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Chapter 21

Bio 1F90 Chapter 21Notes

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Kathryn Belicki

BIOL 1F90 Chapter 21 Notes Species: group of related organisms that share a distinctive form -members of same species can interbreed to produce viable and fertile offspring Community: made up of different species Biological evolution: a heritable change in one or more characteristics of a population or species across many generations Microevolutionary change: small scale, changes in a single gene Macroevolutionary change: larger scale, formation of a new species or groups of species -John Ray (mid-late 1600s) developed early classification system, modern species concept -ideas extended by Carolus Linnaeus (modern classification system) -late 1700s, European scientists suggest life forms are not fixed -George Buffon said life forms change over time Jean-Baptist Lamarck -realized some animals stay the same, others change over time -spoke of inheritance of acquired characteristics -species spontaneously generated, then evolved to become more advanced -“Ladder of Life” analogy, simple organisms remained at the bottom of the ladder, while more evolved were at the top Charles Darwin -evolutionary theory shaped by several different fields of study -Uniformitarism hypothesis from geology: what we see today on Earth is not what it has always been -Thomas Malthus (an economist) claimed only a fraction of a population would survive and reproduce -Voyage of the Beagle (1831-1836) -distinctive traits of island species that provided them with advantages in their native environment -Galapagos Island Finches: Similarities in species, yet differences provided them with specialized feeding strategies -formulated Theory of Evolution by Natural Selection by mid 1840s -1858, Alfred Wallace sent Darwin his manuscript proposing similar ideas -Darwin and Wallace’s papers published together -Darwin’s book The Origin of the Species was published in 1859 -fundamental principle of evolution is species change over course of many generations -Darwin hypothesized existing life forms were modified from pre-existing life forms Evolution Based On -variation within a species -natural selection Natural Selection -individuals with more desirable traits are more likely to survive and reproduce -leads to adaptation -characteristics of a population change, members are better suited to environment -genetics gives us relationship between traits and inheritance Modern Synthesis of Evolution -natural variation exists, caused by random changes in genetic material -may be positive, negative, or neutral -genetic changes that promote survival or ability to reproduce, natural selection may increase prevalence of the gene in future generations Observations of Evolutionary Change -fossil record -biogeography -convergent evolution -selective breeding -homologies Fossil Record Fishapod -shows steps leading to evolution of tetrapods -Transitional form: link between earlier and later generation -broad skull with eyes on top, flexible neck, primitive wrist and 5 fingers -peeked above water for prey Oysters -some oysters underwent shell changes, 200mya -smaller curved shells became larger and flatter -flatter shells more stable in disruptive currents, oysters better adapted to environmental change of currents becoming stronger Horse Family -e
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