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Transcript
Unit 4 – Lecture 1 Reproduction Reproduction – producing offspring by sexual or asexual means Two types: Asexual Reproduction Sexual Reproduction Asexual Reproduction Asexual Reproduction single “parent” cell produces genetically identical offspring on it’s own mostly prokaryotes Asexual Reproduction – cont’d Five Types: binary fission – cell splits into two identical cells used by single celled organisms; mostly prokaryotes Asexual Reproduction – cont’d [Five Types:] fragmentation – parts of organism can grow into complete new organism planaria, sponges, starfish, many plants Asexual Reproduction – cont’d [Five Types:] budding – new cells grow off of original cell and break off [yeast] Asexual Reproduction – cont’d [Five Types:] vegetative reproduction – new plants grow from a part of the living plant that is still connected. [dandelions, potatoes…etc] Asexual Reproduction – cont’d [Five Types:] parthenogenesis – rare occurrence; egg does not need to be fertilized to produce offspring water fleas, bush cricket, dandelion, even types of reptiles and possibly certain sharks Asexual Reproduction – cont’d Advantages: very quick does not depend on multiple of same organism being present Disadvantages: genetic problems all passed to offspring no biodiversity if environment changes and all organisms have same genes…they may not be well-suited to the environment anymore. Discuss With what you just learned about asexual reproduction, what do you think are the advantages and disadvantages of sexual reproduction? Sexual Reproduction Sexual Reproduction two parent organisms donate genetic information to form offspring genetic information is held in the gametes gamete = sex cell [egg, sperm]; formed by meiosis fertilization = gamete + gamete = zygote zygote grows into fetus Sexual Reproduction – cont’d Advantages: genetic diversity more likely to survive in changing environments Disadvantages: must have more than one organism takes more time and energy find mate produce gametes go through meiosis to form gametes Chromosomes Organisms have their own number of chromosomes – specific to their species “ploid” or “ploidy” = refers to chromosomal number Chromosomes – cont’d Sexual reproduction leads to diploid organisms diploid – contain two sets of chromosomes humans = 23 pairs = 46 total chromosomes called “2n” [n = # of chromosome sets] normal, somatic cells are diploid “soma” = body haploid – contains only one set of chromosomes diploid organisms have haploid gametes [sex cells; egg & sperm] called “1n” Chromosomes – cont’d Homologous Chromosomes chromosomes with the same information in the same locations we have 2 sets of homologous chromosomes 1 set from each parent Chromosomes – cont’d [Homologous Chromosomes] karyotype – organized profile of a person’s chromosomes Chromosomes – cont’d [Homologous Chromosomes] 22 pairs are autosomes autosome = non-sex determining chromosome same location on chr = same gene gene = area of a chromosome [or in DNA] which codes for a certain trait 1 pair are sex chromosomes [X or Y] two X [XX] = female one X & one Y [XY] = male Homework: Using your book and your knowledge of Mitosis… notes: similarities and differences between meiosis and mitosis [ch 10 whale; ch 11 cheetah] finish ½ of worksheet by tomorrow [while you take the notes] we will discuss it tomorrow.