Herbivores and Predators in Ecology

12 Questions

What is the purpose of plants producing chemicals that make herbivores sick?

To protect themselves from being eaten

Why are caterpillars able to feed on a poisonous weed without being harmed?

Because they have a special chemical in their body from the plant

Why do plants face a severe problem when dealing with herbivores compared to animals?

Plants are slower and cannot run away

What is the main method of defence used by plants against herbivores?

Creating physical barriers like thorns or spines

What role do cardiac glycosides play in the Calotropis plant's interaction with herbivores?

They make herbivores sick and deter them from browsing

According to Darwin, what did he consider to be a potent force in organic evolution?

Interspecific competition

What is a key point made in the passage about competition?

Interference competition can occur even if resources are abundant.

According to the passage, what is the best way to define competition?

A process where one species significantly lowers its fitness in the presence of another species.

What example is provided in the passage to illustrate competition between totally unrelated species?

Flamingoes and resident fishes in South American lakes competing for food.

Which statement is true regarding competitive exclusion in nature, based on the passage?

Competitive exclusion is not always conclusive in nature.

In what situation might interference competition occur based on the information provided?

When one species interferes with the feeding efficiency of another species.

What did Gause and other experimental ecologists demonstrate according to the passage?

Competitively superior species will eventually eliminate other species when resources are abundant.

Study Notes

Defence Mechanisms in Plants

Some insects, like the monarch butterfly, acquire toxicity by feeding on poisonous weeds during their caterpillar stage.
Plants have evolved various defence mechanisms against herbivores since they cannot flee from predators.

Morphological Defences

Plants like Acacia and Cactus have developed morphological defences such as thorns to deter herbivores.

Chemical Defences

Plants produce and store chemicals that can make herbivores sick, disrupt their reproduction, or even kill them when ingested.
Examples of these chemicals include nicotine, caffeine, quinine, and strychnine, which are extracted from plants on a commercial scale.

Competition in Nature

Interspecific competition occurs when different species compete for the same resources.
Competition can occur even when resources are abundant, due to interference from other species.
The fitness of one species can be significantly lower in the presence of another species.

Evidence of Competition

Laboratory experiments have demonstrated the effects of competition on species fitness.
In some cases, competitive exclusion can lead to the elimination of one species by another.
Evidence of competitive exclusion in nature is not always conclusive, but circumstantial evidence does exist.