Biology Mixed Test - 5 (Class XI / XII)

Twins of this type are mostly genetically identical. Subsequently, they are also called identical twins in contrast to fraternal or dizygotic twins, which come from two separate eggs fertilised by different sperms.

The stem is characterized by the presence of nodes and internodes.

It is negatively phototrophic, so phyllodes cannot be root.

Tap root has its origin in radicle.

This is the region of slow dividing cells present in the root tip.

These are meant for support to the plant body.

These are the characteristic of parasitic roots.

The cranial capacity of man is the highest.

This class includes man, and other higher mammals.

Thumb has played an important role in evolution as it provides better grasp to the man, and is termed as pollex.

Pancreas secrete pancreatic juice for digestion of food.

Upper lip has undergone modifications from apes to Homo sapiens.

They are associated with the movements that are not under will.

Both the original and the new cells normally are identical in their components and functions. This assures that replacement cells in skin and other body tissues are faithful copies.

Somatic cells divide to produce exact copies. This is how skin, and other body parts are replaced. In contrast, sex cells are not identical to the cells from which they came. Sperm and ova contain only half the number of chromosomes as somatic cells.

Cardial refers to heart, and 'peri'  means to surround.

Sperm and ova are very different from the parent cells that produced them. Most notably, they only have half the number of chromosomes. They also show anatomical differences, such as the flagellum (or tail) on a sperm cell.

It lies behind the peritoneum, so it is retroperitoneal.

Ova are produced in the ovaries. At ovulation, a secondary oöcyte passes down one of the fallopian tubes to the uterus where a fetus can develop normally if fertilization has occurred (in the fallopian tube) and meiosis completed.

In humans, about 7 million primary oِcytes are produced at beginning of the fetal stage, before birth. Of these, less than 500 eventually become secondary oِcytes after puberty and are released at ovulation. Oogenesis is completed at conception.

The single cell zygote is created by fertilization of male & female gametes then progressively becomes a complex multicellular embryo by mitosis and eventually develops into a recognizable fetus.

Here the twins bear one head with a single face but have four ears and two bodies.

Here in this type of twins,  the twins are asymmetrically conjoined leading in the formation of one twin, i.e. small, less formed, and dependent on the bigger one for survival.

Siblings usually share many genetic traits, but they do not have identical sets of alleles unless they are monozygotic (i.e. identical) twins.

Law of independent assortment states that when two pairs of independent alleles enter into combination in the F2 generation, they exhibit independent dominant effects. It means that during the formation of gametes, the law of segregation operates but the factors assort themselves independently at random and freely. So, for explaining this principle a monohybrid cross will be insufficient. We will need a dihybrid cross to depict this. Thus, this is the correct answer.