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TOPIC : Classification AIM : What is classification?.
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Thousands of years ago, people started to realize that there were many different groups of living things. There were many different types of plants and animals. They started organizing them into groups based on certain characteristics. This is called CLASSIFICATION.
Scientists have identified more than 2.5 million different organisms. And their job isn’t even close to being finished! Some biologists estimate that there may be at least 7 million different kinds of organisms living in tropical rain forests and in the depths of Earth’s oceans. No wonder why we need to classify!
What is classification? Grouping of organisms based on similarities in structure
What is taxonomy? Branch of biology that deals with classification
The First Classification Systems Greek philosopher Aristotle, in 4th century BC, divided living things in 2 groups: Plants and Animals. He also placed animals into 3 groups according to how they moved (ones that flew, swam, walked). Birds and bats were placed into the same group even though they are quite different. This system was used for almost 2000 years. Around the 17th century scientists started to classify organisms in a more meaningful way (form and structure).
Today’s classification system is based on the work of Swedish scientist Carolus Linnaeus. He classified living things as plants or animals but grouped them according to similarities in form and structure. He used a system that consisted of groups within larger groups within larger groups.
What classification system do we use? Carolus Linnaeus (1700’s) All organisms are divided into 5 Kingdoms and 7 levels of classification
Largest groups Kingdom Phylum Class Order Family Genus Species Smallest groups and most closely related to each other
Kings Play Chess On Fine Green Stools
Kingdom 5 kingdoms Largest classification group Very diverse
Species One kind of organism Can produce fertile offspring with each other
Kingdom Phylum Phylum Phylum Phylum Phylum Phylum
Naming organisms Before Linnaeus developed his naming system, plants and animals were named by a series of Latin words that described the physical appearance of the organism. This was very confusing. For example, let’s look at the first name of the honey bee. Apis pubescens, thorace subgriseo, abdomine fusco, pedibus posticis glabris utrinque margine ciliatus. This means “fuzzy bee, light gray middle, brown body, smooth hind legs that have a small bag edged with tiny hairs.” Linnaeus named it Apis mellifera which means “honey-bearing bee.”
How do we name organisms? Carolus Linnaeus Binomial Nomenclature Two-word system of identifying organisms
Genus species Examples: Humans Homo sapiens Homo = Genus sapiens = species
Dichotomous Key List of characteristics used to identify an organism Arranged in steps (2 statements at each step)