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An ovum (plural ova, from the Latin word ovum meaning egg
Egg (biology)

In most birds and reptiles, an egg is the zygote, resulting from fertilization of the ovum. To enable incubation the egg is usually kept within a favourable temperature range as it nourishes and protects the growing embryo....
 or egg cell
Egg (biology)

In most birds and reptiles, an egg is the zygote, resulting from fertilization of the ovum. To enable incubation the egg is usually kept within a favourable temperature range as it nourishes and protects the growing embryo....
) is a haploid female
Female

Female is the sex of an organism, or a part of an organism, which produces mobile ovum . The ova are defined as the larger gametes in a heterogamous reproduction system, while the smaller, usually motile gamete, the spermatozoon, is produced by the male....
 reproductive cell or gamete
Gamete

A gamete is a Cell that fuses with another gamete during fertilization in organisms that sexual reproduction. In species which produce two morphologically distinct types of gametes, and in which each individual produces only one type, a female is any individual which produces the larger type of gamete?called an ovum ?and a male produces th...
. Both animal
Animal

Animals are a major group of multicellular, eukaryotic organisms of the Kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life....
s and embryophyte
Embryophyte

The embryophytes are the most familiar group of plants. They include trees, flowers, ferns, mosses, and various other green land plants. All are complex multicellular eukaryotes with specialized reproductive organs....
s have ova. The term ovule is used for the young ovum of an animal, as well as the plant structure that carries the female gametophyte
Gametophyte

In plants and algae that undergo alternation of generations, a gametophyte is the multicellular structure, or phase, that is haploid, containing a single set of chromosomes:...
 and egg cell and develops into a seed after fertilization.






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Gray3
An ovum (plural ova, from the Latin word ovum meaning egg
Egg (biology)

In most birds and reptiles, an egg is the zygote, resulting from fertilization of the ovum. To enable incubation the egg is usually kept within a favourable temperature range as it nourishes and protects the growing embryo....
 or egg cell
Egg (biology)

In most birds and reptiles, an egg is the zygote, resulting from fertilization of the ovum. To enable incubation the egg is usually kept within a favourable temperature range as it nourishes and protects the growing embryo....
) is a haploid female
Female

Female is the sex of an organism, or a part of an organism, which produces mobile ovum . The ova are defined as the larger gametes in a heterogamous reproduction system, while the smaller, usually motile gamete, the spermatozoon, is produced by the male....
 reproductive cell or gamete
Gamete

A gamete is a Cell that fuses with another gamete during fertilization in organisms that sexual reproduction. In species which produce two morphologically distinct types of gametes, and in which each individual produces only one type, a female is any individual which produces the larger type of gamete?called an ovum ?and a male produces th...
. Both animal
Animal

Animals are a major group of multicellular, eukaryotic organisms of the Kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life....
s and embryophyte
Embryophyte

The embryophytes are the most familiar group of plants. They include trees, flowers, ferns, mosses, and various other green land plants. All are complex multicellular eukaryotes with specialized reproductive organs....
s have ova. The term ovule is used for the young ovum of an animal, as well as the plant structure that carries the female gametophyte
Gametophyte

In plants and algae that undergo alternation of generations, a gametophyte is the multicellular structure, or phase, that is haploid, containing a single set of chromosomes:...
 and egg cell and develops into a seed after fertilization. In lower plants
Non-vascular plant

Non-vascular plants is a general term for those plants without a vascular tissue . Although non-vascular plants lack these particular tissues, a number of non-vascular plants possess tissues specialized for internal transport of water....
 and algae
Algae

Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms. The largest and most complex marine forms are called seaweeds....
, the ovum is also often called oosphere.

Ova production

In higher animals, ova are produced by female gonad
Gonad

The gonad is the organ that makes gametes. The gonads in males are the testes and the gonads in females are the ovaries. The product, gametes, are haploid germ cells....
s (sexual glands) called ovaries
Ovary

The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in females are homology to testicle in males, in that they are both gonads and endocrine glands....
 and all of them are present at birth in mammal
Mammal

Mammals are a class of vertebrate animals whose name is derived from their distinctive feature, mammary glands, with which they feed their young....
s, and mature via oogenesis
Oogenesis

Oogenesis or rarely o?genesis is the creation of an ovum . It is the female process of gametogenesis. It involves the various stages of immature ova....
.

Human and mammal ova

Sperm Egg
Acrosome Reaction Diagram
In the viviparous animals (which include human
Human

A human being, also human or man, is a member of a species of bipedalism primates in the family Hominidae . Mitochondrial DNA evidence indicates that modern humans originated in east Africa about 200,000 years ago....
s and all other placental mammal
Eutheria

Eutheria are a group of mammals consisting of placental mammals plus all extinct mammals that are more closely related to living placentals than to living marsupials ....
s), the ovum is fertilized inside the female body, and the embryo
Embryo

An embryo is a multicellular organism ploidy eukaryote in its earliest stage of development, from the time of first cell division until birth, Egg , or germination....
 then develops inside the uterus
Uterus

The uterus is a major female hormone-responsive reproductive sex organ of most mammals, including humans. It is within the uterus that the fetus develops during gestation....
, receiving nutrition directly from the mother.

