4.2.2 - Classification and Evolution

Question 1

What is classification?

Answer 1

• the process of sorting organisms into groups

* organisms within each group share similar features

Question 2

Why do scientist classify organisms?

Answer 2

• TO IDENTIFY SPECIES - by using a clearly defined system of classification, the species an organism belongs to can be easily identified
• TO PREDICT CHARACTERISTICS - if several species in a group have a specific characteristic, it is likely that another species in the group will have the same characteristic
• TO FIND EVOLUTIONARY LINKS - species in the same group likely share characteristics because they’ve evolved from a common ancestor

Question 3

What is the taxonomic hierarchy?

Answer 3

Classification system
Split into 7 taxonomic groups
• kingdom
• phylum 
• class 
• order 
• family
• genus
• species
Kingdom is largest and broadest

Question 4

What is the domain?

Answer 4

Further level of classification placed above kingdom

3 domains - archea, bacteria, eukarya

Question 5

How are organisms classified?

Answer 5

Begins by separating organisms into domains

As you move down the hierarchy, there are more groups at each level, but fewer organisms in each group

Organisms in each group become more similar and share more characteristics

The system ends with organisms being classified as individual species

Question 6

What is a species?

Answer 6

• a group of organism that are able to reproduce to produce fertile offspring

Question 7

What is binomial nomenclature?

Answer 7

A universal system of naming species.

Each name has 2 parts:

1) GENERIC NAME - name of the genus. First letter is a capital letter
2) SPECIFIC NAME - indicates the species. Always in lowercase

The name should be written in italics, but can be underlined in handwritten documents

Question 8

What are the advantages of binomial nomenclature?

Answer 8

1) easier for scientists to work internationally, as species will have different common names in different languages
2) binomial nomenclature provides information about relationships between species (if 2 species have the same generic name, they come from the same genus)

Question 9

What are the 5 kingdoms?

Answer 9

THE PROKARYOTES:
• prokaryotae (bacteria)

THE EUKARYOTES:
• protoctista (unicellular eukaryotes)
• fungi (eg yeasts, moulds, mushrooms)
• plantae (plants)
• animalia (animals)

Question 10

What are the general features of prokaryotae?

Answer 10

• 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

Question 11

What are the general features of protoctista?

Answer 11

• mainly unicellular
• a nucleus and other membrane bound organelles
• some have chloroplasts
• some are sessile, but others move by cilia, flagella, or by amoebid mechanisms
• nutrients are acquired by photosynthesis (autotrophic feeders), ingestion of other organisms (heterotrophic feeders) or both - some are parasitic

Question 12

What are the general features of fungi?

Answer 12

• unicellular or multicellular
• have a nucleus and other membrane bound organelles
• cell wall mainly composed of chitin
• no chloroplast or chlorophyll
• no mechanism for locomotion
• most have a body or mycelium made of threads or hyphae
• nutrients acquired by absorption (mainly form decaying material) - they are saprophytic feeders - some are parasitic
• most store their food as glycogen

Question 13

What are general feature of plantae?

Answer 13

• multicellular
• a nucleus and other membrane bound organelles including chloroplasts and a cell wall mainly comprised of cellulose
• all contain chloroplasts
• most don’t move, but gametes of some plants move using cilia or flagella
• nutrients are acquired by photosynthesis - they are autotrophic feeders (make their own food)
• store food as starch

Question 14

What are the general features of animalia?

Answer 14

• multicellular
• a nucleus and other membrane bound organelles (no cell wall)
• no chloroplasts
• move with aid of cilia, flagella or contractile proteins, sometimes in the form of muscular organs
• nutrients inquired by ingestion - heterotrophic feeders
• food stored as glycogen

Question 15

Why do classification systems change?

Answer 15

As scientist learn more about organisms, classification systems change

Eg classification systems were originally based on similarities in observable characteristics, but now genetics and biological molecules can be used to classify organisms

Question 16

What is the 3 domain system?

Answer 16

• the current classification system used by scientists
• proposed by Carl Woese in 1977
• has 3 domains and 6 kingdoms (prokaryotae split into eubacteria and archaebacteria due to chemical differences)
• groups organisms using differences in the rRNA, cell’s lipid structure and sensitivity to antibiotics
• clarifies relationships between species

Question 17

How are organisms classified into different domains using the 3 domain system?

