AS Biology WJEC UNIT 2.1 Classification and Biodiversity Topic Summary Notes
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Course
Unit 2.1 - Biodiversity and Classification
Institution
WJEC
The entire topic of 2.1 condensed in this one document for revision and learning ease.
Simple structure and layout with images and key definitions to help with memory.
Use of bold, italics and underlining to keep a systematic organisation when referencing useful terms
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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