4.2.2 Classification and evolution

Question 1

What is variation?

Answer 1

the differences in characteristics that exist between organisms

Question 2

Intraspecific variation

Answer 2

-variation between organisms of the same species—> can produce fertile offspring, have similar appearance and have similar genetic makeup
-differences between organisms exist in relation to natural selection(observed in the phenotypes of individuals from the same species due to quali/quantitative differences)
-can be understood by looking at discontinuous or continuous variation

Question 3

Interspecific variation

Answer 3

variation between organisms of different species i.e the bee hummingbird is light and the ostrich is heavy
-useful in classifying and identifying diff species(mostly through phenotypic variation, i.e habitats and roles OR genotypes i.e genetic variation)

Question 4

What is continuous variation?

Answer 4

-phenotype varies with a range/continuum between 2 extremes instead of distinct categories e.g height, SA of leaves, length of microorganism
-caused by an interaction between genetics and the environment
-characteristics controlled by a number of genes(polygenic) and influenced by environmental factors.
-occurs when there is quantitative differences in the phenotypes of individuals within a population
-presented in a table/graph(normally histogram)

Question 5

What is discontinuous variation?

Answer 5

-When there are 2 or more categories that the phenotype can be grouped in that are discrete and distinguishable with no intermediates i.e blood groups*, shape of bacteria
-not affected by environmental factors
-occurs with qualitative differences in the phenotypes of individuals
-data is usually plotted on bar charts
*controlled by a single gene(ABO) like other discontinuous characteristics which are controlled by 1 or 2 genes

Question 6

What can cause variation?

Answer 6

-genetic factors(inherited)
-environmental factors
-combination of both

Question 7

Genetic causes of variation

Answer 7

-the alleles an organism has makes up its genotypes + the differences in genotype cause phenotype variations i.e blood types have the alleles O, A or B, antibiotic resistance in bacteria, eye colour
-different genes can have different effects on the phenotype OR different genes can have the same effect(additive effect on phenotype)
-diff alleles at the same locus can have a large/small effect on the phenotype depending on type of variation
-also caused by mutations, random
mating, random fertilisation and crossing over recombination between homologous chromosomes in meiosis

Question 8

Environmental causes of variation

Answer 8

-i.e different soil, temperature changes
-can explain phenotypic variation i.e clones of plants being diff heights
-changes in the environmental factors can affect how an organism grow and develop
-cannot be inherited by offspring(not alteration to genetic components of gametes)

Question 9

What are the environmental factors?

Answer 9

-Length of sunlight hours
-supply of nutrients
-availability of water
-temp range
-oxygen levels

Question 10

Environmental and genetic causes together

Answer 10

i.e inheriting a tall gene but having a poor diet that stunts growth
-in most cases variation happens due to a combination of factors

Question 11

What are adaptations?

Answer 11

-characteristics that evolved in response to the organism’s specific environment that increase an organism’s chance of survival and reproduction in its environment and therefore can pass its genes on to increase chances of offspring reproducing successfully

Question 12

Anatomical adaptations

Answer 12

structural or physical characteristics of an organism that increase its chances of survival i.e tigers camouflage allowing in to blend into environment while hunting prey/ stem of a waterlily contains bubble like structures to help it float
(marram grass is a xerophyte, a plant that has adapted to live with very little water, and is commonly found in sand dunes:
hairs on inside of leaf to trap moisture to reduce diffusion gradient, stomata in pits to prevent loss of water + thick waxy cuticle on leaves and stem to reduce water loss via evaporation)

Question 13

Behavioural adaptations

Answer 13

the way an organism behaves in its environment to increase its chances of survival, can be learned or innate
i.e hibernation, migration, peacocks’ courtship behaviour attracts a mate;increasing its chances to reproduce/ butterfly’s migration allows it to escape cold winters

Question 14

Physiological adaptations

Answer 14

biological processes within an organism that increase its chance of survival
i.e poison production, antibiotic production, oil eating bacteria breaks down crude oil that increases survival after oil spillage/ sperm cells have lots of mitochondria which increases chances to fertilise egg cell

Question 15

What is classification and taxonomy?

