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Diversity of Protists III01:27

Diversity of Protists III

Rhizaria are a diverse group of unicellular protists characterized by their threadlike cytoplasmic extensions known as pseudopodia. These structures aid in both locomotion and feeding, giving Rhizaria an amoeboid appearance. Their amoeboid morphology once led to taxonomic confusion, but molecular phylogenetics has clarified their evolutionary placement and emphasized their shared use of pseudopodia despite divergent lineages.This clade comprises diverse lineages such as Chlorarachniophyta,...
The Fossil Record02:56

The Fossil Record

The fossil record documents only a small fraction of all organisms that have ever inhabited Earth. Fossilization is a rare process, and most organisms never become fossils. Moreover, the fossil record only exhibits fossils that have been discovered. Nevertheless, sedimentary rock fossils of long-lived, abundant, hard-bodied organisms dominate the fossil record. These fossils offer valuable information, such as an organism's physical form, behavior, and age. Studying the fossil record helps...
Lampbrush Chromosomes01:51

Lampbrush Chromosomes

In 1882, Flemming observed lampbrush chromosomes (LBC) in salamander eggs. Later in 1892, Rückert observed LBCs in shark egg cells and coined the term "lampbrush chromosomes" because they looked like brushes used to clean kerosene lamps.
LBCs are made up of two pairs of conjugating homologous chromatids. Each chromatid consists of alternatively positioned regions of condensed-inactive chromatin and loosely placed-active side loops, which can be contracted and extended. The loops resemble the...
Tooth Anatomy01:21

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.
Convergent Evolution01:54

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...
Compact Bone01:27

Compact Bone

Most bones contain compact and spongy osseous tissue, but their distribution and concentration vary based on the bone's overall function.
Compact bone, also called cortical bone, is the denser, stronger of the two types of bone tissue. It is found under the periosteum and in the diaphyses of long bones, where it provides support and protection. The microscopic structural unit of compact bone is called an osteon, or haversian system. Each osteon is composed of concentric rings of calcified...

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Related Experiment Video

Updated: Jul 12, 2026

Characterization of Calcification Events Using Live Optical and Electron Microscopy Techniques in a Marine Tubeworm
15:39

Characterization of Calcification Events Using Live Optical and Electron Microscopy Techniques in a Marine Tubeworm

Published on: February 28, 2017

Conodont pearls?

B F Glenister, G Klapper, K M Chauff

    Science (New York, N.Y.)
    |August 13, 1976
    PubMed
    Summary

    Dimpled spheres found with conodont fossils are likely pearls secreted by the conodont animal. These microfossils offer new insights into the biology of these ancient marine organisms.

    Area of Science:

    • Paleontology
    • Microbiology
    • Geochemistry

    Background:

    • Conodonts are enigmatic, toothlike microfossils from marine rocks (Cambrian-Triassic).
    • Sporadic, dimpled spheres (<1mm) are found with conodonts.
    • These spheres share identical chemical composition and microstructure with conodonts.

    Purpose of the Study:

    • To investigate the nature of dimpled spheres found alongside conodont microfossils.
    • To determine the biological origin of these enigmatic spheres.

    Main Methods:

    • Analysis of mineralogy, morphology, and occurrence of the dimpled spheres.
    • Comparison of sphere characteristics with known biogenic materials.

    Main Results:

    • The dimpled spheres exhibit identical chemical composition and microstructure to conodonts.

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    Characterization Of Multi-layered Fish Scales (Atractosteus spatula) Using Nanoindentation, X-ray CT, FTIR, and SEM
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    Characterization Of Multi-layered Fish Scales (Atractosteus spatula) Using Nanoindentation, X-ray CT, FTIR, and SEM

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    Last Updated: Jul 12, 2026

    Characterization of Calcification Events Using Live Optical and Electron Microscopy Techniques in a Marine Tubeworm
    15:39

    Characterization of Calcification Events Using Live Optical and Electron Microscopy Techniques in a Marine Tubeworm

    Published on: February 28, 2017

    Dissection and Flat-mounting of the Threespine Stickleback Branchial Skeleton
    08:02

    Dissection and Flat-mounting of the Threespine Stickleback Branchial Skeleton

    Published on: May 7, 2016

    Characterization Of Multi-layered Fish Scales (Atractosteus spatula) Using Nanoindentation, X-ray CT, FTIR, and SEM
    10:06

    Characterization Of Multi-layered Fish Scales (Atractosteus spatula) Using Nanoindentation, X-ray CT, FTIR, and SEM

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  • Physical characteristics (mineralogy, morphology, occurrence) are consistent with pearl formation.

    • Conclusions:

    • The dimpled spheres are interpreted as pearls secreted by the conodont-bearing animal.
    • This finding provides potential insights into the biology and behavior of conodonts.