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Lecture 18

Lecture 18 Notes

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University of Toronto St. George
James Thomson

Lecture 18 Development of Agriculture Slide 36There is no substitute for food its more important than medical attentionThere was a time when humans werent agriculturalists as we are nowThere are many aspects of the carrying capacity of Earth that depend on food and others that dont depend on food Slide 37We came to the Americas later than the old world Agriculture started independently in the continents Africa Europe Asia and Americas and has more recently come togetherBefore agriculture humans must have been opportunistic feedersHuntergatherer societiessocial bands that would go out and look for anything they could eatSlide 38Fruits are structures that plants wrap around seedsThe ones we eat have an evolutionary history of making substances that attract animals like us so we can eat it and disperse the seeds ie sweet sugar pulp with energy and seeds in thereoWe ingest the fruit and defecate the seeds so they can disperseIts attractive to us because it has evolved that way Seeds and tubers are small packages of plant material that evolution has designed to get through unfavourable periods to grow into a new plant later oDesigned to store energy and be compact packs of nutrition lots of fats in seeds caloriesSlide 39 Nonshattering seed heads a mutation that has happened in all the cereal crops when seeds are ripe at the end of the growing season the seeds dont get knocked off and dispersed separately they stay attachedA whole cluster of seeds a seed head is something you can harvest much more easily and the artificial selection induced by human agriculture has gone for nonshattering seed heads
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