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Biology 150 Week 1 Notes

by: Morgan Bell

Biology 150 Week 1 Notes Bio 150

Marketplace > Converse College > Biology > Bio 150 > Biology 150 Week 1 Notes
Morgan Bell

GPA 2.9

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Material from 8/29-9/2
Biology of Sexuality
Dr. Steele
Class Notes
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This 3 page Class Notes was uploaded by Morgan Bell on Wednesday October 5, 2016. The Class Notes belongs to Bio 150 at Converse College taught by Dr. Steele in Fall 2016. Since its upload, it has received 13 views. For similar materials see Biology of Sexuality in Biology at Converse College.


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Date Created: 10/05/16
Bio 150­Week 1 Natural Selection vs. Sexual Selection  Natural Selection  There is a variation of individuals in a population.  Some variations useful­populations evolve.  Ex. Malaria and Sickle Cell Anemia  Malaria can kill you if you have normal blood cells because it only attacks the  normal blood cells  Sickle Cell Anemia can kill you because sickle shaped cells don’t let oxygen  travel in the blood stream.  If you have a variation of normal sickle cells you can survive. There will be  enough normal cells to allow oxygen flow in the blood stream and enough sickle  cells to keep malaria from attacking cells.  Sexual Selection   A mode of natural selection  Members of one sex choose mates of the opposite sex to mate with and compete with  members of the same sex for access to members of the opposite sex  Intersexual (opposite) vs. intrasexual (same) selection  Sexual selection explains sexual dimorphism in nature   When males look different than females   Ex. Peacocks   Intrasexual Selection   Sex that invests less is more “competitive”, sex that invests more “choosy”  Intersexual selection (male­male competition): leads to combat, sperm  Competition infanticides, alternative male strategies  Why Are Females Choosy?  Females bear most of the cost of reproduction   Pregnancy  Nursing  Eggs espensive­ovulate­500 eggs in lifetime; not all fertilized  Males   Millions of sperm/day The Reproductive Process  Nature of the reproductive process Asexual Reproduction Sexual Reproduction # of Parents 1 Usually 2 Gametes Involved No Yes Offspring Characteristics Identical Variation  Energy Cost Low High  Rate of Reproduction Fast Slow   Types of Sexual Reproduction  Bisexual Reproduction  Most common  2 genetically different parents­different gametes  Individuals are male or female­ dioecious  Separate sexes  Gonads­meiosis­gametes  Mostly in vertebrates and many invertebrates  Hermaphroditism   Both male and female organs in same individual (monoecious, hermaphrodites)  Many sessile, burrowing and/or endoparasitic invertebrates and some fish  Most avoid self­fertilization  Each individual produces egg  Could potentially produce twice as may offspring as dioecious species  Simultaneous hermaphrodites   Sequential hermaphrodites    Protandrous hermaphrodites   “Male first”  When trigger in environment comes for mating, one must change hormones  for reproduction  Protogynous hermaphrodites  “female first”  Change to male for time to reproduce  Opposite of protandrous hermaphrodites  Parthenogenesis 9virgin origin)  Embryo development from unfertilized egg  Male and female nuclei fail to unite after fertilization  Sexual or asexual (difficult classification)   Sex determination  Chromosomes   XX  XY  Types of Asexual Reproduction  Binary Fission  Bacteria and protozoa   Mitosis­offspring are identical  Lengthwise or transverse  Multiple Fisison  Repeated nuclear division  Before cytoplasm divides  Many daughter cells produced simultaneously  Budding  Will split from parent to become own organism  Unequal division of an organism  Bud is an outgrowth of the parent  Develops organs and then detaches  Fragmentation  Multicellular animal breaking into many fragments that become a new animal   Many anemones, hydroids, planarians  Why do so many animals reproduce sexually rather than asexually?  Disadvantages  More complicated  Requires more time  Uses more energy  High cost­passage of only half of genes to offspring  Production of males reduces resources for females that could produces eggs as most  males do not successfully mate  Favorable gene combinations are broken up  Advantages  Production of new genotypes to survive when environment changes  Allows spread of beneficial genetic combinations and removal of bad ones  In crowded habitats, natural selection is intense and diversity prevents extinction  On a geological time scale, sexual lineages with less variation are prone to extinction  Many invertebrates with both sexual and asexual modes can enjoy the advantages of  both processes 


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