The ovum is the largest cell in the human body, typically visible to the naked eye without the aid of a microscope
Microscope

A microscope is an Laboratory equipment for viewing objects that are too small to be seen by the naked or unaided eye. The science of investigating small objects using such an instrument is called microscopy....
 or other magnification device. The human ovum measures between 100 and 200 µm
Micrometre

A micrometre or micron is one Micro- of a metre, or equivalently one thousandth of a millimetre. It is also commonly known as a micron....
 in diameter.

Protist and plant ova

In protist
Protist

Protists ; eukaryote microorganisms. Historically, protists were treated as the kingdom Protista but this group is no longer recognized in modern taxonomy....
s, fungi
Fungus

A fungus is a Eukaryote organism that is a member of the Kingdom Fungi . The fungi are a monophyletic group, also called the Eumycota , that is phylogeny distinct from the morphologically similar slime molds and water molds ....
 and many plants, such as bryophyte
Bryophyte

Bryophytes are all embryophytes that are non-vascular plant: they have tissues and enclosed reproductive systems, but they lack vascular tissue that circulates liquids....
s, fern
Fern

A fern is any one of a group of about 20,000 species of plants classified in the phylum or division Pteridophyta, also known as Filicophyta....
s, and gymnosperm
Gymnosperm

Gymnosperm is a group of spermatophyte seed-bearing plants with ovules on scales, which are usually arranged in cone-like structures. The other major group of seed-bearing plants, the angiosperms, [from the Greek, 'angion' - container] have ovules enclosed in a carpel, a sporophyll with fused margins....
s, ova are produced inside archegonia
Archegonium

An archegonium , from the ancient Greek ???? and ????? , is a multicellular structure or organ of the gametophyte phase of certain plants producing and containing the ovum or female gamete....
. Since the archegonium is a haploid structure, egg cells are produced via mitosis
Mitosis

Mitosis is the process in which a eukaryotic cell separates the chromosomes in its cell nucleus, into two identical sets in two daughter nuclei....
. The typical bryophyte archegonium consists of a long neck with a wider base containing the egg cell. Upon maturation, the neck opens to allow sperm cells to swim into the archegonium and fertilize the egg. The resulting zygote then gives rise to an embryo, which will grow out of the archegonium as a sporeling
Sporeling

A sporeling is a young plant or fungus produced by a germinated spore, similar to a seedling derived from a germinated seed. They occur in algae, fungus, lichens, bryophytes and Pteridophytes....
 (young sporophyte
Sporophyte

All land plants, and some algae, have life cycles in which a haploid gametophyte generation alternates with a diploid sporophyte, the generation of a plant or alga that has a double set of chromosomes....
).

In the flowering plant
Flowering plant

The flowering plants or angiosperms are the most widespread group of Embryophytes. The flowering plants and the gymnosperms are the only extant groups of Spermatophyte....
s, the female gametophyte
Gametophyte

In plants and algae that undergo alternation of generations, a gametophyte is the multicellular structure, or phase, that is haploid, containing a single set of chromosomes:...
, which usually gives rise to the archegonium, has been reduced to just eight cells referred to as the embryo sac inside the ovule
Ovule

Ovule literally means "small ovum." In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: The integuments forming its outer layer, the nucellus , and the megaspore-derived female gametophyte in its center....
. The gametophyte cell closest to the micropyle opening of the embryo sac develops into the egg cell. Upon pollination
Pollination

Pollination in flowering plants and gymnosperms is the process that transfers pollen, which contain the male gametes to where the female gamete are contained within the carpel; in gymnosperms the pollen is directly applied to the ovule itself....
, a pollen tube delivers sperm
Sperm

The term sperm is derived from the Greek word sperma and refers to the male reproductive Cell . In the types of sexual reproduction known as anisogamy and oogamy, there is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell....
 into the embryo sac and one sperm nucleus fuses with the egg nucleus. The resulting zygote develops into an embryo inside the ovule. The ovule in turn develops into a seed
Seed

A seed is a small Plant embryogenesis plant enclosed in a covering called the seed coat, usually with some Food storage. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant....
 and in many cases the plant ovary
Ovary (plants)

In the flowering plants, an ovary is a part of the female reproductive organ of the flower or gynoecium. Specifically, it is the part of the carpel which holds the ovule and is located above or below or at the point of connection with the base of the petals and sepals....
 develops into a fruit
Fruit

The term fruit has different meanings dependent on context, and the term is not synonymous in food preparation and biology. In botany, which is the scientific study of plants, fruits are the ripened Ovary of flowering plants....
 to facilitate the dispersal
Biological dispersal

Biological dispersal refers to a species movement away from an existing population or away from the parent organism. Through simply moving from one habitat patch to another, the dispersal of an individual has consequences not only for individual fitness, but also for population dynamics, population genetics, and species distribution....
 of the seeds. Upon germination
Germination

Germination is the process whereby growth emerges from a period of dormancy. The most common example of germination is the sprouting of a seedling from a seed of an flowering plant or gymnosperm....
, the embryo grows into a seedling
Seedling

A seedling is a young plant sporophyte developing out of a plant embryo from a seed. Seedling development starts with germination of the seed....
.

