Predation & Prey Defenses

What is predation in ecology?

Predation occur when a predator kills and consumes its prey, causing immediate death. It shapes community structures by reducing prey numbers, and driving evolutionary adaptations in the preys species.

Give two predator strategies with examples:

• Active hunting: Predator seeks out and chases prey (e.g., lion chasing a zebra).

• Sit-and-wait (ambush): Predator remains still and strikes when prey approaches (e.g., spider on its web).

Why is predation such a strong evolutionary force?

Because predation is fatal for prey— it creates strong natural selection. Prey that evade predators (e.g., hares that can outrun lynx) are able to survive and pass on these adaptive traits, leading to evolutionary arms races.

How are plants also affected by predation?

Plants are preyed upon by herbivores. (e.g., a deer eating a tree seedling kills it. As plants cannot move, they rely heavily on defenses, such as; thorns, chemicals, or protective coloration to reduce predation.

What are morphological defenses? Give examples.

Physical traits that makes prey harder to capture or eat.

• Plants: thorns, spines, stinging hairs (e.g., nettles)

• Animals: shells (turtles), quills (porcupines), armour (bettles)

These all reduce predator success, or increase the cost of attacking

What are chemical defenses? Give examples from both animals, and plants.

The use of toxins, sprays, or distasteful chemicals to deter predators.

• Animals: skunks spray noxious sulfur compounds; poison dart frogs secrete toxic alkaloids.

• Plants: produce secondary compounds such as milkweed sap (toxic cardenolides), nicotine, or tannins to deter herbivores.

Why are chemical defenses especially important for plants?

Since plants cannot escape predators, they rely on chemicals to make themselves unpalatable, toxic, or difficult to digest. These secondary metabolites discourage herbivores from feeding on them.

What is cryptic colouration? Give examples.

Also called camouflage; prey blends into the environment to avoid detection.

• Example: grasshoppers resemble blades of grass, stick insects mimic twigs, cuttlefish change colour.
  Effect: predators cannot easily locate the prey.

What is aposematic colouration? Give examples.

Bright warning colours signal toxicity, bad taste, or danger to predators.

• Examples: monarch butterflies (toxic from milkweed diet), poison dart frogs (toxic alkaloids), coral snakes (venomous).
  Effect: predators learn to avoid these species.

How do cryptic and aposematic colouration differ in defense strategy?

• Cryptic colouration (camouflage): prevents detection in the first place.

• Aposematic colouration (warning signal): prevents repeat predation by advertising danger and training predators to avoid attack.