Classification of Organisms. Chapter 18. What is an Organism?. An organism is generally referred to any living thing. More specifically any thing that has “cells”. This includes the smallest of organisms, the single celled bacteria, all the way to the largest redwood tree or Blue Whale.
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An organism is generally referred to any living thing. More specifically any thing that has “cells”.
This includes the smallest of organisms,
the single celled bacteria, all the way to the
largest redwood tree or Blue Whale.
Biologists use classification to organize living things into groups so that the organisms are easier to study.
Divide into groups of 3 or 4
In the following few slides, you will find
14 different organisms, each of them labeled with a letter.
In your groups, write down two main classification (example red/green).
Then place the corresponding letters under
the correct classification.
These organisms have been
classified by their color.
There were actually several different ways to go
about classifying these 14 organisms. You might
have done color, shape, size, number of legs… the possibilities are endless. You might have encountered one or two that really did not fit into either of your two classifications, what should you do when this happens? Make a new classification of course! And this is what scientist have done as well through the years.
two main classifications, plants and animals. Over
the years, scientist came up with certain “plants”
that really did not act like plants, they couldn’t
make their own food. So the kingdom Fungi was
When microscopes were invented, scientist discovered new single celled organisms. Some were animal-like, some were plant like and some were both.
This lead to the creation of the Kingdom Protista.
discovered that many of the single celled
organisms were quite different. Some of them
had a nucleus and others did not. This lead
to the Kingdom Monera, the kingdom of the
most simplistic organisms, Bacteria.
Asistotle – he had the first classification system that group animal according to how the moved or where they lived.
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He also had subgroups for organisms that shared other characteristics
Carolus Linnaeus- Swedish – He placed organisms in groups according to observable features and physical characteristics.
Linnaeus had a two name system called
Felis concoloris the scientific name for a puma.
Is the genus name- it is written first and is always capitalized
Is the species name – it is written second and is always lower case
because that was the language that
was dominate around the world at
that time. This is why even today
organism’s scientific names are always
Plant and Animal, Linnaeus came up
with several sub-classifications for those
kingdoms. They are: Kingdom, Phylum,
Class, Order Family, Genus, and Species.
What Kingdom are you in?
What phylum are you in? Why?
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Animalia (Animal in Latin)
Chordata (Spinal Cord)
Mammalia (have mammary glands)
Primates (two mammary glands)
scientifically, you always use the
genus and the specie names.
Therefore, the human species would
be referred to as:
Biologists usually define species based on appearance and structure
Biological species- group of actually or potentially interbreeding natural populations, reproductively isolated from other such groups
Hybrids can be made between two species
Convergent evolution- organisms evolve similar features independently
Example: anteaters- long, sticky tongue; few teeth; large salivary glands
Analogous characters- similar features of organisms that evolve independently
Phylogeny- evolutionary history of a species
Cladogram- diagram based on patterns of shared, derived traits that shows the evolutionary relationships among groups of organisms
Differences in morphological, physiological, molecular, and behavioral level between organisms
New derived characters will show up on the cladogram as groups evolve
The classification system for organisms
have been around for a long time. It has
endured several changes and is quite
complex. Without it modern biology could
not exist, much in the same way that
a grocery store would go out of business
if it did not have a classification system.