11.Organisms and PopulationsMedium

Name important defence mechanisms in plants against herbivory.

Solution

Several plants have evolved various mechanisms both morphological and chemical to prote themselves against herbivory.

Morphological defence mechanisms:

Cactus leaves (Opuntia) are modified into sharp spines (thorns) to deter herbivores from feeding on them.

Sharp thorns along with leaves are present in Acacia to deter herbivores.

In some plants, the margins of their leaves are spiny or have sharp edges that prevent herbivores from feeding on them.

Chemical defence mechanisms:

All parts of Calotropis weeds contain toxic cardiac glycosides, which can prove to be fatal if ingested by herbivores.

Chemical substances such as nicotine, caffeine, quinine, and opium are produced in plants as a part of self-defence.

Statements

$I.$ Recent studies support competition as suggested in 'Gauses's Competitive Exclusion Principle'

$II.$ Gause's hypothesis says if two species compete for same resources then one will be eliminated by another species

$III.$ More recent studies point out that species facing competition might evolve mechanisms that promote co-existence rather than exclusion

$IV.$ Gause's competitive exclusion principle is effective when resources are in excess

$V.$ Unlimited resources give better opportunity for adaptation

Choose the correct combination of statements

Medium

Medium

Medium

Easy

Medium