Answer 15

the act of arranging organisms into groups based on their similar anatomical features that they share
taxonomy = the study of classification and the formal naming/classifying system

Question 16

Definition of the taxonomic hierarchy

Answer 16

• a hierarchy in which smaller groups are placed within larger groups, with no overlap between groups
  -the organisms are grouped from the most general to the most specific (become more similar + share more characteristics)

Question 17

The taxonomic hierarchy

Answer 17

• 8 taxonomic groups or ‘hierarchical taxa’:
  Domain= similar organisms placed into 1 of 3 large groups i.e Eukarya(plants, animals, fungi), Bacteria and Archaea(single-cell prokaryotes)
  Kingdom i.e Animalia
  Phylum
  Class
  Order
  Family
  Genus
  Species(group of similar organisms that are able to produce fertile offspring)

Question 18

How did organisms used to be named and why was that a problem?

Answer 18

-many organisms were given names according to certain physical characteristics i.e blackbirds
-problematic for international scientists(different languages etc)
-doesn’t provide much info about relationships between organisms i.e common ancestors from the same genus

Question 19

How are organisms named now?

Answer 19

-the binomial nomenclature/name developed by Carl Linnaeus in the 18th century
-internationally accepted scientific name in Latin:
1st word is the generic name that indicates the genus(Capital letter)
2nd word is the specific name that indicates the species(lowercase letter)
-must be written in italics or underlined

Question 20

Why do scientists classify organisms?

Answer 20

-to identify species easily by using clearly defined system of classification
-to predict characteristics by observing members of group
-to find evolutionary links i.e common ancestor between species of the same group due to similar characteristics

Question 21

Why and how were the 5 kingdoms created?

Answer 21

-created by Robert Whittaker and based on principles by Carl Linnaeus
-over time, it became increasingly difficult to divide living organisms into just 2 kingdoms i.e introduction of microscope showed that bacteria is a diff organism
-based on observable features that could
be seen under a light microscope

Question 22

Prokaryotea

Answer 22

-i.e e.coli
-unicellular,(just a ring of ‘naked’ DNA and some small ribosomes)
-no nucleus
-no membrane bound organelles
-has cell wall
-70s ribosomes(electron microscope)
-less that 5 micro meters
-can be heterotrophic(nutrients absorbed via cell wall) OR autotrophic
(internal production i.e photosynthesis)

Question 23

Protoctista

Answer 23

i.e amoeba
-eukaryotic, usually live in water
-mostly unicellular or can be simple multicellular
-have nucleus + other membrane bound organelles
-some have chloroplasts
-most don’t have a cell wall
-80s ribosomes(electron microscope)
-some are sessile, others move by cilia/flagella
-nutrients are acquired via photosynthesis(autotrophic feeders), ingestion of other organisms(heterotrophic feeders) or both(some are parasitic)

Question 24

Fungi

Answer 24

i.e moulds, yeasts, mushrooms
-eukaryotic, can be uni/multicellular
-chitin cell wall
-nucleus + other membrane bound organelles
-80s ribosomes(electron microscopes)
-saprotrophic(absorbs substances from dead/decaying organisms), some are parasitic
-most store their food as glycogen

Question 25

Plantae

Answer 25

i.e mosses, ferns, flowering plants
-eukaryotic, multicellular
-cell walls made of cellulose
-nucleus + other membrane bound organelles
-80s ribosomes
-can photosynthesise
-contain chlorophyll
-nutrients acquired by photosynthesis(autotrophic)
-store food as starch

Question 26

Animalia

Answer 26

i.e nematodes(roundworms), molluscs, insects, fish, reptiles, birds, mammals
-eukaryotic
-multicellular
-no cell walls
-nucleus and other membrane bound organelles
-80s ribosomes
-move with the aid of cilia, flagella or contractile proteins(sometimes in the form of muscular organs)
-heterotrophic(consume plants + animals by ingestion)
-food stored as glycogen

Question 27

Changing the classification of organisms

Answer 27

-originally, classification was based on observable anatomical features but the modern classification system uses new technology i.e DNA analysis techniques and better microscopes, to study DNA, RNA and proteins so new discoveries can be made
-Scientists can share new discoveries in meetings/scientific journals
-classification is continuously revised to take account of new findings i.e Skunks changed families bc molecular evidence revealed DNA sequence was significantly different to 1st family

Question 28

Archaea-bacteria

Answer 28

-‘extremophile prokaryotes’- can live in extreme environments i.e halobacteria(ancient and can survive in extreme heat)
-unicellular
-no nucleus so are prokaryotic
-no membrane bound organelles
-cell wall WITH NO PEPTIDOGLYCAN
-have 70s ribosomes
-RNA polymerase of different organisms contain between 8-10 proteins(very similar to eukaryotic ribosome)
-similar size range to bacteria + metabolism is similar
-DNA transcription more similar to eukaryotes
-can be heterotrophic&autotrophic

