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Ecology Week 5

by: Rheanna Gimple

Ecology Week 5 LIFE 320-001

Rheanna Gimple

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Sex and Evolution Notes
Ed K Hall
Class Notes
Ecology, sex, evolution, Biology: Ecology and Evolution, ecology&evolution, reproduction, Sexual reproduction, asexual reproduction, Genetics
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This 5 page Class Notes was uploaded by Rheanna Gimple on Thursday October 13, 2016. The Class Notes belongs to LIFE 320-001 at Colorado State University taught by Ed K Hall in Fall 2016. Since its upload, it has received 4 views. For similar materials see Ecology in Biology at Colorado State University.


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Date Created: 10/13/16
Ecology Week 5: Sex and Evolution  Reproduction o Source of genetic variation o Two basic forms and lots of subtlety  asexual reproduction  sexual reproduction  Asexual reproduction: single individual produces viable offspring o Reduced genetic variability – no to little genetic migration o Vegetative reproduction  Generates clones  Ex: Pando, aspens, redwoods  Tissue from various parts of plants can regenerate new plants  Leaves  Roots  Shoots o Asexual animals: mainly in coral reef systems  Budding  Outgrowth from parental individual  When clones remain attached, the organism is considered colonial  Fission  Splitting organisms in two (or more) o Ex: sea anemone  Fragmentation is breaking of the body into pieces, some or all of which develop into adults  Fragmentation must be accompanied by regeneration, regrowth of lost body parts o Ex: Planaria (flatworms), sea stars  Parthenogenesis  Single female produces fertile eggs  Multiple processes can produce eggs o Thelytoky - females produce female offspring o Pseudogamy - sperms is required to activate the egg but only maternal genes are expressed  Occurs in polyploid species  Often triploids  Hybrid species  Some plants undergo an alternation of generations  Diploid -> triploid -> diploid ->  Crossing with a tetraploid o Automixis - egg undergoes meiosis  Fusion of two of the products of meiosis  Not clones: still uses independent assortment  Limits genetic diversity  Provides population viability for fragmented or sparsely populated areas o Aptomixis - egg does not undergo meiosis  A cause for parthenogenesis o Wolbachia  Genus of bacteria  Most common parasite on the planet  Infects somewhere between 20- 70% of all insect species, nematodes, spiders, and other invertebrates  Can infect different organs but it's work on the testes and ovaries is a marvel to behold  Infected individuals show one of four phenotypes:  Male killing o Male larvae are killed during development  Feminization o Converts males into females or pseudo-females  Parthenogenesis  Cytoplasmic incompatibility o Infection prevents successful reproduction o Only individuals with same strain can successfully mate  Antibiotics can kill Wolbachia  Reverts parthenogenic individuals back to sexual individuals  Loss of genes for mating in males leads to complete failure to reproduce o In some species the ovaries will not develop o Genes for mating calls lost o Sperm no longer function o Females no longer respond to male advances  Antibiotics are being explored to eliminate a nematode in people because of this effect  Being explored as health tool o Zika and Dengue carried by mosquitos, but infected mosquitos are resistant  Infecting males then releasing them should reduce human infections  Self fertilization  Monoecious plants have both male and female reproductive organs  Can self-fertilize  Some species are considered obligate selfers and many others allow for some fraction of reproduction to be by selfing  Other plants have evolved mechanisms to prevent selfing  Reduces heterozygosity in the population  In Animals: o Some hermaphroditic animals can self-fertilize  Fresh water and land snails  Decollate snail introduced as biocontrol agent  Nonspecific predator o Rivulus marmoratus  Ovotestes allow adults to self-fertilize  Young can outcross  Population are mostly hermaphrodites and males  Hermaphroditism o Many flowers and animals can produce both male and female gametes o Simultaneous hermaphrodites  Can produce both gametes at same time  Gastropods  Annelids o Sequential hermaphrodites  Start as one sex and later change to opposite sex o Variations on hermaphroditism  Protogyny: sequential hermaphroditism  First females then males  If start males stay males  Protandry  First males then become females  If start females stay female  Sex determination o Many animals are XY  Generally this means offspring are 50/50 o In some species female is XY  She has control over sex of offspring/ sex ratio o Environmental effects can control sex  Many reptile's sex is Temperature dependent o Social dynamics can control sex  Blue-headed wrasse young develop as females if isolated, males if in groups as juveniles  Platypus has 10 sex chromosomes but lacks mammalian sex determination gene  Sexual reproduction: two individuals needed to contribute genetic material to offspring  Mating systems o Multiple forms:  Polygamy  Polygyny: one male multiple females  Polyandry: one female and multiple males  Sexual selection manipulates the outcomes o Intrasexual selection o Copulatory plugs and mate guarding  Monogamy  Uncommon in mammals  Common in birds o Lots of cuckolding  Sexual Dimorphism: same species phenotypic differences between males and females o Example: male peacocks are brightly colored while females are mostly brown o Males tend to be flashier in many species because their reproductive success is normally limited by the number of females they mate with  Females limited by number of eggs that can be made o Males tend to provide less parental care than the females in most species


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