Energy Flow

Sunlight is the MAIN source of energy for all life on Earth Only plants, some algae, and certain bacteria can capture energy from the sun and convert it into a USABLE form of energy Autotrophs – organisms that capture and convert the sun’s energy Also called PRODUCERS!

Producers use a process known as photosynthesis Light energy is used to convert carbon dioxide (CO 2 ) and water (H 2 O) into oxygen (O 2 ) and carbohydrates (C 6 H 12 O 6 ) Carbon Dioxide + Water + SunlightCarbohydrates + Oxygen

Some autotrophs can produce food without light by using a process called chemosynthesis Chemical energy is used to convert hydrogen sulfide (H 2 S), carbon dioxide (CO 2 ), and water (H 2 O) into carbohydrates (C 6 H 12 O 6 ) and sulfur compounds (H 2 SO 4 ) This usually occurs in remote locations (e.g. ocean floor and hot springs) Bacteria are the most common autotrophs that use chemosynthesis

Photosynthesis “photo-” means “light” Uses light for energy Chemosynthesis “chemo-” means “chemicals” Uses chemicals for energy

Many organisms cannot use sunlight as food Animals, fungi, some bacteria, some protists These organisms must consume other organisms to obtain energy These organisms are called heterotrophs Also called CONSUMERS!

Five (5) main types of heterotrophs: 1)Herbivore – consumes only plants 2)Carnivore – consumes only animals Some scavengers are considered carnivores 3)Omnivore – consumes plants and animals 4)Detritivores – consumes decaying and rotting material (such as rotting leaves, etc.) Some scavengers are considered detritivores 5)Decomposers – breaks down organic (living) material Finishes the job that scavengers and detritivores start

Energy flows through an ecosystem in one direction Sun/ Inorganic Compounds AutotrophsHeterotrophs

Food Chain – series of steps in which organisms transfer energy by eating and being eaten Shows one-way flow of energy in an ecosystem

Most feeding relationships are more complicated than a food chain Food Web – network of complex interactions and feeding relationships in an ecosystem

Terrestrial Food Web Marine Food Web

Trophic Levels – steps in the food chain/web Producers – 1 st trophic level Consumers – 2 nd, 3 rd, or higher trophic levels Each consumer depends on the previous trophic level

1 st Trophic Level 2 nd Trophic Level 3 rd Trophic Level 4 th Trophic Level 5 th Trophic Level

Ecological Pyramid – diagram that shows the relative amount of energy or matter contained within each trophic level of a food chain/web 3 Types Energy Pyramid – shows the relative amount of energy available at each trophic level Biomass Pyramid – shows the amount of living organic material at each trophic level Pyramid of Numbers – shows the relative number of individual organisms at each trophic level

Only part of the energy that is stored at one trohpic level can be passed to the next trophic level 10% of the energy at one level is transferred to the next Why isn’t ALL the energy transferred to the next level? The other 90% is used by the organism at the previous level

Light or Chemical Energy

Biomass – total amount of living tissue within a given trophic level Usually expressed in terms of grams of organic matter per unit area Biomass pyramid represents the amount of potential food available for each trophic level in an ecosystem

10 %

Based on the actual number of individuals at each trophic level Does not always resemble the shape of a pyramid Ex: tree may be at bottom of “pyramid”