Show Menu
Cheatography

Biology A level - Classification and Evolution Cheat Sheet by

This is a cheat sheet based on the OCR A Gateway Biology A level spec, Chapter 10 module 4. Specification reference: 4.2.2

Linnean classi­fic­ation

Carl Linneaus - Hierarchal classi­fic­ation
Mnemonic: King Prawn Curry Or Fat Greasy Sausage
(Domain)
Kingdom
Phenus
Class
Order
Family
Genus
Species - Organisms able to reproduce to produce fertile offsprings
Binomial nomenc­lature - genus and species in italics genus has a capital letter, not species.

5 kingdom classi­fic­ation

Prokar­yotes
Unicel­lular
 
No nucleus or membra­ne-­bound organelles
 
Absorb nutrient through cell walls / produce it internally
Protists
Mainly unicel­lular
 
Nucleus + membra­ne-­bound organelles
 
Nutrients through photos­ynt­hesis + ingest other organisms
Fungi
Uni/mu­lti­cel­lular
 
Nucleus + membra­ne-­bound organelles
 
Nutrients absorbed from decaying material
Plantae
Multic­ellular
 
Nucleus + membra­ne-­bound organelles
 
Nutrients photos­ynt­hesised
Animalia
Multic­ellular
 
Nucleus + membra­ne-­bound organelles
 
Nutrients ingested

3 domain classi­fic­ation

Proposed by Carl Woese
3 domains (bacteria, arches and eukarya)
6 kingdoms (eubac­teria, archae­bac­teria, protists, fungi, plantae and animalia).
Based on differ­ences in sequence of nucleo­tides in RNA, lipid structure, sensit­ivity to antibi­oti­cs...
Domain
Kingdom
Other details
Bacteria
Eubacteria
70s ribosomes
Eubacteria = "true bacter­ia"
found in all enviro­nments
Archaea
Archae­bac­teria
70s ribosomes
Archaebacteria = "­ancient bacter­ia"
Extreme enviro­nments
Eukaryotes
Protists, fungi, plantae, animalia
80s ribosomes

Phylog­enetic tree

Show evolut­ionary relati­ons­hips.
Simila­rities and differ­ences in physical charac­ter­istics of species.
+ Continuous tree - Don't have to fit into one group or other, no discrete taxono­mical group.
+ Hierarchal nature of Linnean system - Suggests same levels are equivalent when actually not necess­arily compar­able.

Phylog­enetic tree

 

Natural selection

Variation
New alleles because of mutations
Survival
Selection pressure increases chance of survival for best adapted organisms
Reprod­uction
Successful organisms reproduce (survival of the fittest)
Genes
Successful organisms pass on advant­ageous alleles. Frequency of allele in gene pool increases.
Time
Over time, whole population has advant­ageous allele. Speciation - Can become different species.

Evidence for evolution

Paleon­tology (fossil record)
Allows us to study phylog­enetic relationships.
Biases - Incomplete because not all organisms fossilise, specific conditions necessary for fossils format­ion...
Anatomical evidence
Homologous structures - Structures that look different (and may have different purposes) but have the same underlying structure (e.g. forelimbs in vertebrates).
Example of divergent evolution - common ancestors with different adapta­tions. Closely related species in different habitats.
Bioche­mical evidence
Differ­ences between proteins - some important molecules are the same in different species (e.g. cytochrome C, rRNA...).
Embryo­logical evidence
Simila­rities in embryos between species. Shows they develop in a similar way (e.g. human and fish embryos both have gills).
Evolut­ionary history can be traced through embryonic develo­pment.

Variation

Inters­pecific variation
Differ­ences between species
Intras­pecific variation
Differ­ences within species
Causes of variation
Enviro­nment
Sunlight, nutrient, and water availa­bility
Genetic
Alleles, mutations, sexual reprod­uction, meiosis...
or both

Types of adapta­tions

Anatomical
Body covering
Mimicry
Camouflage
Teeth
Physio­logical
Poison / antibiotic production
Water holding
(Animals - blinking, reflex­es...)
Behavi­oural
Survival behaviours (e.g. playing dead)
Courtship
Seasonal behaviours (e.g. migration, hibern­ati­on...)

Explan­ations for convergent evolution

Convergent evolution
Different species start to share simila­rities, adapt in a similar enviro­nment / selection pressures.
e.g. Marsupials (in Australia) and placental mammals (USA) are species that resemble each other and because adapted in a similar enviro­nment.
Analolgous structures
Structures that perform the same function but aren't struct­urally similar (e.g. wings in different animals)
Founder effect
Small number of indivi­duals separate to form new colony. Rate alleles become more common.
 

Modern examples of evolution

MRSA
Variation - Some resistant to antibi­otics
 
Selection pressure - Antibi­otics
 
Antibi­oti­c-r­esi­stant bacteria survive, advant­ageous alleles are passed on
 
After genera­tions, more S. aureus becomes resistant to antibi­otics.
 
Peppered moths
Variation - Some white, some black
 
Selection pressure - Change in tree colour because of industrial revolu­tion.
 
White ones survive pre-re­vol., black ones survive during and white ones again after.
 
Moths therefore change colour through genera­tions to match tree colour.
                           
 

Comments

Add a Comment

Your Comment

Please enter your name.

    Please enter your email address

      Please enter your Comment.

          Related Cheat Sheets

          Biology A level - Manipulating genomes Cheat Sheet
          Biology A level - Patterns of Inheritance Cheat Sheet
          Biology A level - Hormonal communication Cheat Sheet

          More Cheat Sheets by Anais_Pe

          Physics GCSE Paper 2 Cheat Sheet
          Biology A level OCR - Eukaryotic Cell Structure Cheat Sheet
          Biology A level - Genetics of Living Systems Cheat Sheet