Search results
Results From The WOW.Com Content Network
They fix nitrogen from dinitrogen (N 2) in the air using the enzyme nitrogenase, in order to provide the cells in the filament with nitrogen for biosynthesis. [2] Nitrogenase is inactivated by oxygen, so the heterocyst must create a microanaerobic environment. The heterocysts' unique structure and physiology require a global change in gene ...
In algae, akinetes form when environmental signals indicate impending change unfavorable to growth, such as the arrival of winter. Like cyanobacterial akinetes, they accumulate storage materials, but also develop thick cell walls and suspend active metabolism. [10] When conditions improve, the akinete germinates via the cell wall breaking open ...
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.
For a simple explanation, let D 1 = divergence between species, or the number of fixed differences in locus one. Similarly D 2 = divergence in locus two. Let P 1 and P 2 = the number of polymorphic sites in loci one and two, respectively (a measure of polymorphism within species). If there is no directional evolution, then D 1 /D 2 = P 1 /P 2.
The Differential Ability Scales (DAS) is a nationally normed (in the US), and individually administered battery of cognitive and achievement tests. Into its second edition (DAS-II), the test can be administered to children ages 2 years 6 months to 17 years 11 months across a range of developmental levels.
The heterocyst is a terminal single cell within which nitrogen fixation occurs, while the rest of the trichome is made up of vegetative cells within which photosynthesis occurs. [2] Some Richelia are made up of many vegetative cells and a terminal heterocyst , while others only contain a terminal heterocyst . [ 3 ]
One of the first changes of note was the increased age range, allowing for testing of children and adolescents from 3 to 16 years of age. The NEPSY-II test battery also added a new domain, Social Perception, and eleven new subtests in addition to removing four of the old subtests. The test battery thus consists of six domains comprising 32 ...
The Draw-A-Scientist Test (DAST) is an open-ended projective test designed to investigate children's perceptions of the scientist. Originally developed by David Wade Chambers in 1983, the main purpose was to learn at what age the well known stereotypic image of the scientist first appeared.