Chapter 2.1: Energy Flow in Ecosystems

Energy Flow in Ecosystems Biomass is the total mass of all living things in an area Measured in g/m2 or kg/m2 What do you think is greater on Earth? The biomass of plants or the biomass of animals? - biomass of plants is 100x greater

Within an organism’s niche, the organism interacts with the ecosystem by: Obtaining food from the ecosystem Contributing energy to the ecosystem The flow of energy from an ecosystem to an organism and from one organism to another is called energy flow.

In an ecosystem, there are: PRODUCERS  Produce food in the form of carbohydrates during photosynthesis. CONSUMERS  Organisms that feed on other organisms. DECOMPOSERS  Organisms that help with the process of biodegradation and changes wastes and dead organisms into usable nutrients for other organisms in soil and water.

Energy flow in an ecosystem can be shown through the use of: Food chains Food webs Food or Ecological pyramids

1. Food chains Food chains show the flow of energy in an ecosystem from producer to consumer and from consumer to consumer Each step in a food chain is a TROPHIC level: 1st trophic level  primary producers 2nd trophic level  primary consumers 3rd trophic level  secondary consumers 4th trophic level  tertiary consumers

Each trophic level represents the number of energy transfers away from the original solar energy entering the food chain.

Consumers in a food chain can be classified as: DETRIVORES – consumers that obtain energy and nutrients from dead organisms and waste matter Examples include earthworms, bacteria and fungi. Feed at every trophic level and have their own, separate food chains and are very numerous.

HERBIVORES – primary consumers Eat plants (producers) only. CARNIVORES – secondary or tertiary consumers Secondary consumers eat non-producers such as herbivores. Tertiary consumers eat secondary consumers. (Top consumers or top carnivores). OMNIVORES – consumers that eat both plants and animals Examples include humans and bears.

2. Food Webs Most organisms are part of many food chains because they eat more than one kind of food for their energy requirements. Ex. squirrels can be a primary consumer (nuts), secondary consumer (insects), tertiary consumer (young birds) Food webs represent interconnected food chains. Arrows in a food web represent the flow of energy and nutrients. Following the arrows leads to the top carnivore(s).

3. Food / Ecological Pyramids Food pyramids show the changes in available energy (energy loss) from one trophic level to another in a food chain. Energy enters at the first/lowest trophic level (producers), where there is a large amount of biomass and therefore much energy.

Energy Loss in Ecological Pyramids Each trophic level of an ecological pyramid loses large amounts of the energy it gathers through basic processes of living. Approximately 90% of energy taken in by consumers is used in chemical reactions in the body and is lost as thermal energy. There is very little energy left over for growth or increase in biomass.

Therefore lower trophic levels have much larger populations than higher trophic levels. It takes large quantities of organisms in one trophic level to meet the energy needs of the next trophic level.

Food pyramids are also known as ecological pyramids. Ecological pyramids may show : PYRAMID OF NUMBERS

PYRAMID OF BIOMASS PYRAMID OF ENERGY

The amount of life an ecosystem can contain is based on the bottom level of the ecological pyramid, where producers capture energy from the Sun. Ex. Tundra ecosystem has little vegetation and cannot support many organisms This shows how important plant life is for making energy available in ecosystems!!

Each level in the energy pyramid = a loss of 90% of total energy available  only 10% of the energy in one levels transfers to the next level!!

HEADS UP / PASSWORD ROUND 1: abiotic climatograph niche predation biome

ROUND 2: adaptation ecosystem species commensalism mutualism

ROUND 3: food chain decomposers trophic level primary consumers producers

ROUND 4: biomass omnivores food web photosynthesis energy flow

Homework: Read pages 56 to 66 Food Web or Pyramid