A report on Sexual reproduction

In the first stage of sexual reproduction, "meiosis", the number of chromosomes is reduced from a diploid number (2n) to a haploid number (n). During "fertilisation", haploid gametes come together to form a diploid zygote, and the original number of chromosomes is restored.
An Australian emperor dragonfly laying eggs, guarded by a male
Flowers contain the sexual organs of flowering plants.
Puffballs emitting spores

Type of reproduction that involves a complex life cycle in which a gamete with a single set of chromosomes (haploid) combines with another to produce a zygote that develops into an organism composed of cells with two sets of chromosomes (diploid).

- Sexual reproduction
In the first stage of sexual reproduction, "meiosis", the number of chromosomes is reduced from a diploid number (2n) to a haploid number (n). During "fertilisation", haploid gametes come together to form a diploid zygote, and the original number of chromosomes is restored.

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Fungus

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Any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms.

Any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms.

Fungal cell cycle showing Dikaryons typical of Higher Fungi
Omphalotus nidiformis, a bioluminescent mushroom
Bracket fungi on a tree stump
In 1729, Pier Antonio Micheli first published descriptions of fungi.
Armillaria solidipes
Mold growth covering a decaying peach. The frames were taken approximately 12 hours apart over a period of six days.
Polyporus squamosus
The 8-spore asci of Morchella elata, viewed with phase contrast microscopy
The bird's nest fungus Cyathus stercoreus
Prototaxites milwaukeensis (Penhallow, 1908)—a Middle Devonian fungus from Wisconsin
Main groups of fungi
Arbuscular mycorrhiza seen under microscope. Flax root cortical cells containing paired arbuscules.
Diagram of an apothecium (the typical cup-like reproductive structure of Ascomycetes) showing sterile tissues as well as developing and mature asci.
A pin mold decomposing a peach
The dark filaments are hyphae of the endophytic fungus Epichloë coenophiala in the intercellular spaces of tall fescue leaf sheath tissue
The lichen Lobaria pulmonaria, a symbiosis of fungal, algal, and cyanobacterial species
The plant pathogen Puccinia magellanicum (calafate rust) causes the defect known as witch's broom, seen here on a barberry shrub in Chile.
Gram stain of Candida albicans from a vaginal swab from a woman with candidiasis, showing hyphae, and chlamydospores, which are 2–4 µm in diameter.
Ergotamine, a major mycotoxin produced by Claviceps species, which if ingested can cause gangrene, convulsions, and hallucinations
Saccharomyces cerevisiae cells shown with DIC microscopy
The mold Penicillium rubens was the source of penicillin G.
A selection of edible mushrooms eaten in Asia
Stilton cheese veined with Penicillium roqueforti
Amanita phalloides accounts for the majority of fatal mushroom poisonings worldwide. It sometimes lacks the greenish color seen here.
Grasshoppers killed by Beauveria bassiana

The apothecium—a specialized structure important in sexual reproduction in the ascomycetes—is a cup-shaped fruit body that is often macroscopic and holds the hymenium, a layer of tissue containing the spore-bearing cells.

In meiosis, the chromosome or chromosomes duplicate (during interphase) and homologous chromosomes exchange genetic information (chromosomal crossover) during the first division, called meiosis I. The daughter cells divide again in meiosis II, splitting up sister chromatids to form haploid gametes. Two gametes fuse during fertilization, forming a diploid cell with a complete set of paired chromosomes.

Meiosis

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In meiosis, the chromosome or chromosomes duplicate (during interphase) and homologous chromosomes exchange genetic information (chromosomal crossover) during the first division, called meiosis I. The daughter cells divide again in meiosis II, splitting up sister chromatids to form haploid gametes. Two gametes fuse during fertilization, forming a diploid cell with a complete set of paired chromosomes.
Meiosis Prophase I in mice. In Leptotene (L) the axial elements (stained by SYCP3) begin to form. In Zygotene (Z) the transverse elements (SYCP1) and central elements of the synaptonemal complex are partially installed (appearing as yellow as they overlap with SYCP3). In Pachytene (P) it's fully installed except on the sex chromosomes. In Diplotene (D) it disassembles revealing chiasmata. CREST marks the centromeres.
Schematic of the synaptonemal complex at different stages of prophase I and the chromosomes arranged as a linear array of loops.
Diplontic life cycle
Haplontic life cycle.
Overview of chromatides' and chromosomes' distribution within the mitotic and meiotic cycle of a male human cell

Meiosis (, since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells.

Sperm and ovum fusing

Fertilisation

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Fusion of gametes to give rise to a new individual organism or offspring and initiate its development.

Fusion of gametes to give rise to a new individual organism or offspring and initiate its development.

Sperm and ovum fusing
In the Bryophyte land plants, fertilisation takes place within the archegonium. This moss has been genetically modified so that the unfertilised egg within the archegonium produces a blue colour.
Acrosome reaction on a sea urchin cell.
Fertilisation in humans. The sperm and ovum unite through fertilisation, creating a zygote that (over the course of 8-9 days) implants in the uterine wall, where it resides for nine months.
Red-veined darters (Sympetrum fonscolombii) flying "in cop" (male ahead), enabling the male to prevent other males from mating. The eggs are fertilised as they are laid, one at a time.

The cycle of fertilisation and development of new individuals is called sexual reproduction.