Ova development in oviparous animals

In the oviparous animals (all bird
Bird

Birds are wing, Bipedalismal, endothermic , vertebrate animals that lay egg . There are around 10,000 living species, making them the most numerous tetrapod vertebrates....
s, most fish
Fish

A fish is any marine biology vertebrate animal that is typically ectothermic , covered with scale , and equipped with two sets of paired fins and several unpaired fins....
es, amphibians and reptile
Reptile

Reptiles, or members of the class Reptilia, are air-breathing, cold-blooded vertebrates that have skin covered in scale as opposed to hair or feathers....
s) the ova develop protective layers and pass through the oviduct
Oviduct

In oviparous animals , the passage from the ovary to the outside of the body is known as the oviduct. The eggs travel along the oviduct. These eggs will either be fertilized by sperm to become a zygote, or will degenerate in the body....
 to the outside of the body. They are fertilized by male sperm
Sperm

The term sperm is derived from the Greek word sperma and refers to the male reproductive Cell . In the types of sexual reproduction known as anisogamy and oogamy, there is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell....
 either inside the female body (as in birds), or outside (as in many fishes). After fertilization, an embryo
Embryo

An embryo is a multicellular organism ploidy eukaryote in its earliest stage of development, from the time of first cell division until birth, Egg , or germination....
 develops, nourished by nutrients contained in the egg. It then hatches from the egg, outside the mother's body. See egg (biology)
Egg (biology)

In most birds and reptiles, an egg is the zygote, resulting from fertilization of the ovum. To enable incubation the egg is usually kept within a favourable temperature range as it nourishes and protects the growing embryo....
 for a discussion of eggs of oviparous animals.

The egg cell's cytoplasm
Cytoplasm

The cytoplasm is the part of a Cell that is enclosed within the plasma membrane. In eukaryote cells the cytoplasm contains organelles, such as mitochondrion, that are filled with liquid kept separate from the rest of the cytoplasm by biological membranes....
 and mitochondria (and chloroplast
Chloroplast

Chloroplasts are organelles found in plant cells and other eukaryote organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve Thermodynamic free energy in the form of Adenosine triphosphate and reduce NADP to NADPH through a complex set of processes called photosynthesis....
s in plants) are the sole means of the egg being able to reproduce by mitosis
Mitosis

Mitosis is the process in which a eukaryotic cell separates the chromosomes in its cell nucleus, into two identical sets in two daughter nuclei....
 and eventually form a blastocyst
Blastocyst

The blastocyst is the structure formed in early embryogenesis, after the formation of the blastocoel, but before implantation.It possesses an inner cell mass, or inner cell mass which subsequently forms the embryo proper, and an outer layer of cells, or trophoblast which later forms the placenta....
 after fertilization.

Ovoviviparity

There is an intermediate form, the ovoviviparous
Ovoviviparity

Ovoviviparous, also known as oviviparous, animals develop within Egg s that remain within the mother's body up until they hatch or are about to hatch....
 animals: the embryo develops within and is nourished by an egg as in the oviparous case, but then it hatches inside the mother's body shortly before birth, or just after the egg leaves the mother's body. Some fish, reptiles and many invertebrate
Invertebrate

An invertebrate is an animal lacking a vertebral column. The group includes 98% of all animal species ? all animals except those in the Chordate subphylum vertebrate ....
s use this technique.

See also

  • Egg (biology)
    Egg (biology)

    In most birds and reptiles, an egg is the zygote, resulting from fertilization of the ovum. To enable incubation the egg is usually kept within a favourable temperature range as it nourishes and protects the growing embryo....
  • Fertilisation
    Fertilisation

    Fertilisation , is the fusion of gametes to produce a new organism. In animals, the process involves a sperm fusing with an ovum, which eventually leads to the development of an embryo....
  • Insemination
    Insemination

    Insemination is the introduction of spermatozoon into the female uterus of a mammal or the oviduct of an oviparous during copulation with another animal....
  • Menstrual cycle
    Menstrual cycle

    The menstrual cycle is a recurring cycle of physiology changes that occurs in reproductive-age females. Overt menstruation occurs primarily in humans and close evolutionary relatives such as chimpanzees....
  • Ovulation
    Ovulation

    Ovulation is the process in the menstrual cycle by which a mature ovarian follicle ruptures and discharges an ovum that participates in reproduction....
  • Pollination
    Pollination

    Pollination in flowering plants and gymnosperms is the process that transfers pollen, which contain the male gametes to where the female gamete are contained within the carpel; in gymnosperms the pollen is directly applied to the ovule itself....
  • Pregnancy


External links

  • description of 1800 genes involved in ovarian functions