Unit Two: Biodiversity. Chapter 4

Transcription

1 Unit Two: Biodiversity Chapter 4

2 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 / \ Life Variety new species are constantly being discovered

3 How do we distinguish between things that are living and those that are non-living? ( do Thinking Lab - page ) 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.

4 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

5 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. )

6 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

7 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? million different kinds ( species ) of organisms have been identified - maybe 20 million (?) more that are waiting to be discovered

8 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!)

9 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

10 (Eg. some organisms moved like animals but were photosynthetic 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)

11 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. / \ Taxon Taxa (Singular) (Plural)

12 originally, common names in local languages were used around the 18 th century, this was discontinued and Latin was used everywhere however, these names were very long and descriptive

13 then, a Swedish botanist, named Carolus Linnaeus developed a system for naming plants and animals called binomial nomenclature / \ two names a system for naming things this is still the system we use today

14 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)

15 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)

16 The taxa used are as follows: Kingdom Phylum Class Order Family Genus Species

17 Classification Categories Kingdom Phylum Class Order Family Genus Species E.g. Humans Chordata Mammalia Primates Hominidae Animalia Homo Homo sapiens

18 These are in order from the most general taxon (Kingdom) to the most specific taxon (Species) Refer to p. 109, Table 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.

19 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?

20 - 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 this confusion would make it very difficult for scientists to communicate with one another

21 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

22 - 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)

23 Complete the worksheets - LAB - Creating a Dichotomous Key page

24 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

25 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 page 122 )

26 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.

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28 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.

29 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 6 th kingdom was created.