Generally smaller, cannot be seen through a common microscope Larger than viruses, can be observed microscopically Host requirement Needs a host cell to reproduce Does not need to invade a host cell to reproduce Type of infection Systemic, spread throught the body Usually localized, but can spread systemically if not treated Host relationship Harmful most of the time Sometimes beneficial, sometimes harmful Antiviral drugs, antibiotics have no effect Antibiotics Viruses Viruses are microscopic pathogens that infect living cells and tissues. They are the smallest kind of microbe, with the size ranging from around nanometers, around 35 times smaller than a human red blood cell and around th the size of a regular bacteria. Viruses are not living things. They are complex molecules of proteins and genetic material but they do not have their own cell structure.
What is Sexual Reproduction Sexual reproduction is the fusion of two morphologically distinct types of gametes, which are called male and female gametes, in order to form a diploid zygote.
Male gamete is small and is known as the sperm. Female gamete is large and is known as the ovum or egg. Each gamete is haploid and is formed through a process called meiosis.
Meiosis only occurs in eukaryotes. During meiosis, chromosomal crossing over occurs at synapsis via points called chiasmata.
The recombination of non-sister chromatids leads to the genetic variation in the producing gametes. Genetic variation promotes the evolution by producing new traits. Two rounds of cell divisions occur during meiosis, producing four haploid gametes from a single diploid germ cell.
Fertilization is the event where the two gametes are fused to form the diploid zygote. A human somatic cell contains 46 chromosomes which can be divided into two homologous sets; one bears a maternal origin and the other bears a paternal origin.
By the law of independent assortment, one set, which containing 23 chromosomes, bearing both maternal and paternal origins separates into one gamete. Independent assortment of chromosomes in the genome while the formation of gametes also promotes the genetic variation during sexual reproduction.
During fertilization, the fusion of a sperm with an ovum regenerates the diploid status, consisting of 46 chromosomes in the zygote. Sexual cycle of eukaryotes is shown in figure 1. Sexual Cycle Finding a mate for the sexual reproduction is known as sexual selection, which promotes the natural selection in evolution.
But, lateral gene transfer, which occurs during conjugation, transformation and transduction are considered as sexual reproduction mechanisms.
Sexual Reproduction of Fungi In fungi, resting spores are produced by sexual reproduction. These spores are used to survive during harsh conditions.
Three phases can be identified in the sexual reproduction of fungi: During plasmogamy, the two parent cells are fused by their cytoplasm.
The two nuclei of those fused cells are then fused during karyogamy. Finally, during meiosis, haploid gametes are produced, which are then developed into spores. A fungus emitting spores is shown in figure 2.
Puffballs Emitting Spores Sexual Reproduction of Plants Bryophytes like liverworts, mosses, and hornworts consist of motile sperms with flagella.
Hence, they need water for reproduction. The life cycle of these plants consists of a haploid spore, which grows into the dominate form of the life cycle. The haploid dominate is known as the gametophyte, which is a photosynthesizing multicellular body, consisting of leaf-like structures.
This multicellular body consists of antheridia, producing haploid gametes by mitosis. Fertilization of gametes produces a diploid zygote. The zygote divides by the mitotic division, producing the sporophyte.
Fulfillment by Amazon (FBA) is a service we offer sellers that lets them store their products in Amazon's fulfillment centers, and we directly pack, ship, and provide customer service for these products. CHAPTER Algae structure and reproduction. Introduction. Algae (singular:alga) are eukaryotes ("true-nucleus"). An informal grouping of primitive, mainly aquatic plants that possesses chlorophyll a as their primary photosynthetic pigment and can manufacture their own food through the process of . The evolution of sexual reproduction describes how sexually reproducing animals, plants, fungi and protists could have evolved from a common ancestor that was a single celled eukaryotic species. There are a few species which have secondarily lost the ability to reproduce sexually, such as Bdelloidea, and some plants and animals that routinely reproduce asexually (by apomixis and.
Spore capsules are produced in the sporophyte. They produce spores by meiosis.
In ferns, diploid sporophyte produces spores. Spores germinate to produce gametophytes, which produces sperms and eggs. Sperms swim through a film of water in order to fertilize the egg. Produced zygote grows into a new sporophyte.Both the number of offspring and the length of the gestation periods vary widely according to the species.
It is possible that a female of some species may have only two offspring, but some other species may have between 40 and Echinoderm, any of a variety of invertebrate marine animals belonging to the phylum Echinodermata, characterized by a hard, spiny covering or skin. Beginning with the dawn of the Cambrian Period ( million to million years ago), echinoderms have a rich fossil history and are well represented by many bizarre groups, most of which are now extinct.
Dikaryan hyphae are also septate - they have cross-walls called septa at regular intervals. These miniature bulkheads give the hyphae some physical rigidity, and . All living organisms on Earth are divided into kaja-net.com main concept of cell theory is that cells are the basic structural unit for all organisms.
Cells are small compartments that hold the biological equipment necessary to keep an organism alive and successful. Main Difference – Sexual vs Asexual Reproduction. Sexual and asexual reproduction are two mechanisms that produce offsprings of the living organisms. The evolution of sexual reproduction describes how sexually reproducing animals, plants, fungi and protists could have evolved from a common ancestor that was a single celled eukaryotic species.
There are a few species which have secondarily lost the ability to reproduce sexually, such as Bdelloidea, and some plants and animals that routinely reproduce asexually (by apomixis and.