Answer 17

EUKARYA:
• have 80s ribosomes
• RNA polymerase contains 12 proteins

ARCHAEA:
• have 70s ribosomes
•RNA polymerase of different organism have between 8-10 proteins, and is similar to eukaryotic ribosome

BACTERIA:
• have 70s ribosomes
• RNA polymerase has 5 proteins

Question 18

What is phylogeny?

Answer 18

The name given to the evolutionary relationships between organisms

Question 19

What is the relationship between classification and phylogeny?

Answer 19

Classification can occur without any knowledge of phylogeny

However, it is the aim of many scientist to develop a classification system that correctly takes into account the phylogeny of an organism

Question 20

What is a phylogenetic tree?

Answer 20

A diagram used to represent evolutionary relationships between organisms

They are branched diagrams which show that different species have evolved from a common ancestor

They are produced by looking at physical and genetic similarities and differences

Earliest species found at the base of the tree and most recent species are found at the tips of the branches

Question 21

How do you interpret phylogenetic trees?

Answer 21

• tips of the tree represent groups of descendant organisms (often species)
• the nodes on the tree (points where new lines branch off) represent common ancestors of the descendants
• two descendants that split from the same node are called sister groups
• the closer the branches on the tree are, the closer the evolutionary relationship

Question 22

What are the advantages of phylogenetic classification?

Answer 22

• can be done without reference to Linnaean classification (taxonomic hierarchy)
• phylogeny produces a continuous tree whereas classification requires discrete taxonomical groups (scientists aren’t forced to put organisms into a specific groups where they don’t quite fit)
• hierarchal nature of Linnaean classification can be misleading as it implies different groups within the same rank are equivalent

Question 23

What is evolution?

Answer 23

• could refer to the general theory of evolution (the way in which species have changed over time and continue to change
• could be the shorthand way of referring to the theory of evolution by natural selection (the specific process by which evolution occurs)

Question 24

How did Charles Darwin and Alfred Russel Wallace contribute to the theory of evolution from natural selection?

Answer 24

• Wallace spent many years travelling South America and South-East Asia and collecting specimens from these places
• Darwin took part in a voyage around the world and collected specimens and information about many species
• these experiences and the notes + samples they collected led to both men publishing a joint scientific paper proposing their theory of evolution by natural selection in 1858

Question 25

What were Darwins key observations that helped him develop the theory of evolution?

Answer 25

*  all organisms produce more offspring that could ever actually survive (ie not all offspring survive) *  populations of organisms fluctuate (change over time) but not significantly (their numbers usually stay fairly constant) *  populations of the same species of organisms show variation in characteristics between individuals (intraspecific variation) *  offspring inherit characteristics from their parents

Question 26

What are the key sources of evidence for the theory of evolution by natural selection?

Answer 26

*  fossil evidence - the study of fossils and the fossil record * comparative anatomy - the study of similarities and differences between organisms anatomy * comparative biochemistry - similarities and differences between the chemical makeup of organisms

Question 27

How do fossils provide evidence for the theory of evolution by natural selection?

Answer 27

Fossils are preserved remains of organisms or other features left by organisms (eg footprints, burrows) • we can tell from fossils that environments (and organisms living in them) have changed significantly over millions of years • fossils and rocks they are found in can be dates, allowing us to accurately put fossil organisms into a sequence of oldest to youngest to see how organisms changed through evolutionary time • fossils show us similarities between extinct species (how related they are), and also between extinct and living species All this has provided evidence for the gradual change from simple life forms, such as archaea and bacteria, to complex eukaryotic life forms and the evolutionary relationships between organisms

Question 28

How does comparative anatomy provide evidence for the theory of evolution by natural selection?

Answer 28

A homologous structure is a structure that appears superficially different in different organisms, but has the same underlying structure Eg vertebrate limbs are similar, but adapted to perform different functions The presence of homologous structures provides evidence for divergent evolution, which describes how different species have evolved from a common ancestor. This type of evolution occurs when closely related species diversify to adapt to new habitats as a result of migration/loss of habitat

Question 29

How do differences in DNA provide evidence for the theory of evolution by natural selection?

