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 1^st & 2^nd Laws…)