Search results
Results from the WOW.Com Content Network
The switch between sexuality and parthenogenesis in such species may be triggered by the season (aphid, some gall wasps), or by a lack of males or by conditions that favour rapid population growth (rotifers and cladocerans like Daphnia). In these species asexual reproduction occurs either in summer (aphids) or as long as conditions are favourable.
The list of organisms by chromosome count describes ploidy or numbers of chromosomes in the cells of various plants, animals, protists, and other living organisms.This number, along with the visual appearance of the chromosome, is known as the karyotype, [1] [2] [3] and can be found by looking at the chromosomes through a microscope.
Some chromosomal sex determination systems in animals. A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. [1] Most organisms that create their offspring using sexual reproduction have two common sexes and a few less common intersex variations.
The ZW sex-determination system is a chromosomal system that determines the sex of offspring in birds, some fish and crustaceans such as the giant river prawn, some insects (including butterflies and moths), the schistosome family of flatworms, and some reptiles, e.g. majority of snakes, lacertid lizards and monitors, including Komodo dragons.
In animals, the process involves a sperm fusing with an ovum, which eventually leads to the development of an embryo. Depending on the animal species, the process can occur within the body of the female in internal fertilization, or outside in the case of external fertilization. The fertilized egg cell is known as the zygote. [2] [5]
A monoploid has only one set of chromosomes, and the term is usually only applied to cells or organisms that are normally diploid. Males of bees and other Hymenoptera, for example, are monoploid. Unlike animals, plants and multicellular algae have life cycles with two alternating multicellular generations.
In both the non-animals and the comb jellies, researchers found 14 groups of genes located on separate chromosomes. But in the sponges, researchers found that those 14 groups had been rearranged ...
A strain is inbred when it has undergone at least 20 generations of brother x sister or offspring x parent mating, at which point at least 98.6% of the loci in an individual of the strain will be homozygous, and each individual can be treated effectively as clones.