The entire topic of 2.1 condensed in this one document for revision and learning ease.
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Biology Notes 05.01.21
-------------Unit 2.1 Biodiversity and Classification-------------
CLASSIFICATION
----CLASSIFICATION PRINCIPLES------------------------------
1. Artificial Classification:
○ Divides organisms according to set differences
○ Accounts for analogous features- when species have the same function and similar shape
but have a different developmental origin. [i.e hierarchical taxonomy]
2. Natural Classification:
○ Based on evolutionary relationships
○ Arranges species into hierarchies [i.e phylogenetic tree]
----PHYLOGENETIC TREES------------------------------
● Groups closely related organisms together → closely related
organisms may show similar physical properties
○ Organisms in the same group have a common ancestor
● Shows how life evolved and organisms evolutionary theory
● Branch points show a common ancestor
○ The common ancestor of all life is called: LUCA
---- HIERARCHICAL CLASSIFICATION------------------------------
● Taxa → levels of classification
○ Large taxa contain smaller ones
● Scientists use classification to look at evolutionary relationships, monitor population and
biodiversity
● Needs to be internationally accepted
● Taxa are discrete→ an organism cannot belong to more than one taxon at any level
○ So we use phylogenetic classifications
○ We predict characteristics based off of known ones if new species is discovered
○ For example, new species with beak + feathers→ predict characteristics from what we
already know about birds
● The taxons are:
● Before kingdom is a Domain
● Carl Linnaeus discovered this. [Godfather of Taxonomy]
● He took all life, assessed physical features and placed them in particular groups
that show species are similar and different
○ Plants and animals are different → so 2 different kingdoms
● Human Taxonomy:
● Animals → Chordates → Mammals → Primates → Hominids → Homo → Sapiens
● Kingdom → Phylum → Class → Order → Family → Genus → Species
● Species: a group of organisms that share a large number of physical features and
can interbreed and produce offspring
● Genus: a group of similar organisms
, Biology Notes 05.01.21
---- DOMAINS------------------------------
● Domains are the largest taxon and all living things belong to one
○ Originally defined on rRNA base sequence basis but now similarities between DNA base
sequences are considered
● Domains are: Eubacteria - Archaea - Eukaryota
● Eubacteria: familiar bacteria like E.coli and are prokaryotes
● Archaea: bacterial prokaryotes that have unusual metabolisms
● Eukaryota: all eukaryotic organism including Plantae - Animalia - Fungi - Protista
----KINGDOMS------------------------------
● Five main types under a domain called eukarya
● Prokaryota: includes all bacteria and unicellular organisms
○ no membrane-bound organelles
● Protocista: eukaryotic organisms, single-celled with no tissue differentiation
● Fungi: saprophytic (feed on dead organisms) eukaryotes with a chitin cell wall.
○ Reproduce by spores
● Plantae: autotrophic (make own food) and photosynthetic
○ Have cellulose cell walls
● Animalia: heterotrophic organisms (feed on other organisms) and multi-cellular eukaryotes
○ No cell wall and capable of whole-body movement
----HOW ORGANISMS ARE RELATED------------------------------
● Theory of evolution suggested that:
○ Groups of organisms share common ancestors if they have similar basic features
○ Groups with little in common suggest differentiation from a common ancestor was much
earlier
----ASSESSING IF ORGANISMS ARE RELATED------------------------------
● To assess if organisms are related a biologist looks for:
○ Homologous Features: structures in different species with
a similar anatomical position and developmental origin
derived from a common ancestor
● An example would be looking at the pentadactyl → five-digit
structure
○ In a bat, whale, cat and human, all is present so
homologous feature but developed over long periods. This
is called a divergent evolution
● Analogous Features: when species have the same function and similar shape but have a different
developmental origin.
○ In other words, a butterfly and bat → both fly with wings but one is an insect and one is a
mammal
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