4.2.2 classification Flashcards
classification
The sorting of living organisms into groups which share similar characteristics
(physical, biochemical, behavioural)
what is the study of classification
taxamony
order of hierarchical system
Kingdom
Domain
Phylum
Class
Order
Family
Genus
species
as you move up the hierarchical systems levels what happens?
more organisms present in each
group, but they will have less in common
(increase in numbers, decrease in similarities)
define kingdom
highest taxonomic rank, and the most general taxon used in classifying organisms
define species
group of closely related organisms that are very similar to each other
physically & biochemically. They can
interbreed to produce fertile offspring.
horses & donkeys can breed to produce mules but are classed as different species. why?
- a mule is infertile, mules cannot breed to produce any offspring
- horses have 64 chromosomes in a normal body cell, so 32 in a gamete
- a donkey has 62 chromosomes in a normal body cell, so 31 in a gamete
- so the zygote has 63 chromosomes
- an odd number of chromosomes means they can’t pair up and do meiosis, so a mule is infertile
why do scientists classify organisms?
- to identify species
- to predict characteristics
- to find evolutionary links - may have evolved from same ancestor so share similar characteristics
how has the classification system changed overtime?
- originally, there was just 2 kingdoms, animals & plants
- animal kingdom included all organisms that moved, ate & grew to a certain size
- plant kingdom included all organisms that did not move or eat, and continued to grow throughout life
- more new species were discovered, it became difficult to divide all organisms into 2 groups.
- scientific equipment, like the microscope showed that some cells had different structures (prokaryotes + eukaryotes)
- so the five kingdom system was introduced
how were species originally named?
according to physical characteristics, habitat or behaviour
how are species named now?
according to the binomial naming system.
- Genus speices
- underline it
describe the 5 kingdom for classification
- all living organisms are either prokaryotae or eukaryotae
- prokaryotae (no true nucleus) includes bacteria
- eukaryotae includes, fungi, protoctsita, plantae, and animalia
features of prokaryotae/ monera
- unicellular
- no nucleus/ membrane bound nucleus
- ring of DNA
- 70s ribosomes
- no visible feeding mechanism (nutrients absorbed through cell wall or made during photosynthesis)
- heterotrophs (rely on the absorption of ready-made organic molecules from other organisms))
features of protoctista
- some are autotrophs, some heterotrophs
- unicellular
- nucleus + membrane bound organelles
- can have chloroplasts
- some don’t move, some can by cilia or flagella
features of fungi
- uni/multicellular
- nucleus + membrane bound organelles
- chitin cell wall
- no chloroplasts
- no locomotion
- made of threads of hyphae
- saphrotrophs (gets nutrients by absorption from DOM)
- store food as glycogen
what are saphrotrophs?
- feed on DOM
- hyphae grow over the DOM, releasing enzymes onto it, digesting molecules &
reabsorbing the useful monomers
how can fungi reproduce?
sexually using SPORES which are released into the air
features of plantae
- multicellular
- nucleus + membrane bound organelles
- cellulose cell wall
- chloroplasts
- can or cannot move
- autotrophs
- store starch from glucose
features of animalia
- multicellular
- nucleus + membrane bound organelles
-move with cilia/flagella
-heterotrophs - store glycogen from glucose
Why is DNA analysis so useful in classification?
- to compare the DNA of different organisms to see the different proteins that are coded for
- so you can find evolutionary relationships between species
- as when species evolve overtime mutations (changes in the DNA base sequence) occur
- which leads to a change in characteristics
- mutations take time to occur
- so more differences from mutations means the longer ago the species diverged from each other
what can help find out how closely related organisms are?
comparison of haemoglobin
developments in our ability to analyse DNA & proteins has led to what?
updated version of how we classify organisms. The “3-domain / 6-kingdom”
why do we use the 3-domain / 6-kingdom system?
Carl Woese found that prokaryotes fall into 2 different groups, with different chemical structures in their cells
what is archaebacteria?
- no peptidoglycan cell walls
- RNA polymerase enzyme contains 8-10 different proteins
- live mainly in extreme environments like thermal vents, anaerobic conditions, very acidic conditions
- “ancient bacteria”
what is eubacteria?
