CLASSIFICATION OF LIVING ORGANISMS Summarized Notes

BIOLOGISEDTEAM™

7 Apr, 2022

This should Take You About 2 hours To Understand, Please Do Not Worry If It Takes You Longer Than Expected, As We All Don't Learn At The Same Pace:

WHAT'S ORGANISATION

Grouping organisms according to their structural similarities is what we call Classification, in biology organisms that share similar features are placed in one group just like the way you will organise your study materials, rulers together, pencils together, pens together, books together, erasers and so on all in one place so you won't have to confuse just the same way organisms are grouped accordingly so scientists or we cannot confuse ourselfs. In Biology we arrange organisms in groups from the smallest to the largest group, the groups from the largest to smallest, are arranged as follows: kingdom, phylum (plural: phyla), class, order, family, genus (plural: genera) and species as the last and smallest group of organisms, you can remember better this by memorizing it as [King Philip Came Over For A Ginger Snack] i remember it better this way

THE BINOMIAL SYSTEM OF NAMING SPECIES

Organisms were given two scientists name in Latin by Carl Linnaeus a swedish botanists, this process is called the binomial system of naming species, this system is important because it allows scientists to accurately identify individual species, we can take the European robin which is Erithacus rubecula, it's much smaller than the American robin Turdus migratorious, which is from a different genus. The names of organisms genus and species are used to give it a two-word latin name called binomial nomenclature. The genus name is written first and starts with a capital letter, while the species name is written second and is written and in small letters. The binomial name is written in italics when typed and underlined seperately when handwritten. The tiger belongs to the genus called Panthera and the species called tigris, therefore it's scientific name will be typed as Panthera tigris or handwritten as Panthera tigris. This names are universal cause for instance every biologist will understand that Felis catus means 'house cat' without resorting to the dictionary, no matter what language they speak

THE USE OF HIERARCHICAL CLASSIFICATION SYSTEM

As you go through the classiffication hierachy, you'll notice that scientists have used broader features to put organisms into kingdoms which are the largest groups of organisms, features become specific, in other words two organisms that belong to the same species share more features than those that are in the same kingdom but in different species.
A group of organisms with similar features an this organisms capable of breeding and producing fertile offsprings are called species, just like horses and donkeys belong to the same kingdom, phylum, class, order, family, genus but from different species, therefore if this organisms breed they'll produce an offspring called a mule. The mule is infertile meaning that it cannot reproduce another offspring because it is a product of organisms of different species. Hierachy Classification has many uses, but the four are the most important, 1) Helps scientists sort organisms in order, 2) Te tell about the evolution of species, 3) To keep track of org, and lastly 4) To communicate globally and internationally about organisms

HIERARCHICAL CLASSIFICATION SYSTEM

-The are various sizes of groups into which living organisms are put, the largest group is the kingdom, the are five kingdoms
• Prokaryotes (including bacterias)
• Protoctista
• Fungi
• Plants
• Animals

-Each kingdom is further divided into groups called phyla, based on a few features that are shared by some organisms. For example the arthropod phylum contains all the animals without a backbone that also have jointed legs, and a hard exoskeleton and segmented bodies, such as insects, crustaceand arachnids. A phylum is then subdivided into classes, orders, families, genera, and finaly species.
In this system of classification the various groups are called taxa (singular: taxon) , here is the hierarchical classification system of classification

[KINGDOM] [PHYLUM] [CLASS] [ORDER] [FAMILY] [GENUS] [SPECIES]

(now let's use this chart to classify a lion)

:remember the first name with a capital and second name with a small letter.

A SIMPLE DICHOTOMOUS KEY

If you want to find the name of a plant or animal that you don't recognize, you might try to look through your books until you see a picture of it or google it, however this process can be time consuming, a quicker way of identifying unknown organisms is to use a simple dichotomous key. A dichotomous key is similiar to the key that you would use to unlock a door, it helps you to identify organisms by unlocking their names. A dichotomous key is a series of questions asking you about features that you can see on the organism. In each case two descriptions are given, you have to choose the one that applies, the key will then tell you which questions to go to next, this process repeats itself until eventually you arrive at the identify of the unknown organism.

HERE IS HOW TO CONSTRUCT A DICHOTOMOUS KEY

We'll use this three images to try and contruct a dichotomous key, as you might be asked in your exams to do so

Organism A

Organism B

Organism C

STEPS

• Write the numbers 1 and 2 -one less than the organisms to be classified
• Add the letters a) and b) to each number, for example

CHARACTERISTICS KEY

1. a)
b)
2. a)
b)
• Use visible and opposing differences (characteristics) to divide the group into two.
• Characteristics must be suitable and unambiguous
• Do not use the words 'and/or' in the description

CHARACTERISTICS KEY

1. a) Single leaf
b) more than one leaf Organism C
2. a)
b)

• Indicate the characteristics of the group not yet classified

CHARACTERISTICS KEY

1. a) single leaf go to 2
b) more than one leaf Organism C

2. a) veins parallel
b) veins branched

• Follow the same procedures as in Step 1

CHARACTERISTICS KEY

1. a) single leaf                              go to 2
     b) more than one leaf             Organism C
2. a) veins parallel Organism B
    b) veins branched Organism A

•Cross check by choosing any of the organisms, and using the key to determine if your key is working

HERE IS HOW TO USE A DICHOTOMOUS KEY

The simple dichotomous key is made up of numbered descriptions, each description comprises a pair of sentences. If you want to use the dichotomous key to identify organisms, follow these steps;
• Step 1: Read the instructions carefully first
• Step 2: Find the organism that you want to identify
• Step 3: Read the first pair of descriptions and find out which one matches the organism you are trying to identify. Opposite to the description that you choose there is a number, this number tells you which pair of descriptions to read next.
•Step 4: Go to the pair of descriptions as you are directed in step 3, read these descriptions again and decide which one describes the organism. If opposite to that description there is still a nimber, continue to the next pair of descriptions as per instructions. If opposite to the description that matches with the organism is a name, that is the name of the organism you are trying to identify
• Step 5: Repeat this procedure until you have identified all the organisms

This Is The End, I Hope You Learnt Something, Posted by Mrs Smith Merlin.