ch 7 Sexual or Asexual Asexual involves a single parent organism and produces offspring or daughter cells that are clones Sexual Reproduction involves genetic contribution in the form of gametes from two sources ID: 565101
Download Presentation The PPT/PDF document "Reproduction" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Reproduction
ch
: 7Slide2
Sexual or AsexualAsexual – involves a single parent organism and produces off-spring or daughter cells that are clonesSexual Reproduction – involves genetic contribution in the form of gametes from two sourcesSlide3
Asexual ReproductionProkaryotes: Binary Fission Eukaryotes:
Sponges: BuddingInsects: Virgin BirthVegetative Reproduction:RunnersCuttingsRhizomes
SuckersPlantlets without sexSlide4
Binary FissionProkaryotes (Bacteria) reproduce this way.Binary = Two ; Fission = split
Stages:Replication of the circular molecule of DNAAttachment of these DNA molecules to plasma membraneLengthening of cell
Division of cell via constriction in the middle. Each daughter cell contains one circular molecule of DNASlide5
BuddingGroups of cells formed by mitosis break away from main organismApproach taken by sponges & other simple organism such as Hydra
Hydra
SpongeSlide6
Virgin Birth (Parthenogensis)Young are produced from unfertilised eggs (no sperm required)
Eggs produce by mitosisUsually invertebrates, but some reptiles and sharks
Whiptail Lizard species
Cnemidophorus
neomexicanusAphidDaphniaSlide7
Vegetative ReproductionRunnersCuttings/fragmentationTubersRhizomesSuckers
PlantletsSlide8Slide9
Identify the type of Vegetative ReproductionActivitySlide10Slide11
Biozone p.173Slide12
Asexual Reproduction using TechnologyCloning using:Tissue cultureEmbryo cells
Somatic cellsHigh rates of embryo loss and survival rate after birth limits Mammalian cloning.Slide13
Identical TwinsEmbryo cell cloning is the artificial form of natural cloning.Is this mitosis or meiosis?Slide14
Sexual ReproductionMale + Female contributionContribute genetic material in a single cell (egg or sperm) called a GAMATEThis is produced by the process of
MEIOSISSlide15
What may be some advantages/disadvantages of asexual/sexual reproduction?Slide16
NOB: table p.186
Feature
Asexual Reproduction
Sexual Reproduction
Numbers of parents or parental contribution onetwoProcesses involvedBinary fissionCell replication (mitosis)Gamate production involving meiosisFertilisationAbsentFusion of gamates requiredOffspringNo genetic variability; offspring are clones of single parentOffspring differ from parents and from each other
Rate of offspring reproduction
faster
slowerSlide17
Simplified: Mitosis/Meiosishttp://www.bbc.co.uk/schools/gcsebitesize/science/add_edexcel/cells/mitosisact.shtmlSlide18
Meiosis: Making GamatesCell division that is vital for sexual reproductionOccurs in the Testes (Sperm production) & Ovaries (Egg production) –
germ line cellsResults in formation of haploid (half the number of chromosomes) gametesThe four daughter cells are not genetically identicalSlide19Slide20
Modelling Meiosisfile:///C:/Users/Susan/Desktop/School/Biology%20Resources/SWF%20Files%20Biology/Cell%20Division/Meiosis%20narrated.swfSlide21
Where does genetic variation come from?Random segregation of chromosomes
Crossing overSlide22
Random SegregationDuring metaphase 1 homologous chromosomes arrive at the equatorThey arrange themselves in a random order on the
equatorIn human cells with 23 chromosomes there are 223 different possible ways the chromosomes can segregate!That is over 8 000 000 different types of gameteSlide23
Crossing OverDuring prophase 1 of meiosis homologous chromosomes come together in pairs
Each chromosome is divided into two chromatidsThe homologous chromosomes twist around each other, creating tension and breaks on the chromatids
During cross over, corresponding fragments may get swapped over.This “cutting and sticking” means that genetic material is exchanged.
This creates new genetic combinations and variation in the gametes is increased.Slide24
Your Tasks:Using the following points to draw up a table comparing mitosis & meiosis:Where & how often it occursNumber of nuclear divisionsProphase
MetaphaseAnaphaseTelophaseMeiosis 2Number of daughter cells at the end of meiosis 2Slide25
MeiosisActivity – Work in groups of two or three. view the video clip and produce a script to describe what is happening.Need to use all these terms:- germ-line, diploid, haploid, homologous chromosomes, synapses,
chiasma, genetic variation, gamate, zygote & describe phases