B10 - Classification and Evolution

Question 1

What is the classification system?

Question 2

Why do scientists classify organisms?

Question 3

How are organisms classified?

Question 4

How are organisms named?

Question 5

What are the five kingdoms?

Question 6

What are the features of prokaryotae?

Question 7

What are the features of protoctista?

Question 8

What are the features of fungi?

Question 9

What are the features of plantae?

Question 10

What are the features of animalia?

Question 11

What are the six kingdoms?

Question 12

What are the features of archae/eubacteria?

Question 13

What is phylogeny?

Question 14

What are phylogenetic trees?

Question 15

What are the advantages of phylogenetic classification?

Question 16

Who developed the theory of evolution?

Question 17

What evidence is used for the process of evolution?

Question 18

What is palaeontology?

Question 19

What is comparative anatomy?

Question 20

What is comparative biochemistry?

Question 21

What is variation?

Answer 21

• the differences in characteristics between organisms

Question 22

What are the different types of variations?

Answer 22

• interspecific = variation between members of different species
  
  • e.g. mouse has four legs, fur, and teeth whereas bird has two legs, two wings and feathers
• intraspecific = variation between organisms within a species
  
  • e.g. people vary in height, build, hair colour

Question 23

What causes variation?

Answer 23

• organism’s genetic material:
  
  • differences in genetic material and organism inherits from its parents leads to genetic variation
• environment:
  
  • causes environmental variation

Question 24

What are the genetic causes of variation?

Answer 24

• alleles:
  
  • gene for a particular characteristic can have different alleles that produce different affects
  • e.g. human blood groups have three different alleles (A, B, O)
  • depending on the parental combination, four different blood groups can be formed (A, B, AB, O)
  • individuals in a species population may inherit different alleles of the same gene
• mutation:
  
  • changes in the DNA sequence (genes) can change proteins they code for
  • can affect physical/metabolic characteristics
  • if it occurs in just the body (somatic) cells it only affects that one organism
  • but if it occurs in the gametes it can be passed on to the offspring (both result in variation)
• meiosis:
  
  • gametes (ovum/sperm) are produced which receive half the genetic material of a parent cell
  • independent assortment and crossing over occurs before the nucleus divides and chromatids separate (mixes genetic material)
  • leads to the gametes showing variation
• sexual reproduction:
  
  • offspring inherits genes (alleles) from both parents
  • so each individual produced differs from the parents
• chance:
  
  • many different gametes are produced from parental genome
  • so during sexual reproduction, it is a result of chance as to which two gametes combine (random fertilisation)
  • so individuals produced are different to their siblings
• ** there is much more variation in organisms that reproduce sexually than asexually **
• ** asexual reproduction produces clones and can only increase variation as a result of mutation **

Question 25

What are the environmental causes of variation?

Answer 25

• plants may be more affected than animals as they lack mobility
  
  • e.g. a bush planted with a greater access to the sun will more likely grow larger than the one in the shade
  • as it cannot move into the sunlight, it is more affected by the environment than an animal
• pure environment variation
  
  • presences/absence of a scar
  • this may have occurred due to an accident or a disease (cannot be inherited from a parent)

Question 26

What are environmental and genetic causes of variation?

Answer 26

• height:
  
  • tall parents = inherit genes to grow tall
  • poor diet = you may only grow below average height
• skin colour:
  
  • determined by how much melanin your skin contains
  • at birth = purely determined by genetics
  • when exposed to sunlight, more melanin is produced to protect skin from UV rays (causing your skin to turn darker/tan)
• ** it can be diffuse to draw conclusions about the causes of variation in any particular case **
  
  • ** this is referred to as the ‘nurture vs nature’ argument **

Question 27

What is discontinuous variation?

Answer 27

• characteristic that can only result in certain values (no in-between values)
• variation determined purely by genetics fall into this category
  
  • e.g. animal’s sex (male/female)
  • human blood group
• in microorganisms:
  
  • shape of bacteria
  • spherical
  • rods
  • spiral
  • comma
  • corkscrew shaped

Question 28

How is discontinuous variation represented?

Answer 28

• bar chart (or pie chart)

Question 29

What is continuous variation?

Answer 29

• characteristic that can take any value within a range
• there is a graduation in values from one extreme to the other of a characteristic (continuum)
  
  • e.g. height/mass of plants
• these characteristics are not controlled by a single gene but a number of them (polygenes)
• they are also often influenced by environmental factors

Question 30

How is continuous data represented?

