Trophic Cascade Dynamics in Ecosystems

The video tutorial from biologyexams4u.com explains the concept of trophic cascade in ecosystems. It defines trophic cascade as an indirect effect by predators that alters the biomass, abundance, or productivity of populations at lower trophic levels. The tutorial provides a simple example involving a food chain with plants, deer, and tigers to illustrate the concept. It further distinguishes between two types of trophic cascades: top-down, where predators control prey populations affecting lower levels, and bottom-up, where nutrient availability impacts higher trophic levels. The video concludes with a summary of these concepts.

What is a trophic cascade?

• A direct effect of prey on predators

• An indirect effect by predators on lower trophic levels

• A direct effect of plants on herbivores

• An indirect effect by plants on higher trophic levels

In a food chain, what forms the first trophic level?

• Herbivores

• Decomposers

• Green plants

• Carnivores

What happens if the tiger population decreases in a food chain?

• The prey population decreases

• The prey population increases

• The plant population decreases

• The plant population remains unchanged

How do predators indirectly affect the producer level?

• By increasing the number of prey

• By directly consuming plants

• By increasing the number of predators

• By decreasing the number of prey

What is the main characteristic of a top-down trophic cascade?

• Influence of nutrients on higher trophic levels

• Influence of prey on higher trophic levels

• Influence of space on higher trophic levels

• Influence of predators on lower trophic levels

Which of the following is an example of a top-down trophic cascade?

• Nutrient deficiency affecting plant growth

• Predators controlling prey population

• Space availability affecting plant growth

• Herbivores increasing plant abundance

What is a bottom-up trophic cascade?

• Influence of predators on lower trophic levels

• Influence of space and nutrients on higher trophic levels

• Influence of prey on predators

• Influence of plants on herbivores

What can cause a bottom-up trophic cascade?

• Increase in predator population

• Nutrient deficiency in the soil

• Increase in prey population

• Decrease in plant population

Which trophic level is directly affected by nutrient deficiency?

• Primary consumer level

• Producer level

• Tertiary consumer level

• Secondary consumer level

What is the effect of food shortage at the primary consumer level?

• Increase in predator population

• Decrease in predator population

• No effect on predator population

• Increase in plant population