10.1 - Classification Flashcards
Why do we classify ?
- to help identify new species
- to predict characteristics
- to find evolutionary links
- to make the study or living things more manageable
How do we classify ?
Observable characteristics ( gross and microscopic ) biochemistry ( DNA , proteins rRNA )
Define classification
The name given to the process by which living organisms are sorted into groups - the organisms within each group share similar features
What are the 7 taxonomic groups ?
* remember the song*
Kingdom
Phylum
Class
Order
Family
Genus
Species
Define taxonomy
The focus on physical similarities
What is the binomial naming system ?
Genus species ( italics )
Why is the binomial naming system useful ?
- analyse evolutionary relationships between organisms
- predict characteristics
- identify species
- share findings internationally
What are the 5 kingdoms?
- prokaryotae
- protoctista
- fungi
- plantae
- animalia
What are the 3 domains ?
- Bacteria
- archaea
- eukarya
What are the general features of prokaryotae ?
- unicellular
- no nucleus or other membrane bound organelles
- a ring of ‘naked’ DNA
- small ribosomes
- no visible feeding mechanism - nutrients are absorbed through the cell wall or produced internally by photosynthesis
- eg. Escherichia coli
What are species ?
A group of organisms that can inbreed to produce fertile offspring
What species are humans?
Homo sapiens
What is binomial nomenclature?
- developed in the 18th century by Carl Linnaeus
- all species are given a scientific name consisting of two parts :
- the first word indicates the organisms genus ( generic name )
- the second word indicates the organisms species ( specific name )
- no two species have the same generic and specific name
What are the general features of the protoctista?
- mainly unicellular
- a nucleus and other membrane bound organelles
- some have chloroplasts
- some are sessile but others move by cilia, flagella or by amoeboid mechanisms
- nutrients are acquired by photosynthesis ( autorophic feeders ) ingestion of other organisms ( heterorophic feeders ) or both - some are parasitic
- eg. Amoeba
What are the general features of fungi ?
- unicellular or multicellular
- a nucleus and other membrane bound organelles and a cell wall - mainly composed of chitin
- no chloroplasts or chlorophyll
- no mechanisms for locomotion
- most have a body for mycelium made of threads or hyphae
- nutrients are acquired by absorption - mainly from decaying material - they’re SAPROPHYTIC feeders - some are parasitic
- most store their food as glycogen
- eg. Mushrooms, moulds and yeast
What are general features of plantae ?
- over 250,000 species - the plant kingdom is the second largest of the kingdoms
- multicellular
- a nucleus , other membrane bound organelles including chloroplasts and a cell wall —> composed of cellulose
- all contain chlorophyll
- most do not move - although gametes of some plants move using cilia or flagella
- nutrients are acquired by photosynthesis - they’re autotrophic feeders ( organisms that make their own food )
- store food as starch
- eg. Flowering plants such as Roses , trees such as oak and grasses
What are some features of animal?
- largest kingdom
- multicellular
- nucleus and other membrane bound organelles —> no cell walls
- no chloroplasts
- move with the aid of cilia, flagella or contractile proteins —> sometimes in the form of muscular organs
- nutrients are acquired by ingestion - they’re heterotrophic feeders
- food stored as glycogen
- eg. Mammals , reptiles, birds , insects etc.
What is a saprotroph ?
An organism that feeds on or derives nourishment from decaying organic matter
Define heterotroph
An organism that feeds on other organisms
Define autotroph
An organism that makes its own food
What is Archaebacteria ?
- ancient bacteria
- can live in extreme environments
- eg. Hot thermal vents , anaerobic conditions and highly acidic environments
What is Eubacteria ?
- true bacteria
- found in all environments
State two differences between fungi and plants
- plants have chloroplasts where as fungi don’t
- plants are autotrophs whilst fungi are heterotrophs
Explain why prokaryotes are now classified as two separate domains
- old classification does not show correct phylogeny
- cell walls differ - peptidoglycan not found in archaea
Describe how and why classification systems have changed over Time
- living organisms classified into two kingdoms based on major differences in characteristics
- for eg. Those that moved and ate animals and those that didn’t
- there is more scientific advances and the use of microscope allowed smaller details to be observed
- organisms divided into 5 kingdoms - plants,animals, fungi, protoctista and prokaryotes
- advances in DNA and proteins to be studied
- provided evidence for evolutionary relationships
- three domain proposed
- relevant scientists eg. Linnaeus, Whittaker or Woese
What is phylogeny ?
The study of evolutionary relationships between organisms
What is a species according to phylogeny ?
The smallest group that shares a common ancestor - end of the branch
What are some advantages of phylogeny over classification ?
- produces a continuous tree whereas classification uses discrete taxonomic groups
- shows the history of different species far more accurately
- hierarchal nature of Linnaean classification can be misleading as it implies different groups within the same rank are equivalent
What are phylogenetic trees ?
- A diagram used to represent the evolutionary relationships between organisms
- they’re branches diagrams - show that different species have evolved from a common ancestor
- the earliest species is found at the base of the tree and the most recent species are found at the tips of the branches
How are phylogenetic trees produced ?
