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Chapter 3

BIOLOGY Chapter 3.docx

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York University
BIOL 1000
Paula Wilson

BIOLOGY Chapter 3: Selection, Biodiversity, and Biosphere 9/13/2012 12:59:00 PM - biodiversity: measured as the number of species of organisms, biodiversity reflects the reality hat life on Earth exists from the ocean floor to well into the atmosphere - the study of biology focuses on the levels of life (FIGURE 3.1 PAGE 48)  from molecules and organelles, cells, organisms, ecosystems, and the biosphere - biosphere: all regions of Earth’s crust, waters and atmosphere that sustain life How many different types of organisms live on Earth? - answer depends on how we define “type” of organism i. using a taxonomic definition (defined in chapter 18), we can consider the number of organisms in each kingdom - numbers are easier to determine for some kinds of organisms than for others, but we can still determine an overview of life on Earth by groups of organisms (FIGURE 3.3 PAGE 50) - information about large, easily observed organisms such as mammals, birds, and flowering plants is quite accurate compared to information about the numbers of species of microscopic organisms that live in habitats where they are hard to observe - we only have rough estimates of the numbers of species of soil fungi and aquatic prokaryotes ii. when we group organisms by factors other than their taxonomic categories, we get a different picture of the diversity of life on Earth A. one approach is to consider how organisms obtain carbon (carbon is the “backbone” of all organic molecules synthesized by an organism - most plants are autotrophs (auto = self; troph = nourishment)  they synthesize organic carbon molecules using inorganic carbon (CO2) (*note: even though CO2 contains a carbon atom, oxides containing carbon are considered inorganic molecules.) - all animals are heterotrophs, meaning they obtain carbon from organic molecules, either from living hosts or from organic molecules in the products, wastes, or remains of dead organisms Organisms are also divided according to the source of the energy they use to drive biological activities. - chemotrophs (chemo = chemical; troph = nourishment) obtain energy by oxidizing inorganic or organic substances - whereas phototrophs obtain energy from light Combining the carbon and energy sources allows us to group living organisms into four categories (TABLE 3.1 PAGE 50) - prokaryotes show the greatest diversity in their modes of securing carbon and energy Study Question: Describe the differences among heterotrophs, autotrophs, photoautotrophs, and chemoautotrophs. Provide an example of each. I use light as a energy source and glucose as a organic molecule, what am I?  photoheterotroph because light as energy source = photo, and glucose as organic = heterotropgh, because autotrophs use CO2 (inorganic molecule) and synthesize organic molecules from that Selection 9/13/2012 12:59:00 PM - selection: occurs when some force or phenomenon affects the survival of individual organisms Examples: i. outbreak of some disease in a hospital is an example of the outcome of selection.  bacteria that are resistant to antibiotics can survive and reproduce ii. emergence of pests that are resistant to pesticides - selection occurs when a large population of individuals is exposed to a lethal factor and only resistant individuals survive to reproduce - if resistance is inherited, the offspring of survivors will be resistant - if the resistant population is able to reproduce quickly, there is potential for explosive growth of a population of individuals who are resistant to the lethal factor Thus: the key factors behind selection are a selective force (pressure) and the capacity for explosive population growth  consequences of this can be deadly for humans Here are three examples of selection in action: A) Case 1: Syphilis: Migration and Emergence of a Disease Treponematoses are diseases caused by bacteria in the genus Treponema - Treponema pallidum pallidum is the bacterium that causes syphilis – a venereal disease also known as “the pox” First signs  small, painless sores (chancres) at the site of contact Secondary stages  Rash  Fever  Fatigue Tertiary syphilis  Disfigurement  Neurological disorders  Cardiovascular problems Syphilis and other treponemal diseases, except pinta, leave distinct marks on the skeleton which have allowed paleoanthropologists to study these diseases in human skeletal remains and determine their prehistoric distribution The history if T. Pallidum appears to have involved in three steps:  First, T. Pallidum appeared as a nonvenereal infection and spread with humans throughout the Middle East, Europe and the New World. At that point, the pathogen cause
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