Subject

Biology

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

71.

Which one of the following is linked to the discovery of bordeaux mixture as a popular fungicide?

  • Bacterial leaf blight of rice

  • Downy mildew of grapes

  • Loose smut of wheat

  •  Black rust of wheat


B.

Downy mildew of grapes


72.

The fleshy receptacle of syconus of fig encloses number of

  • Achenes

  • Samaras

  • Berries

  • Mericarps


A.

Achenes


73.

Chromosomes are arranged along the equator during

  • Prophase

  • Metaphase

  • Anaphase

  • Telophase


D.

Telophase

In plant cells, during metaphase chromosomes line up around the equator of the spindle and attached by their centromere to the spindle fibres (microtubules). In animal cells, during metaphase, smaller chromosomes are usually central in position with larger ones peripheral in position.


74.

Unisexuality of flowers prevents

  • Autogamy, but not geitonogamy

  • Both geitonogamy and xenogamy

  • Geitonogamy, but not xenogam

  • Autogamy and geitonogamy


A.

Autogamy, but not geitonogamy


75.

Width of the DNA molecule is

  • 15 Ao

  • 20 Ao

  • 25 Ao

  • 34 Ao


B.

20 Ao

The 3-D structure of DNA is represented by a double helix, in which each turn has a diameter of 34 Å and contains 10 base pairs at a distance of 3.4 Å. The width of DNA molecule is 20 Å.


76.

Which of the following floral parts forms pericarp after fertilization?

  • Nucellus

  • Outer integument

  • Ovary wall

  • Inner integument


C.

Ovary wall

After fertilization, the mature, ripened ovary develops into fruit. The ovary wall forms the covering of the fruit called fruit wall or pericarp. Some other post fertilization changes also occur like nucellus develops into perisperm, ovules develop into seeds, outer integument forms testa, inner integument forms tegmen, etc.


77.

Prothallus of the fern produces

  • Spores

  • Gametes

  • Both (a) and (b)

  • Cones


C.

Both (a) and (b)

Prothallus is a small, flattened, multicellular structure that represents the independent gametophyte generation of a fern. The prothalli bear antheridia (male sex organs) and archegonia (female sex organs) which produce male and female gametes, respectively.


78.

 Development of an embryo without fertilization is called as

  • Apomixis

  • Polyembryony

  • Parthenocarpy

  • Parthenogenesis


D.

Parthenogenesis

Parthenogenesis (virgin origin) is the development of an embryo from an unfertilized egg or if a spermatozoan does penetrate the egg, there is no union of male and female pronuclei. It is found in many plants (dandelions and hawk weeds) and (aphids and honey bees).


79.

Female cone of Pinus is a

  • Modified needles

  • Modified long shoot

  • Modified dwarf shoot

  • Modified scale


D.

Modified scale

The female cone of Pinus is formed by the aggregation of megasporophylls, which bear ovules. Each megasporophyll consists of a lower bract scale and a larger upper ovuliterous scale.


80.

A fern differs from a moss in having

  • Swimming archegonia

  • Swimming antherozoids

  • Independent gametophytes

  • Independent sporophytes


D.

Independent sporophytes

Fern (pteridophyte) differs from a moss s(bryophyte) in having independent gametophyte, while in moss the sporophyte is simpler than the gametophyte and remains attached to the parent gametophyte throughout its life. This sporophyte is dependent upon gametophyte partially or wholly for its nutrition.