Download Lesson 5

Review:
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mutation and mutagen
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chromosomes and genes
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stages of mitosis
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interphase and cytokenesis
Jan 3­10:43 AM
Asexual Reproduction:
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asexual reproduction is when only one parent is required to produce an offspring
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this differs from sexual reproduction where two parents are needed
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asexual reproduction produces an exact copy of the parent
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bread mold and bacteria are examples of organisms which use asexual reproduction
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sexual reproduction is practiced in more complex organisms such as mammals
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Jan 3­10:50 AM
Methods of Asexual Reproduction:
(a) Binary Fission:
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a single parent cell replicates its genetic material and divides into two equal parts
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algae and protozoa use this type of reproduction
Paramecium Binary Fission:
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(b) Fragmentation:
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an organism breaks apart perhaps due to injury and each part develops into a copy of the parent
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starfish use fragmentation to regrow lost limbs
Short Starfish Video:
Jan 3­10:55 AM
(c) Budding:
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occurs when part of a cell pushes outward to form an outgrowth or bud
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this bud pinches off to form a new identical cell
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common in yeast and hydra
Yeast Budding:
Hydra Budding:
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(d) Vegetative Reproduction:
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occurs when special cells in plant stems or roots divide into structures which will grow into new plants
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this can include sprouts (eyes) in tubers (potatoes)
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bulbs which form tulips and daffodils
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runners which form strawberries
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cuttings which are small pieces of plant which will grow into a new plant (house plants)
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(e) Spore Reproduction:
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some organisms produce spores which will grow into new organisms through mitosis
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spores are lightweight and can spread easily
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they are used by bread molds and fungi such as puffballs (horse farts)
Fungi and Spores:
Jan 3­11:02 AM
Advantages and Disadvantages of Asexual Reproduction
(a) Advantages
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large number of offspring produced quickly
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large colonies can form and take food and water from other organisms
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large numbers help survival
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energy not needed to make offspring
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(b) Disadvantages:
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because offspring are clones they are more susceptible to diseases
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offspring may be physically close together thus they all compete for the same food and space
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change in the environment such as temperature could destroy them all
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Readings:
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Pages 152 ­ 161
Questions:
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Page 165: #'s 1,3,4,14
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