape.
  • The term body plan is the "blueprint" encompassing aspects such as symmetry, segmentation, and limb disposition.
  • Body plans have been considered to have evolved in a geologically-sudden flash during the Cambrian Explosion (roughly 542 million years ago).
  • However, there is also evidence of a more gradual development of body plans.

• Animal Characterization Based on Body Symmetry

  • Animals can be classified by three types of body plan symmetry: radial symmetry, bilateral symmetry, and asymmetry.
  • At a very basic level of classification, true animals can be largely divided into three groups based on the type of symmetry of their body plan: radially symmetrical, bilaterally symmetrical, and asymmetrical.
  • This form of symmetry marks the body plans of animals in the phyla Ctenophora (comb jellies) and Cnidaria (corals, sea anemones, and other jellies) .
  • Only members of the phylum Porifera (sponges) have no body plan symmetry.
  • Differentiate among the ways in which animals can be characterized by body symmetry

• Class Anthozoa

  • The class Anthozoa includes all cnidarians that exhibit a polyp body plan only ; in other words, there is no medusa stage within their life cycle.
  • It may extend for up to two-thirds the length of the body before opening into the gastrovascular cavity.
  • The sea anemone (a), like all anthozoans, has only a polyp body plan (b).

• Phylum Cnidaria

  • Animals in this phylum display two distinct morphological body plans: polyp or "stalk" and medusa or "bell" .
  • Some cnidarians are polymorphic, having two body plans during their life cycle.
  • All cnidarians show the presence of two membrane layers in the body that are derived from the endoderm and ectoderm of the embryo.
  • The nervous system is primitive, with nerve cells scattered across the body.
  • Cnidarians have two distinct body plans, the medusa (a) and the polyp (b).

• Class Scyphozoa

  • In scyphozoans, nerve cells are scattered over the entire body.
  • These animals possess a ring of muscles lining the dome of the body, which provides the contractile force required to swim through water.
  • The life cycle of these animals can be described as polymorphic because they exhibit both a medusal and polypoid body plan at some point .

• Vertebrate Axis Formation

  • Through the expression patterns of different genes, the three axes of the body are established, aiding in tissue and organ development.
  • As the body forms, it must develop in such a way that cells, tissues, and organs are organized correctly along these axes.
  • In early embryonic development, the formation of the primary body axes is a crucial step in establishing the overall body plan of each particular organism.
  • Wnt signaling is also involved in the axis formation of specific body parts and organ systems that are a part of later development.
  • Animal bodies have three axes for symmetry: anterior/posterior (front/behind), dorsal/ventral (back/belly), and lateral/medial (side/middle).

• Neurons and Glial Cells

  • The nervous system coordinates the body's voluntary and involuntary actions and transmits signals between different parts of the body.
  • The PNS consists mainly of nerves, which are long fibers that connect the CNS to every other part of the body.
  • Even fundamental functions, like breathing and regulation of body temperature, are controlled by the nervous system .
  • There is debate among evolutionary biologists as to whether these different nervous system plans evolved separately or whether the invertebrate body plan arrangement somehow "flipped" during the evolution of vertebrates.
  • An athlete's nervous system is hard at work during the planning and execution of a movement as precise as a high jump.

• Morphology of Sponges

  • Water can enter into the spongocoel from numerous pores in the body wall.
  • In addition to the osculum, sponges have multiple pores called ostia on their bodies that allow water to enter the sponge.
  • In other sponges, ostia are formed by folds in the body wall of the sponge.
  • The cell body is embedded in mesohyl.
  • The sponge's (a) basic body plan is a cylinder shape with a large central cavity.

• Types of Circulatory Systems in Animals

  • Organisms that are more complex, but still have only two layers of cells in their body plan, such as jellies (Cnidaria) and comb jellies (Ctenophora), also use diffusion through their epidermis and internally through the gastrovascular compartment.
  • Exchange of fluids is assisted by the pulsing of the jellyfish body.
  • The blood then continues through the rest of the body before arriving back at the atrium; this is called systemic circulation.
  • The result is a limit in the amount of oxygen that can reach some of the organs and tissues of the body, reducing the overall metabolic capacity of fish.
  • The advantage to this arrangement is that high pressure in the vessels pushes blood to the lungs and body.