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Location of ovules inside a Helleborus foetidus flower. In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the integument, forming its outer layer, the nucellus (or remnant of the megasporangium), and the female gametophyte (formed from a haploid megaspore) in its center.
The epiblast was first discovered by Christian Heinrich Pander (1794-1865), a Baltic German biologist and embryologist. With the help of anatomist Ignaz Döllinger (1770–1841) and draftsman Eduard Joseph d'Alton (1772-1840), Pander observed thousands of chicken eggs under a microscope, and ultimately discovered and described the chicken blastoderm and its structures, including the epiblast. [1]
The chalaza (/ k ə ˈ l eɪ z ə /; from Ancient Greek χάλαζα (khálaza) 'hailstone'; pl.: chalazas or chalazae / k ə ˈ l eɪ z i /) is a structure inside bird eggs and plant ovules. It attaches or suspends the yolk or nucellus within the larger structure.
The eggs are usually few in number, and the embryos have enough food to go through full fetal development in most groups. [7] Macrolecithal eggs are only found in selected representatives of two groups: Cephalopods and vertebrates. [7] [22] Macrolecithal eggs go through a different type of development than other eggs.
During blastulation, a significant amount of activity occurs within the early embryo to establish cell polarity, cell specification, axis formation, and to regulate gene expression. [7] In many animals, such as Drosophila and Xenopus , the mid blastula transition (MBT) is a crucial step in development during which the maternal mRNA is degraded ...
Six small non-avian dinosaur eggs, no bigger than grapes, were discovered during a field study in Ganzhou, China, in 2021. These eggs now mark the smallest-ever found in the world.
An oocyte (/ ˈ oʊ ə s aɪ t /, oöcyte, or ovocyte is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in a female fetus in the ovary during female gametogenesis. The female germ cells produce a primordial germ cell (PGC), which then undergoes mitosis ...
The creatures were found in “absolutely lightless” areas of forest caves, researchers said. ‘Giant’ cave-dwelling creature — carrying 6 eggs — found in Ecuador. It’s a new species