- ” true bacteria”
- have peptidoglycan cell walls
- RNA polymerase enzyme (used for transcription) contains 5 different proteins
- found in all environments
overview of revised classification system
- 3 domains include bacteria, archaea and eukarya
- bacteria includes eubacteria
- archae includes archaebacteria
- eukarya includes protoctista, fungi, animalia, plantae
what is phylogeny?
- represents the evolutionary history of a group of organisms, represented by an evolutionary tree
- branches show how closely related different groups of organisms are what order they diverged from a common ancestor
what is used to compare the genetic make-up of the different groups? how does it work?
DNA sequencing. The more similar their DNA, the more closely related they are in evolutionary terms.
what is found at the base of the tree?
earliest species
what is found at the tips of the branches?
more recently evolved species
phylogenetic definition of a species
a SPECIES is the smallest group that share
a common ancestor
main advantages of phylogenetic classification considering evolutionary relationships & DNA profiles
- more flexible than traditional methods – it
produces a continuous flowing tree rather than putting organisms into distinct groups - considers evolutionary relationships that are not obvious by looking at characteristics
- hierarchical traditional system can be misleading as it implies that
organisms at the same level are directly comparable, no hierarchy
3 types of evidence for evolution
- study of fossils & fossil records (palaeontology)
- comparison of similarities & differences between the anatomy of organisms (comparative anatomy)
- similarities & differences in the chemical make-up of organisms (comparative biochemistry – looking at proteins & DNA)
describe how fossils are formed
- animal and plant remains preserved
- sediment is deposited which forms layers (strata)
of rock - different layer = different geological era
- forming a sequence from oldest to newest
- shows organisms have evolved over time
describe how of fossils & fossil records (palaeontology) is evidence
- fossils of simplest organisms found in oldest rocks
- fossils of more complex organisms are found in more recent rocks
- supports idea that simple life gradually evolved overtime to more complex ones
- sequence in which organisms are found matches ecological links to each other
- shows how closely related organisms evolve from the same ancestor
- allow links between extinct and living organisms
why are fossil records incomplete?
- soft bodied organisms (no skeleton) decompose without fossilising
- sometimes the necessary conditions (specific temp+ pressure) of fossilisation don’t occur
- fossils have been destroyed due to Earth’s movement
what is comparative anatomy?
- comparison of similarities & differences between the anatomy of organisms
- look at homologous structures (appear different but have same underlying structure)
- provides evidence for divergent evolution
what is comparative biochemistry?
- study of the biochemistry of molecules common to all living
organisms e.g. RNA, DNA, Proteins - to study how closely related 2 species are, the molecular sequence of a particular molecule can be compared
- molecules change over time due to chance mutations in the DNA
- give us an idea of how long ago 2 species diverged from each other as they occur at predictable rates for particular types of molecules
what are 2 of the most common molecules studied in comparative biochemistry?
- cytochrome c
- ribosomal RNA
cytochrome c
- protein involved in cell resp
- in all living organisms
- comparison of the amino acid sequence of cytochrome-c in different organisms allows us to see how closely related they are (more closely related, more similar amino acid sequence)
ribosomal RNA
- substance that ribosomes are made of
- in all living organisms
- comparing the base sequence of the
ribosomal RNA gives an idea of how closely related 2 organisms are (more
similar base sequence = more closely related)
what is DNA hybridisation?
- sample of DNA from 2 organisms that you want to compare
- heat the DNA to make is ss (H bonds break)
- mix the ss DNA from the 2 organisms together & give it time to see how well it hybridises (do the strands join together)
- If the ss DNA molecules from the 2 organisms hybridise completely, they are the same species
- If it hybridises partially, they are related to some degree
- If it does not hybridise at all, they are not related
intraspecific variation
variation within a species
interspecific variation
variation between different species
2 main causes of variation
- genes
- environment
how are genes a cause for variation?
genetic variation is due to the alleles and organism has for a gene, these are inherited
how is the environment a cause for variation?
