Tag: botany

Quizzes (264) Questions (5276)

Questions Related to botany

Multiple choice botany stem - external morphology habit of plants plant classifications type of plants

Choose the correct answers from the alternatives given.
Annual rings are the number of

  1. Rings of vascular bundles in a monocot stem

  2. Layers of secondary xylem in a stem

  3. Internodes in a stem

  4. Both (b) and (c)
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Each year, the tree forms new cells, arranged in concentric circles called annual rings or annual growth rings. These annual rings show the amount of wood produced during one growing season. As the stem grows, complete ring called the cambial ring is formed. Cambial ring leads to the formation of secondary xylem and secondary phloem. 

Hence, the correct answer is 'Layers of secondary xylem in a stem'.

Multiple choice botany stem - external morphology habit of plants plant classifications type of plants

Choose the correct answers from the alternatives given.
During the secondary growth in the dicotyledonous stems the cork cambium gives rise to

  1. Secondary xylem and secondary phloem

  2. Secondary cortex and cork

  3. Pith and medullary rays

  4. Multicellular hairs
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Cork cambium is a tissue found in many vascular plants as part of the epidermis. The cork cambium is a lateral meristem and is responsible for secondary growth that replaces the epidermis in roots and stems. It gives rise to cork outside and secondary cortex inside. 

Hence, the correct answer is 'Secondary cortex and cork'.

Multiple choice botany classical genetics variation and its type natural selection introduction to genetics

Which is the source of variations?

  1. Mutation

  2. Recombination

  3. Deletion

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Mutations, recombinations and deletions all are the sources of genetic variation. A Mutation occurs when a DNA gene is damaged or changed in such a way as to alter the genetic message carried by that gene. Recombination involves the exchange of genetic material either between multiple chromosomes or between different regions of the same chromosome. Deletion is a mutation in which a part of a chromosome or a DNA sequence is missing. 

Multiple choice botany classical genetics variation and its type natural selection introduction to genetics

Which is a source of variation and genetic diversity that is shared between prokaryotes and eukaryotes?

  1. Random fertilization involving a unique sperm and a unique egg

  2. Independent assortment of each chromosome pair during metaphase I of meiosis

  3. Crossing-over during prophase I of meiosis

  4. Random mutation
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The genetic material in prokaryotes is not confined into a nucleus and they do not have a nuclear membrane and the genetic material is present in the form of chromatin and cytoplasm and there is no chance of crossing over during meiosis and no fertilization but random mutations do arise in them and it results change in the genetic material.

So, the correct option is 'Random mutation'

Multiple choice botany classical genetics variation and its type natural selection introduction to genetics

The major/ ultimate source of variations are

  1. Polyploidy

  2. Mutations

  3. Chromosome aberrations

  4. Segregation
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Ultimate source of variation is MUTATION and nothing else. Mutations are mistakes that occur in DNA sequence of genome:
  • Point mutation e.g. nonsense and missense mutations
  • Frame-shift mutation e.g. insertion or deletion mutations
Any change in genetic DNA will be translated into a defect in the corresponding protein. Thus mutation is responsible for appearance of a phenotypic variation. Such a variation may help the organisms carrying the new variation to survive better. If it produces more progeny the variation will appear in more members. Variations which provide adaptive advantage get selected by nature, thus help organisms to evolve.

So, the correct answer is 'Mutations'.
Multiple choice botany classical genetics variation and its type natural selection introduction to genetics

Discontinuous variations are :

  1. Essential features

  2. Acquired character

  3. Non-essential changes

  4. Mutations
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Discontinuous variations are where individuals fall into a number of distinct classes or categories and are based on features that cannot be measured across a complete range. You either have the characteristic or you don't. 
Discontinuous variation is controlled by alleles of a single gene or a small number of genes. As variations caused by mutations affect DNA in such a way that either organism has a certain characteristic resulting from mutation or not, it is an example of discontinuous variations.
So, the correct answer is 'Mutations'
Multiple choice botany classical genetics variation and its type natural selection introduction to genetics

Height in humans is

  1. Somatogenic variation

  2. Discontinuous variation

  3. Continuous variation

  4. Both B and C
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A.Somatogenic variation – These are acquired variations and non inheritable in nature. Eg:phenotypic plasticiy.

B.Discontinuous variations – These are responsible for the formation of a new species and the organism, thus, formed is called mutant. Eg:Mutations.

C.Continuous variations – These are fluctuating variations and cannot give rise to new species. Eg:Human height.

So, the correct option is ‘Continuous variations’.

Multiple choice botany classical genetics variation and its type natural selection introduction to genetics

Primary source of allelic variation is

  1. Independent assortment

  2. Recombination

  3. Mutation

  4. Polyploidy
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Primary source of allelic variation is recombination. Recombination is the natural process of breaking and rejoining DNA strands to produce new combinations of genes and, thus, generate genetic variation. This is the phenomenon that occurs during meiosis I.


So, the correct answer is 'Recombination'.