Question 29

The 3 domain system

Answer 29

-Archaea, Bacteria or Eukarya
-proposed by Carl Woese in 1990
-advances in molecular biology, biochem and cell structure showed that prokaryotea are not one uniform group –} too much variation
-split into eubacteria, archaea-bacteria(both prokaryotes so share a lot of similar features) making 6 kingdoms
- made Eukarya(eukaryotes) by combining animalia, plants and fungi because they had a lot in common

Question 30

Difference between the five kingdom system and the three domain system

Answer 30

-all organisms used to be placed under one of the 5 kingdoms which were the largest groups
-3 domain system proposed larger superkingdoms that are at the top of the taxonomic hierarchy
-organisms that were formerly in Prokaryotae got separated into Archaea and Bacteria + organisms with nuclus containing cells were placed in Eukarya

Question 31

Eubacteria

Answer 31

-prokaryotic + unicellular
-70s ribosomes
-no nucleus or membrane bound organelles
-cell wall WITH PEPTIDOGLYCAN
-can be heterotrophic&autotrophic
-vary in size
-found in all environments i.e e.coli
-divide by binary fission
-RNA polymerase contains 5 proteins

Question 32

Eukarya

Answer 32

-have eukaryotic cells with nuclei and membrane bound organelles
-linear chromosomes
-have glycerol + ester lipids in cell membrane
-80s ribosomes in cytosol + 70s ribosomes in mitochondria and chloroplasts
-cell walls sometimes present WITHOUT PEPTIDOGLYCAN
-vary massively in size
-divide by mitosis
-can reproduce sexually/asexually

Question 33

Key differences between archaea and bacteria

Answer 33

-MEMBRANE LIPIDS: ones in archaea are completely unique + consist of branched hydrocarbon chains bonded to glycerol by ether bonds, whereas ones in bacteria consist of unbranched hydrocarbon chains bonded to glycerol by ester bonds
-rRNA: primary structure + base sequence of 70s ribosomes in archaea are more similar to eukaryotic ones than bacterial
-CELL WALL COMPOSITION: bacterial cell walls contain peptidoglycan whereas archaea cell walls don’t
-also, development of flagellae are different

Question 34

What used to be the main evidence source for classification and why is that bad?

Answer 34

-comparative morphology = observable features i.e anatomical or behavioural
-problematic because physical features do not indicate close relations i.e sharks’ backbone made of cartilage and whales’ made out bone
-scientists may not always agree on relative importance of different features

Question 35

Modern types of evidence for classification

Answer 35

-fossil record = provides evidence of how organisms evolved from one another
-embryological evidence = similarities in the early stages of an organism’s development
-molecular evidence = how similar DNA is of 2 organisms = RNA/amino acid sequences are in enzymes + antibodies

Question 36

Molecular evidence

Answer 36

-involves analysing similarities in proteins and DNA–} closely related organisms will have more similar molecules i.e how DNA is stores and sequence of DNA bases can be compared to determine relationships
-each change in a nucleic acid = one evolutionary event(more events mean more distantly related species)

Question 37

Examples of proteins used for evidence/phylogeny

Answer 37

-Cytochrome C is a small protein found loosely associated with inner membrane of mitochondria + involved in the electron transport chain(final stage of respiration)–} more similar amino acid sequence is between two species, the closer related they are
-Haemoglobin is made up of 4 polypeptide chains–} highly conserved and found in many organisms so it is good to use for phylogeny

Question 38

What is phylogeny?

Answer 38

-study of evolutionary history of organisms–} tells us who’s related to who and how close they are
-classification systems have recently taken it into account to confirm taxa are correct whereas phylogeny can be done independently/doesn’t need classification

Question 39

Phylogenetic trees

Answer 39

-diagram used to represent evolutionary relationships between organism by looking at similarities + differences in physical characteristics + genetic makeup
-tells us about ancestors, duration of evolutionary lineages, amounts of evolutionary change that has occurred
-first branch point represents common ancestor of all family members and following branches represent another common ancestor from which a diff group diverged
-closer the branches are, the closer their evolutionary relationship is vice versa

Question 40

Advantages of phylogeny

Answer 40

-highlight evolutionary relationships
-produces a continuous tree rather than forcing organisms into discrete taxonomical groups
-distinguish evolutionary timetable

Question 41

What is evolution?

