Topic 10:
Why Big Fierce Animals Are Rare
Announcements:
How many different types of food did you eat this weekend...?
Today: continuing our exploration of how ecological communities are put together... one of the key features involves who eats whom...!
Example animal presentation
Reading Q's for Beast in the Garden on Moodle - follow instructions: write answers to (...maybe...) turn in for Information Qs; be prepared to talk about Discussion Qs
Field Trip Wednesday - Aquatic Foodwebs; Rotary Park (Gazebo) on Animas River
Goals for Day:
Ø Where do atoms go in ecosystems?
Nutrient cycling
Bioaccumulation
Brainstorm reasons why “big fierce animals” (i.e. top predators) could be rare
Ø Understand the ultimate reason for their rarity
Ø Be able to name the groups of organisms found at each level in a food chain
Ø Ultimate source of energy for most ecosystems
How much energy is actually transferred from one level of a food chain to the next
o Implications for the abundance of different types of organisms, and for the rarity or abundance of species
Question 1:
Why are big fierce animals rare?
Brainstorm in your groups, and come up with as many reasons as you can
Be prepared to share responses with the class
Question 2:
To be able to answer this question (Why are big fierce animals rare?), need to study Food Chains & Food Webs
What are Trophic Levels?
Link to pertinent Powerpoint slides
Question 3:
How many links can there be in a food chain?
Is there an upper limit?
If so, what is it? Why??
Question 4:
Where does the energy in food chains come from (ultimate source)?
Where does most of it go?
Remember the laws of thermodynamics:
Energy cannot be created or destroyed, only converted to a different form.
Energy conversions are, by their very nature, inefficient - some energy is always lost (as heat) in the process.
Question 5:
How much energy is transferred from one trophic level to the next?
Question 6:
What - in the light of all you've seen today - is the ultimate reason for the rarity of big, fierce animals (aka top predators)?
Assess – Goals:
Ø What are the “Trophic Levels” in a food chain?
Ø How many different trophic levels can there be in a food chain? What’s the maximum ever recorded?
o could you just keep adding levels to the top of a food chain, indefinitely?
o why are the longest food chains found in marine habitats?
Ø If energy isn’t all transferred between trophic levels when 1 critter eats another, where does that other energy go? Why?
Ø How does all of this relate to the Laws of Thermodynamics? (…you might have to go look them up somewhere – the 1st & 2nd Laws…)