Exam 4 Notes: Set 3
Exam 4 Notes: Set 3 Bio 1144
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This 2 page Class Notes was uploaded by Murry on Thursday April 14, 2016. The Class Notes belongs to Bio 1144 at Mississippi State University taught by Thomas Holder in Spring 2015. Since its upload, it has received 25 views. For similar materials see Biology II in Biology at Mississippi State University.
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Date Created: 04/14/16
Exam 4 Notes: Set 3 The Reproductive System • Organismal Reproduction – production of new organism (offspring) • Asexual Reproduction – reproduction that does not involve sexual activity and produces genetically identical offspring o One parent o No gametes o No reproductive organs (usually) o Produces genetically identical organism o Mostly the result of mitosis/cytokinesis o Simple, fast, and energetically cheap o Types of Asexual Reproduction: § Binary Fission – parent divides by mitosis into 2 approx. equal parts • Transverse (split vertically/across) • Longitudinal (split horizontally/lengthwise) § Budding – unequal division of an organism where an outgrowth is produced called a “bud” that detaches and becomes a new individual § Gemmulation – an internal bud forms inside the parental body and when parent is damaged or dies, the internal bud is released • Gemmule – the encapsulated (internal) bud § Fragmentation – multicellular animal breaks into 2 or more parts, and each fragment may become a new individual o No genetic variation o Some animals exhibit both asexual and sexual reproduction: In a good environment, they will reproduce asexually. In a bad environment, they will reproduce sexually. • Sexual Reproduction – involves production of sex cells (gametes) o Male = sperm o Female = egg o Mostly involves 2 parents o At least 2 types of reproductive organs o Energetically expensive, particularly on the female side o Takes lots of time o Genetic variation of offspring o Gametes – haploid cell that is direct result of meiosis/cytokinesis (egg or sperm); halves the chromosome number (23 chromosomes in humans) o Fertilization – fusion of male and female gametes; restores chromosome number in a new genetic arrangement (46 chromosomes in humans) o Zygote – fertilized egg o Types of Sexual Reproduction: § Hermaphroditism – individuals have both male and female reproductive organs • Monoecious – conditions of having box sex organs in the same body o Ex: parasitic worms and earthworms • Some fish experience sex reversal: the same organism can produce either eggs or sperm and switch between the two, sometimes during the same breeding season • Self fertilization – sperm and eggs are produced in the same body (limits genetic variation) • Cross fertilization – 2 individuals; each individual capable of producing offspring, but eggs and sperm can cross over § Parthenogenesis – the development of an embryo from an unfertilized egg; sperm may or may not initiate development • Identified in all vertebrates except Class Mammalia § Biparental Sexual Reproduction – 2 individuals with separate sex organs and sex cells; offspring produced from union of male and female gametes from genetically different individuals • Reproductive Patterns (Modes) In Vertebrates: o Oviparous – condition of female laying eggs outside of the body; fertilization can happen either internally or externally § Fish, amphibians, reptiles, birds, mammals § Ranges from abandonment to extensive care depending of species o Ovoviviparous – condition of eggs enclosed in a structure retained within the female’s body before giving birth to live young; internal fertilization § Nutrition comes from egg yolk § No maternal connection § Fish, amphibians, reptiles o Viviparous – condition of live bearing with a maternal connection; fertilization must be internal § Placenta is advanced feature allowing offspring to be born in more advanced state and allows for maternal connection; provides nourishment and gas exchange § Development within oviduct or a uterus § Parental care and protection § Highly energetically expensive for female § Mammals (except 3) and some reptiles • Sexual Reproduction over Asexual Reproduction o Why is sexual reproduction more common, esp. in vertebrates? § SR is more costly, takes more times, and requires more complex structures. § Main advantage of SR is genetic variation à some individuals will survive tough environmental conditions and changes § Natural Selection – measure of the differential survival and differential reproduction § AR produces little/no genetic variation (“clones”) à little chance of survival in tough conditions à natural selection will wipe out nearly all of them so they are most subject to extinction
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