Tài liệu Khoa Học Tự Nhiên

Evolution is change in species over time. There is overproduction of offspring, which leads to competition for resources. Heritable variations exist within a population. These variations can result in differential reproductive success. Over generations, this can result in changes in the genetic composition of the population. Remember: Individ...

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Point mutations: changes in one base (eg. sickle cell) Chromosomal mutations: delete, duplicate, disrupt, rearrange  usually harmful Sexual recombination: contributes to most of genetic variation in a population Crossing Over (Meiosis – Prophase I) Independent Assortment of Chromosomes (during meiosis) Random Fertilization (sperm + egg)

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Many new species arise from a single common ancestor Occurs when: A few organisms make way to new, distant areas (allopatric speciation) Environmental change  extinctions  new niches for survivors Eg. Hawaiian archepelago

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Sedimentary rock (layers called strata) Mineralized (hard body structures) Organic – rare in fossils but found in amber, frozen, tar pits Incomplete record – many organisms not preserved, fossils destroyed, or not yet found

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Principle of maximum parsimony: use simplest explanation (fewest DNA changes) for tree – “keep it simple” Molecular clocks: some regions of DNA appear to evolve at constant rates Estimate date of past evolutionary events Eg. Origin of HIV infection in humans= 1930’s

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Anchors plant, absorbs H2O & minerals, stores sugars/starches Root hairs – tiny extensions of epidermal cells, increase surface area for H2O and mineral absorption Mycorrhizae: fungus + plant root symbiotic relationship

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Review: Selectively permeable membrane: osmosis, transport proteins, selective channels Proton pump: active transport; uses E to pump H+ out of cell  proton gradient Cotransport: couple H+ diffusion with sucrose transport Aquaporin: transport protein which controls H2O uptake/loss

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Rhizobium bacteria supply nitrogen at roots (fix atmospheric N2 to usable N) Plant supplies sugar & amino acids Mycorrhizae (plant + fungus)

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Egg cell  plant embryo Ovules inside ovary  seeds Ripe ovary  fruit Fruit protects enclosed seed(s) Aids in dispersal by water, wind, or animals

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Anatomy: the study of the biological form (STRUCTURE) of an organism Physiology: the study of the biological FUNCTIONS an organism performs Structure dictates function!

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