Unit Two: Biodiversity
Chapter 4
A. Classifying Living Things
(Ch.4 - page 100)
Scientific knowledge is constantly evolving (
changing ):
 new evidence is discovered
 laws and theories are tested and possibly restricted,
 revised or even replaced
 paradigm shift?
Why is this happening?
 because of the wide variety of living things on Earth
Bio diversity
/
Life
\
Variety
 new species are constantly being discovered
 How do we distinguish between things that
are “living” and those that are “non-living”?
 ( do Thinking Lab - page 102-103 )
 In your lab groups, read the top of page 102 and
then follow the directions to complete the
Thinking Lab.
 You will have 20 minutes to complete the lab and
the results will then be compiled on the board.
How Biologists Describe Living Things:
(page 104)
1.
Living things are organized systems made
up of one or more cells:
 - unicellular ( one cell )
 - multicellular ( more than one cell )
 - in multicellular organisms these can be
organized into organs and organ systems
2.
Living things metabolize matter and energy:
 - chemical reactions used to digest and use food:
 - release energy to be used by cells
 - build molecules and compounds to maintain cells
3.
Living things interact with their environment
and are homoeostatic:
 - homeostasis ( staying the same )
 - even though organisms interact with their
environment, they maintain a constant internal
environment that is different from their environment (
eg. Your temp. )
4. Living things grow and develop:
 - unicellular living things grow and split ( reproduce )
 - multicellular living things grow and develop
( sperm + egg —> organism )
5. Living things reproduce themselves:
 - biogenesis ( make other living things like themselves )
6. Living things are adapted to their surroundings:
 - physical features and abilities that make them well-suited
for the way they live in a certain environment
eg. obtain food
transport nutrients
excrete wastes
move ( those that do move )
reproduce
communicate
How can all this information about living things be
organized in such a way that it can be best understood
and used?
 -development of “scientific classification systems”
 classify? - to put things in groups based on certain
characteristics
Why classify?
 - 1.5 million different kinds ( species ) of organisms have been
identified
 - maybe 20 million (?) more that are waiting to be discovered
To organize all this information, we have developed
classification systems:
 can be as simple as you classifying your CD’s
 or can be as complicated as trying to classify
all the living organisms on this Earth
 early biologists like Aristotle, didn’t have as
many organisms to classify (they hadn’t been
discovered!)
 Aristotle classified all organisms into one of two
kingdoms: Kingdom Plantae or Kingdom Animalia
 (These are still part of the classification system
used today)
 around the mid-nineteenth century, the invention
of the microscope led to the discovery of other
organisms that could not be placed in either of
these groups
 (Eg. some organisms moved like animals but were photo-
synthetic like plants - called euglena)
 thus, scientists had to revise their original ideas
 Ernst Haeckel then proposed that these organisms be put into
a new Kingdom called Protista
 as more organisms were discovered, Kingdom Fungi and
Kingdom Monera were added
 and just recently new discoveries about Kingdom Monera have
led Scientists to split this group into Kingdom Bacteria and
Kingdom Archaea (more later)
Naming and Classifying Organisms
 biologists need specific details to identify
organisms
 classification systems allow the accurate
identification of a particular organism
 Taxonomy -the science of naming organisms and
assigning
them to groups.
/
\
Taxon
Taxa
(Singular) (Plural)
 originally, common names in local languages were
used
 around the 18th century, this was discontinued and
Latin was used everywhere
 however, these names were very long and descriptive
 then, a Swedish botanist, named Carolus
Linnaeus developed a system for naming plants
and animals called
binomial nomenclature
/
\
two names
a system for naming things
 this is still the system we use today
 in his system of binomial nomenclature, Linnaeus
gave each organism a two-part scientific name
 eg. red maple =

Acer rubrum
/
genus
Or Acer rubrum
/
specific epithet
|
species name
(Both words have to be in italics, with the first
word CAPITALIZED)
 a “genus” name refers to the relatively small
group of organisms to which a particular organism
belongs
eg. all maple trees carry the genus name
Acer
 a “species” name is usually a Latin description of
some important characteristic of the organism
eg. rubrum is Latin for ‘red’
 this system is used by scientists everywhere
 organisms that share important characteristics,
are classified in the same taxon (group)
The taxa used are as follows:
Kingdom

Phylum

Class

Order

Family

Genus

Species
Classification Categories
 Kingdom
E.g. Humans
 Chordata
 Phylum
 Mammalia
 Class
 Primates
 Order
 Hominidae
 Family
 Animalia
 Genus
 Homo
 Species
 Homo sapiens
 These are in order from the most general taxon
(Kingdom) to the most specific taxon (Species)
 Refer to p. 109, Table 4.1 - notice how “kingdom”
contains the greatest number of organisms and as
you move down to “species”, you have narrowed the
number of organisms in the taxa down to one
particular species.
 Eg. All animals belong to Kingdom Animalia –
- BUT only some of them belong to Phylum Chordata –
- only some of there Chordata’s belong to the Class
Mammalia, … and so on until you have only one
species.
Common Names
 Why isn’t it practical for scientists to use common
names for organisms? ( ie. cat, dog, daisy)
 When you say “cat”, not everyone calls what you think
of as a “cat” that particular name ( ie. French -chat )
 - also, there are many different species of “cats” (ie.
lions, tigers, house cat) -which one are you referring
to?
 - also, within the same language people may use
different names for the same organism (ie. puma,
cougar or mountain lion are all the same animal)
 - also, common names can be misleading - look
at Figure 4.7 on page 112
 - this confusion would make it very difficult for
scientists to communicate with one another
Dichotomous Keys
(Also called Identification Keys or Taxonomic Keys)
 - people can use these keys as a guide or blueprint to
name organisms already identified by taxonomists
 - such keys move from general to specific
descriptions
 - the keys usually consists of a series of paired
statements that describe alternative (opposite)
characteristics of an organism
 - these paired statements usually deal with the
presence or absence of some characteristic or
structure that is easily seen
 - as each pair of statements gets more specific, a
smaller grouping of organisms is produced until
the species is finally identified
 - you can also create a dichotomous key of your
own to identify organisms (or anything)
 Complete the worksheets
 - LAB - Creating a Dichotomous Key page 110-
111
Viruses - Where do they fit?
 both bacteria and viruses cause many diseases for all
kingdoms, however, bacteria are classified as living
while viruses are not?????????
 viruses have no cellular structures (cytoplasm,
organelles, cell membrane) and they no carry out
respiration or other life processes.
- Most importantly they DO NOT have the ability to
reproduce “themselves” (they need to take over a cell).
 therefore, they are not classified in any of the kingdoms
 What are viruses?
 they consist of strands of DNA surrounded by a
protective protein coat called a capsid.
 they infect other cells
 there are 160 major groups which differ in size and
shape ( Fig. 4.20 page 122 )
 viruses multiply but NOT on their own
 they depend on the metabolism of prokaryotic
and eukaryotic cells to multiply
 - refer to the Life Cycle of the “T4" virus (
Fig.4.21 page 123 ) next slide.
Difficulties with Categorizing
 When we are trying to organize, we must recognize that
various problems can arise when we try to put organisms into
groups
 Organisms that ‘changed’ (mutated, evolved, etc…)
 Newly discovered species
 Therefore - no classification system is carved in stone.
 A valuable classification system needs to be adaptable and able
to accommodate change.
 Example - as learned earlier:
 we originally had a 2 kingdom system
 Then went to 3 Kingdoms.
 Then for a long period of time a 5 Kingdom system
 Recently new technology have identified that some bacteria are so
different from each other that the 6th kingdom was created.