Class on September 11 2018

Jeremy provided a lecture on basic ecological concepts

Primary production is when living organisms (e.g. plants) make their own food and use that food to live and grow. These plants do not depend on other plants, animals, or insects for their food. They can make their own with help from the sun, water, and air. Common primary producers in a schoolyard ecosystem are grass while phytoplankton are primary producers in the ocean.

Secondary production comes through living organisms consumimg other living matter. What happens to the food energy that is consumed? C = F + U + M + P (Consumption = Feces + Urine + Metabolism + Production)

Ecological Efficiency is defined as the ratio of Production/Consumption (which is always less than one and so typically referred to by a percentage).

a Food Web is a system of interlocking and interdependent food chains.

A Food Chain is a linear network of links in a food web starting from producer organisms and ending at apex predator species, detritivores, or decomposer species. A food chain also shows how the organisms are related with each other by the food they eat. Each level of a food chain represents a different trophic level.

An Ecosystem is a biological community of interacting organisms and their physical environment.

A Trophic Level refers to each of several hierarchical levels in an ecosystem, comprising organisms that share the same function in the food chain and the same nutritional relationship to the primary sources of energy.

A Production Pyramid (also trophic pyramid, ecological pyramid, energy pyramid, or sometimes food pyramid) is a graphical representation designed to show the biomass or bio productivity at each trophic level in a given ecosystem.

Predation and Competition are two major processes involved in one trophic level securing food from a lower trophic level.

The Biomass is the total mass of organisms in a given area or volume. Biomass pyramids show how much biomass (the amount of living or organic matter present in an organism) is present in the organisms at each trophic level.

Challenge Questions

  1. How can some food chains have more predator biomass than prey biomass? E.g. Line Islands inverted biomass pyramid.
  2. Why do some lakes have many small trout while other lakes have few large trout?

Answer: Some lakes do not have pelagic forage fish during the period of summer stratification. In these lakes, lake trout are planktivorous. Lake trout in planktivorous populations are highly abundant grow very slowly and mature at relatively small sizes. In lakes with deep-water forage fish, lake trout become piscivorous. Piscivorous lake trout grow more quickly, mature at a larger size, and are less abundant. Notwithstanding differences in abundance, the density of biomass of lake trout is fairly consistent in similar lakes.