A human spermatozoon penetrating a human ovum. The spermatozoon is approximately 100,000 times smaller in size than the human ovum.

Gamete

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A human spermatozoon penetrating a human ovum. The spermatozoon is approximately 100,000 times smaller in size than the human ovum.

A gamete (, ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually.

Diagram of a replicated and condensed metaphase eukaryotic chromosome. (1) Chromatid – one of the two identical parts of the chromosome after S phase. (2) Centromere – the point where the two chromatids touch. (3) Short arm (p). (4) Long arm (q).

Chromosome

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Long DNA molecule with part or all of the genetic material of an organism.

Long DNA molecule with part or all of the genetic material of an organism.

Diagram of a replicated and condensed metaphase eukaryotic chromosome. (1) Chromatid – one of the two identical parts of the chromosome after S phase. (2) Centromere – the point where the two chromatids touch. (3) Short arm (p). (4) Long arm (q).
Organization of DNA in a eukaryotic cell
The major structures in DNA compaction: DNA, the nucleosome, the 10 nm "beads-on-a-string" fibre, the 30 nm fibre and the metaphase chromosome.
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Human chromosomes during metaphase
Stages of early mitosis in a vertebrate cell with micrographs of chromatids
The 23 human chromosome territories during prometaphase in fibroblast cells
Karyogram of a human male
In Down syndrome, there are three copies of chromosome 21.

Chromosomal recombination during meiosis and subsequent sexual reproduction play a significant role in genetic diversity.

Production of new individuals along a leaf margin of the miracle leaf plant (Kalanchoe pinnata). The small plant in front is about 1 cm (0.4 in) tall. The concept of "individual" is obviously stretched by this asexual reproductive process.

Reproduction

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Biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents.

Biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents.

Production of new individuals along a leaf margin of the miracle leaf plant (Kalanchoe pinnata). The small plant in front is about 1 cm (0.4 in) tall. The concept of "individual" is obviously stretched by this asexual reproductive process.
Hoverflies mating in midair flight
Illustration of the twofold cost of sexual reproduction. If each organism were to contribute to the same number of offspring (two), (a) the population remains the same size each generation, where the (b) asexual population doubles in size each generation.

There are two forms of reproduction: asexual and sexual.

A haploid set that consists of a single complete set of chromosomes (equal to the monoploid set), as shown in the picture above, must belong to a diploid species. If a haploid set consists of two sets, it must be of a tetraploid (four sets) species.

Ploidy

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Number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes.

Number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes.

A haploid set that consists of a single complete set of chromosomes (equal to the monoploid set), as shown in the picture above, must belong to a diploid species. If a haploid set consists of two sets, it must be of a tetraploid (four sets) species.

Virtually all sexually reproducing organisms are made up of somatic cells that are diploid or greater, but ploidy level may vary widely between different organisms, between different tissues within the same organism, and at different stages in an organism's life cycle.

Life cycle of a mosquito. An adult female mosquito lays eggs which develop through several stages to adulthood. Reproduction completes and perpetuates the cycle.

Biological life cycle

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Series of changes in form that an organism undergoes, returning to the starting state.

Series of changes in form that an organism undergoes, returning to the starting state.

Life cycle of a mosquito. An adult female mosquito lays eggs which develop through several stages to adulthood. Reproduction completes and perpetuates the cycle.
Zygotic meiosis
Gametic meiosis
Sporic meiosis
Life cycle of the apicomplexan, Babesia, Life cycle of the single-celled parasite Babesia, including the infection to humans

Transitions of form may involve growth, asexual reproduction, or sexual reproduction.

A human egg cell with surrounding corona radiata

Egg cell

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A human egg cell with surrounding corona radiata
Human egg cell
Diagram of a human egg cell
Ovum and sperm fusing together
The process of fertilizing an ovum (Top to bottom)
Gene expression pattern determined by histochemical GUS assays in Physcomitrella patens. The Polycomb gene FIE is expressed (blue) in unfertilized egg cells of the moss Physcomitrella patens (right) and expression ceases after fertilization in the developing diploid sporophyte (left). In situ GUS staining of two female sex organs (archegonia) of a transgenic plant expressing a translational fusion of FIE-uidA under control of the native FIE promoter

The egg cell, or ovum (plural ova), is the female reproductive cell, or gamete, in most anisogamous organisms (organisms that reproduce sexually with a larger, female gamete and a smaller, male one).

Plant

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Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae.

Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae.

Green algae from Ernst Haeckel's Kunstformen der Natur, 1904.
A variaty of fungi species
Dicksonia antarctica, a species of tree fern
A petrified log in Petrified Forest National Park, Arizona
Range of pangaea glossopteris.
The leaf is usually the primary site of photosynthesis in plants.
There is no photosynthesis in deciduous leaves in autumn.
Plant cell structure
The Venus flytrap, a species of carnivorous plant.
Mechanical harvest of oats.
Melocactus plants being used as medicine.
Timber in storage for later processing at a sawmill
A rose espalier at Niedernhall in Germany.
Capitals of ancient Egyptian columns decorated to resemble papyrus plants. (at Luxor, Egypt)
Barbara McClintock (1902–1992) was a pioneering cytogeneticist who used maize (corn) to study the mechanism of inheritance of traits.
Musk Thistle are invasive species in texas.

Plants are characterized by sexual reproduction and alternation of generations, although asexual reproduction is also common.