Select the statement which explains best parasitism.

Study the following four statements $(1-4)$ and select the two which are correct:
$(1)$ Lion eating deer and sparrow feeding on grain are ecologically similar in being consumers.
$(2)$ The predator starfish $Pisaster$ helps in maintaining species diversity of some invertebrates.
$(3)$ Predators often lead to the extinction of prey species.
$(4)$ Production of chemicals such as nicotine and strychnine by plants is a metabolic disorder.
Which two statements are correct?

Which adaptations have parasites evolved to exhibit parasitism?

Name important defence mechanisms in plants against herbivory.

Identify the correct types of ecological interactions represented by $P$,$Q$,$R$ and $S$.

Interaction between Species $A$ and Species $B$	Type of interaction
$+$,$-$	$P$
$-$,$-$	$Q$
$+$,$0$	$R$
$-$,$0$	$S$

In which of the following interactions are both partners adversely affected?