Biology lecture 5

Biology lecture 5 - Biol-111 (2011) Lecture 5 Rajinder...

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1 Evolution of Land Plants Biol-111 (2011) – Lecture 5 Rajinder Dhindsa
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2 Do you have a clicker? ( I need to check if my clicker receiver is working Y e s . Wha t is a cl i c .. I d on’t like c. 82% 10% 9% 1. Yes. 2. What is a clicker? 3. I don’t like clickers
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3 During the evolution of land plants, plants moved to land from water. What challenges did they confront? A partial list of necessities of life and how a plant living in water fulfills them. What challenges a plant on land would face in fulfilling the same necessities.
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4 Structural changes needed: 1. Protection of gametes and embryo. Gamete transfer. Retention of the egg on the mother plant 2. Dehydration of the body – waxy covering (cuticle) 3. Water provides considerable buoyancy. On land they will have to support almost all their weight. 4. to obtain water and nutrients from the soil and means to distribute them to all parts of the body – roots, shoots, stomata etc, vascular system. 5. To benefit from higher intensity of light on land – increased photosynthetic surface area – leaves with increased surface area 4. Apical growth and branching to achieve maximum growth. Clicker question next!
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5 If density of water is 1.0 and that of human body is 1.1. How much of his weight would a 100-kg man would have to support in water? Ap p ro x i m a t e ly 9 kg Approximat ly 1 k g App xim ly 9 0 k I don’t know 34% 7% 42% 17% 1. Approximately 9 kg 2. Approximately 1 kg 3. Approximately 90 kg 4. I don’t know
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6 A body density of 1.1 implies that a 100 kg man has an approximate volume of 91 liters. On complete submersion in water, his body will displace 91 liters of water which weighs 91 kg. So, man’s weight will decrease by 91 kg and he will have to support only 9 kg or 9%. Another Clicker Question !
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7 Air is 800 times less dense than water. How much of his weight would the same man have to support in the air? 9 0 .00 % 99.90% 9.00% I don’ t know 15% 3% 8% 73% 1. 90.0 % 2. 99.9 % 3. 9.0 % 4. I don’t know
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Man’s body displaces the same volume of air as water but weight of this air 1/800 th of water, i.e. = 91/800 = 0.114 kg
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Biology lecture 5 - Biol-111 (2011) Lecture 5 Rajinder...

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