兔子不吃番茄樹，因為有微毒性。番茄苗本來好好的，最近快死了，不知是生病還是前一陣子天天下雨被淹死了？讓我心疼不已。家附近野兔、松鼠多，不停地破壞我的小花園。先是謀殺了常春藤，今天早上我又氣急敗壞地發現泰國辣椒半顆不見了。難道兔子不覺得辣嗎？和平百合、鳳仙、和其他的植物也不時慘遭毒手，這些鼠輩好像就算不吃，也喜歡把葉子啃幾口，拉扯到地上，或是亂挖盆栽裡的培養土。
希望這棵可以長大，開很多花，最好還結一些種子讓我留下來。還敢吃？毒死你，要不然就享受Datura有名的精神錯亂幻覺吧！
Saturday, June 8, 2013
兔子還敢吃嗎？
希望這棵可以長大，開很多花，最好還結一些種子讓我留下來。還敢吃？毒死你，要不然就享受Datura有名的精神錯亂幻覺吧！
My First Scholarship
Me at the Undergraduate Award Ceremony (May 9, 2013) receiving my Hilldale Award (the first scholarship in my life), with the chancellor, Mr. David Ward. I received the scholarship for my research project on the Manduca juvenile hormone binding protein.
Me and my two friends from the Department of Entomology.
Saturday, June 1, 2013
The Two Assumptions of Heritability Studies
Evolution cannot occur without at least some traits being heritable. Heritability is a measure of parent-offspring resemblance; so a trait with high heritability has a high genetic component to it, right?
No.
This is one strange and paradoxical thing about heredity studies: heritability is defined as something specific to a certain population in certain circumstances. It is neither a property of an individual nor a property of a trait.
In parent-offspring correlation studies, heritability is simply the slope that measures the resemblance between the average trait value of the two parents and the trait value of the offspring. In twin studies, heritability is the correlation between the trait values of the twins.
From my reading about scientific and philosophical articles on heritability, I figured that two assumptions are implied in those studies without even being mentioned:
(1) Parents and offspring always resemble, instead of differ from, each other. (In other word, the slope of heritability on the parent-offspring graph is always positive.)
(2) Heritability can never equal to zero. This is because of how the math works out. Heritability is a correlation: a covariance over the product of two standard deviations. Covariances and standard deviations are always positive numbers.
Think about it: pick any measurable trait, its heritability will be a non-zero positive number, even if in reality it does not have genetic component. So what does heritability really tell us?
What would our evolution looks like if parents and offspring always tend to differ, not resemble, each other? Would we evolve backwards? Within one generation, the evolutionary response in the offspring will shift in the opposite direction as the selective pressure; however, the response will be cancelled in the grand-offspring generation under the same selective pressure. Just thinking about this weird scenario gave me a giggle fit in my philosophy-biology class.
No.
This is one strange and paradoxical thing about heredity studies: heritability is defined as something specific to a certain population in certain circumstances. It is neither a property of an individual nor a property of a trait.
In parent-offspring correlation studies, heritability is simply the slope that measures the resemblance between the average trait value of the two parents and the trait value of the offspring. In twin studies, heritability is the correlation between the trait values of the twins.
From my reading about scientific and philosophical articles on heritability, I figured that two assumptions are implied in those studies without even being mentioned:
(1) Parents and offspring always resemble, instead of differ from, each other. (In other word, the slope of heritability on the parent-offspring graph is always positive.)
(2) Heritability can never equal to zero. This is because of how the math works out. Heritability is a correlation: a covariance over the product of two standard deviations. Covariances and standard deviations are always positive numbers.
Think about it: pick any measurable trait, its heritability will be a non-zero positive number, even if in reality it does not have genetic component. So what does heritability really tell us?
What would our evolution looks like if parents and offspring always tend to differ, not resemble, each other? Would we evolve backwards? Within one generation, the evolutionary response in the offspring will shift in the opposite direction as the selective pressure; however, the response will be cancelled in the grand-offspring generation under the same selective pressure. Just thinking about this weird scenario gave me a giggle fit in my philosophy-biology class.
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