Food Webs We will examine the components of an ecosystem in order to analyze and construct food webs.

The Source of All Energy?

Anatomy of a Food Chain The source of energy for almost all food chains is the sun The first organism in every food chain is an autotroph or producer.

The Characters A PRODUCER is an organism that can make it’s own food (AUTOTROPH).

Organisms that eat, or consume, the producers or other animals are called CONSUMERS.

When organisms die… Decomposers feed off of dead and decaying matter.

Niche An organism’s niche is the role that it plays in an ecosystem. Includes: The type of food it eats How it gets its food Other organisms that use it for food Examples: Carnivore Predator Consumer

Energy Flow Energy flows in one direction through an ecosystem. consumer sun producer

The Food Chain Energy flow through an ecosystem can be represented by a food chain. Arrows show the direction of energy flow.

In reality, it’s not that simple…

The reality is called a “Food Web” A food web shows the complex interactions between all of the organisms in an ecosystem; it usually consists of several food chains.

Types of Consumers The first, or primary consumer, in every food chain eats the producers. It would be an herbivore (eats plants only) or an omnivore (eats plants and animals).

Types of Consumers The next, or secondary consumer, eats the primary consumers. These would be carnivores (eats meat only) or omnivores. We might also call them predators.

Types of Consumers The chain continues with tertiary consumers, who eat the secondary consumers, etc.

Working on the Food Chain

Pyramids TROPHIC LEVELS are feeding levels. Food webs can be represented by a pyramid, with the producers forming the base, because the most energy is stored at that level.

To feed 1 human… Fish Frog Grasshopper Grass Pyramid of Numbers Man Energy Flow Grasshopper Grass Pyramid of Numbers

Energy Flow Energy Pyramid H E A T Producers Primary consumers Tertiary consumers Secondary consumers Primary consumers Producers Energy Flow H E A T

The RULE OF 10 As energy flows through an ecosystem, only ~10% of stored energy gets passed from one level to the next. The rest returns to the environment as heat. 0.001% 0.01% 0.1% 1% 10% 100%

Everything decreases! Biomass (dry weight) decreases Energy decreases Numbers decrease