Videos de Conceptos Relacionados
Types of Selection
Natural selection influences the frequencies of particular alleles and phenotypes within populations in several different ways. Primarily, natural selection can be directional, stabilizing, or disruptive. Directional selection favors one extreme trait and shifts the population towards that phenotype while selecting against individuals displaying alternate traits. Stabilizing selection favors an intermediate trait with a narrow range of variation. Deviation from the optimal phenotype towards an...
Convergent Evolution
Evolution shapes the features of organisms over time, ensuring that they are suited for the environments in which they live. Sometimes, selection pressure leads to the rise of similar but unrelated adaptations in organisms with no recent common ancestors, a process known as convergent evolution.The structures that arise from convergent evolution are called analogous structures. They are similar in function even if they are dissimilar in structure. Further, structures can be analogous while also...
Cranial Bones: Superior and Posterior View
The superior view of the cranium shows the frontal and paired parietal bones.
The frontal bone is the single bone that forms the forehead. At its anterior midline, between the eyebrows, there is a slight depression called the glabella. The frontal bone also forms the supraorbital margin of the orbit. Near the middle of this margin is the supraorbital foramen, the opening that provides passage for a sensory nerve to the forehead. The frontal bone is thickened just above each supraorbital margin,...
The frontal bone is the single bone that forms the forehead. At its anterior midline, between the eyebrows, there is a slight depression called the glabella. The frontal bone also forms the supraorbital margin of the orbit. Near the middle of this margin is the supraorbital foramen, the opening that provides passage for a sensory nerve to the forehead. The frontal bone is thickened just above each supraorbital margin,...
The Hyoid Bone
The hyoid bone is a small U-shaped bone located in the upper neck at the level of the inferior mandible, with its tips pointing posteriorly. It does not directly articulate with any other bone in the body. The hyoid acts as the attachment site for the tongue, the larynx, and the pharynx. It is held in position by a series of small muscles attached from above or below. These muscles help to move the hyoid up/down or forward/back in coordination with movements of the tongue, larynx, and pharynx...
Teeth
The formation of teeth, also known as odontogenesis, is a complex process that begins in utero, around the sixth week of embryonic development. There are three stages to this process: the bud stage, the cap stage, and the bell stage.
In the bud stage, the tooth germ (an aggregation of cells) starts to form in the developing jawbone. During the cap stage, the tooth germ differentiates into enamel organ, dental papilla, and dental sac, which will later develop into the tooth's enamel, dentin and...
In the bud stage, the tooth germ (an aggregation of cells) starts to form in the developing jawbone. During the cap stage, the tooth germ differentiates into enamel organ, dental papilla, and dental sac, which will later develop into the tooth's enamel, dentin and...
Tooth Anatomy
The human tooth enables us to eat a variety of foods, speak clearly, and even aid in shaping our faces. Teeth are composed of various elements that work together. Here's a detailed look at the anatomy of a human tooth.
The Crown, Neck, and Root
The visible part of the tooth is referred to as the crown. It's covered by enamel, the hardest substance in the human body. The crown is uniquely shaped for each type of tooth, allowing for different functions such as cutting, tearing, or grinding food.
The Crown, Neck, and Root
The visible part of the tooth is referred to as the crown. It's covered by enamel, the hardest substance in the human body. The crown is uniquely shaped for each type of tooth, allowing for different functions such as cutting, tearing, or grinding food.
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Los dientes en el ichthyornis (clase: aves)
Science (New York, N.Y.)
|March 25, 1977
Resumen
Las aves dentadas como Ichthyornis y Hesperornis tenían dientes aplanados. Nuevos fósiles sugieren que los dientes de Ichthyornis estaban en ranuras, no en cuencas, potencialmente variando con la edad.
Área de la Ciencia:
- Paleontología Paleontología.
- Biología evolutiva Biología evolutiva.
- Zoología de los vertebrados Zoología de los vertebrados.
Sus antecedentes:
- Hesperornis e Ichthyornis son aves dientes extintas.
- Estas aves, junto con Archaeopteryx, poseían dientes aplanados únicos con raíces expandidas.
- La comprensión previa sugería que los dientes de Ichthyornis tenían encajones, similares a los de Archaeopteryx.
Objetivo del estudio:
- Para investigar el implante dental en Ichthyornis.
- Para comparar la morfología dental y la implantación entre Hesperornis, Ichthyornis y Archaeopteryx.
- Para determinar si la presencia de alvéolos dentales en las aves depende de la edad.
Principales métodos:
- Análisis comparativo de la dentición de aves fosilizadas.
- Examen de nuevos ejemplares fósiles de Ichthyornis.
- Evaluación morfológica de las raíces de los dientes y las estructuras de la mandíbula.
Principales resultados:
- Nuevos especímenes de Ichthyornis revelan que los dientes estaban colocados en una ranura, no en cuencas.
- Esto contrasta con informes anteriores y se alinea con la implantación dental de Hesperornis.
- Los fósiles de Ichthyornis estudiados eran de un individuo adulto, pero no envejecido.
Conclusiones:
- La implantación dental en Ichthyornis parece ser una ranura, no un zócalo, tipo.
- La presencia o ausencia de cuencas dentales en las aves podría estar influenciada por la edad.
- Este hallazgo ofrece nuevos conocimientos sobre la evolución dental de las aves.

