Biology 150 Week 1 Notes
Biology 150 Week 1 Notes Bio 150
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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