STEM Explorers Day 3: Ecology, Sustainability & Field Work
Exploring evolution using Jelly Beans
Today we learned about evolution and cleared up some common misconceptions. We gave students a jelly bean population of assorted colors, had them count the occurrence of each color and the percent of the population it accounted for. We then gave them the opportunity to play predator and capture and eat a third of the population, choosing their favorite colors for first consumption. After a reproductive phase where the remaining jelly beans repopulated the population making more of their own colors, we asked students to again document the proportion of each color in the population. We posed the question: has evolution occurred in your jelly bean populations? Although students were initially unsure, their populations had indeed evolved! Biological evolution is simply a change in the gene frequencies of a population (here represented by jelly bean color) from one generation to the next. Since every student had changed the color frequencies of their jelly beans, they’d all caused evolution for their populations, plus they’d gotten to eat some tasty sugar!
If you’d like to learn more about ongoing evolution and its sometimes dangerous consequences for humanity, check out this video on the evolution of antibiotic resistance in bacteria https://www.youtube.com/watch?v=yybsSqcB7mE
Exploring change in populations
Today explorers learned about biodiversity – genetic variation among and within species – and about how biodiversity in a population can change over time. We talked about the four main mechanisms of population change: mutation (creates variation), gene flow (migration moves variation between populations), genetic drift (random events like natural disasters), and natural selection (when more successful gene variations become more frequent in the population). In our activity, explorers got a chance to run a simulation of a population and see how different scenarios (representing different mechanisms) affected the population as a whole.
Today, explorers learned about food webs and acted as ecologists – scientists who study the relationships among organisms and between organisms and their environment. Our young ecologists learned about different producers (plants), lower-level consumers (herbivores), and higher-level consumers (carnivores,) and that all organisms in an ecosystem are interconnected, even if they are not directly eating – or are eaten by – one another. Explorers also learned to be grateful for decomposers, without which we’d be surrounded by piles of dead things!
Working as a team, explorers constructed a food web of the California Bay ecosystem. While constructing their food webs, explorers were confronted with ecosystem disruptions. They were forced to adjust their food webs to the addition of a new species or the loss of a native species. Explorers learned that food webs are very complex, with many intertwined organism relationships and that adding or removing a single species can have far reaching consequences!
To follow up this lesson, we recommend: building a Soda Bottle Composter to learn more about decomposition. Directions can be found at http://compost.css.cornell.edu/soda.html or at http://homebiology.blogspot.com/2009/06/soda-bottle-compost.html.
Field Study – Bug Hunting & Scientific Drawings
STEM Explorers had fun searching for bugs using the beautiful Foothill campus as their field. They collected bugs of all sorts – dragon flies, ants, spiders and others more difficult to identify. The Explorers then created scientific drawings of their bugs after identifying its parts under a microscope and/or a magnifying glass.
Population: Fishing for Answers
Today, explorers learned all about populations. We began by discussing world population and how it has increased from 1 billion to 7 billion people in just over 200 years. Explorers correctly identified China (1.3 billion) and India (1.2 billion) as the most populous countries in the world. Explorers learned about two major concepts in population ecology – carrying capacity and the Tragedy of the Commons. Carrying capacity is the maximum number of individuals that an area can support without exhausting or depleting the available resources.
We also explored the Tragedy of the Commons in a game where explorers grouped together in villages that survived by fishing. Inevitably, villagers who caught the maximum number of fish allowed each year ended up not leaving enough fish in the pond to reproduce to provide food for the next year. Villagers starved and villages collapsed until some explorers realized that if they fished enough to survive, but not enough to deplete the fish resource, the game could continue indefinitely – or as we say in ecology – sustainably – for many generations.
We watched a great video about population that you can review here. http://www.npr.org/2011/10/31/141816460/visualizing-how-a-population-grows-to-7-billion
Watch this short video to find out more about Tragedy of the Commons. https://www.youtube.com/watch?v=KZDjPnzoge0