classification and evolution Flashcards
why do scientists classify organisms?
to identify species
to predict characteristics
to find evolutionary links (phylogeny)
why do scientists classify organisms?: TO IDENTIFY SPECIES
by using a clearly defined system of classification, the species an organism belongs to can be easily identified e.g. based on physical and molecular similarities
why do scientists classify organisms?: TO PREDICT CHARACTERISTICS
if several members of a group have similar characteristics (anatomical, physiological, behavioural), it is likely they belong to the same/similar taxonomic group
why do scientists classify organisms?: TO FIND EVOLUTIONARY LINKS
species in the same taxonomic group will likely share characteristics as they will have descended from the same common ancestor
what is taxonomy
naming and grouping species within a ranking system
organisms are grouped into taxa (singular= taxon)
biological classification definition
organising both living and extinct species into systematic groups based on DNA sequence (genome) and physical characteristics
who invented hierarchical classification
what is it
Linnaeus
largest group (top rank) contains the most different species
smallest group (lowest rank) contains 1 distinct species
what are the 8 taxonomic ranks
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
mnemonic for taxonomic ranks
Do
King
Prawns
Cook
Oysters
For
Giant
Squid
what is the biggest and broadest taxonomic group
domain
what is the smallest and most specific taxonomic group
species
who discovered domains
Woese
how are species named?
binomial system
2 names
dandelion name
Taraxacum officinale
rules for binomial system naming
genus name must start with a capital letter
2nd part must start with lower case letter
underline entire name to indicate italics
advantages of binomial naming (classification) system
universal language
useful in predicting characteristics
allows us to distinguish between some species within the same genus that are similar
why are ligers not classified as species but their parents are
cannot interbreed to produce fertile offspring (lions and tigers)
BUT lions can breed with other lions to produce fertile offspring
the biological species concept defines a species as a group of organisms that can breed to produce fertile offspring
suggest why this definition does not include all organisms and therefore might lack accuracy
doesn’t take into account organisms which reproduce asexually
members of the same species may have low sperm counts/low quality sperm/egg
no account of genetic diversity within a species
3 domains
eubacteria
archaea
eukaryotic
6 kingdoms
bacteria
archaea
protista
plantae
fungi
Animalia
5 kingdoms
protista
fungi
plantae
animalia
prokaryotae
protista:
type of body
nuclear envelopes
cell walls
unicellular, eukaryotic
yes
SOME have cellulose cell wall (plant-like)
protista:
cell vacuoles
organelles and fibres
type of nutrition
yes
cilia/flagella
nucleus
autotrophic, heterotrophic or both
protista:
motility
nervous coordination
examples
cilia/flagella or amoeboid mechanisms
no
Amoeba proteus
Plasmodium falciparum
Euglena graciis
prokaryotae:
type of body
nuclear envelopes
cell walls
unicellular
no (DNA= circular chromosome and plasmids)
murein cell wall
prokaryotae:
cell vacuoles
organelles and fibres
type of nutrition
no
no MBOs
saprotrophic, act as decomposers, autotrophic
prokaryotae:
motility
nervous coordination
examples
some do
no
E. coli, Streptococcus pneumonia, Salmonella enterica
fungi:
type of body
nuclear envelopes
cell walls
sometimes multicellular, sometimes unicellular e.g. yeast
yes
chitin
fungi:
cell vacuoles
organelles and fibres
type of nutrition
yes
no cilia or flagella, yes nucleus
decomposition, saprotrophic (absorption, extracellular enzymes)
fungi:
motility
nervosa coordination
examples
no
no
Saccharomyces cerevisiae, Rhizopus stolonifer, Amanita rubescens
plantae:
type of body
nuclear envelopes
cell walls
multicellular
yes
cellulose CW
plantae:
cell vacuoles
organelles and fibres
type of nutrition
yes, large and permanent
flagella, nucleus and chloroplasts
autotrophic (P/s), requires sunlight
plantae:
motility
nervous coordination
examples
some gametes use cilia/flagella. most don’t move
no
Rosa acicularis, Acer rubrum, Vaccinium macrocarpon
Animalia:
type of body
nuclear envelopes
cell walls
multicellular
yes
no
Animalia:
cell vacuoles
organelles and fibres
type of nutrition
sometimes small and temporary
cilia/flagella and nucleus
heterotrophic (ingestion)
Animalia:
motility
nervous coordination
examples
cilia, flagella or muscular organs based on contractile proteins e.g. actin, myosin
yes
Panthera tigris, Varanus comodoensis, Coccinella septumpunctata
key differences between archaebacteria and eubacteria
A found in extreme environments, are simpler in organisation, have introns
E exhibit glycolysis and Kreb’s cycle, RNA polymerase has simpler subunit pattern
membrane lipids: BOTH ester linked, E= branched, aliphatic, D-glycerol phosphates. A= straight, chained, L glycerol phosphates
E types= gram positive and negative
A types= methanogens (in O2 env), halophiles (water w high salt content), thermophiles (hot water in acid sulphur springs)
A cell wall= pseudo peptidoglycans, E= peptidoglycans and muramic acid
A= asexual reproduction e.g. binary fission, budding, fragmentation. E= spore production during unfavourable conditions
how does Woese’s system group organisms?
uses differences in sequences of nucleotides in the cells’ ribosomal RNA, plasma membrane’s lipid structure and sensitivity to antibiotics
observations of these differences was made possible through advances in scientific techniques
bacteria domain:
cell structure
cell wall of peptidoglycan
cytoskeleton
MBOs
DNA
non-coding nucleotide sequences within genes (introns)
histone proteins in combination with DNA
unicellular
yes
v simple
no
circular DNA (nucleic)
no
no
archaea domain:
cell structure
cell wall of peptidoglycan
cytoskeleton
MBOs
DNA
non-coding nucleotide sequences within genes (introns)
histone proteins in combination with DNA
unicellular
pseudo-peptidoglycan
more complex than bacteria
no
circular DNA (nucleoid)
some introns
yes some
eukaryotic domain:
cell structure
cell wall of peptidoglycan
cytoskeleton
MBOs
DNA
non-coding nucleotide sequences within genes (introns)
histone proteins in combination with DNA
unicellular or multicellular
no
very complex
yes
chromosomes in nucleus
yes lots
yes lots
extremophiles have proteins with high numbers of amino acids with polar R groups
suggest how this relates to their ability to survive at high temps
more polar R groups= more H bonds formed= stronger and more stable 2ary and 3ary protein structure
extremophiles in high temp env.s also have greater numbers of disulphide bonds e.g. more cysteine residues
examples of using biological molecules in classification
using DNA sequences
using protein/amino acid sequences e.g. cytochrome C
how to use DNA sequences in classification
base sequences in various regions of DNA are used to establish evolutionary relationships between different species (mapped out using phylogeny)
DNA extracted from fossils (FOSSIL RECORD)
MORE SIMILAR DNA=MORE CLOSELY RELATED SPECIES
similarities & differences between key regions of DNA in different species can be used to build up family trees, suggesting when different species evolved from common ancestors
how to use protein/amino acid sequences in classification
changes to DNA cause changes to the structure of proteins e.g. cytochrome C (key respiratory protein)
summarise role of cytochrome C as evidence in classification
all living organisms that respire must have cytochrome C (but its not identical in all species) so amino acids in CC can be identified and their sequences can be compared in samples from diff species
draw conclusions: same sequences= closely related, different sequences= less closely related species, more differences found= less closely related
e.g. AA sequences in cytochrome C of humans and chimpanzees= identical so v closely related species
phylogeny definition
the study of evolutionary relationships between different species
very closely related to cladistics
based on physical traits