By looking at similarities and differences in species physical characteristics and genetic makeup
Much of the evidence has been gained from fossils
State the main difference between early classification systems and systems based on phylogeny
Historical classification systems are based ok physical characteristics where as phylogeny is based on evolutionary relationships
What is a homologous structure ?
- structure that appears superficially different and may perform different different functions in different organisms but has the same underlying structure
What is evolution ?
The way in which organisms change as a result of natural selection over many generations
What is molecules evidence ?
Gathering molecular evidence and analysing the similarities in proteins and DNA
What is phylogeny evidence ?
Comparing the fossil record
What is embryological evidence ?
Comparing the development of organisms from an embryo
What are 3 points of evidence for evolution ?
- Palaeontology - the study of fossils and the fossil record
- Comparative anatomy - the study of similarities and differences between organism’s anatomy
- Comparative biochemistry - similarities and differences between the chemical makeup of organisms
How are fossils formed ?
- when animal and plant remains are preserved in rocks
- over long periods of time - sediment is deposited on the earth to form layers of rock
- different layers corresponded to different geological eras
- within the different rock strata the fossils found are quite different - forming a sequence from oldest to youngest which shows that organisms have gradually changed over time = fossil record
What are some evidence provided by fossil records ?
- fossils of the simplest organisms such as bacteria and simple algae are found in the oldest rocks - more recent rocks have more complex organisms such as vertebrates
- this supports the evolutionary theory that simple life forms gradually evolved over an extremely long time period into more complex ones
- the sequence in which the organisms are found matched their ecological links to each other for eg. Plant fossils appear before animal fossils —> this is consistent with the fact that animals require plants to survive
- by studying similarities in the anatomy of fossil organisms scientists can show how closely related organisms have evolved from the same ancestor
- fossils allow relationships between extinct and living organisms to be investigated t
Why is sometimes the fossil records not complete ?
- many organisms are soft bodied and decompose quickly before they have a chance to fossilise
- the conditions needed for fossils to from are not often present
- many other fossils have been destroyed by the earths movement such as volcanoes or still lie undiscovered
What is comparative anatomy ?
Comparative anatomy is the study of similarities and differences in the anatomy of different living species
What does the presence of homologous structures provide evidence for ?
Divergent evolution
What does divergent evolution explain ?
- describes how from a common ancestor different species have evolved
- each with a different set of adaptive features
- this type of evolution will occur when closely related species diversify to adapt to new habitats as a result of migration or loss of habitat
What is comparative biochemistry ?
The study of similarities and differences in the proteins and other molecules that control life processes
Explain evolutionary embryology
- study of the embryos
- an embryo is an unborn animal in its earliest phases of development
- embryos or many different animals look very similar and it is often difficult to tell the, apart
- this shows that the animals develop in a similar way —> implying that the processes of embryonic Development gave a common origin and the animals share common ancestry but have gradually evolved different traits
What are the two common molecules studied ?
- cytochrome C ( a protein involved in respiration )
- ribosomal RNA
What is the hypothesis of neural evolution ?
- states that most of the variability In the structure of a molecule does not affect its function
- due to the fact that most of the variability occurs outside of the molecule’s functional regions
- changes that do not affect a molecules function are called = NEUTRAL
- since they have no effect on function —> their accumulation is not affected by natural selection
- as a result neutral substitutions occur at a fairly regular rate - although that rate is different for different molecules
What do you compare to discover how close two species are together ?
The molecular sequence of a particular molecule
How can scientists estimate the point at which the two species last shared a common ancestor ?
- the number of differences that exist are plotted against the rate the molecule undergoes neutral base pair substitutions
What is the molecular evidence to back up the difference between Archaea and bacteria ?
RNA polymerase is different and only Archaea have similar histories to Eukarya
What is the cellular evidence to back up the difference between Archaea and Bacteria ?
Different bonding of lipids and different development and composition of flagellae
Describe what is shown on a phylogenetic tree
- a diagram is used to show evolutionary relationships between organisms
- the closer the branches of the tree the closer the evolutionary relationships
Describe two advantages and disadvantages or using the fossil record as a source of evidence for evolution
Advantages :
- radioisotopes can be used to date fossils
- changes can be tracked over time
- chronological order apparent in rock strata
Disadvantages :
- many organisms decompose quickly before they have a chance to fossilise / destroyed by volcanoes or destroyed by earthquakes
Describe how the work of three scientists was used in the development of the theory of evolution
LYELL - suggested that fossils were actually evidence of animals that have lived millions of years ago
HUTTON - proposed theory of uniformitarianism
DARWIN - came up with the theory of evolution by natural selection through observations in the Galápagos Islands
WALLACE - came up with the theory of evolution by natural selection in Borneo
Explain how comparative biochemistry provides evidence of evolution
- study of similarities and differences in proteins and nucleic acid / DNA of an organism
- changes in highly conserved molecules can help identify evolutionary links
- such as cytochrome C / ribosome RNA
- species that have the most similar DNA and proteins
