Difference Between Spores and Gametes

Main Difference – Spores vs Gametes

Both spores and gametes are produced during reproduction and are collectively called gonites. Both spores and gametes are haploids. Diploid sporophytes produce spores and haploid gametophytes produce gametes. This process is referred to as the alteration of generations seen in both fungi and plants. The key difference between spores and gametes is that spores germinate to develop haploid sporeling independently and a gamete should combine with another gamete to form the diploid zygote which is further developed into form a new sporophyte.

This article explains, 

1. What are Spores
      – Definition, Function, Characteristics
2. What are Gametes
      – Definition, Function, Characteristics
3. What is the difference between Spores and Gametes

What are Spores

Spores are a kind of reproductive cells, which bear the ability of developing into a new individual of the species, without the fusion of the other reproductive cells. They can be a unit of either asexual or sexual reproduction. Spores are unicellular, haploid cells. They are produced in the meiosis of the sporangium of diploid sporophyte.

Spores are produced by bacteria, algae, protozoa, fungi and plants. One of the most characteristic features in spores is that they are adapted to dispersal and survival in unfavorable conditions. But under favorable conditions, spores develop into new organisms. They produce multicellular gametophytes by mitotic cell division which eventually produce gametes. Bacteria produce spores as resistant units in order to survive under unfavorable conditions. Thus, bacterial spores are not sexually reproductive units. The spores of the seed plants are produced internally.

The spores producing vascular plants can be divided into two groups: homosporous and heterosporous. Homosporous plants produce spores of same size and type. Heterosporous plants, usually seed plants, spikemosses, quillworts and aquatic ferns, produce spores in two different sizes. The large spores are called megaspores and function as “female” spores. Small spores are called microspores, and function as “male” spores.

Spores can be classified by their origin during the life cycle as meiospores and mitospores. Meiospores are haploid and are produced by meiosis. They are produced in the gametophytes of angiosperms or gymnosperms. Meiospores consist of megaspores and microspores. Mitospores can be either haploid or diploid. Fungi is also classified into several taxa depending on the spore producing structure. Spore producing structures in fungi are Sporangiospores, Zygospores, Ascospores, Basidiospores, Aeciospores, Urediniospores, Teliospores, Oospores, Carpospores and Tetraspores. Spores can also be classified by mobility and function. Fungal spores are shown in figure 1.

Figure 1: Fungal spores

What are Gametes

Gametes are haploid reproductive cells, containing a half of the genetic material needed to form an individual of a particular species. Gametes are produced during meiosis. They need to be fused with reproductive gametes of the other type in the same species in order to form a complete organism. Gametes can be divided into two groips depending on the morphology: anisogamy and isogamy.

Morphologically two distinct types of gametes can be identified in anisogamy: female gamete which is comparatively larger and male gamete which is smaller. Female gamete is called ovum whereas the male gamete is called as the sperm. In humans, ovum is 100,000 times larger than the sperm in volume. Human gametes are shown in figure 2. Fertilization is the fusion of the male and female gametes which forms the zygote.

Isogamy is the production of morphologically similar gametes by both sexes.These gametes are composed of different mating types noted as “+” and “-” strains. Fertilization of the two strains produce the zygote. Isogamy is mainly found in fungi. It is considered as the early stage of sexual reproduction. Several lineages of plants and animals are evolved independently to anisogamy species from isogamy.

Figure 2: Human gametes

In human sex determination, two sex chromosomes can be identified: X and Y. The combination of XX is determined as a female and XY is determined as a male. Then, ovum, which is the female gamete, can only carry X chromosomes. But, sperms which are the male gametes can carry either X or Y chromosomes. Therefore, the male gamete is considered to have the main role in sex determination during the formation of zygote. ZW-sex determination system is used in the determination of sex in birds.

The alteration of generations is a characteristic feature of a plant life cycle. Plant gametes are produced by the meiosis of the gametophyte. In flowering plants, meiosis is occurred in flowers, producing the haploid generation. This haploid generation produces gametes by mitosis. Ovule is the female haploid cell which is produced by ovaries of the flower. Mature ovule produces the female gametes. Pollen is the male haploid cell which is produced by the anther. After landing the pollen on a mature stigma, sperms are produced by mitosis.

Difference Between Spores and Gametes

Abilities

Spores: Spores independently germinate to form a sporeling.

Gametes: Gametes should fuse with another gamete to form the zygote.

Reproduction Type

Spores: Spores are used in both asexual or sexual reproduction.

Gametes: Gametes are only used in sexual reproduction.

Production

Spores: Meiospores are produced by the meiosis of the diploid sporophyte. Mitospores can be either haploid or diploid. They are produced by mitosis and are characteristic of Ascomycetes.

Gametes: In plants, haploid ovule and pollen cells produces gametes by mitosis.

Unfavorable Conditions

Spores: Spores are capable of surviving in unfavorable conditions.

Gametes: Pollen can survive in unfavorable conditions.

Morphological Types

Spores: The spores producing vascular plants can be divided into two sections: homosporous and heterosporous.

Gametes: Gametes can be divided into two sections depending on the morphology: anisogamy and isogamy.

Animals

Spores: Animals do not produce spores.

Gametes: Animals only produce gametes.

Conclusion

Both spores and the gametes are known as gonites, the types of reproductive cells found in kingdom: Protista, Fungi, Plantae and Animalia. Bacteria produces spores for the survival under the unfavorable conditions. They lack gametes since they reproduce only by binary fission. The survival under unfavorable conditions is the most characteristic feature found in spores, unlike in gametes. However, the main difference in spores and gametes is spores ability to develop an individual independently, without fusing into other spores.

Reference:
1. “Spore”. Wikipedia, the free encyclopedia, 2017. Accessed 23 Feb 2017
2. “Gamete”. Wikipedia, the free encyclopedia, 2017.Accessed 23 Feb 2017

Image Courtesy:
1. “Fungal spores in lemon grass leaf no scale bar”. By Philippa Uwins – Own work (CC-BY-SA-3.0) via Commons Wikimedia
2. “Human gametes: ovum & spermatozoon”  by Karl-Ludwig Poggemann (CC BY 2.0) via Flickr