EDUQAS WJEC BIOLOGY A LEVEL COMPONENT 2: ALL ORGANISMS ARE RELATED THROUGH THEIR EVOLUTIONARY HISTORY

TAKEN DIRECTLY FROM WJEC EDUQAS GCE A LEVEL IN BIOLOGY TEACHERS GUIDE

The hierarchy of taxon groups

Domain, kingdom, phylum, class, order, family, genus, species

DELICIOUS KING PRAWN CURRY OR FAT GREASY SAUSAGES

The need for classificaiton and its tentative nature

Classification is needed to organise organisms into groups based on similarties. Classification may change as additional information becomes available

The 3 domains in our 5 kingdom system

Bacteria, Archea, Eukaryota

Domain - Bacteria

True bacteria

Contains peptidoglycan

Many can cause disease

Domain - Archae

Extremophile prokaryotes

No peptidoglycan

No known pathogenic archae

Domain - Eukrayota

Includes all eukaryotic organisms, animals, platns, fungi and protoctista

The five Kingdoms

Prokaryotae, Protoctista, Plantae, Fungi, Animalia

Characteristic features of kingdoms - Prokaryotae

• Circular DNA free in cytoplasm

• Lack a nuclear envelope

• Lack membrane-bound organelles

• 70s ribosomes

• The cell wall does not contain cellulose or chitin

Characteristic features of kingdoms - Protoctista

• Eukaryotic

• Contains a nucleus

• Usually unicellular

• Membrane-bound organelles

• No tissue differentiation

Characteristic features of kingdoms - Plantae

• Euraryotic

• Multicellular

• Cell walls made of cellulose

• Contains chloroplasts with chlorophyll

• Carry out photosythensis (autrophic/photoautotrophic nutrition)

• Store carbohydrate mainly as starch

• Characteristic features of kingdoms - Fungi

• Eukaryotic cells

• Unicellular OR multicellular

• Cell walls made of chitin

• Sapotrophic nutrition

• Store carbohydrates as glycogen

• Multicellular fungi are made fo hyphae to form mycelium

Characteristic features of kingdoms - Animalia

• Eukaryotic cells

• Multicellular

• No cell wall

• No chloroplsats

• Feeds by ingesting other organisms (heterotrophic nutrition)

• Store carbohydrates as glycogen

• Usually have a nervouse coordination and can move at some stage of their life cycle

Morphological covergence

When unrelated organisms evolve to have similar physical features due to their habitat e.g wings of birds, bats - similar functions but evolved seperately from difference ancestors

Assessing relatedness of oragnisms using physical features and biochemical methods such as enzyme studies and genetic fingerprinting - without the problem of morphological covergence

Principle of genetic profliing is required - biochemical methods can measure the proporiton of DNA or proteins shared between species to assess relatedness. Biochemical methods can reduce the mistakes made in classification due to convergent evolution

Homologous features

• Structures from same evolutionary origin

• May have different functions

• Shows divergent evolution

Analogous features

• Structures with different evolutionary origins

• Have similar functions

• Evolved independantly due to similar selection pressures

• Result of convergent evolution

Use of binomal system in naming organisms

Genus name (Capital letter), species name (lowercase)

e.g Homo sapien

Genus - Homo

Species - sapien

The concept of Species

A species is a group of similar organisms that can interbreed to produce fertile offspring

Biodiversity

The number of species and the number of individuals of each species in a given environment

What factors can affect biodiversity?

• Genetic

• Environmental

• Human factors

Polymorphism

When a population has two or more distcint forms of the same trait, and these forms and present in significant numbers

e.g Human blood groups

e.g Peppered moths