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Chapter 5

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Department
Natural Science
Course
NATS 1880
Professor
Paul Delaney
Semester
Summer

Description
 Species are a group of organisms that have 5–T HE N ATURE OF L IFE ON E ARTH common characteristics (and can interbreed). 5.1 D EFINING L IFE They are genetically distinct o Genus (generic) Species (Specific): Homo Sapiens (humans) WHAT ARE THE GENERAL PROPERTIES OF LIFE ?  We focus our search on life that is similarWtHAT IS THE ROLE OF EVOLUTION IN DEFINING LIFE? own. We do not look for silicon life because we don’t have any examples on Earth. AN ANCIENT IDEA  Evolution means “change with time” SIX KEY PROPERTIES  Order: Materials in  Anaximander said life arose in water and evolved into more complex forms. living organisms always  Aristotle said species are fixed and independent exhibit some type of and do not evolve or go extinct. order. For example, molecules in living cells  Lamarck suggested that fossils were related by evolution. Life adapted by using some traits more are not scattered and passing them onto kids. Like Arnold having randomly about but instead are arranged in super babies.  Fossils prove it occurred, Darwin proved HOW patterns that make cell structures. THE M ECHANISM FOR E VOLUTION  Reproduction: Living  Charles Darwin described observations of living organisms and showed how they supported that organisms reproduce or are products of evolution does occur reproduction  Overproduction and competition for survival: mules can not reproduce (horse/donkey) but are still living organisms populations can make more offspring than environment can support but can’t due to limited viruses cannot reproduce by themselves but can resources. This leads to competition infect other organisms and use them prions cause other proteins to become abnormal Individual Variation: individuals are unique and some have traits that are more competitive  Inescapable conclusion:  Growth and Development: Living organisms unequal reproductive success: those with best grow and develop directed by genetics suited traits will survive.  Energy Utilization: Living organisms use enIt is this unequal reproductive success that is called to create order, reproduce, and grow. natural selection. This explains how species change in Without an input of energy, systems tend response to their environment – by favouring traits that towards disorder (second law of improve adaptation thermodynamics) EVIDENCE FOR EVOLUTION BY NATURAL SELECTION  Reponse to the environment: Living organisms  An ancestral pair of finches reached the respond to environment Galapagos from the mainland and over time they adapted to the different islands to become the  Evolution: Involves ability to reproduce and and different species.  He also discovered fossils of extinct organisms respond to environment. Differences in organismal traits mean that some has a survival that were related to modern species advantage over others. Those traits become dominant.  He made two inferences: natural selection can explain the differences between species, and can also produce new species that replace old ones.  He also found evidence for evolution by looking at artificial selection. o For example, wild mustard can be selected to make other vegetables. o Natural selection also allows resistant bacteria to become more common THE MOLECULAR BASIS OF EVOLUTION  Evolution by natural selection means species that have adaptations to their environment survive and pass on hereditary traits to offspring.  The medium for natural selection is DNA. W HAT IS LIFE?  Something that can reproduce and evolve  Darwin’s theory does not tell us how life started, so we assume at one point, chemistry became biology. EARTH LIFE IS CARBON BASED 5.2 C ELLS : THE BASIC UNIT OF LIFE  Life on Earth is made up of more WHAT ARE LIVING CELLS ? than 20 elements o C, O, H, N accounts for  All organisms are composed of cells and surrounded by a membrane 96%  Some are single celled others are multicellular  A cells structure and function is due to carbon  All cells pass on their hereditary data through DNA  Why is carbon so important? o It can bind to four  This led to the conclusion that all life on Earth atoms at a time shares a common ancestor o It can to itself in endless lengths o It can bind in various branches o It can form double bonds WATER o It can form rings  Used by organisms – plants use it for o Not too strong, not too weak photosynthesis  Used as a solvent – transporting NON -CARBON BASED LIFE mechanism  Silicon is the only element besides carbon  Is a polar molecule due to slightly positive that can bind to 4 atoms hydrogen and slightly negative oxygen  Silicon has three strikes against it o This makes it a great solvent o Bonds formed are weaker o Does not form double bonds Properties o Mixed with oxygen it is solid, immobile 1. Water is abundant  1000x more abundant yet carbon is basis of life 2. It is good at dissolving – can carry molecules  It turns out carbon is common in the universe 3. High heat capacity and high vaporization WHATARETHEMOLECULARCOMPONENTS energy – regulate temperature 4. High surface tension – keeps cells together OFCELLS? 5. Breaks down in UV light – produce ozone CARBOHYDRATES 6. Water floats when it is ice – insulated water below for organisms  Polymers of monosaccharide’s 7. Liquid for 100 degree range  Used for energy storage o Cellulose
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