Classification and evolution- classification, the five kingdoms, phylogeny Flashcards
what is classification?
the process by which living organisms are sorted into groups. The organisms within each group share similar features.
what is taxonomy?
the practice of biological classification. This allows us to arrange species into taxonomic groups (taxa) based on their evolutionary origins and relationships.
what are the seven taxonomic groups?
kingdom, phylum (plural phyla), class, order, family, genus (plural genera) and species.
describe the kingdoms group
-biggest and broadest group
-least specific
Describe the species group
-smallest
-most specific
who first proposed the heirarchal classifications system?
Carl Linnaeus in the 18th century
what level of classification is placed at the top of the hierarchy?
the domain, based on recent studies of genetic material. As new scientific discoveries are being made, the current system of classification may change again
why do scientists classify organisms?
-to identify species
-to predict characteristics
-to find evolutionary links: common ancestor
what are the three domains?
archaea, bacteria and eukarya. These are the broadest groups
Describe the pattern as you go down the heirarchy from the broadest group (domain)
-As you go down, there are more groups at each level, but fewer organism in each group.
-the organisms in each group become more similar, sharing same characteristics
how does the heirarchal system end?
organisms become classified as individual species, smallest unit of classification. Each group contains only one type of organism.
what is a species?
group of organisms that are able to reproduce to produce fertile offspring
why are infertile offspring produced when two organisms of different species reproduce?
odd number of chromosomes produced so meiosis and gamete production cannot take place correctly as all chromosomes must pair up
humans belong to what species (scientific name for humans)?
Homo sapiens
Before classification, organisms were given names based on their physical characteristics. Why is this not useful?
-not usefully when working internationally as organisms may have more than one common name and in different languages
-does not provide information about relationships between organisms
How do scientists ensure they are discussing the same organism Internationally?
using binomial nomenclature system where binomials are the scientific names given to an individual species
binomials consist of an organism’s?
genus (first word) and species/specific name (second word) name
what is the genus?
name shared by close relatives
could two species have the same generic and species name?
no but they could have the same specific name but genus would be different
how is the binomials for a species written?
always in italics. Genus name should have capital letter but species name shouldn’t
what are the five kingdoms?
-prokaryotae (bacteria)
-protoctista (the unicellular eukaryotes)
-fungi (yeasts, moulds an mushrooms)
-plantae (the plants)
-animalia (the animals)
what are the general features of prokaryotae?
-unicellular
-no nucleus or membrane bound organelles.
-a ring of ‘naked’ DNA and small ribosomes
-no visible feeding mechanism: nutrients are absorbed through the cell wall or produced internally by photosynthesis
what are the general features of protoctista?
-(mainly) unicellular
- a nucleus and other membrane-bound organelles
-some have chloroplasts
-some are sessile, but others move by cilia, flagella or amoeboid mechanisms
-nutrients from photosynthesis (autotrophic feeders), ingestion of other organisms (heterotrophic feeders) or both- some are parasitic
what are the general features of fungi?
-unicellular or multicellular
-nucleus and membrane bound organelles and a cell wall mainly composed of chitin.
-no chloroplasts or chlorophyll
-no locomotion mechanism
-most have a body or mycelium made of threads or hyphae
-nutrients from absorption, mainly decaying material (saprophytic feeders). Some are parasitic.
-most store their food as glycogen
what are the general features of plantae (second largest kingdom)?
-multicellular
-nucleus and other membrane bound organelles including chloroplasts and a cell wall mainly composed of cellulose
-all contain chlorophyll
-most don’t move, but gametes of some plants more using cilia or flagella
-nutrients from photosynthesis (autotrophic feeders- make own food)
-store food as starch
what are the general feature of Animalia (largest kingdom)?
-multicellular
-nucleus and membrane-bound organelles (no cell wall)
-no chloroplasts
-move with aid of cilia, flagella or contractile proteins, sometimes in the form of muscular organs
-nutrients acquired by ingestion (heterotrophic feeders)
-food stored as glycogen
How have classification systems changed?
before it was based on observable features, now it is based on DNA
What are the domains?
a further level of classification the top of the hierarchy proposed by Carls Woese.
How does Woese’s domain system group organisms?
based on differences in the sequence of nucleotides in the cells ribosomal RNA (rRNA) as well as the cell membranes lipid structure and their sensitivity to antibiotics
what are the three domains?
-Archaea
-Bacteria
-Eukarya
Describe the domain of Eukarya?
-80s ribosomes
-RNA polymerase contains 12 proteins
Describe the domain of Archaea?
-70s ribosomes
-RNA polymerase of different organisms contains between eight and 10 proteins and is very similar to eukaryotic ribosome
Describe the domain of Bacteria?
-70s ribosome
-RNA polymerase contains 5 proteins
How does Woeses kingdom system differ?
Prokaryotae kingdom divides into two kingdoms- Archaebacteria and Eubacteria. The six kingdoms are therefore, Archaebacteria, Eubacteria, Protoctista, Fungi, Plantae and Animalia
why is Eubacteria classified in its own kingdom?
Because its genetic makeup is different from Archaebacteria
Describe Archaebacteria?
Ancient bacteria, can live in extreme environments (thermal vents, anaerobic conditions and highly acidic places)
Describe Eubacteria?
True bacteria, found in all environments . Most common bacteria
What is phylogeny?
the evolutionary relationships between organisms
What is a phylogenetic tree (evolutionary tree)?
diagram used to represent evolutionary relationships between organisms
How are phylogenetic trees produced?
by looking at similarities and differences in a species physical characteristics and genetic makeup. Much evidence is gained from fossils.
what are the advantages of phylogeny?
-can be done without reference to Linnaean classification
-phylogeny produces a continuous tree whereas classification requires taxonomical groups
-the hierarchal nature of Linnaean classification can be misleading as it implies different groups within the same rank are equivalent.
