Spindle fibers form a protein structure that divides the genetic material in a cell. the spindle is necessary to equally divide the chromosomes in a parental cell into two daughter cells during both toes of nuclear division: mitosis and meiosis
Diastole is when the ventricles relax and fill with blood
Answer:
B. F1
Explanation:
Plants used in first-generation crosses were called P, or parental generation, plants (Figure 8.3). Mendel collected the seeds produced by the P plants that resulted from each cross and grew them the following season. These offspring were called the F1, or the first filial (filial = daughter or son), generation.
Hair is a keratinous filament growing out of the epidermis. It is primarily made of dead, keratinized cells. Strands of hair originate in an epidermal penetration of the dermis called the hair follicle. The hair shaft is the part of the hair not anchored to the follicle, and much of this is exposed at the skin’s surface. The rest of the hair, which is anchored in the follicle, lies below the surface of the skin and is referred to as the hair root. The hair root ends deep in the dermis at the hair bulb, and includes a layer of mitotically active basal cells called the hair matrix. The hair bulb surrounds the hair papilla, which is made of connective tissue and contains blood capillaries and nerve endings from the dermis.
Natural selection, is based upon the principle of "Survival of The Fittest" ensures that those who are more well adapted, especially having a better immune system, will survive. and the weaker ones will die out. Human evolution made the human immune system even better as time went by, and the system was more well adapted to diseases it was more exposed to like the Europeans were more resilient to smallpox than the native americans