Answer 30

• collected in frequency table
• plotted on histogram
• curve is then drawn to show a trend

Question 31

What is a normal distribution curve?

Answer 31

• bell-shaped curve produced when continuous variation data is plotted
• data is normally distributed
• characteristics:
  
  • mean, mode, median are the same
  • bell-shape is symmetrical about the mean
  • 50% greater than mean, 50% less than mean
  • most values lie close to the mean value (no. of individuals at extremes are low)

Question 32

What is standard deviation?

Answer 32

• how spread out the data is
• greater the standard deviation, the greater the spread of data (larger amount of variation)
• normal distribution:
  
  • most of the data lies close to the mean (99.7%)

Question 33

What are other statistical tests used to calculate significance of data?

Answer 33

• student’s t test = compare means of data values of two populations
  
  • data must be normally distributed (enough data should be collected)
  • different sample sizes may be used
• (Spearman’s rank) correlation coefficient = considers relationships between two sets of data
  
  • no correlation
  • +ve correlation
  • -ve correlation

Question 34

What are adaptations?

Answer 34

• characteristics that increase an organism’s chance of survival and reproduction in its environment
• three groups:
  
  • anatomical adaptations (physical features)
  • behavioural adaptations (can be inherited/learned from parents)
  • physiological adaptations (internal processes)
• many adaptations fall into more than one category

Question 35

What are examples of anatomical adaptations?

Answer 35

• body covering:
  
  • hair, scales, spines, feathers, shells
  • can help to stay warm, fly, provide protection
  • thick waxy layers on plants prevent water loss
  • spikes can deter herbivores and protect tissues from sun damage
• camouflage:
  
  • outer colour allows it to blend into its environment
  • snowshoe hare is white in winter and turns brown in summer
  • this makes it harder for predators to spot it
• teeth:
  
  • shape and type are related to its diet
  • herbivores have growing molars to chew tough grass/plants
  • carnivores have sharp large canine to kill prey/tear meat
• mimicry:
  
  • copying another animal’s appearance/sounds to fool predators
  • harmless organisms do this to appear poisonous/dangerous
  • e.g. harmless milk snake mimics appears of deadly coral snake

Question 36

How is marram grass adapted?

Answer 36

• it is a xerophyte and lives in an environment with very little water
• to reduce rate of transpiration:
  
  • curled leaves to minimise SA of moist tissue exposed to the air
  • hairs on inside surface of leaves to trap moist air (reduces diffusion gradient)
  • stomata sunk into pits (less likely to open)
  • thick waxy cuticle on leaves and stems

Question 37

What are examples of behavioural adaptations?

Answer 37

• survival:
  
  • e.g. opossum plays dead and a rabbit freezes when they think they have been seen
• courtship:
  
  • many exhibit elaborate courtship behaviours to attract a mate
  • increases their chance of reproduction
• seasonal behaviours:
  
  • adaptations allow for them to cope with changes in environment
  • migration (move from one region to another and then back again)
  • hibernation (period of inactivity which helps to conserve energy, reducing requirement for food)

Question 38

What are the types of behavioural adaptations?

Answer 38

• innate:
  
  • ability to do this is inherited through genes
  • e.g.spiders building webs
  • allows for organism to survive in its habitat
• learned:
  
  • learnt from experience or observing other animals
  • e.g. use of tools (sea otters use stones to hammer shells off rocks)

Question 39

What are examples of physiological adaptations?

Answer 39

• poison production:
  
  • many reptiles produce venom to kill their prey
  • plants also produce poisons in their leaves to protect themselves from being eaten
• antibiotic production:
  
  • some bacteria produce antibiotics to kill other species of bacteria
• water holding:
  
  • e.g. water-holding frog stores water in its body
  • allows it to survive in the desert for more than a year without access to water
  • many desert plants/cacti can also hold large amounts of water
• other:
  
  • reflexes
  • blinking
  • temp. regulation

Question 40

What are analogous structures?

Answer 40

• different species have a structure with the same function but originate from a different genetic origin
• they are adapted to perform the same structure

Question 41

What is convergent evolution?

Answer 41

• where unrelated species begin to share similar traits
  
  • they evolve as organisms adapt to similar environments/other selection pressures
  • these organisms live in a similar way to each other
• e.g. whales and fish share similar characteristics as they have evolved over time to move efficiently through water

Question 42

What are examples of convergent evolution?

