Classification Aim and Principles from the Textbook of Biology, Class 9, Federal Board of Intermediate and Secondary Education (FBISE) is explained.

1. 3.2 CLASSIFICATION AIMS AND PRINCIPLES
Dr. Syed Abdullah Gilani
Textbook of BIOLOGY
CLASS 9
FBISE, Islamabad Pakistan
Chapter 3
BIODIVERSITY

2. • Only small percentage of the total different types (species) of plants
and animals on earth are known:
– 1.5 million different types of animals
– Less than 0.5 million types of plants (391,000 plants species)
• Range from simple and small bacteria to complex and large human
beings
• Where do they live?
– Sea and land – some fly, some walk, and some stationary
• Way of Life of organisms is diverse and varies also:
– Modes of nutrition
– Avoiding unfavourable environmental conditions
– Finding a place to live (habitats)
– Different types of reproductions

3. • So many diverse kinds of organisms – difficult to learn about
characteristics of each organism.
• To study large collection, biologists classify the organisms into
groups and subgroups, for which they require some system
• Biological Classification is a method by which biologists divide
organims into groups and subgroups.
Taxonomy Systematics
Deals with classification Deals with classification and
traces the evolutionary history
of organisms

4. Aims of Classification
• to determine similarities and differences among organisms so that
they can be studied easily
• To find the evolutionary relationships among organisms.

5. Monera
Protista
Plantae
Fungi
Animalia
Evolution of Five Kingdoms
https://microbiologysociety.org/uploads/assets/ed5c08a4-9251-4c71-
9c645ea022933d66/600x400_highestperformance_/bacterial-shapes-thinkstock.jpg
https://pixfeeds.com/images/14/384801/1200-
384801-500461659.jpg
https://cdn.britannica.com/24/162724-
050-6C219853/Date-palm.jpg

6. Basis of Classification
• Study similarities in characters
• Similarities in characters gives idea about the relationship among
organism.
• Similarities suggest that all organisms are related to one another at
some point in their evolutionary histories.
https://download.ams.birds.cornell.edu/api/v1/asset/63742431/1800
Sparrows and pigeons are more closely related than Ants
Conclusion:
Sparrows and pigeons have common evolutionary history

7. • Classifying organisms into groups and subgroups is based on
similarities in
– External structures (morphology)
– Internal structures (anatomy)
– Stages of development (embryology)
– Genetics (modern genetics)
• Modern Genetics provides information about similarities and
differences in the DNA of two organisms
– gives idea about their similarities and differences in their structure and
functions.

8. Taxonomic Hierarchy
• Taxon (pl: Taxa): also known as taxonomic categories in which the
groups of organisms are classified.
• The taxa form the ladder called Taxonomic Hierarchy.
• “Taxonomic hierarchy is the process of arranging various organisms
into successive levels of the biological classification either in a
decreasing or an increasing order from kingdom to species”.
• Organisms are divided into five kingdoms (largest taxon)
https://study.com/cimages/multimages/16/charthierarchy.jpg
A hierarchy is an arrangement of
items from higher rank to lower
rank or vice versa

9. Taxonomic Hierarchy
• Kingdom: there are five kingdoms and each with group of Phyla
(Divisions).
• Phylum (Division in plants and fungi): group of related classes.
• Class: group of related orders.
• Order: group of related families
• Family: group of related genera.
• Genus: group of related species.
• Species: consists of similar organisms (basic unit of classification; can
interbreed freely among them and produce fertile offspring but
reproductively isolated from all other groups in nature)

10. Classification
Taxa Human Pea
Kingdom Animalia Plantae
Phylum (Division) Chordata Magnoliophyta
Class Mammalia Magnoliopsida
Order Primates Fabales
Family Hominidae Fabaceae
Genus Homo Pisum
Species Homo sapiens Pisum sativum
Taxonomic
Hierarchy

11. • Species – The Basic Unit of Classification
• consists of similar organisms
• basic unit of classification
• “can interbreed freely among them and produce fertile offspring
but reproductively isolated from all other groups in nature”.
• Each species possesses its own distinct structural, ecological, and
behavioral characteristics.
https://www.economist.com/sites/default/files/20181006_BLP501.jpg
https://store-images.s-microsoft.com/image/apps.25758.14302936925643487.4d207f31-f506-432a-b6bd-72a91caf91f8.4752c3f6-0871-4ac4-b6bf-8fb2e382c8ed?mode=scale&q=90&h=1080&w=1920
can interbreed freely among them reproductively isolated from all
other groups

12. Artificial Cross-Breed (between two closely related species)
results
Infertile (cannot produce children) Offspring
https://www.quora.com/How-far-apart-genetically-can-2-species-still-interbreed-successfully
Infertile

13. Species recognition and Criteria of interbreeding
• can be used among the same group of organisms
• But cannot be used for species that
– Produce asexually (no sexual reproduction) and
– Do not interbreed with one another (e.g., many unicellular organism)
https://www.bbc.co.uk/schools/gcsebitesize/science/images/9_sex_cells.gif
https://eschooltoday.com/science/asexual-reproduction/images/what-is-binary-fission.png
Asexual Reproduction
Sexual Reproduction