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
rules for interpreting phylogenetic trees
earliest species at base of tree, most recent species at tips of branches
branches for extinct species will end before present day
the closer the relationship, the more recently they will have branched from a common ancestor
branch length is proportional to time
nodes at branching points represent common ancestors
explain why the structure of a phylogenetic tree may change over time
random mutations may occur, producing new alleles, which may make 2 species more/less closely related
speciation could occur due to isolating mechanisms (geographical/reproductive)
new evidence discovered e.g. DNA sequences, fossils so relationships are re-evaluated
suggest what advantages phylogenetic classification has over traditional hierarchical taxonomic classification
gives time scales and indicates precisely where 2 species evolved from a common ancestor
more/better visual representation
explain why eggs produced by 2 different species of macaw don’t hatch
different species
different genus
genetically incompatible
different chromosome numbers
physical/behavioural reason for reproductive incompatibility
outline the features of the domain system of classification compared with the five kingdom system
based on differences in DNA
more accurately reflects origins of prokaryotes/eukaryotes
divides prokaryotes
domain reflects differences between eubacteria and archaea e.g. cell wall/ cell membrane
idea that domain reflects the fact that there are similarities between eukaryotic kingdoms
groups eukaryotes together e.g. all have nuclei/ MBOs/80s ribosomes
suggest what criteria a taxonomist might take into account when classifying a new species
anatomy
biochemistry/cytochrome C
genes/DNA
behaviour
phylogeny
what were Darwins ideas on adaptation?
individuals which are better adapted to their environment compete better so survive longer, reproduce more so pass on successful characteristics
(survival of the fittest)
what were the observations that Darwin built his theory on?
populations are usually fairly constant in size
individuals within a species differ from each other (variation)
offspring resemble their parents: characteristics are inherited
far more offspring are generally produced than survive to maturity: suffer from predation, disease and competition
explain the process of natural selection
random mutation leads to variation
better adapted when selection pressure applied
survive, reproduce and pass on alleles so frequency of allele in gene pool increases
how is selective breeding carried out by humans?
risk of selective breeding?
desirable characteristics chosen by humans, and only those individuals with the bets characteristics are used for breeding
repeat
the species is changed over a long period of time (1000s of years)
risk=inbreeding
explain what and organism will be able to do if it lives longer
reproduce more, so pass on more of their successful characteristics to the next generation
describe why Darwin thought that giraffes have long necks
random variation in neck length due to mutation
env. with trees and bushes: longer-necked animals are better adapted so competed well compared to shorter-necked individuals bc they could feed off taller branches
therefore live longer, reproduce more and pass on genes
what is molecular biology
studying the sequences of DNA bases/ amino acid sequences in proteins e.g. cytochrome C
how does molecular biology provide evidence of evolution?
shows that all life evolved from a single common ancestor
provides a record of genetic changes over time
techniques e.g. DNA hybridisation, DNA molecular clocks and DNA profiling can be used to strengthen this evidence
what is biogeography?
the study of the geographical distribution of organisms, follows patterns that are best explained by evolution (and movement of tectonic plates)
how does biogeography provide evidence of evolution?
provides info about how and when species may have evolved
e.g. Australian marsupials, Galapagos finches= endemic, but have distant relationships to ancestral species on mainlands, therefore arise from their (due to landmass breaking off/ individuals being separated e.g. birds by storm)
what is direct observation
observing evolutions in the natural world e..g drug resistance or species adaptations (behavioural, physiological, anatomical) to a changing environment
how does direct observation provide evidence for evolution?
evidence due to the selection pressures (e.g. blue mussel has thickened shell over 15 year period bc of predation)
evidence of struggle for existence (Darwin uses this to explain natural selection)
what is DNA and protein sequencing?
comparing the base sequences of DNA or amino acids in different species
how does DNA and protein sequencing provide evidence of evolution?
had proven which organisms evolve from a common ancestor and how recently they have diverged
can map out these findings on a phylogenetic tree/ cladogram
what is anatomy and embryology?
embryology= studies of how embryos develop
anatomy can be homologous or analogous
homologous= physical features shared due to evolutionary history ( a common ancestor )
analogous= physical similarities evolved independently in different organisms due to similar environments or selective pressures (convergent evolution)
how does anatomy and embryology provide evidence of evolution?
evolutionary history of life forms a branching tree w/ many levels so all species can be traced back to a common ancestor
what is a fossil/ fossil record
fossils= preserved remains of previously living organisms or their traces, dating from the distant past
limitation of using fossils
rarely found by humans
most organisms never fossilise
need to know how old they are in order to interpret accurately
how do fossil records provide evidence of evolution?
document the existence of now-extinct species, showing that different organisms have lived on earth during different periods of the planet’s history
help scientists to re-construct the evolutionary histories of present-day species
what can the DNA base sequences of 2 species tell us about their evolutionary relationship?
more similar DNA base sequences= closer evolutionary relationship
how recently 2 species diverged
DNA hybridisation= a good comparison
suggest why fossil record fails to provide a complete picture of evolutionary history
rarely found by humans
need to know how old they are to interpret accurately
DNA degrades over time
most organisms never fossilise (no exoskeleton)
explain the parallels between natural and artificial selection that Darwin observed
variation persists
in both cases, desirable traits are inherited (alleles) and frequency of these desirable alleles increases over many generations
what is interspecific variation?
the broadest type of variation
between members of different species
e.g. birds display a variety of colour patterns
what is intraspecific variation?
differences between organisms within a species
e.g. people (Homo sapiens) differ in height, build, hair colour, intelligence
causes of variation
inherited (genetic) variation
environmental variation
combined effects
what is inherited variation
differences caused solely by genes
causes of inherited variation
DNA mutation
crossing over (meiosis)
independent assortment (meiosis)
random fertilisation
how is variation introduced by DNA mutations?
