Activity #16: Energy in a Ecosystem

EQ How do different organisms get the energy they need to survive? How does energy move through an ecosystem? What are some of the roles of the organisms in ecosystems?

Challenge Question Describe how energy moves through an ecosystem.

Vocabulary Autotroph Food chain Chemosynthesis Food web Heterotroph Consumer Carnivores Herbivores Omnivores Scavengers Decomposers Detritivores

Energy, Producers, and Consumers

Energy Organisms must get energy in order to function Different organisms get their energy in different ways Almost all energy on Earth starts from the sun!

1. Autotrophs Organisms that capture energy from sunlight or chemicals and turn it into food Also called primary producers

Primary Producers Most commonly use energy from the sun to create sugars and starches (photosynthesis) Important examples: plants, algae, photosynthetic bacteria

Chemosynthesis When primary producers turn the energy in chemicals (like hydrogen sulfide) into carbohydrates. Mostly bacteria Found in extreme environments (deep ocean, hot springs, volcanoes)

2. Heterotrophs Eat other organisms for food. Also called consumers

Types of Consumers Classified by the way they acquire energy * Put these definitions in the correct bubbles on pg. 5 in the notes. Classified by the way they acquire energy Carnivores- kill and eat other animals Herbivores- eat plant materials Omnivores- eat both plant and animal materials Scavengers- consume carcasses of organisms that have died or that were killed by predators Decomposers- feed by chemically breaking down organic matter into detritus, debris from decomposing plants and animals (Ex: fungi and bacteria) Detritivores- feed on detritus particles (Ex: earthworms)

Energy Flows One Way Almost all energy on Earth starts from the sun! Energy flows through an ecosystem in a one way direction from producers to consumers

Food Chain Food Chain- a series of steps in which organisms transfer chemical energy by eating and being eaten. food molecules are chemicals Phytoplankton = algae that is floating and not attached to something **Read an arrow as “is eaten by”

Food Webs Algae Plants Food web- a network of complex interactions formed by the feeding relationships among the organisms of an ecosystem

Decomposers and Detritivores are Important in Food Webs Dead plant and animal material must be broken down so the molecules can be reused for new life Decomposers (bacteria and fungi) are heterotrophs that break down this dead plant and animal material into detritus Releases nutrients into the soil for new primary producers to grow (“recycles nutrients”) Detritus is eaten by detritivores (like crayfish, grass shrimp, and worms), further releasing nutrients into the soil

Food Web Disturbances Environmental changes can cause changes in a food web Krill

Think About It… How would a decrease in the krill population affect the Antarctic food web? What do ecologists mean when they say that killer whales indirectly depend on krill for survival?

Trophic Levels Each step of a food chain or food web is called a trophic level First trophic level- always primary producers All other trophic levels are occupied by different types of consumers

Ecological Pyramids Illustrations used to show the amounts of energy or matter in each trophic level of a food web Three types of pyramids: energy, biomass, and numbers

Pyramids of Energy Show the amount of energy available at each trophic level Only 10% of the energy in one trophic level is passed to the next level up. The rest of the energy is either used by the organisms to do life processes (like growth, reproduction, respiration, etc.), or released as heat How much of the energy available to the producers is available to the third-level consumers?

Pyramids of Biomass Biomass is the total amount of living tissue in a trophic level Primary Producers will have the greatest biomass There must be enough producers to provide energy for all of the consumers

Pyramids of Numbers Show the number of individuals at each trophic level If the main producer is a large organism, the base of the numbers pyramid will be small Pyramid of Numbers Grass Pyramid of Numbers

Example **Read an arrow as “is eaten by” Phytoplankton = algae that is floating and not attached to something **Read an arrow as “is eaten by”

Example Algae Plants