Do you know which fungus product used in Organ transplatation ?

The soil-inhabiting fungus Tolypocladiurn inflatum is the source of cyciosporin, a medication that suppresses the immune reactions that cause organ transplant rejections. Cyclosporin does not cause the undesirable side effects that other immune-suppressing medications do. This remarkable drug became available in 1979, making it possible to resume organ transplants. which had essentially been abandoned. As a result of cyclosporin. successful organ transplants are almost common place today.

How do angiosperms differ from gymnosperms?

First, the seeds of the angiosperms, a more recently evolved and highly successful division of the tracheophytes, are enclosed within a protective chamber, the ovary. A ripened ovary containing seeds is called a fruit. The fruit not only encloses the seeds but may also aid in seed dispersal. The fruit is either carried or eaten by animals that migrate to distant sites, carrying the seeds with them; the seeds are ultimately dropped or eliminated from the animals’ digestive tracts.

The seed also forms a little differently in angiosperms. One sperm nucleus from the pollen tube unites with an egg nucleus to produce the zygote. A second sperm nucleus unites with two haploid nuclei in the gametophyte (embryo sac) to produce the triploid endosperm, an important source of food within the seed for such seeds as corn.

In gymnosperms, pollination (transfer of pollen to female reproductive structure) can be only wind-borne. In flowering plants, pollen may be transferred by wind or by animals. Although insects have been stressed as prime agents for pollination, recent studies suggest that mice and other small mammals may also play a role, particularly
in tropical plants.

A major internal modification of the angiosperms is the development of specialized xylem cells, the vessels and fibers, in addition to tracheids. The vessels are particularly significant because they are large-bore columnar cells that anastomose (join) end to end. When their inner cellular contents degenerate, they collectively form long tubes that greatly facilitate the passage of water in the plant. Fibers, on the other hand, function solely to provide support. In conifers, the single xylem elements, the tracheids, represent a more primitive condition

Criticize the following statement: Plants carry on photosynthesis; animals carry on respiration instead.

This is an incorrect view. Both plants and animals carry on respiration as a major source of energy for vital functions. Only plants, however, are also capable of carrying out photosynthesis. The components of photosynthesis are sequestered within the chloroplast, whereas the major steps of respiration occur within the mitochondrion. Thus, both processes may be occurring simultaneously in any plant cell, since the compartmentalization of these functions precludes their interfering with each other. Many of the sequences in the pathways of respiration are found as part of the photosynthetic process; this suggests a close evolutionary association of the two processes. The balance between respiration and photosynthesis will determine whether there is a net uptake of O2 or CO2 from a particular plant region.

Describe some asexual processes occurring in animal reproduction. What is the chief disadvantage of this form of reproduction?

Parthenogenetic development of unfertilized eggs as a regular procedure in the production of male ants and bees and Artificial stimulation of sea urchin eggs induces cleavage. Although the egg is a sex cell, the development of unfertilized eggs is an asexual process.Among sponges and hydra, budding is a common occurrence. This involves an outgrowth of a portion of the parent’s body to produce a new individual. Occasionally, the new growth will remain attached to the parent stock, but usually the bud breaks away to produce an individual organism.
In the phylum, Platyhelminthes, a process called fragmentation occurs in which some of these flatworms spontaneously separate into separate lengths. Each of the fragments produces a new flatworm.

Related to fragmentation is regeneration, or the restoration of lost parts. Seemingly, this is a mechanism for compensating for the accidental removal of organs or extended structures. However, among the echinoderms
(starfish, brittle stars, etc.), the removal of an arm and part of the central disk leads to the formation of a new organism from that arm, so that the process may be considered both fragmentation and regeneration.

Asexual reproduction is a simple procedure for producing progeny, but it tends to minimize the variation which is grist for the mill of evolution. It also tends to eliminate the existence of parents, except in the instance of budding. In almost all animal organisms, asexual reproduction is only a supplement to sexual reproduction.

Stripping a thin layer of bark completely around a tree trunk will kill the tree, but a deep gouge along one side will not. Why?

It must be remembered that the bark contains the phloem in its innermost region. The circumcision of even a thin layer of bark completely disrupts the movement of organic nutrients from the leaves and upper stem to the lower stem and roots. In a clear sense, the roots and lower stem would be starved and their functions suspended. Survival would be impossible.
On the other hand, a deep cut along one side of the trunk would disrupt completely both nutrient flow in the phloem and fluid movement in the xylem, but only in the narrow band of elements actually destroyed. The rest of the trunk would continue to provide a conduit for necessary fluids and the sugars and other organic foodstuffs manufactured by the leaves. Sometimes, it is possible for trees to survive even though their heartwood has rotted or burned. Although this diminishes their strength, it does not reduce their ability to transport nutrients, and so they survive.