Species-specific sperm attraction has been documented in numerous species, including cnidarians, molluscs, echinoderms, and urochordates (Miller 1985; Yoshida et al. 1993). In many species, sperm are attracted toward eggs of their species by chemotaxis, that is, by following a gradient of a chemical secreted by the egg. In 1978, Miller demonstrated that the eggs of the cnidarianOrthopyxis caliculata not only secrete a chemotactic factor but also regulate the timing of its release. Developing oocytes at various stages in their maturation were fixed on microscope slides, and sperm were released at a certain distance from the eggs. Miller found that when sperm were added to oocytes that had not yet completed their second meiotic division, there was no attraction of sperm to eggs. However, after the second meiotic division was finished and the eggs were ready to be fertilized, the sperm migrated toward them. Thus, these oocytes control not only the type of sperm they attract, but also the time at which they attract them.
The mechanisms of chemotaxis differamong species (see Metz 1978; Ward and Kopf 1993). One chemotactic molecule, a 14-amino acid peptide called resact, has been isolated from the egg jelly of the sea urchin Arbacia punctulata (Ward et al. 1985). Resact diffuses readily in seawater and has a profound effect at very low concentrations when added to a suspension of Arbacia sperm (Figure 7.9). When a drop of seawater containing Arbacia sperm is placed on a microscope slide, the sperm generally swim in circles about 50 μm in diameter. Within seconds after a minute amount of resact is injected into the drop, sperm migrate into the region of the injection and congregate there. As resact continues to diffuse from the area of injection, more sperm are recruited into the growing cluster. Resact is specific for A. punctulata and does not attract sperm of other species. A. punctulata sperm have receptors in their plasma membranes that bind resact (Ramarao and Garbers 1985; Bentley et al. 1986) and can swim up a concentration gradient of this compound until they reach the egg.
No. Each gamete is genetically different from the other gametes and from the parent cell.
Chlamydomonas is considered isogamous because it produces gametes that are morphologically similar in size and structure (flagellated and motile) during sexual reproduction. This means that the gametes produced by different mating types are indistinguishable from each other.
Actually, gametes are haploid, not diploid. This means they contain half the number of chromosomes typical for the species. During fertilization, two haploid gametes (one from each parent) combine to form a diploid zygote, restoring the normal chromosome number for that species. This ensures genetic diversity and proper development.
Meiosis results in gametes that have half the number of chromosomes of other cells. A gamete carries one of each pair of homologous chromosomes. Their are 46 chromosoes in Meiosis I and 23 in Meiosis II.
Dihybrid F1 individuals produce 4 types of gametes. This is because of independent assortment during meiosis, where the alleles for each gene segregate independently of each other, resulting in all possible combinations of alleles in the gametes.
No. Each gamete is genetically different from the other gametes and from the parent cell.
Yes, according to the Bible, believers will recognize each other in heaven.
Chlamydomonas is considered isogamous because it produces gametes that are morphologically similar in size and structure (flagellated and motile) during sexual reproduction. This means that the gametes produced by different mating types are indistinguishable from each other.
Sex cells are also called gametes. Each has 23 chromosomes or half the number of other cells.
Yes, courtship behavior is adaptive to ensure members of the same species mate. This is important for the survival of organisms.
Actually, gametes are haploid, not diploid. This means they contain half the number of chromosomes typical for the species. During fertilization, two haploid gametes (one from each parent) combine to form a diploid zygote, restoring the normal chromosome number for that species. This ensures genetic diversity and proper development.
Recognising your own species is important when you're looking for a mate because interspecies mating is generally unviable or, at best, produces sterile offspring. this would mean the species would go extinct. Also if animals of the same species did not recognise other animals of the the same species they might fight which would not be good and also eat each other which could cause fatal diseases.
Gametes contain different genetic information to each other and to the parent cell.
Meiosis results in gametes that have half the number of chromosomes of other cells. A gamete carries one of each pair of homologous chromosomes. Their are 46 chromosoes in Meiosis I and 23 in Meiosis II.
Dihybrid F1 individuals produce 4 types of gametes. This is because of independent assortment during meiosis, where the alleles for each gene segregate independently of each other, resulting in all possible combinations of alleles in the gametes.
Yes, cats from the same litter typically recognize each other through scent and visual cues, even if they have been separated for a period of time.
When the subject is mating, organisms will have to rely on each other to provide the male or female gametes that will produce a new organism.