Ecology Week 5
Ecology Week 5 LIFE 320-001
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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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