Sunday, 5 February 2012

Is Sunflower an Inflorescence or a simple flower?

Sunflower is an inflorescence. Even though the flower appears to be a single flower but it formed of so many floral units or small flowers called 'florets'.  The florets present in Sunflower are of two kinds- (a) Disc florets present at the center of the flower and (b) Ray florets present at the periphery of the flower. The disc florets are bisexual in nature whereas ray florets are unisexual or female or sometimes neutral in nature. In this inflorescence the peduncle is highly condensed to form a disc shaped receptacle on which the florets are arranged  in a centripetal (develops from periphery to inwards)  fashion. This type of inflorescence is known as Heterogamous Head or Capitulum or Anthodium inflorescence. This inflorescence is most commonly found in Asteraceae family. The scientific name of Sunflower is Helianthus annus.

Monday, 30 January 2012

What is the difference between Identical Twins and Fraternal            Twins?                                                                                                 
If a woman give birth to two babies in a single delivery who are similar in all respects including their sex are known as identical twins. Even though identical twins are similar in most of their aspects they differ in their finger prints, hand writing, birth marks.  In identical twin births,  it is always both of them may be boys or both of them may be girls.  Scientifically speaking, identical twins are caused when a fertilized egg cell split completely into two bits and each bit by repeated divisions will transform into an embryo which later grow in the uterus of the mother into two individuals. Since both the embryos are formed from the same zygote and they include the same genetic make up, the two babies will have the same sex as well as the exact similar features. Identical twins are biologically known as known as Monozygotic i.e. two individuals are produced from a single zygote.

If a woman give birth to two babies in a single delivery but they are not similar like that of identical twins are known as fraternal twins. The two babies may differ in all their features and even also in their sex. The two babies born in a single delivery may one of them may be a boy and the other may be a girl  or both of them may be boys or both of them may be girls. Usually in a woman's monthly menstrual cycle only one egg will be released in every month. If this get fertilized by a sperm, there is possibility of the woman can give birth to a single individual. Rarely in a woman's menstrual cycle two eggs may be released at a time and both of them get fertilized by two different sperms leading to the development of two embryos in the mother's womb. Since the two zygotes are formed from two different eggs and two different sperms, the genetic constitution of both the individuals quite vary from each other. Hence the two individuals not only vary in their features but also may vary even in their sex except for that both of them were born at the same time with few minutes difference. Fraternal twins are biologically known as Dizygotic i.e. two individuals are produced from two different fertilized eggs.

Sunday, 29 January 2012

What is the meaning of the term 'Metabolism' biologically?

Cell is the basic structural and functional unit of living organisms. The various life activities the organism it carries out are the out come of the various chemical reactions which occur in the protoplasm of the cells of the organisms. Some of the chemical reactions which occur in the cells are constructive in nature and some others are destructive in nature.  So, the total sum of chemical reactions which occur in a cell or in an organism which allow the body to get energy as well as materials to grow is known as 'Metabolism'.  Constructive chemical reactions provide materials for the organism to grow and the destructive reactions help the body to get energy to carry out its life processes. Constructive and destructive reactions go in hand and hand with each other in an organism to show its growth and development.

Metabolism in an organism or a cell can be divisible into two parts-

1. Anabolism

The chemical reactions of an organism or cell by which complex molecules are formed from simple molecules is known as 'Anabolism'.

Examples: Photosynthesis, Protein synthesis, Fat synthesis, Cell membrane synthesis etc.

2. Catabolism

The chemical reaction of an organism or cell by which simple molecules are formed from complex molecules is known as 'Catabolism'.

Examples: Respiration, Digestion etc.