Answer 42

• marsupials in Australia and placental mammals
  
  • placental = placenta connects the embryo to its mother
  • nourished the embryo and allows it to mature before birth
  • marsupials = start life in uterus (complete development by suckling milk)
• these two subclasses were separated from a common ancestor more than 100 million years ago
  
  • each lineage evolved independently
• North America has produced similar bear species
  
  • this is because they have adapted to similar climates/food supplies
• their different methods of reproduction accurately reflects their distinct evolutionary relationships

Question 43

What are other specific examples of convergent evolution?

Answer 43

• marsupial and placenta mice:
  
  • both small and agile climbers
  • live in dense ground cover
• flying phalangers and flying squirrels:
  
  • both are gliders that eat insects and plants
  • skin is stretched between forelimbs
• marsupial and placental moles
  
  • both burrow through soft soil to find worms and grubs
  • streamlined body shape
• plants:
  
  • aloe and agave have both adapted to survive in the desert
  • however, they have developed entirely separately
  • aloe = old world
  • agave = new world

Question 44

What is natural selection?

Answer 44

• selection pressures = factors that affect the organism’s chances of survival/reproductive success
• organisms that are best adapted to their environment are more likely to survive and reproduce
  
  • these characteristics will become more common in the population
  • the characteristics of those who die out will be less common

Question 45

What are the steps of natural selection?

Answer 45

• organisms within a species show variation in their characteristics that are caused by differences in their genes
  
  • e.g. they may have different alleles of a gene (can arise by mutation)
• organisms with characteristics best adapted to selection pressure (predation, competition, disease) have an increased chance of survival
  
  • they will go on to reproduce and pass on their genes
  • this is survival of the fittest
• the successful organisms pass the allele with the advantageous characteristic onto their offspring
  
  • those who die out cannot do this
• this process is repeated for every generation
  
  • as the proportion of individuals with the advantageous allele increases, the frequency of it in the gene pool also increases
• over long period of time (many generations), this process can lead to the evolution of a new species

Question 46

What are modern examples of evolution?

Answer 46

• antibiotic resistant bacteria
• peppered moths
• sheep blowflies
• flavobacterium

Question 47

How have antibiotic resistant bacteria evolved?

Answer 47

• methicillin resistant (bacteria) = MRSA
• bacteria are able to reproduce very rapidly and so they evolve in a short amount of time
  
  • when they replicate their DNA can be altered and results in the bacteria dying
• when the bacteria are exposed to the antibiotic, the resistant individuals survive and reproduce
  
  • they pass on their allele for resistance on to their offspring
  • over time he resistant individuals in the population increased

Question 48

How have peppered moths evolved?

Answer 48

• before the industrial revolution, most peppered moths were pale coloured
• this allowed for camouflage against the light-coloured tree bark (increased chance of survival)
  
  • the darker ones were easily spotted and eaten
• during the industrial revolution, trees became darker (covered in soot, loss of lichen covers due to pollution)
  
  • this meant that the darker coloured moths were now better adapted to survive
  • they went on to reproduce and pass on their dark allele
• since Clean Air Act of 1956, levels of pollution have decreased
• the bark on trees have become lighter which has increased the frequency of the light allele in the moth gene pool

Question 49

How have sheep blowflies evolved?

Answer 49

• they lay their eggs in faecal matter around sheep’s tail
  
  • larvae hatch and cause sores (flystrike)
• in Australia, the pesticide diazinon was used to kill the blow flies
  
  • within six years, they had developed a high level of resistance
  • individual insects survived this exposure and passed on this characteristic through their allele, allowing a resistant population to survive
• scientists extracted DNA from an old blowfly, two Australian sheep blowflies were studied
  
  • they compared the resistance genes before and after the introduction of the pesticide
  • 70-year-old = resistance genes were not found
  • but when investigating mathalion (organophosphate pesticide), they found that both blowflies had resistance genes for it
  • this shows pre-adaptation which helped to contribute to the development of the diazinon resistance
• pre-adaptation = when the organism’s existing trait is advantageous for a new situation and allows for the rapid development of another one
• the existence of pre-adaptation in an organism may help researchers predict potential insecticide resistance

Question 50

How has Flavobacterium evolved?

Answer 50

• an example of evolution due to new opportunities in environment
• new strain of F. bacterium living in waste water from factories
  
  • digests the nylon which this produced in waste water
  • this is beneficial to humans as they help to clear up factory waste
• bacteria uses enzymes to digest the nylon (nylonases)
  
  • unlike other enzymes in F. bacterium, they do not help the bacteria digest anything else
• they believe this has occurred due to a gene mutation
  
  • duplication, frame shift mutation