Thursday, February 25, 2016

Pond Biology Class #3

Essential questions for class:
– – Are really replicating a pond with the algae bins? What other lifeforms would we find?
– – How are protists related to animals and plants? What does the family tree look like?

All detail below from our extraordinary teacher; more photos at the class blog.
Plan: We are going to make student “ponds” (using small restaurant bins with tops) to observe over time. We’ll start with sand/gravel, adding some algae water from the class bins, and some water plants.

Report on class:
Draft for third week of pond biology class

We started with what might seem like a detour, but evolution and natural selection is a cornerstone of modern biology. When studying pond biology and the world of protists, fungi, plants and animals (the 4 main categories of eukaryotes), it is important to understand how these life forms evolved over time to  what they are today.

And before we can even start with evolution, we need to think about classification. All I mean by classification is the system we use to look at life forms on earth in a way that shows how they are related and connected to each other. For example, would we put fish into the same category as birds?  It seems obvious that fish and birds aren't very related, but are fish and birds more related than fish and bacteria? Hmm. This is pretty complicated.

To give the kids a taste of what a huge job this is, we started class with a quick 20 Questions game: I told them that I was thinking of a machine. We then brainstormed all the different kinds of machines we could think of: washing machines, cars, computers. We consolidated some of the ideas into one category, but quickly realized that splitting up the category of "machine" is tough. Many things are in more than one category, and it is hard to come up with a simple system of classification.

20 Questions is when someone thinks of an item (usually no clues), and then you ask questions to give you clues in order to guess before you run out. Someone asked

Answer: a CD player

I highly recommend playing 20 Questions in general, it is an excellent logic game, and if you do life forms, you play with some of these classification and evolution ideas in a fun way. Try it and see.

Back to class: the first scientist to even attempt the classification of life on Earth was Carl Linnaeus. We could do an entire class on Linnaeus and the eventual classification system we now use every day in biology, but here are some learning links to get you started:

Short and sweet overview of Carl Linnaeus:

A little dense with information, but good for parents and those really interested: http://www.ucmp.berkeley.edu/history/linnaeus.html


Really interesting (but again, dense) post about how classification of life forms (usually called taxonomy by biologists) is still a controversial and still not settled topic in biology today: http://www.ucmp.berkeley.edu/history/linnaeus.html

Taxonomy is complex and difficult.

After our quick introduction on taxonomy and classification(more next week), we started in on evolution. Someone asked "what is evolution?", and what a good question that is. I didn't use this in class, but the official definition is "descent with modification", but that is pretty useless unless you are already know your evolution!

Descent = passing traits or genetic information (our DNA) from parent to child. It is a one word description of the numerous generations that have happened for all species of life on earth.

Modification = change in genetic information. Change happens on Earth all the time that has nothing to do with evolution (leaves falling from tree, geologic changes in a mountain range over millennia), but it is that change being incorporated in the DNA of a species that is the foundation of evolution.

What did we talk about in class? We talked about evolution being change in a species over time. As an example, we talked for a little bit about how dogs have evolved from the Grey wolf. This is an example of artificial selection (or man-driven evolution), but it does illustrate the important components of evolution. Here's a great video about how dogs evolved:



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