The correct answer is option 2: Three. There are three types of ecological pyramids in an ecosystem.

1. Pyramid of numbers: It represents the number of individuals at each trophic level. It shows how the population size changes as we move up the food chain.

2. Pyramid of biomass: It represents the total amount of living or organic matter (biomass) at each trophic level. This pyramid gives a more accurate representation of the energy flow within an ecosystem, as it takes into account the mass of the organisms.

3. Pyramid of energy: It represents the total energy present or available at each trophic level. This pyramid shows the energy transfer and loss as we move up the food chain. The energy decreases as it is lost through metabolic processes, heat, and waste.

So, there are three types of ecological pyramids: pyramid of numbers, pyramid of biomass, and pyramid of energy.