Question

Arrangement of ovules on the placentae developed from central axis of ovary is
A) Parietal placentation
B) Basal placentation
C) Marginal placentation
D) Axile placentation

Answer 1

It is the type of placentation located in the bicarpellary ovary of the syncarpous multicarpellary ovary. In order to form septa, the carpels merge to create a central axis and ovules are placed on the axis.

Complete answer:
First we should know about the placentation to answer this question. Placentation applies to the placenta’s creation, sort and function, or organisation. The aim of placentation is to move food, respiratory gases and water to a developing embryo from maternal tissue and, in some cases, to extract waste from the embryo. In live-bearing mammals, placentation is known primarily, but also exists in some fish, amphibians, reptiles, a variety of flowering plants and invertebrates.
Now, let us find the solution from the options-
- Ovules build on the wall or minor outgrowths of the wall that create fragmented partitions inside a compound ovary during parietal placentation. Thus, option A is not the correct option.
- Basal placentation happens when the placenta is at the base of an ovary and is bound to it by a single ovule. Thus, option B is not the correct option.
- There is marginal placentation of the ovary wherein the placenta creates a ridge along its ventral needle of the ovary and the ovules mature in two distinct rows. In peas, this type of placentation is noticed. Thus option C is not the correct option.
- The ovary is segmented by radial spokes of placentas in distinct locules of axile placentation. The ovules are arranged around the placenta's central axis. The number of chambers is equivalent to the number of carpels .It is located in ovaries that are bi- or multilocular or multicarpellary

Thus, the correct answer is option (D) Axile placentation.

Note: During the development of live birth, placentation frequently results in more than 100 sources of live birth in snakes that have had close to an equal number of individual placentation sources. This indicates that the occurrence of placentation is more common in squamata than compared in all other vertebrates, making them suitable for research into the origin of placentation and viviparity themselves.