Answer 29

DNA found in the nucleus of cells can be sequenced and used to provide evidence of evolutionary relationships between species and how the genetic code of species has changed as they have evolved The differences between the nucleotide sequences in the analogous genes of different species can provide a lot of information • the more similar the sequence, the more closely related the species are • two groups of organisms with very similar DNA will have become into separate species more recently than two groups with less similar DNA • as a result, DNA sequence analysis and comparison can be used to create phylogenetic trees that show the evolutionary relationships between species

Question 30

How does comparative biochemistry provide evidence for the theory of evolution by natural selection?

Answer 30

* studies similarities and differences in proteins + other molecules that control life processes *  eg haemoglobin, ATP synthase, cytochrome c (involved in respiration), rRNA, DNA/ nucleotide order * the more similar molecules are, the closer related the species are

Question 31

What is interspecific variation?

Answer 31

Variation between species

Question 32

What is intraspecific variation?

Answer 32

Variation between species

Question 33

What are the 2 main factors that cause variation?

Answer 33

• an organisms genetic material - causes genetic variation An organisms environment - causes environmental variation

Question 34

What are the genetic causes of variation?

Answer 34

1) alleles 2) mutations 3) meiosis 4) sexual reproduction 5) chance (Note: 3,4 & 5 are all aspects of sexual reproduction)

Question 35

How do alleles cause genetic variation?

Answer 35

* genes have different alleles (alternative forms) * different alleles produce different characteristics (eg 1 allele may produce blue eyes, another brown eyes) * individuals in a species population may inherit different alleles of a gene

Question 36

How do mutations cause genetic variation?

Answer 36

* changes to the DNA sequence, and therefore to genes, can lead to changes in the proteins that are coded for * these protein changes can affect physical and metabolic characteristics * mutations in somatic cells affect the individual * mutations in gametes may be passed onto offspring

Question 37

How does meiosis cause genetic variation?

Answer 37

* gametes are produced by meiosis in organisms that carry out sexual reproduction *  before the nucleus divides and the chromatids of a chromosome separate, the genetic material inherited from the 2 parents are ‘mixed up’ by independent assortment and crossing over * this leads to gametes of an individual showing variation

Question 38

How does sexual reproduction cause variation?

Answer 38

* offspring from the 2 individuals inherit alleles from each parent * each individual produces therefore differs from their parents, increasing variation

Question 39

How does chance cause variation?

Answer 39

*  many different gametes are produced form the parental genome * which 2 gametes combine in sexual reproduction is due to chance - this is random fertilisation * individuals produced therefore differ from their siblings, as each contains a unique combination of genetic material

Question 40

How does the environment cause variation?

Answer 40

* all organisms are affected by the environment, but plants may be affected more than animals due to the lack of mobility * eg a plants growth may be affected by sunlight, water, nutrients * eg scars are purely caused by the environment - they can’t be inherited

Question 41

How can environmental and genetic factors cause variation?

Answer 41

*  height - tall parents mean you are likely to have inherited genes to be tall. However, a poor diet can lead to you being below average * skin colour - determined by amount of melanin contained in skin. Skin colour at birth purely determined by genetics. However, exposure to sunlight causes skin to produce more melanin *  scarring - some people have skin that scars easily, some that heals with minimal scarring (determined by genetics). However, the scars themselves are purely environmental - they cant be inherited

Question 42

What is discontinuous (discrete) variation?

Answer 42

* only has certain values (no in between values) * determined purely by genetic factors * usually represented as a bar chart or pie chart * eg sex, shape of bacteria, blood type

Question 43

What is continuous variation?

Answer 43

* a characteristic that can taker any value within a range * there is a continuum - gradation in values form one extreme to the other * not controlled by a single gene , but by a number of genes (polygenes). often influenced by environmental factors as well * data usually collected in a frequency table and then plotted onto a histogram. A curve is usually drawn to show the trend * eg height and mass

Question 44

What is a normal distribution curve?

Answer 44

When continuous data is plotted onto a graph, they usually result in the production of a normal distribution curve Characteristics: • mean, median and mode are the same • distribution has a characteristic 'bell' shape • 50% of all values are less than the mean and 50% are greater than the mean • most values lie close to the mean - the number of individuals at the extremes are low

Question 45

What is standard deviation?

Answer 45

* a measure of how spread out the data is from the mean | * the greater the standard deviation, the more variation there is

Question 46

What is the students t-test?

