Exploring & Classifying Life

Chapter 1

 What is Life?

•       All living things are                              called organisms

•       Organisms must meet certain requirements (Your book mentions 5)

1     - All living things are organized

–    Organisms are organized by cells

–    A cell is the smallest unit of an organism that carries on the functions of life.

–    Each cell has an orderly structure and contains hereditary material (DNA)

 

 

 2. Respond to Environment

•      All living things respond to their environment

–    This means they can respond to a stimulus

•      A stimulus is anything that causes some change in an organism

–    I.e., heat, pain, sunlight

•      A response is the way an organism reacts to a stimulus

–    I.e., sweat, move away, grow towards light

•      Homeostasis is the maintaining of                               proper conditions inside an organism

–    Keep temperature, ph, mineral                                levels, etc. relatively constant

 

 3. Take in & Use Energy

•       Living things take in and use energy

•       Three different ways:

–    Producers perform photosynthesis and get energy from the sun

–    Some producers perform  chemosynthesis  and get energy from chemical sources

–    Consumers perform respiration and get energy from their food

 4. Grow & Develop

•      Living things grow and develop

•      Growth of multicellular organisms is due to an increase in the number of cells

•      Growth of unicellular organisms is due to an increase in the size of the cell

•      Development involves any changes that take place during the life of an organism

 5. Reproduce

•      Living things reproduce

•      Reproduction can be either sexual or asexual

•      Sexual reproduction is when two reproductive cells unite

–   Ex:  pollen and egg

•      Asexual reproduction is when one organism either splits or makes a copy of itself

–   Ex:  bacteria and binary fission 

 What Do Living Things Need?

•       Living things need a place to live that provides for all of the organism’s needs

–    Called a habitat

•       Living things need raw materials, like water, proteins, fats, and sugars

–    Used for food, energy, building blocks for new material

Spontaneous Generation

•       The early theory that living things could come from nonliving things

–    If you left out food, maggots, flies, etc. would appear - no knowledge of “little things.”

•       Was replaced by the theory of biogenesis

–    Living things can only come                        from other living things

•       Why was this replaced                             you say?

–    I’m glad you asked!

 A Little History

•       Francesco  Redi  (1668)

–    Put decaying meat in some jars, then covered half of them. When fly maggots only appeared on uncovered meat, concluded they came from fly eggs, not from the meat.  

 

 

 

 

•       John  Needham  (1745)

–    Heated broth in sealed flasks.                                  Broth became cloudy with microorganisms - concluded that they came from spontaneous generation

 A Little More History

•       Lazzaro Spallanzi  (1768)

–    Broiled broth in sealed containers for          longr than Needham. Only containers            that were opened  became cloudy. 

–  Louis Pasteur (1859)

»   “Disproved spontaneous generation by boiling broth in S-necked flasks that were open to the air. The broth became cloudy only when a flask was tilted and the broth was exposed to dusk in the S-neck.” Glencoe, p.22

 Alexander I.  Oparin  (1924)

•       Hypothesizes that gases in Earth’s early atmosphere combined to form more complex compounds found in living things

–    With help from the Sun, lightning, and geothermal energy, they combined

•       The original gases were:

–    Ammonia

–    Hydrogen

–    Methane

–    Water vapor

•       New compounds washed into ocean and formed “primordial soup.”

 Stanley L. Miller and
Harold  Urey

•      Tested Oparin’s hypothesis

•      Showed that chemicals found in living things can be produced artificially

•      They sent an electric current through a mixture of gasses (ones mentioned previously)

•      When they cooled, they condensed into the hypothesized “primordial soup.”

–    Contained amino acids

 

 

 Aristotle

•       Greek philosopher

•       First to classify organisms

•       Two groups

–    Plants and Animals

•       These groups were split up further

–    Ex:  Animal group was split into four legs, fewer legs, blood, no blood, etc.

 Carolus Linnaeus

•       Introduced a system based on similar structures of organisms

•       Came up with the most commonly used classification system

•       Kingdom (humans - Animalae)

–     Animalae, Plantae, Fungi, Protista, Monera   

•       Phylum (humans - Chordata)

•       Class (humans - Mammalia)

•       Order (humans - Primata)

•       Family - (humans - Homonidae)

•       Genus (humans - Homo)

•       Species (humans - sapiens)

–    Organisms in the same species can mate and produce fertile offspring

 Changes to  Linnaeun  Taxonomy

•       Some people add a division “above” kingdom called a domain

–    Bacteria,  Archaea ,  Eukaryota

•       Many people also use a 6 (some would say 8) kingdom system

–    Animal, Plant, Fungus, Protist, Eubacteria, Archaebacteria

–    Some split Protista into animal-like protists, plant-like progists, and fungus-like protists

 

 

 Modern Classification

•      Modern systems are based on phylogeny

–   Phylogeny is the evolutionary history of an organism

•      The same divisions are used (Kingdom, Phylum, etc.), some animals are just put into different places

 

 Binomial Nomenclature

•       Two-word system used by  Linnaeus  to name species

–    Homo sapiens

•       The first word identifies the genus, or group of similar species

–    Always capitalized, italicized when typed, underlined when written

•   Homo

•       The second word identifies the species

–    Always lower-case, italicized when typed,  underlinen  when written

•   sapiens

 

 Why Use Scientific Names?

•       Avoid mistakes - common names can be misleading

–    It’s also a universal language

•       Show that organisms in the same genus are related

–    Ex:

•       To give descriptive information

–    The names mean something (in some language)

•       To allow information to be organized easily

Tools for Classification

•      Field Guides - descriptions and illustrations of organisms

•      Dichotomous keys - detailed lists of identifying characterisstics that include scientific names

•      Example in Book (some mice of North America):