a random change to the DNA base sequence causes a different sequence of amino acids (1ary structure)
how is variation introduced by crossing over?
in prophase 1
random exchange of DNA between non-sister chromatids in a homologous pair produces new combinations of alleles in daughter cells
how is variation introduced by independent assortment?
in metaphase 1: random orientation of homologous pairs either side of equator
in metaphase 2: random orientation of sister chromatids
how is variation introduced by random fertilisation?
any male could mate with any female
any sperm could fertilise the egg
many combinations of alleles in offspring
what is environmental variation?
example
differences caused solely by an environmental condition
e.g. when hydrangeas are exposed to alkaline soil, a gene is switched on and pink pigments are produce. (blue in acidic soil)
what are combined effects
most characteristics are controlled by a combination of genes and the environment
e.g. hair colour, mass, height
example of skin colour as combined effects
controlled by melanin concentration in the skin
exposure ot UV light increase production of melanin and has a protective effect
2 types of graphical representation of variaiton
discontinuous
continuous
discontinuous vs continuous variation:
nature of the data
D: discrete w/ distinct categories
C: continuous so has many intermediate values
discontinuous vs continuous variation:
genetic influence
D: 1 or 2 genes
C: polygenic (many genes)
discontinuous vs continuous variation:
environmental influence
D: none
C: significant
discontinuous vs continuous variation:
how is it represented?
D: bar/pie chart
C: line graph/ histogram
discontinuous vs continuous variation:
examples
D: blood group, eye colour, biological sex
C: height, mass, leaf length
what are adaptations
characteristics that increase an organisms chance of survival and reproduction in its new environment
types of adaptation w/ brief description
anatomical/structural adaptations: physical feature
behavioural adaptations: a response/reaction to a stimulus/situation
physiological adaptations: process that occurs in response to a stimulus
examples of anatomical/structural adaptations
milk/coral snakes
extremophile bacteria
fennec foxes
marram grass
Galapagos finches
example of anatomical/ structural adaptation: snakes
milk snake vs coral snake
MIMICRY: harmless milk snake copies the markings of the deadly coral snake, so tricks predators into thinking it is dangerous
red of coral snake has evolved as a ‘danger’ colour
example of anatomical/structural adaptation: bacteria
extremophile bacteria
Archaea
Sufolobus acidocaldarius
lives in volcanic springs, which are highly acidic/sulfurous/hot
has ether bonds rather than ester bonds between glycerol and fatty acids in phospholipids so stronger plasma membrane
supercoiled DNA (many histones) to withstand heat
proteins have high numbers of polar amino acids so more hydrogen bonds so stronger
examples of anatomical/structural adaptation: fennec fox
large ears increase surface area for heat loss
thick layer of fur to retain heat in cold desert night
large eyes to enhance peripheral vision
examples of anatomical/structural adaptation: finches
adaptive radiation in Galapagos finches
1 species diverges into multiple new subspecies/species
each finch adapted to fill a specific ecological niche
examples of behavioural adaptation
eucalyptus
fennec fox
courtship, survival behaviours (i.e. playing dead) and migration/hibernation
example of behavioural adaptation: eucalyptus
in forest fires, eucalyptus is sensitive to heat and releases its seeds after the fires
increases chance of survival
example of behavioural adaptation: fennec fox
nocturnal (remains underground for most of the day) to avoid predation by eagles
examples of physiological adaptations
land snails (aestivation)
plants produce defensive chemical in response to pathogens
animals that live in v. dry places reabsorb large volumes of water (have long Loop of Henle)
examples of physiological adaptation: land snails
AESTIVATION= period of inactivity in hot.dry places allowing them to cope with extreme heat
what kind of adaptation is sweating
physiological
what kind of adaptation is phototaxis (directional movement towards light)
behavioural
what kind of adaptation are opposable digits
anatomical
what kind of adaptation is lactose tolerance
physiological
anatomical adaptations of bacterial cells
have plasmids, flagella, cell wall
behavioural adaptations of bacterial cells
chemotaxis
movement towards host cell
physiological adaptations of bacterial cells
binary fission
production of proteins involved in resistance and production of anitbodies
mechanism of natural selection
- random mutation produces a new allele which gives an organism a selective advantage (e.g. taller-necked giraffe, resistant bacteria)
- when a selection pressure is applied, those best-adapted survive and are more likely to reproduce
- advantageous allele is passed to offspring
- over many generations the frequency of the advantageous allele increases in the gene pool, so a greater proportion of population have this selective advantage
modern examples of evolution
Staphylococcus aureus
Flavobacterium
Drosophila
Peppered moths
Sheep blowfly
modern examples of evolution: Straphylococcus aureus
adaptation that has evolved?
implication for humans?
resistance to many antibiotics, incl. Methicillin
less are killed by antibiotics, so more danger to humans. disease may be untreatable and lead to death
modern examples of evolution Flavobacterium
adaptation that has evolved
implication for humans
can digest nylon using nylonases (enzymes)
provides bacteria w a source of nutrients
helpful, can clear up factory waste
modern examples of evolution peppered moths
adaptation that has evolved
during industrial revolution, trees became darker bc covered with soot, so dark moths better adapted to camouflage and hide from predators. increased frequency of dark allele
bark became lighter after revolution, so increased frequency of pale allele
modern examples of evolution sheep blowfly
adaptation that has evolved
implication for humasn
resistance to pesticide diazonin
-partly helped by pre-adaptation
less killed by pesticide so more sheep die so less food and less profit for farmers
