Slide 6 - How many species are there?
• Not an easy question to answer. Estimates of the total number of living species range from 10 to 100 million, depending on the source of your information. Likely actual number is on the order of 13 to 14 million, a number based on a large body of scientific data.
• Most being insects and microscopic life forms in tropical regions.
• Approx 1.75 million species have been given scientific names. We will be discussing scientific names on Thursday.
• Nearly 2/3 of these are insects
• We may never know how many there are because many of them will become extinct before being counted and described
Slide 6
How many species are there?
Go through data.
Cite source
Which kingdom has the largest number of species identified?
Which kingdom has the fewest?
Which has the second fewest?
I believe that they have identified almost all of us vertebrates – why?
KINGDOM # OF SPECIES
Bacteria.................................. 4,000
Protoctists (algae, protozoa, etc)........ 80,000
Animals, vertebrates.......................52,000
Animals, invertebrates.................... 1,272,000
Fungi..................................... 72,000
Plants.................................... 270,000
Total number of described species... 1,750,000
Possible number of unknown species: 14,000,000
from the United Nations publication: UNEP-WCMC (2000). Global Biodiversity: Earth's living resources in the 21st century. Cambridge, World Conservation Press.
Slide 8 - How many species are there?
• Tremendous diversity in life today is not new to our planet. Noted paleontologist Stephen Jay Gould estimated that 99% of all plant and animal species that have existed have already become extinct with most leaving no fossils.
• Humbling to realize that humans and other large animals are freakishly rare life forms. Bacteria, bacteria, fungi and invertebrates - half of the kingdoms and approximately ¾ of all identified species – are all minuscule compared to us vertebrates.
• 99% of all known animal species are smaller than bumble bees.
Slide 9 - When did scientists begin to classify things?
• A little trip into the past. Forgive me; I love history as much as science. What people did and why they did it is fascinating to me. This of course, is called social science.
• Aristotle classified animals into logical groups more than 2,000 years ago. Aristotle did not view animals as being related by descent, he arranged all living things into an ascending ladder with humans at the top.
Aristotle philosophized on virtually every other subject. He classified animals in a "Scala Naturae" or "Chain of Being" which consisted of God, man, mammals, oviparous with perfect eggs (e.g., birds), oviparous with non-perfect eggs (e.g., fish), insects, plants, and non-living matter. He considered each link in the chain as a "species."
Animals were separated into two major groups – those with red blood and those without red blood – that correspond very closely to our modern classification of vertebrates and invertebrates. Animals were further classified according to their way of life, their actions, and their body parts.
Aristotle categorized plants as herbs, shrubs, or trees depending on their size and appearance.
• Then, in terms of Taxonomy, nothing really changes for several centuries.
In the late 1600’s, the English scientist John Ray established the species as the basic unit of classification.
• Just kidding! Linneaus is going to be our main man; along with Darwin and we will be talking a lot about him.
• Baron Georges Cuvier first divided the animal kingdom into subgroups in 1817.
Slide 10 - When did scientists begin to classify things?
• Today we have classification based on genetics and evolution.
• Back in the days of Aristotle and Reyes, we call it taxonomy - classification of organisms into different categories based on their physical characteristics.
• Leading naturalists of the 18th and 19th centuries spent their lives identifying and naming newly discovered plants and animals. However, few of them asked what accounted for the patterns of similarities and differences between the organisms. This basically non-speculative approach is not surprising since most naturalists two centuries ago held the view that plants and animals (including humans) had been created in their present form and that they have remained unchanged. As a result, it made no sense to ask how organisms have evolved through time. Similarly, it was inconceivable that two animals or plants may have had a common ancestor or that extinct species may have been ancestors of modern ones.
• One of the most important 18th century naturalists was a Swedish botanist and medical doctor named Karl von Linné. He wrote 180 books mainly describing plant species in extreme detail.
• Since his published writings were mostly in Latin, he is known to the scientific world today as Carolus Linnaeus, which is the Latinized form he chose for his name.
• In 1735, Linnaeus published an influential book entitled Systema Naturae in which he outlined his scheme for classifying all known and yet to be discovered organisms according to the greater or lesser extent of their similarities. This Linnaean system of classification was widely accepted by the early 19th century and is still the basic framework for all taxonomy in the biological sciences today.
Slide 11 – The Linnaean System
• The Linnaean system uses two Latin name categories, genus and species, to designate each type of organism.
• A genus is a higher level category that includes one or more species under it.
• Such a dual level designation is referred to as a binomial nomenclature or binomen (literally "two names" in Latin).
• For example, Linnaeus described humans in his system with the binomen Homo sapiens, or "man who is wise"--Homo is our genus and sapiens is our species.
• Linnaeus also created higher, more inclusive classification categories. He placed all monkeys and apes along with humans into the order Primates.
o His use of the word Primates (from the Latin primus meaning "first") reflects the human centered world view of Western science during the 18th century.
o It implied that humans were "created" first. However, it also indicated that people are animals.
Slide 12 – Branching Evolution
• While the form of the Linnaean classification system remains substantially the same, the reasoning behind it has undergone considerable change. For Linnaeus and his contemporaries, taxonomy served to demonstrate the unchanging order inherent in Biblical creation and was an end in itself. From this perspective, spending a life dedicated to precisely describing and naming organisms was a religious act because it was revealing the great complexity of life created by God.
• This static view of nature was overturned in science by the middle of the 19th century by a small number of radical naturalists, most notably Charles Darwin. He provided conclusive evidence that evolution of life forms has occurred. In addition, he proposed natural selection as the mechanism responsible for these changes.
Late in his life, Linnaeus also began to have some doubts about species being unchanging. Crossbreeding resulting in new varieties of plants suggested to him that life forms could change somewhat. However, he stopped short of accepting the evolution of one species into another.
• Since Darwin's time, biological classification has come to be understood as reflecting evolutionary distances and relationships between organisms. The creatures of our time have had common ancestors in the past. In a very real sense, they are members of the same family tree.
• The great diversity of life is largely a result of branching evolution or adaptive radiation. This is the diversification of a species into different lines as they adapt to new ecological niches and ultimately evolves into distinct species. Natural selection is the principal mechanism driving adaptive radiation.
With the advent of DNA technology, the Linnaean system is rapidly changing. Given the relationships that we can see at the genetic level, many species we thought were unrelated are actually closely related.
