Optionals IAS Mains Botany: Questions 283 - 291 of 422

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Question 283

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Appeared in Year: 2016

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Draw well-labelled floral diagrams of a pentamerous actinomorphic flower showing the following conditions of stamens:

Obdiplostemonous and pseudo-Obdiplostemonous conditions of stamens, each one in a separate floral diagram.

Explanation

Obdiplostemonous

  • It is a condition of stamens, they are twice the petals and as they are twice the number of petals.
  • Example- Murraya paniculata
The Murraya paniculata

The Murraya Paniculata

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Pseudo-Obdiplostemonous

  • In this type of condition the stamens are not in the condition of Obdiplostemonous but as a result of mechanical pushing of the stamens of the inne

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Question 284

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Appeared in Year: 2016

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Differentiate between the Isokont and Heterokont.

Question 285

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Appeared in Year: 2016

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Explain the progressive sterilization of the sporogenous tissue in Bryophytes.

Explanation

Progress Sterilisation of the Sporogenous Tissue in Bryophytes

  • Evolution of sporophyte by progressive sterilisation of sporophyte is also known as theory of progressive evolution.
  • The sporophytes of complex forms have evolved due to progressive sterilisation of the potential fertile tissue of the simpler forms.
  • In primitive form the sporophyte is simp

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Question 286

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Appeared in Year: 2016

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Describe the economic importance of Gymnosperms.

Explanation

Economic Importance of Gymnosperms

Food Value

  • Cycads are a good source of starch.
  • Sago is type of starch obtained from the pith of Cycas revolute and Cycas rumphi stem.
  • Seed starch is obtained from Cycas rumphii seed. it is prepared into flour and cooked before eating.
  • Pinus gerardiana seeds called chillgoza are used for eating.
  • The stem pith of Encephal

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Question 287

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Appeared in Year: 2016

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Explain briefly the Coenocytic mycelium.

Explanation

Coenocytic Mycelium

  • Many filamentous hyphae aggregate together and collectively called mycelium.
  • In non-septate hyphae the mycelium has many nuclei present in a common mass of cytoplasm. Such type of mycelium is called Coenocytic mycelium.
  • They are also known as aseptate mycelium.
  • A coenocyte capabilities as a single coordinated unit composed of a coup

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Question 288

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Appeared in Year: 2016

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How is cell signal transduction effected?

Explanation

Signal Transduction

  • A process by which chemical or physical signal is transmitted through cell.
  • A series of molecules events which cause cellular response.
  • Proteins are responsible for detecting stimuli. They are called receptors.
  • Changes occur when ligand bind to receptor.
  • These changes give rise to chain of biochemical events called signalling pathway

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Question 289

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Appeared in Year: 2016

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Discuss the role of RNA in evolution. Describe the various modifications that RNA undergoes ever since its synthesis until it reaches the stage of translation.

Explanation

Role of RNA in Evolution

  • RNA it is a single standard ribose nucleic acid.
  • RNA is a cornerstone of biological function.
  • It is also considered that life’s origin began with RNA.
  • RNA is a genetic material in many of the organism till now.
  • Some adaption that happen to RNA due to change in environment.
  • Adaption like riboswitches, ribonucleoproteins, RNA editi

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Question 290

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Appeared in Year: 2016

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Describe the functional roles of plastidial pigments.

Question 291

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Appeared in Year: 2016

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Comment on nuclear pore complex.

Explanation

Nuclear Pore Complex

  • The nuclear envelope in all eukaryotic is perforated by nuclear pores.
  • Nuclear pore are complex structure and also called nuclear pore complex.
  • The complex has 70 - 100 Dalton molecular weights.
  • The nuclear pores complex has eight fold or also called octagonal symmetry.
  • The pore complex consists of two rings with the periphery and i

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