Classification

Learning Objectives The biological classification of species To include the taxonomic hierarchy of kingdom, phylum, class, order, family, genus and species AND domain. The binomial system of naming species and the advantage of such a system (i) the features used to classify organisms into the five kingdoms: Prokaryotae, Protoctista, Fungi, Plantae, Animalia to include the use of similarities in observable features in original classification. (ii) the evidence that has led to new classification systems, such as the three domains of life, which clarifies relationships to include the more recent use of similarities in biological molecules and other genetic evidence AND details of the three domains and a comparison of the kingdom and domain classification systems. The relationship between classification and phylogeny (covered in outline only at AS level)

Classification, phylogeny and taxonomy Key definitions to match The process of sorting living things into groups up and learn! The study of principles of classification Taxonomy The study of evolutionary relationships between organisms Phylogeny Classification

Early systems Aristotle – Plants or Animals Animals split into groups: Live and move in the water Live and move on land Move through the air Linnaeus and other scientists: Observable features Use of microscopes

Grouping species together – principles of classification Classification –the grouping of organisms often on the basis of simple observable features Taxonomy – the study of biological classification Artificial classification Divides organisms by what is useful at the time e.g. Colour, size, no of legs (analogous features) Natural classification Based on the evolutionary relationships between organisms and their evolutionary descent e.g. Shared features and derived from ancestors (homologous characteristics)

The concept of a species Mule – result of horse & donkey mating. Hybrid. Mule has 63 chromosomes & is nearly always infertile A species is the basic unit of classification. Individuals of the same species are capable of breeding to produce living offspring which themselves are fertile Horse – 64 chromosomes in a body cell, 32 chromosomes in a gamete Donkey – 62 chromosomes in a body cell, 31 in a gamete

Naming species Carl Linnaeus – father of taxonomy Binomial naming system Uses two Latin names: Generic (genus organism belongs to) Specific (species that the organism belongs to) There are rules! Handwritten – Generic name starts with a capital, both parts underlined. In type – in italics, generic name starts with a capital

The five kingdoms Can you name them?

Kingdom Examples Main Features Prokaryotae Protoctista Fungi Plantae bacteria Single cell no nucleus peptidoglycan cell wall Less than 5μm Protoctista Algae, protozoa such as malaria Eukaryotic cells often single cells or simple organisms, often live in water Fungi Yeast, mushrooms, mould Eukaryotic cells, chitin cell walls, saprotrophic nutrition using hyphae, single or multicellular. No photosynthesis Plantae Mosses, ferns, flowering plants, conifers Eukaryotic cells, multicellular, cellulose cell walls, autotrophs which photosynthesise, contain chlorophyll. Store starch Animalia Nematodes, (roundworms) fish, insects, mammals Eukaryotic cells, heterotrophic nutrition, multicellular, no cell wall

Ordering taxonomic ranks – using eight taxa Do I have Domain King Kingdom Prawn Phylum Curry Class (e.g. Mammals) Or Order Fat Family Greasy Genus Sausages Species Number of similarities Largest group Distant ancestor Smallest group Recent ancestor

KINGDOM Protoctista PHYLUM Euglenophyta CLASS Euglenophyceae ORDER Euglenales FAMILY Euglenidae GENUS Euglena SPECIES Euglena gracilis KINGDOM Animalia PHYLUM Chordata CLASS Mammalia ORDER Primates FAMILY Hominidae GENUS Gorilla SPECIES Gorilla gorilla

June 2010 F212

Phylogeny The study of how closely different species are related. Grouping based in evolutionary relationships and evolutionary history A species is the smallest group that share a common ancestor   Common ancestor of humans and chimpanzees

Classifying organisms based on their phylogeny is known as cladistics

Molecular Evidence DNA Comparison of DNA sequences in common genes Cytochrome C A protein used in respiration. All organisms except chemosynthetic organisms must respire so therefore contain this protein.

DNA and protein analysis can give evidence for phylogenies The lengths of the branches in this tree are drawn proportional to the number of differences in the primary sequence. The tree clearly reveals the three main kingdoms of eukaryotes: fungi, animals, and plants. Such trees tend to agree closely with those constructed by evolutionary biologists using morphological data, and provide independent evidence of common descent.

LUCA Last Universal Common Ancestor All life had one common ancestor – we know this because all life on earth uses the same genetic code to determine the amino acid sequence of its proteins

The three domains Carl Woese 1990 Ideas based on new evidence from detailed studies of RNA Bacteria are fundamentally different from Archaea and the Eukaryotae

The three domain model Within the eukaryota, the classification from Kingdom-species remains UCMP History of Life Animation re 3 domains

Bacteria Very different to everything else Different cell membrane structure Different structure to the flagella Different enzymes to make RNA e.g. RNA polymerase Naked DNA without proteins (histones) Different method of DNA replication and building RNA

Archea Share some features with eukaryotes Similar enzymes to make RNA Similar method of DNA replication and building RNA Production of some proteins that bind to DNA UCMP Intro to Archea

Bacteria Archea Eukarya LUCA

Adaptations Organisms need features which help them survive in the environment. Natural selection is the mechanism that enables them to adapt. Adaptations can be Anatomical Behavioural Physiological

Anatomical Adaptations Examples include Size Body shape Camouflage Mimicry Colour Surface covering

Behavioural Adaptations Courtship rituals Migration patterns Hibernation Innate and learned behaviour Survival strategies such as playing dead Possum playing dead

Physiological Adaptations Making venoms and poisons Making antibiotics C4 plants use a different metabolic pathway to carry out photosynthesis to reduce water loss

Convergent Evolution Some anatomical adaptations in different species are very similar although have arisen via different paths. This creates Analogous Structures Examples include Fish and whale fins, Octopus and mammalian eyes Convergent evolution leads to different species appearing to have similar features because they are subject to similar selection pressures e.g. moving in water.

Marsupials and Placentals Mammals that lay eggs Duck billed platypus/ Echidna The division between marsupials and placentals occurred about 100MYA They have very different reproductive strategies but there is much evidence for convergent evolution between the 2 groups

Marsupial and Placental Moles Both live in burrows and need to dig them with well adapted front limbs Streamlined body shape Soft fur reduces friction