Classification Of Living Organisms Flashcards
How many species have scientist described and named
1.5 million
There are estimated to be how many species total
7 million
Summary of Darwin’s theory
- Organisms produce more offspring than can survive. Of the offspring that do survive, many will never reproduce
- Because more organisms are produced than can survive, there is intense competition for limited resources, such as food, water, and shelter
- Individuals that are best suited to their environment survive, reproduce and pass their traits on to their offspring. Other organisms that are less suited for their environment often die, or will not be reproductively competitive.
- The species that are alive on earth today descended with modification from ancestral species that live in past.
What is taxonomy
The branch of biology that classifies organisms and assigns each organism a universally accepted name
Organisms were first classified more than 2000 years ago by??
Greek philosopher Aristotle
Aristotle sorted organisms into two groups
1.Plant
a) Shrubs
b) Herbs
c) Trees
Animals:
a) Air dwellers
b) Water dwellers
c) Land dwellers
Problems with the early attempts at classification
- Many organisms were placed in groups to which they had no real relationship with other members of the group
- The use of common names was very confusing.
- Many new organisms were being discovered and needed to be classified.
Who developed binomial nomenclature
Carolus Linnaeus
Carolus Linnaeus classification system was based on??
Structural similarities. He thought that the organisms that looked alike were the most closely related
What is binomial nomenclature
The system of assigning scientific name that consists of two parts
Levels of classification
Kingdom
Phylum
Class
Order
Family
Genus
Species
Rules of binomial nomenclature
- The scientific name always consists of two words: the genus and the species
- All scientific names are in Latin. It is understood by all scientists
- The genus is always capitalized. The species is never capitalized
- The two names are always written in italics (in print/computer) or underlined in written form
- No two organisms can have the same name
What is phylogeny
It is the evolutionary history of an organism
What is a phylogenetic tree
It is a family tree that shows the evolutionary relationships thought to exist among different groups of organisms
Modern taxonomy is based on ??
1.Morphology ( structural similarities)
2. Fossil record
3. Cellular Organisation
4. Evolutionary Relationships
5. Biochemical Similarities
6. Genetic similarities
7. Embryological similarities
Classificayion based on morphology
Morphology is a classification based on the structures possessed by the organisms, this was the basis for linnaeus’ system of classification
i) Homologous structures: have same structure but different function e.g the bones found in the wing of a bird, the wing of a bat
ii) Analogous structures: similar in function but not in structure. Analogous structures are not derived from a common ancestor e.g the wing of a butterfly have the same function, but there is nothing common in Thier structure
iii) Vestigial structure: A structure that is reduced in size and seems to be “left over” from a previous ancestors e.g appendix
The greater the number of homologous structures two organisms share, the more closely related they are thought to be
Fossil record
The Fossil record gives us many clues as to the morphology of ancient species, but it is an incomplete record
Cellular organization
- Similarity in cell provides evidence that organisms may be related
- Examples: what plastids are present, Does the cell possess a nucleus, is there a cell wall present
Evolutionary Relationships
- Fossils shows that organisms alive today are similar to organisms that are now extinct
- 25 breeds of dogs all came from a wolf-like ancestor
Biochemical Similarities
- Similarities of chemical compounds found within cells can be used as evidence to show relationship between organisms
- A comparison between the protein of two organisms serves as a “molecular clock.” Simple mutations occur all the time, causing slight differences in the DNA and the proteins being built. When the protein of two different organisms are compared, the number of differences in amino acid sequences is a clue as to how long ago two species diverged from a shared common ancestor
Genetic similarities
- Do two organisms being compared have the same number of chromosomes? The same type of chromosomes?
- Two organisms that bear no resemblance to one another anatomically may still be related to one another. Two different “ looking” organisms may have similar genes in their DNA.
Humans and yeast share common ancestry
Embryological similarities
- Similarities in embryological development provide evidence of phylogenetic relationships
- Some organisms show no similarities as adults, but are very similar as embryos
What is cladistics
Cladistics uses features called “shared derived characters” to establish evolutionary relationships. A “derived character” is a feature that evolved only within the group under consideration. Examples feathers of birds.Birds are the only animals to have feathers. It is therefore assumed that feathers evolved within the bird group and were not inherited from a distant ancestor. Shared derived characters are strong evidence of common ancestry, cladistics is a relatively new method of classifying organisms.
What is a cladogram
A diagram that shows the evolutionary relationship among a group of organisms.