Answer 41

the change in inheritable characteristics of biological populations over time (as a result of natural selection)

Question 42

Darwin’s 4 observations

Answer 42

-organisms produce more offspring than survive
-there’s variation in the characteristics of members of the same species
-some of these characteristics can be passed on from 1 generation to the next
-individuals that are best adapted to their environment are more likely to survive
(also noticed that the population of species still remained constant)

Question 43

Define population and community

Answer 43

-population = amount of one species
-community = amount of all species

Question 44

The theory of evolution by natural selection

Answer 44

-individuals within a population show variation in their phenotypes (characteristics) due to mutations
-exposed to selection pressures(environmental factors i.e disease) create a struggle for survival and reproduction
-individuals with better adaptations/selective advantage are more likely to survive and reproduce
-they pass on beneficial alleles to their offspring, causing them to be more likely to survive and reproduce
-over time the proportion of the population processing the advantageous allele increases
-over generations, this leads to more advantageous alleles becoming more common in the population’s phenotype

Question 45

Wallace’s contribution to natural selection

Answer 45

-independently came up with it and wrote to Darwin about it–} didn’t always agree about mechanisms involved
-W’s observations provided lots of evidence i.e warning colours used to deter predators was an advantageous adaptation
-Darwin went on to independently write ‘origin of species’ and became renowned for it

Question 46

Fossil evidence for natural selection

Answer 46

preserved remains of organisms that aren’t fully decomposed(lack of CO2/O2) or features left i.e footprints
-can be time-stamped/arranged in chronological order to show gradual changes in an organisms(older=simpler)
-can create sequence from oldest to youngest to create evolutionary links
-common ancestors by looking at fossil anatomy
-relationship between living + extinct fossils can be formed

Question 47

Limitations of fossils

Answer 47

-fossil record is incomplete
-many organisms decompose too quickly
-fossils can be destroyed by volcanic/tectonic activity

Question 48

Comparative anatomy as evidence for natural selection

Answer 48

-appear different but have homologous underlying structures i.e skeleton
-evolutionary embryology(study of embryos, can distinguish common ancestors)

Question 49

Comparative biochemistry as evidence for natural selection

Answer 49

newer and more reliable technique
-must sequence their genome–} find the sequence of bases in the DNA for organisms being compared, similar genome= similar organism
-can be used to provide evolutionary relationships between species and how genetic code has changed via evolution
(humans + chimps share 94% DNA)
-can also use RNA/amino acid sequences and sometimes just sections are used for ease
-can be used to create phylogenetic trees

Question 50

Comparative biochemistry - proteins

Answer 50

i.e haemoglobin(found in many organisms and is highly conserved), so is a good protein for comparing/phylogeny

Question 51

Biotechnology

Answer 51

-software used alongside computational bio(analysing) to compare genomes as humans cannot do this

Question 52

Advantages of binomial names

Answer 52

-universally accepted by scientists no matter the language they speak
-specify which genus an organism belongs to

Question 53

Difference between heterotrophic and autotrophic

Answer 53

-Heterotrophic take in nutrients by absorbing other organisms whereas autotrophic produce their own nutrients i.e photosynthesis

Question 54

What helps scientists understand intra specific variation?

Answer 54

Discontinuous and continuous variation

Question 55

What is convergent evolution?

Answer 55

When two organisms that don’t share a common ancestor show similar characteristics due to adaptation to similar environments/to fit similar economical niches

Question 56

Differences between marsupial and placental mammals

Answer 56

-M have a shorter gestational period than P
-P develop a FULL placenta during pregnancy to allow exchange of nutrients and waste products between foetus and other whereas M do not
-M are born early in there devs and climb into mother’s pouch where they attach to a tear and receive milk whilst developing whereas P are born more fully developed

Question 57

Similarities between marsupial and placental moles

Answer 57

-scoop shaped, powerful front claws good for digging
-limites eyesight due to small/non existant eyes
-silky fur
-no external wars to keep a streamlined head for burrowing
(evolved to live in similar environments)

Question 58

What is natural selection?

