Romer's gap

Examples of Romer's gap in the following topics:

• Gaps in the Fossil Record

  • Romer's gap is an example of an apparent gap in the tetrapod fossil record used in the study of evolutionary biology.
  • These gaps represent periods from which no relevant fossils have been found.
  • Romer's gap is named after paleontologist Alfred Romer, who first recognized it.
  • Romer's gap spanned from approximately 360 to 345 million years ago, corresponding to the first 15 million years of the Carboniferous Period.
  • The bank of the Whiteadder Water in Scotland is one of the few known localities bearing fossils of tetrapods from Romer's gap.

• Intercellular Junctions

  • Plasmodesmata are junctions between plant cells, whereas animal cell contacts are carried out through tight junctions, gap junctions, and desmosomes.
  • Lastly, similar to plasmodesmata in plant cells, gap junctions are the third type of direct junction found within animal cells.
  • Structurally, however, gap junctions and plasmodesmata differ.
  • Gap junctions are particularly important in cardiac muscle.
  • The electrical signal for the muscle to contract is passed efficiently through gap junctions, which allows the heart muscle cells to contract in tandem.

• Interphase

  • The first stage of interphase is called the G1 phase (first gap) because, from a microscopic aspect, little change is visible.

• Forms of Signaling

  • There are four categories of chemical signaling found in multicellular organisms: paracrine signaling, endocrine signaling, autocrine signaling, and direct signaling across gap junctions .
  • Gap junctions in animals and plasmodesmata in plants are connections between the plasma membranes of neighboring cells.
  • The distance between the presynaptic cell and the postsynaptic cell—called the synaptic gap—is very small and allows for rapid diffusion of the neurotransmitter.
  • In chemical signaling, a cell may target itself (autocrine signaling), a cell connected by gap junctions, a nearby cell (paracrine signaling), or a distant cell (endocrine signaling).
  • Signaling via gap junctions involves signaling molecules moving directly between adjacent cells.

• Complex Tissue Structure

  • As multicellular organisms, animals differ from plants and fungi because their cells don't have cell walls; their cells may be embedded in an extracellular matrix (such as bone, skin, or connective tissue); and their cells have unique structures for intercellular communication (such as gap junctions).

• Types of Leaf Forms

  • The leaf shape may also be formed of lobes where the gaps between lobes do not reach to the main vein.

• ATP and Muscle Contraction

  • As soon as the actin-binding sites are uncovered, the high-energy myosin head bridges the gap, forming a cross-bridge.

• Neurons

  • Along these types of axons, there are periodic gaps in the myelin sheath.
  • These gaps, called "nodes of Ranvier," are sites where the signal is "recharged" as it travels along the axon.

• DNA Replication in Prokaryotes

  • The primers are removed by the exonuclease activity of DNA pol I, while the gaps are filled in by deoxyribonucleotides.
  • DNA ligase seals the gaps between the Okazaki fragments, joining the fragments into a single DNA molecule.

• DNA Repair

  • Once the bases are filled in, the remaining gap is sealed with a phosphodiester linkage catalyzed by DNA ligase .
  • The gap is now filled with the correctly-paired base.