Biological classification 4.3

• For convenience • To make the study of living things more manageable • To make it easier to identify organisms • To help see the relationships between organisms

• Domain • Kingdom • Phylum • Class • Order • Family • Genus • Species Lower down the taxonomic levels, it becomes harder to differentiate between species

The universal naming system using the genus and species of an organisms Common naming systems do not work because - Different countries may have different names for an organisms - Different countries may have the same name but for a different organism - Translation of languages may give different names

the phylogenetic definition of a species is - a group of organisms that are very similar in appearance, anatomy, physiology etc. Early classification systems were created based off of appearance and anatomy. The development of microscopes allowed for a more detailed classification originally, there were two kingdoms (plants and animals) but there was lots of crossover

• Have no nucleus • Have DNA that is non-linear and not wound around histone proteins • Have no membrane bound organelles • Have smaller ribosomes and smaller cells • May be free living or parisitic example; bacteria

• Are eukaryotic • Show a wide variety of forms • Mostly single-celled and free-living • Have autotrophic or heterotrophic nutrition

• Eukaryotic • Single-celled or they have a mycelium that consists of hyphae • Have cell walls made of chitin • Have cytoplasm that is multinucleate • Are mostly free-living and sacrophitic (can cause decay of organic matter)

• Eukaryotic • Multicellular • Contain a cellulose cell wall • Are autotrophic • Contain chlorophyll

• Heterotrophic • Eukaryotic • Multicellular • Can move around

May be used to show evolutionary patterns - Two organisms with similar molecules will be closely related - The more differences between the molecules of species, the less closely related they are, as they have evolved separately for longer

A protein involved in respiration - All molecules that respire will have cytochrome C - The amino acid chain will vary between species - e.g. humans and chimpanzees have the exact same chain, very closely related

DNA provides genetic code for organisms - It is universal, the code is the same for all organisms - We can analyse different species’ genetic code to determine how closely related they are - Mutations are a random change in the DNA sequence

Based on the RNA gene as bacteria are fundamentally different to eukaryote and archaea - Different cell membrane - Differnent internal structure of flagella - Different enzymes and mechanisms for synthesising RNA - No proteins bound to genetic material Archaeae are similar e.g - Similar enzymes and mechanisms for synthesising RNA - Proteins bound to DNA

• Limited information • Stable • Does not use evolutionary trees • Uses few characteristics

• Uses many characteristics • May change with new knowledge • Provides useful information • Reflects evolutionary relationships

The study of evolutionary relationships between species - Any two species have evolved from a common ancestor - The more recent the common ancestor, the more closely related the species are

• Offspring appear genetically identical to their parents • No two individuals are the same • Organisms have the ability to produce large no.s of offspring • Populations in nature tend to remain fairly stable in size

• There is a struggle to survive • Better adapted individuals survive and pass on their characteristics • Over time, a number of changes give rise to a new species

shows: - In the past, there were species different to today - Old species have died and new species have arisen - The new species that have appeared are often similar to ones in the past Fossil species gave rise to modern species, which are better adapted to the environment. Example: In the past, fossils show that species were much bigger

Intra - variation between members of the same species Inter - variation between members of the same species

Data with two extremes and a range of values in between - Most individuals are close to the mean value - May be influenced by the environment - Determined by more than one gene Examples: height in humans, no. of flagella, length of leaves

Data with two or more distinct values, with no intermediate values between them - Members of a species may be evenly distributed amongst categories - Not influenced by the environment - Determined by only one gene Examples: blood groups, gender, existence of flagella

The combination of genes inherited from our parents - Unique to each individual - May share many alleles within species - Share genes with other species - Never identical unless the case of an identical twin