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相关概念视频

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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相关实验视频

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

没有珍珠吗?

B F Glenister, G Klapper, K M Chauff

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

    在虫化石中发现的形球体很可能是虫动物分泌的珍珠. 这些微化石为这些古代海洋生物的生物学提供了新的见解.

    科学领域:

    • 古生物学的古生物学
    • 微生物学 微生物学
    • 地质化学 地质化学

    背景情况:

    • 孔诺顿是一种神秘的,类似牙的微化石,来自海洋岩石 (坎布里亚-三叠纪).
    • 偶发的,有的球体 (<1毫米) 在鱼身上被发现.
    • 这些球体与体具有相同的化学成分和微观结构.

    研究的目的:

    • 为了研究与虫微化石一起发现的形球体的性质.
    • 为了确定这些神秘的球体的生物起源.

    主要方法:

    • 分析矿物学,形态学和洞穴状球体的发生情况.
    • 球体特征与已知的生物原材料进行比较.

    主要成果:

    • 洞穴状的球体表现出与鱼相同的化学成分和微观结构.
    • 物理特征 (矿物学,形态学,发生) 与珍珠形成是一致的.

    结论:

    • 洞穴状的球体被解释为由牙动物分泌的珍珠.
    • 这一发现提供了潜在的洞察力,对生物学的生物学和行为conodonts.

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    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

    Published on: July 10, 2014

    相关实验视频

    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

    Published on: July 10, 2014