Chapter 4

Unit Two: Biodiversity

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

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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.

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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

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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 Or Acer rubrum

/ /

genus 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

Phylum

Class

Order

Family

Genus

Species

E.g. Humans Chordata

Mammalia

Primates

Hominidae

Animalia

Homo

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.