Darwin’s Theory of Evolution 1. Like organisms beget like organisms 2. Few organism in natural environment actually survive 3. In a population there are variations among individuals 4. Some variations are more “favorable” than others for that given environment 5. Given time, small accumulated changes can lead to differentiate groups of organisms from one another

Artificial Selection: Domestication Domestication: Growing a plant and consciously or unconsciously causing it to change genetically from its wild ancestor to better benefit humans Human domestication of plants began in the Fertile Crescent (modern day Middle East) about 10,000 years ago Domestication almost certainly began as an accidental or unconscious act

What Plants Do Since plants are relatively immobile, they must have developed ways to spread their offspring out as far as possible so that they could have as many viable offspring as possible Plant seeds are, therefore, quite crafty. They can be transported by wind, water, explosive power or by hitching a ride on animals. Berries are a particular vehicle for this travel as they entice birds with their sweet fruit and bitter seeds to ingest them without destroying them

Where did Humans start domesticating plants?

The Fertile Crescent

Why was the fertile crescent a great area to domesticate plants? Has a Mediterranean climate (mild wet winters, long,hot dry summers) Plants adapted to these conditions annuals: seeds remain dormant during summer rapid growth in spring energy put into producing large seeds Large number highly productive of wild plants Few changes were needed to be made to the plants Easy to domesticate Many of the plants were hermaphroditic pollinate themselves, don’t lose traits some cross pollination helped create new hybrids

Early domestication: a hypothetical situation When picking berries in the hot sun amongst the mosquitos, Achmel, a hunter-gatherer from modern Iran, chooses the ones that are biggest, sweetest and most visible. The berry seeds pass through Achmel and begin growing new bushes at the latrine that have generally large, sweet, visible berries.

What were humans looking for in a plant? Humans naturally selected large, sweet seeds to eat. Fleshy or seedless fruits, oily seeds, and long fibers. Olives for oil, hemp, and flax for fibers.

Some Example Domesticates Peas: Selected for non-exploding pods Wheat/Barley: Selected for non-exploding husks Almonds: Selected for lack of Cyanide… good idea Cotton: Selected for fiber or, more recently, oil The Mustard Plant...

The mustard family Selected mustard plant for the bulbous root

The mustard family Or selected for the leafy section

The mustard family Or selected for the buds

The mustard family The flower and stalk

The mustard family Or selected just for the size of individual side buds

Waves of Domestication 10,000 Years ago: Barley/Wheat, Peas 4,000 Years ago Olives, figs, dates, pomegranites, grapes, corn More recent Apples, pears, plums, cherries, strawberries Why these different times?

Genetics and Acorns Why were some crops domesticated before others, and some still haven’t been? --- it’s all about the genes A quick review of Punett Squares Polygenic and Pleiotropic So why not acorns? 10 year growth squirrels Bitterness is Polygenic in acorns

Why is it hard to domesticate some plants Why is it hard to domesticate some plants? More than one gene controls a trait, like bitterness in Oak acorns Slow growth Competition from other organisms in selecting traits Reproduction was not self-pollinating Plant did not have many initial desirable traits to start with

What plant domestication tell us about Natural selection? It acts as a model to show how natural selection works. Most plants produce offspring that are like them There is variation in plant populations (mutations) Plants are adapted for their environment (fertile crescent) Over time Humans have been able to create new varieties of plants using artificial selection Traits are controlled by genes