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The egg cell or ovum (pl.: ova) is the female reproductive cell, or gamete, [1] in most anisogamous organisms (organisms that reproduce sexually with a larger, female gamete and a smaller, male one). The term is used when the female gamete is not capable of movement (non- motile ).
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 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.
This glossary of biology terms is a list of definitions of fundamental terms and concepts used in biology, the study of life and of living organisms.It is intended as introductory material for novices; for more specific and technical definitions from sub-disciplines and related fields, see Glossary of cell biology, Glossary of genetics, Glossary of evolutionary biology, Glossary of ecology ...
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 ...
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 ...
The protective external layer of tissue on the stem s and root s of woody trees and shrubs; includes all of the living and non-living tissue external to the cambium. basal Situated or attached at or close to the base (of a plant or a phylogenetic tree diagram). basifixed Something attached by its base, e.g. an anther attached to the filament.