Classification Of Living Organisms

Question 1

How many species have scientist described and named

Answer 1

1.5 million

Question 2

There are estimated to be how many species total

Answer 2

7 million

Question 3

Summary of Darwin’s theory

Answer 3

1. Organisms produce more offspring than can survive. Of the offspring that do survive, many will never reproduce
2. Because more organisms are produced than can survive, there is intense competition for limited resources, such as food, water, and shelter
3. 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.
4. The species that are alive on earth today descended with modification from ancestral species that live in past.

Question 4

What is taxonomy

Answer 4

The branch of biology that classifies organisms and assigns each organism a universally accepted name

Question 5

Organisms were first classified more than 2000 years ago by??

Answer 5

Greek philosopher Aristotle

Question 6

Aristotle sorted organisms into two groups

Answer 6

1.Plant
a) Shrubs
b) Herbs
c) Trees

Animals:
a) Air dwellers
b) Water dwellers
c) Land dwellers

Question 7

Problems with the early attempts at classification

Answer 7

1. Many organisms were placed in groups to which they had no real relationship with other members of the group
2. The use of common names was very confusing.
3. Many new organisms were being discovered and needed to be classified.

Question 8

Who developed binomial nomenclature

Answer 8

Carolus Linnaeus

Question 9

Carolus Linnaeus classification system was based on??

Answer 9

Structural similarities. He thought that the organisms that looked alike were the most closely related

Question 10

What is binomial nomenclature

Answer 10

The system of assigning scientific name that consists of two parts

Question 11

Levels of classification

Answer 11

Kingdom
Phylum
Class
Order
Family
Genus
Species

Question 12

Rules of binomial nomenclature

Answer 12

1. The scientific name always consists of two words: the genus and the species
2. All scientific names are in Latin. It is understood by all scientists
3. The genus is always capitalized. The species is never capitalized
4. The two names are always written in italics (in print/computer) or underlined in written form
5. No two organisms can have the same name

Question 13

What is phylogeny

Answer 13

It is the evolutionary history of an organism

Question 14

What is a phylogenetic tree

Answer 14

It is a family tree that shows the evolutionary relationships thought to exist among different groups of organisms

Question 15

Modern taxonomy is based on ??

Answer 15

1.Morphology ( structural similarities)
2. Fossil record
3. Cellular Organisation
4. Evolutionary Relationships
5. Biochemical Similarities
6. Genetic similarities
7. Embryological similarities

Question 16

Classificayion based on morphology

Answer 16

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

Question 17

Fossil record

Answer 17

The Fossil record gives us many clues as to the morphology of ancient species, but it is an incomplete record

Question 18

Cellular organization

Answer 18

1. Similarity in cell provides evidence that organisms may be related
2. Examples: what plastids are present, Does the cell possess a nucleus, is there a cell wall present

Question 19

Evolutionary Relationships

Answer 19

1. Fossils shows that organisms alive today are similar to organisms that are now extinct
2. 25 breeds of dogs all came from a wolf-like ancestor

Question 20

Biochemical Similarities

Answer 20

1. Similarities of chemical compounds found within cells can be used as evidence to show relationship between organisms
2. 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

Question 21

Genetic similarities

Answer 21

1. Do two organisms being compared have the same number of chromosomes? The same type of chromosomes?
2. 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

Question 22

Embryological similarities

Answer 22

1. Similarities in embryological development provide evidence of phylogenetic relationships
2. Some organisms show no similarities as adults, but are very similar as embryos

Question 23

What is cladistics

Answer 23

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.

Question 24

What is a cladogram

Answer 24

A diagram that shows the evolutionary relationship among a group of organisms.

Question 25

Brief history of classification kingdoms

Answer 25

1700: Plantae and Animalia
1800: Protista, Plantae and Animalia
1950: Monero, Protista, Fungi, Plantae and Animalia
1990: Archaebacteria, Eubacteria, Protista, Fungi, Plantae and Animalia

Question 26

Names the Domains

Answer 26

Bacteria, Archae and Eukarya(eukaryotes)

Question 27

Barrier’s between species

Answer 27

1. Physical Characteristics: mating is impossible under natural conditions for many organisms
2. Mating occurs but the offspring do not survive: A bullfrog may be fertilized by the sperm of the leopard frog. The eggs develop to a point, but do not survive. There’s too much difference in chromosomes.
3. The offspring may survive but are not fertile: example, horse + donkey = mule
4. Geographical Barriers: many organisms simply do not come into contact with one another
5. Behavioral Barriers: many organisms, especially in the animal kingdom, will not mate unless certain behaviors are exhibited

Question 28

What does L.U.C.A stand for

Answer 28

Last Universal Common Ancestor