various factors like diet, climate, lifestyle
describe alleles as a genetic cause for variation
- genes can have diff alleles
- which are inherited and passed onto offspring
describe mutations as a genetic cause for variation
- changes in DNA sequence which can lead to change in proteins coded for
- if occur in somatic “normal body” cells, they can’t be passed onto offspring
- if occur in gamete formation during meiosis they can be passed on
describe reshuffling of alleles during meiosis as a genetic cause for variation
- during meiosis, gametes formed have half the original number of chromosomes
- variation occurs due to crossing over and independent assortment
describe sexual reproduction as a genetic cause for variation
- offspring produced from 2 different parents inherits half their alleles from each
- makes offspring genetically different to their parents
describe chance as a genetic cause for variation
- gametes are made during meiosis
- when sexual reproduction occurs, it is chance when 2 gametes fuse together
- lots of variation in offsprings
examples of characteristics controlled by just genes
blood type, eye colour, rolling your tongue
why are plants more effected by environment than animals?
- they can’t move
- if a plant is nutrient poor soil it can’t move
- so it won’t grow as big as plant in nutrient rich soil
- if animal was in habitat with little food it would move
examples of characteristics controlled by only the environment
scars, tattoos, piercings, plant shape
How is your height effected by both environment and genes?
E- diet - poor diet during development means you might not reach full height potential
childhood illnesses- limit growth
G- tall allele or short allele passed on
How is your skin colour effected by both environment and genes?
E- more exposure to sunlight = more melanin production to protect skin from harmful UV rays = darker skin
G- alleles for amount of melanin we produce
why are identical twin studies useful when trying to find out if variation is caused by nature or nurture?
- genetically identical
- any differences between them are due to environment
continuous data
- variation within a range
- no distinct catergoires
- range of values from one extreme to the other
discontinuous data
- 2 or more distinct categories for a characteristic
- no intermediates
give examples of discontinuous data
- blood groups (A. B, AB, O)
- eye colour
- ability to roll tongue
- plant seed shape
is blood group caused by genes or environment and why?
genes, one gene has diff alleles (monogenetic inheritance)
give examples of continuous data
- height + weight in humans
- SA of leaves
- length of leaves
- bacterium flagellum length
how is continuous data usually collected and shown?
- collected as a frequency table/ tally chart
- plotted as histogram
- converted in a bell shaped/ normal distribution curve
what is standard deviation?
- measurement to show how spread out the data values are around the mean, e.g. small SD = more values close to mean, data more repeatable (smaller spread of data)
- shows how repeatable data is
if a characteristic has a high standard deviation, what does this mean?
there is a large amount of variation
define adaptation
- change in structure, function, behaviour that helps organism survive in a particular habitat
- useful adaptations increase organisms chance of survival, so they can reproduce
what do random mutations cause?
new characteristics to form. so environmental selection pressures will favour the survival of organisms best adapted to that particular environment
3 types of adaptations
- anatomical
- behavioural
- physiological
what is an anatomical adaptation?
physical or structural feature (internal or external)
what is a behavioural adaptation?
way organism behaves or acts. (inherited or learnt)
what is a physiological adaptation?
the metabolic processes occurring inside an organism (biochemical reactions)
examples of anatomical adaptations
- thick fur for warmth in cold climates
- shells/ spikes for protection from predators and damage
- waxy cuticle to reduce water loss in xerophytes
what is marram grass?
- species with lots of anatomical adaptations, which allow it to live on sand dunes
examples of anatomical adaptations for marram grass
- curled leaves to decrease SA of moist tissue exposed to air and to protect leaves from wind
- hairs inside surface of leaf to trap moist air, reducing the diffusion gradient
- thick waxy cuticle to minimise water loss through transpiration
- sunken stomata into pits which makes them less likely to open and lose water
examples of physiological adaptations
- production of poisons / toxins
- production of antibiotics
- production of less urine to conserve water
- ability to switch from aerobic and anaerobic resp depending of O2 availability
examples of behavioural adaptations
- courtship displays to attract mates and reproduce
- migration
- playing dead to avoid being eaten
- mimicking other animals to confuse predators
- curling up into a ball to avoid being eaten
innate behavioural adaptations
inherited through genes
learned behavioural adaptations
learnt from experience or observing other animals
convergent evolution
where 2 different non-related species evolve similar characteristics independently of each other
why does convergent evolution occur?
