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Food Chains ~ Food Webs ~ Energy Pyramids
How does energy flow through an ecosystem?
Energy and nutrients in an ecosystem move…
from organisms that capture energy from the sun and store it in food
to organisms that get energy by consuming other organisms
Why do organisms need energy?
To maintain homeostasis (survive)
To mate (reproduce)
Why do organisms need nutrients?
To build cellular and body structures
Producers = Autotrophs Producers – organisms
that capture energy and store it in the chemical bonds of carbohydrates
Producers/autotrophs are the foundation of all ecosystems because they bring energy into the ecosystem.
How do autotrophs produce food? Photoautotrophs – use solar energy to make glucose
Examples – plants, algae, cyanobacteria
What is the reaction for photosynthesis?
+ CO2 + H2O
C6H12O6 (glucose)
O2 +
How do autotrophs produce food? Chemoautotrophs – use inorganic compounds to make
carbohydrates (chemosynthesis)
Examples - Archaebacteria
Consumers = Heterotrophs
Consumers – organisms that obtain energy and nutrients by eating other organisms
Many different types.
Types of Consumers Herbivore – eats only producers
Examples: cow, rabbit, grasshopper
Types of Consumers Carnivore – eats other
consumers
Examples: lynx, wolf, tiger
Types of Consumers
Omnivore – eats both producers and consumers
Examples: humans and grizzly bears/black bears
Types of Consumers Decomposer – breaks down the
remains of dead organisms
Returns nutrients to the ecosystem
Examples: bacteria, fungi, and worms
Food Chain – a simple pathway that shows how energy flows through an ecosystem
Always begins with a producer
The direction of the arrow shows energy flow.
Simplest food chain = PRODUCER DECOMPOSER
Modeling Energy Flow
Producer Primary
Consumer Secondary
Consumer Tertiary
Consumer
Producers get energy from _________.
Primary consumers get energy from _________.
Secondary consumers get energy from ________________.
Tertiary consumers get energy from __________________.
Quaternary consumers get energy from __________________.
Decomposers get energy from ______________________.
the sun
producers
primary consumers
secondary consumers
tertiary consumers
producers and consumers
Food Web – all the interconnected pathways by which energy flows through an ecosystem
Modeling Energy Flow
Which food chain is the longest? (5 trophic levels)
Which organism consumes the most organisms?
How many producers are found in this ecosystem?
How many consumers are found in this ecosystem?
Food Web
Modeling Energy Flow
Trophic Level – a step (level) in a food chain or food web
A feeding level
Energy is transferred from one trophic level to the next
Modeling Energy Flow Energy changes forms as it moves through the ecosystem.
Energy Pyramids
Energy Pyramid – a triangular diagram that shows an ecosystem’s loss of energy, which results as energy passes through the food chain
Available energy decreases as you move up the food chain
Only 10% of the energy stored in one trophic level can be transferred to the next trophic level
Energy is used during metabolism and released from the organisms as heat.
How does energy flow in an ecosystem?
Energy Pyramids
Which level has the most energy?
Which level has the least energy?
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