Answer 46

* used to compare mean values of two sets of data * data must be normally distributed and enough data should be collected to calculate a reliable mean * different sample sizes may be used

Question 47

What is Spearmen's rank correlation coefficient?

Answer 47

* is a measure of how correlated data is * value of 1 = perfect positive correlation * value of -1 = perfect negative correlation * value of 0 = no correlation

Question 48

What are adaptations?

Answer 48

Characteristics that increase an organisms chance of survival 3 types: • anatomical - physical features (internal and external) • behavioural adaptations - the way an organism acts. can be inherited or learned from parents • physiological - processes that take place inside an organism many adaptations fall into more than one category

Question 49

What are some examples of anatomical adaptations?

Answer 49

* body covering: fur keeps polar bears warm, snails shell protects it, waxy layer on plants prevents water loss, spikes can deter herbivores form eating a cactus * camouflage - outer colour of an animal allows it to blend into environment, making them harder to spot * teeth - shape and type of teeth present in animals jaw are related to its diet eg herbivores have lots of molars, carnivores have sharp canines * mimicry - copying another animals appearance or sounds allows a harmless organisms fool predators into thinking it is poisonous/dangerous

Question 50

What are some examples of behavioural adaptations?

Answer 50

* survival behaviours - eg opossum plays dead, rabbit freezes * courtship - elaborate courtship to attract a mate, increasing chance of reproducing offspring * seasonal behaviours - eg migration and hibernation enable organism's to cope with changes to the environment

Question 51

What categories do behavioural adaptations fall into?

Answer 51

* innate (instinctive) behaviour - inherited through genes eg spiders to build webs, woodlice to avoid light. allows organisms to survive in habitat * learned behaviour - learned form experience or observing other animals eg sea otters use stones to hammer shells off rocks and then crack the shell open

Question 52

what are some examples of physiological adaptations?

Answer 52

* poison production - reptiles produce venom to kill prey, plants produce poison in leaves to prevent them being eaten * antibiotic production - some bacteria produce antibiotics to kill other species of bacteria in the surrounding area * water holding - allows organisms to survive in dry conditions eg cacti, water-holding frog other examples include reflexes, blinking and temperature regulation

Question 53

What are analogous structures?

Answer 53

* structures that have adapted to perform the same function, but have different genetic origin * provides evidence for convergent evolution

Question 54

What is convergent evolution?

Answer 54

* takes place when unrelated species share similar traits | * similarities evolve due to organisms adapting to similar environments or other selection pressures

Question 55

How do the marsupial mole and placental mole show convergent evolution?

Answer 55

similarities: • both burrow through soft soil to find worms and grubs • streamlined body shape and modified forearms for digging • velvety fur which allows for smooth movement through soil Differences: • marsupial mole - colour ranges from white to orange. • placental mole - grey

Question 56

what are selection pressures?

Answer 56

factors that affect the organisms chances of survival or reproductive success

Question 57

What is natural selection?

Answer 57

The process by which organisms best suited to the environment survive and reproduce, passing on their characteristics to their offspring through their genes

Question 58

What is the mechanism for natural selection?

Answer 58

1) organisms within a species show genetic variation (due to varying alleles and mutations) 2) those with characteristics best adapted to selection pressures (eg predation, competition for mates and resources, disease) have a higher chance of surviving and successfully reproducing. Less well adapted organisms die or fail to reproduce - this is ‘survival of the fittest’ 3) successful organisms pass on the alleles for advantageous characteristics onto their offspring. Those with the non-advantageous allele are less likely to pass it on 4) process reports for each generation. Proportion of individuals with advantageous allele increases over time, so frequency of allele in gene pool increases 5) over many generations, this process repeats for many alleles, and may lead to your evolution of a new species

Question 59

HOW TO ANSWER QUESTION WHY A PARTICULAR CHARACTERISTIC HAS INCREASED IN A POPULATION

Answer 59

1) identify adaptation 2) explain how it is advantageous for survival and successful reproduction 3) explain how allele coding for the characteristic is passed onto the next generation 4) state how this increases the frequency of the allele in the population

Question 60

What implications can evolution have on humans?

Answer 60

Pesticide resistance in insects: • eg sheep blowflies because resistant to a certain pesticide Infection of these parasites can be fatal to sheep Drug resistance resistance in microorganisms: • eg MRSA has developed resistance to many antibiotics Due to natural selection • now very hard to treat