AnisogamyAnisogamy is a form of sexual reproduction that involves the union or fusion of two gametes that differ in size and/or form. The smaller gamete is male, a sperm cell, whereas the larger gamete is female, typically an egg cell. Anisogamy is predominant among multicellular organisms. In both plants and animals gamete size difference is the fundamental difference between females and males. Anisogamy most likely evolved from isogamy.
SpermatozoonA spermatozoon (spərˌmætəˈzoʊ.ən,_ˌspɜrmətə-; also spelled spermatozoön; : spermatozoa; ) is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote. (A zygote is a single cell, with a complete set of chromosomes, that normally develops into an embryo.) Sperm cells contribute approximately half of the nuclear genetic information to the diploid offspring (excluding, in most cases, mitochondrial DNA).
Multicellular organismA multicellular organism is an organism that consists of more than one cell, in contrast to unicellular organism. All species of animals, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni- and partially multicellular, like slime molds and social amoebae such as the genus Dictyostelium. Multicellular organisms arise in various ways, for example by cell division or by aggregation of many single cells. Colonial organisms are the result of many identical individuals joining together to form a colony.
OvuleIn 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 female gametophyte — specifically termed a megagametophyte— is also called the embryo sac in angiosperms. The megagametophyte produces an egg cell for the purpose of fertilization. The ovule is a small structure present in the ovary.
MitosisIn cell biology, mitosis (maɪˈtoʊsɪs) is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is maintained. Therefore, mitosis is also known as equational division. In general, mitosis is preceded by S phase of interphase (during which DNA replication occurs) and is often followed by telophase and cytokinesis; which divides the cytoplasm, organelles and cell membrane of one cell into two new cells containing roughly equal shares of these cellular components.
GenomeIn the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as regulatory sequences (see non-coding DNA), and often a substantial fraction of junk DNA with no evident function. Almost all eukaryotes have mitochondria and a small mitochondrial genome.
Somatic cellIn cellular biology, a somatic cell (), or vegetal cell, is any biological cell forming the body of a multicellular organism other than a gamete, germ cell, gametocyte or undifferentiated stem cell. Such cells compose the body of an organism and divide through the process of binary fission and mitotic division. In contrast, gametes are cells that fuse during sexual reproduction, germ cells are cells that give rise to gametes, and stem cells are cells that can divide through mitosis and differentiate into diverse specialized cell types.
IsogamyIsogamy is a form of sexual reproduction that involves gametes of the same morphology (indistinguishable in shape and size), found in most unicellular eukaryotes. Because both gametes look alike, they generally cannot be classified as male or female. Instead, organisms undergoing isogamy are said to have different mating types, most commonly noted as "+" and "−" strains. The literal meaning of isogamy is "equal marriage" which refers to equal contribution of resources by both gametes to a zygote.
StamenThe stamen (: stamina or stamens) is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium. A stamen typically consists of a stalk called the filament and an anther which contains microsporangia. Most commonly anthers are two-lobed (each lobe is termed a locule) and are attached to the filament either at the base or in the middle area of the anther. The sterile tissue between the lobes is called the connective, an extension of the filament containing conducting strands.
ArchegoniumAn archegonium (: archegonia), from the ancient Greek ἀρχή ("beginning") and γόνος ("offspring"), is a multicellular structure or organ of the gametophyte phase of certain plants, producing and containing the ovum or female gamete. The corresponding male organ is called the antheridium. The archegonium has a long neck canal or venter and a swollen base. Archegonia are typically located on the surface of the plant thallus, although in the hornworts they are embedded.
