background: selecting the best embryo for transfer, with the highest chance of achieving a vital pregnancy, is a major goal in current in vitro fertilization (ivf) technology. the high rate of embryonic developmental arrest during ivf treatment is one of the limitations in achieving this goal. chromosomal abnormalities are possibly linked with chromosomal arrest and selection against abnormal f...

this research examines dynamics and change in the iranian family during the recent half- century especially subsequent to the islamic revolution in 1979. developmental positions and changes are discussed and consideration is given to the extent to which family dynamics and change have been influenced by structural changes or ideational forces. we will focus on ideational forces based on a new a...

BACKGROUND In the present study, various freezing containers were tested for mouse embryos of respective developmental stages; embryos were vitrified and then their survival rate and developmental rate were monitored. Mouse two cell, 8 cell, and blastula stage embryos underwent vitrification freezing-thawing and then their recovery rate, survival rate, development rate, and hatching rate were i...

The life history of Bemisia argentifolii Bellows & Perring (Homoptera: Aleyrodidae) on tomato (Lycopersicum spp.) was studied based on the age-stage, two-sex life table at 15, 20, 25, 28, 30, and 35 degrees C. The intrinsic rate of increase (r) at these temperatures is -0.0176, 0.0667, 0.1469, 0.1611, 0.1745, and 0.0989 d(-1), respectively. The relationship among the gross reproductive rate (GR...

Rearing oxygen level is known to affect final body size in a variety of insects, but the physiological mechanisms by which oxygen affects size are incompletely understood. In Manduca sexta and Drosophila melanogaster, the larval size at which metamorphosis is initiated largely determines adult size, and metamorphosis is initiated when larvae attain a critical mass. We hypothesized that oxygen e...

Heterochrony—variation in the rate or timing of developmental processes or events over evolutionary time—plays an important role in the study of evolutionary developmental biology. I review the historical background of heterochrony, and highlight examples of how both physical structure and behavior are influenced by changes in the rate of development. I also describe neurogenetic models of evol...

Developmental pathways may evolve to optimize alternative phenotypes across environments. However, the maintenance of such adaptive plasticity under relaxed selection has received little study. We compare the expression of life-history traits across two developmental pathways in two populations of the butterfly Pararge aegeria where both populations express a diapause pathway but one never expr...