due to the species experiencing similar selection pressures in their environments, so they evolve structures with similar function that are still very different anatomically (analogous structures)
explain convergent evolution in marsupial and placental mammals
- in placental, a placenta connects the embryo to the circulatory system of the mother in the uterus, allowing the embryo to develop before leaving. (long gestation period)
- in marsupial animals the embryo starts of in uterus but leaves at early stage and enters a pouch. (short gestation period)
- they both diverged from each other and have similar resemblance
divergent evolution
where members of the same species diverge overtime, and become more different until they are classed as separate species
why does divergent evolution occur?
due to the different groups of organisms experiencing different selection pressures in their environments, so will have body parts that are diff to each other and are used for different roles but have the same underlying structure (homologous structure)
analogous structures
structures with similar function that are still very different anatomically
homologous structure
body parts that are diff to each other and are used for different roles but have the same underlying structure
give examples of selection pressures
- completion for food
- threat of predators
- disease
- climatic factors (changes in temp, sunlight availability, rainfall)
what is a selection pressure?
factors in an organisms environment that affect the chance of survival and reproduction
what gives variation within a population?
presence of alleles
what happens within a particular selection pressure exerts itself on a population?
- those that are best adapted are more likely to survive and breeds, so pass on their useful alleles to their offspring, so the offspring show similar characteristic to the parents
- changes in the allele frequency over time cause evolution of species as a whole
- this is natural selection and it causes the increase and decrease of certain alleles in a pop overtime
4 observations Darwin made in his theory of natural selection
- over production of offspring
- the pop stays fairly stable
- variation in organisms characteristics
- offspring resemble parents
4 of darwin’s conclusions on the theory of evolution
- competition for resources between organisms in the same pop where resources are limited
- the best adapted survive
- they reproduce and pass on useful alleles to next gen
- allele frequency changes overtime
7 points on how to answer natural selection question
- mutations occur randomly in pop
- these result in the formation of new alleles coding for certain characteristics
- diff alleles cause variation with a pop
- selection pressures act on the pop
- they will favor the survival of certain organisms (those that are the best adapted to that environment)
- these individuals more likely to survive and breed and then pass on their alleles to their offspring/ next gen
- these alleles will increase in the pop over time
explain how natural selection has resulted in 2 forms of the peppered moth
- colour difference due to random mutations which led to diff alleles and genetic variation
- during the industrial revolution the dark moths were selected for so more likely to survive
- more of the dark moths reproduced to pass on their alleles
- the frequency of the allele for dark colour increases
describe the evolution of insect pests that are now resistant to insecticides
- random mutations occurred which caused the formation of new alleles
- the selection pressure is the use of the insecticide
- it favors the survival of those insects that are resistant so those ones can survive and breed to pass on their alleles to the next generation
consequences of pesticide resistant pests
- insect pests living on crops are harder to control
- takes lots of attempts with diff pesticides to get them off
- causing whole crop to be destroyed
- farmers might have to use broader acting insecticides which could kill beneficial insects
- disease carrying insects become resistant then the spread of disease will increase
- new pesticides have to be produced which takes time and costs money
describe the evolution of bacteria that are now resistant to antibiotics
- the first antibiotic resistant bacteria appeared from a random mutation
- the use of the antibiotic is the selection pressure
- it favors the survival and reproduction of those bacteria that are resistant so the alleles for resistance are passed on to next gen
consequences of resistant bacteria for humans
- bacterial infections caused by antibiotic resistant bacteria harder to treat
- takes time for doctors to find antibiotic that works
- so patient can become ill or die
- takes time and money to for new drugs to be developed and found
bioremediation
biological process that stimulates helpful microbes to use harmful contaminants as their source of food and energy ( breaks down harmful pollutants and waste products from human activity and industrial processes)