Answer 58

the mechanism by which evolution occurs
-organisms that are better adapted to their environment have a higher change of surviving and reproducing, passing onto their alleles to their offspring

Question 59

Evolution of drug resistance

Answer 59

-In a population, some of the bacteria will undergo mutation giving them an allele that codes for drug resistance
-results in genetic variation within population
-resistant bacteria will have a higher change to survive & reproduce via natural selection
-pass on advantageous allele to offspring
HOWEVER
-non resistant bacteria have lower chance of survival and reproduction so less change to pass on genes
-the drug is the selection pressure for resistance bacteria/against non resistant
-over generations, increased frequency of drug resistant bacteria over time

Question 60

Implications of drug resistance for humans

Answer 60

-infections caused by drug resistant microorganisms become hard to treat= can take doctors a while to figure out which drugs will stop infection, patient could get more ill or die
-a pathogen could become resistant to all the drugs used to combat it—> must develop new drugs which is expensive and time consuming

Question 61

Evolution of pesticide resistance

Answer 61

-genetic variation for pesticide resistant/non pesticide resistant insects
-pesticide resistant insects have greater chance to survive and reproduce
-offering inherits allele that codes for pesticide resistance
-increased frequency of pesticide resistance insects over time

Question 62

Implications of pesticide resistance for humans

Answer 62

-crop infestations with resistant insects is harder to control= some are resistant to a lot of pesticides so it takes farmers a while to find the right one, and in that time all crop could be destroyed
-broader pesticides could kill beneficial insects
-if disease carrying insects become resistant, spread of disease could increase
-population of insects could evolve resistance to all pesticides in use, and developing new ones is expensive and time consuming

Question 63

How is discontinuous variation represented?

Answer 63

normally with a bar chart

Question 64

How is continuous variation represented?

Answer 64

characteristics are collected on a frequency table and then plotted on a histogram(no gaps between bars, x axis is a range instead of discrete categories)

Question 65

What is the mean and what is its formula?

Answer 65

-an average of all the values collected in a sample and can tell us if there is variation between samples
mean=total of all the values in your data/the number of values in your data

Question 66

What is the normal distribution curve?

Answer 66

the production of a bell shaped curve on a continuous variation graph–} symmetrical around the mean

Question 67

What are the characteristics of a normal distribution?

Answer 67

-mean, mode and median are the same due to symmetry
-50% of values are less than the mean and 50% are greater
-more values lie close to the mean value(number of individuals at the extremes are low)

Question 68

What is range use for and why is it not always reliable?

Answer 68

-range can be used to measure dispersal BUT it is heavily affected by extreme values

Question 69

What is standard deviation?

Answer 69

-measure of the dispersal of data(around the mean)
-takes into account all values in data set, less likely to be affected by extremes
-the greater the SD= the more the values vary
-affects confidence in repeatability and reproducibility of results
mean+/-SD

Question 70

What do error bars represent?

Answer 70

-a line through a point on a graph which represent SD relative to the mean
-less overlap between bars= results are less significantly different

Question 71

Calculating standard deviation

Answer 71

√Σ(x-x̄)^2/n-1
1) work out the mean, x̄
2)take mean away from each value and then square each answer, (x-x̄)^2
3)add up all these answers to find total, Σ
4) divide total by the number of values minus 1, /n-1
5) square root to get final answer, √

Question 72

What is Spearman’s rank correlation coefficient?

Answer 72

-a statistical test to see if there is a statically significant correlation between 2 sets of data and how strongly they are related
-only a 5% probability that results are due to chance(and not significant)
-all results are between -1 and +1–} closer to 1=positive correlation, closer to -1=negative correlation, closer to 0=no correlation between data

Question 73

What is a null hypothesis and why is it used?

Answer 73

-always states the negative assumption of your investigation
-the purpose is so the researcher can purely prove whether the test is supported or not, separate from bias and personal conclusions

Question 74

How to work out Spearman’s rank correlation coefficient?

Answer 74

r^s= 1- 6 Σ D^2/n(n^2-1)
1) write null hypothesis
2) rank both sets of data(1 being highest, then 2 etc)
3)work out difference in rank between the 2 values in each data pair(d) and calculate d^2
4)now count number of data pairs(n)
5)write all values into formula and work out which correlation it is

Question 75

Conclusion of spearman’s rank

Answer 75

-where n is… our value is..(answer).. which is more/less than the critical value
-this means there is/is not a significant correlation between .. and .. so the null hypothesis is accepted/rejected