IGCSE Biology Paper-2: Specimen Questions with Answers 133 - 133 of 203

Question 133

Question

MCQ▾

The diagram shows a flowering plant.

The Diagram Shows a Flowering Plant

To which group these plants belong?

Choices

Choice (4)

a.

Ascomycetes

b.

Pteridophytes

c.

Gymnosperm

d.

Angiosperm

Answer

d.

Explanation

(ERIG Plants)

  • Angiosperms are most dominant and most evolved plants on this earth, appeared about 130 million years ago in Jurassic (dicot plant) and cretaceous (monocot plants) period of Mesozoic era. Tertiary period of Cenozoic era is called as Age of angiosperms.
  • Angiosperms are found in every habitat. They constitute more than 50 % of total plants on this earth.
  • Angiosperms are seed bearing, flowering vascular plants in which seeds are enclosed in fruits. The term angiosperm means ‘enclosed seeds’ as seeds (ovules) are found enclosed in the ovary wall.
  • Instead of cone, angiosperms bear flowers. The flower is the most characteristic structure of the angiosperms.
  • Flower is defined as a modified shoot meant essentially for the reproduction of the plant.
  • The flower usually develops as a branch from a bud, growing in the axil of a small leaf like structure known as bract. A stalk called pedicel, supports the flower in the axil of the bract. The upper swollen end of the pedicel called receptacle or thalamus bears all the floral parts.
  • A typical angiospermic flower consists of 4 whorls, viz. , calyx, corolla, androecium and gynoecium. Both, calyx and corolla are known as accessory or helping whorls. The androecium and gynoecium are called reproductive or essential whorls.
  • Androecium (stamen) is microsporophyll and gynoecium (carpel) is megasporophyll.
  • Megasporophyll is differentiated into ovary, style, and stigma.
  • Angiosperms lack both archegonia and antheridia. The archegonium is replaced by gynoecium (pistil) and antheridium by pollen tube.
  • Flowers are adapted for various modes of pollination by birds, air, water, insects, etc. The outer most axillary whorl of the flower is the calyx, represented by the sepals.
  • Corolla is the second whorl of flower present inner to calyx and is composed of petals. The bright color of the petals combined with the scent of essential oils present in some flowers make the flower highly attractive to insects, which act as agents for pollination.