In-depth bullet pointed notes on topics 2.1-2.4 of Unit 2 Biology AS level WJEC Classification and Biodiversity Unit.
Notes made using combination of lectures, online resources, textbook, study guide, and exam mark schemes.
Biology 2.1 Classification and Biodiversity 26/2/22
Classification - sorting organisms into groups based on evolutionary history (phylogenetic)
Taxonomy - study of classification & diversity of living things
Why do we classify?
● Universal system of naming/grouping organisms - no confusion between languages
● quick access to information
● Shows evolutionary relationships & common features between organisms
Phylogenetic tree - shows evolutionary descent
Group Definition Example
Kingdom Subgroup of one of 3 domains Animalia
Phylum Subgroup of Kingdom Chordata
Class Subgroup of phyla Mammalia
Order Subgroup of class Primates
Family Group within an order Hominoidea
Genus Group within a family of similar organisms Homo
Species Group of organisms with common features. Interbreed to produce fertile offspring Sapiens
Divided into groups from morphological (physical) features
Main features of 5 kingdoms
● Kingdom Prokaryotae
○ Unicellular
○ No organelles with membrane
○ cell wall made of murein
○ Eg. salmonella
● Kingdom Protoctista
○ Unicellular (few are multicellular - have simple cell structure)
○ Organelles with membrane
○ No tissue differentiation
○ Eg. Algae
● Kingdom Fungi
○ Rigid cell walls made of chitin
○ Asexual reproduction (some sexually by spores)
○ Most made of mycelium
○ Eg. mushrooms, moulds, yeast
, ● Kingdom Plantae
○ Multicellular
○ Contain chlorophyll
○ Cell walls of cellulose
○ Tissue differentiation (root, stems, leaves etc)
○ Eg. mosses, conifers, flowering plants
● Kingdom Animalia
○ Multicellular
○ Hetero nutrition
○ No cell walls
○ Most have nervous system
○ Growth occurs through body
○ Vertebrates (chordate) and invertebrates (non-chordata)
Physical features for relatedness
Theory of Evolution - all descended from common ancestor
Divergent evolution - development of different structures from equivalent structure in related
organisms over a long period of time
1. Pentadactyl limb:
● Limb from vertebrate groups
● Homologous structure - similar structures with different functions, evolved
from common ancestor
Convergent Evolution - structures evolve similar properties but different development origins
Analogous structures - different structures that perform a similar function
Comparative biochemistry
DNA sequences:
● All organisms share same genes for DNA polymerase & ATP synthesis
● More closely related species, more similar the base sequence of genes
● DNA analysis shows how closely related organisms are
Differences between DNA of species (DNA hybridisation):
● 1 gene makes 1 protein - organisms share DNA sequences produce similar proteins
● DNA strands from both species are extracted
● Restriction enzymes cut up DNA into smaller pieces
● Electrophoresis used to see how many common strands present
Immunology:
● Antibodies made by most organisms against foreign antigens (proteins)
● Human serum containing albumin (antigen) injected into rabbit
● Rabbit serum containing anti-human antibodies added to serum of other animals
● Anti-human albumen antibodies stick to antigen
● Closer the evolutionary relationship, the more precipitation
Concept of Species
● Fertile offspring produced if homologous chromosomes present to be arranged in
metaphase 1 of meiosis - necessary for gametes with right number of chromosomes
● Hybrids can mate but cannot produce fertile offspring (ligers, mule)
● Sexual dimorphism - male & female of specieis is non-identical (eg. lions)
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