Diversity and Classification

Question 1

Artificial Classification

Answer 1

Divide organisms based on features like colours, size, number etc.

Question 2

Phylogeny

Answer 2

• Study of the evolutionary history of groups of organisms
• Tell’s us who’s related to whom and how closely related they are
• All organisms have evolved from shared common ancestors (relatives)- this can be shown on a phylogenetic tree
• Tree shows relationship between members of the Hominidae family (great apes and humans)
• First branch point represents a common ancestor of all the family members (this ancestor is now extinct)
• Orangutans were the first group to diverge (evolve to become a different species) from this common ancestor
• Each of the following branch points represents another common ancestor from which a different group diverged (Gorillas divereged, then humans etc…)
• Closely related species diverged away from each other most recently e.g. humans and chimpanzees are closely related, as they divereged very recently (branches are close together)
  *

Question 3

Taxonomy

Answer 3

• Science of classification
• Involves naming organisms and organising them into groups (makes it easier to identify and study them)
• Scientists now take into account phlogeny when classifying organisms, and group organisms according to their evolutionary relationships
• There are 8 levels of groups used to classify organisms (groups are called taxa and each group is called a taxon)
• Groups are arranged in a hierarchy, with largest groups at top and smallest groups at bottom
• Organisms can only belong to one group at each level in the hierarchy- there’s no overlap

Question 4

How are organisms sorted in taxonomy?

Answer 4

• First sorted into 3 large groups (or taxa) called domains- the Eukarya, Bacteria and Archaea
• Related organisms in a domain are then sorted into slightly smaller groups called kingdoms e.g. all animals in animal kingdom
• More closely related organisms from that kingdom are then grouped into a phylum, then grouped into a class, and so on down the 8 levels of the hierarchy
• As you move down the hierarchy, there are more groups at each level but fewer organisms in each group
• Organisms in each group also become more closely related
• Hierarchy ends with species- groups that contain only one type of organisms
• Scientists constantly update classification systems because of discoveries about new species and new evidence about known organisms e.g. DNA sequence data
• (demanding kids prefer chips over floppy green spinach)

Question 5

Species

Answer 5

Group of similar organisms able to reproduce to give fertile offspring

Question 6

The Binomial System

Answer 6

• Nomenclature used for classification- all organisms are given one internationally accepted scientific name in Latin that has 2 parts
• First part of the name is the genus name and has a capital letter
• The second part is the species name and begins with a lower case letter
• Names are always written in italics (or underlined)
• Humans are Homo Sapiens- Genus is Homo and species is sapiens
• Giving organisms a scientific name enables scientists to communicate about organisms properly to avoid confusion
• First name denotes the genus to which the organism belongs
• Second name denotes species to which organism belongs
• Some species have the same genus and species name

Question 7

What is courtship behaviour?

Answer 7

• Carried out by organisms to attract a mate of the right species
• Simple courtship behaviours- Releasing a chemical, using sound, visual displays
• Complex courtship behaviours- Dancing, building
• Can be performed by either the male or female, may sometimes involve both sexes

Question 8

Using courtship behaviour to classify species

Answer 8

• Courtship behaviour is species specific- only member of the same species will do and respond to that courtship behaviour
• Allows members of the same species to recognise each other, preventing interbreeding and making reproduction more successful (as mating with the wrong species won’t produce fertile offspring)
• Because of this specificity, courtship behaviour can be used to classify organisms
• The more closely related species are, the more similar thier courtship behaviour
• (Fireflies give off pulses of light, crickets make sounds, male peacocks show off colourful tails)

Question 9

Why courtship behaviour exists?

Answer 9

• Recognise members of own species to ensure mating occurs between members of same species- fertile offspring
• Identify a mate that is capable of breeding- sexually mature, fertile and receptive to mating
• Form a pair bond- lead to successful mating and raising offspring
• Synchronise mating so it takes place when maximum probability of sperm meeting egg
• Being able to breed by bringing opposite sex in physiological state for breeding to occur

Question 10

How do we clarify evolutionary relationships?

Answer 10

• New and improved technologies can result in new discoveries being made and the relationships between organisms being clarified
• This can lead to classification systems being updated
• Frequency of measurable or observable characteristics
• Amino acid sequence of the proteins encoded by DNA and mRNA
• Base sequence of mRNA
• Base sequence of DNA

Question 11

Genome Sequencing

Answer 11

• Advances in genome sequencing have meant that the entire base sequence of an organism’s DNA can be determined
• The DNA base sequence of one organism can then be compared to the DNA base sequence of another organism, to see how closely related they are
• Closely similar related species will have a higher percentage of similarity in their DNA base sequence

Question 12

Comparing amino acid sequence

Answer 12

• Proteins are made of amino acids- sequence of amino acids in a protein is coded for by the base sequence in DNA
• Related organisms have similar DNA sequences and so similar amino acid sequences in their proteins

Question 13

Immunological comparisons

Answer 13

• Similar proteins will also bind the same antibodies
• Proteins that bind antibodies will often form a precipitate in solution
• The more antibodies the protein binds, the more precipitate will form- so the amount of precipitate can be used to determine how similar 2 proteins are

Question 14

Comparing classifications

Answer 14

Question 15

How are gene technologies used to assess genetic diversity?

Answer 15

• Early estimates of genetic diversity were made by looking at the frequency of measurable or observable characteristics in a population e.g. people with particular eye colour
• Since different alleles determine different characteristics, a wide variety of each characteristic in a population indicates a high number of different alleles- and so a high genetic diversity
• However, gene technologies have now been developed that allow us to measure genetic diversity directly
• Example= Different alleles of the same gene will have slightly different DNA base sequences
• Comparing the DNA base sequences of the same gene in different organisms in a population allows scientists to find out how many alleles of that gene there are in that population
• Different alleles will also produce slightly different mRNA base sequences, and may produce proteins with slightly different amino acid sequences, so these can also be compared
• These new technologies can be used to give more accurate estimates of genetic diversity than can be made just by looking at the frequency of observable characteristics
• Also allow genetic diversity of different species to be compared more easily

Question 16

Variation

Answer 16

• Differences that exists between individuals
• There’s variation between species and within species
• Interspecific- variation between species
• Intraspecific- variation within species

Question 17

Causes of variation

Answer 17

• Can be caused by genetic factors
• Different species have different genes, which causes variation between species
• Individuals of the same species have the same genes, but different alleles which causes variation
• Can be caused by differences in the environment e.g. climate, food, lifestyle
• Combination of genetic and environmental factors e.g. genes determine how tall we are but nutrients affect growth too
  *

Question 18

Population Samples

Answer 18

• Only look at sample of population, not whole thing
• For most species it would be too ti e-consuming or impossible to catch all the individuals in the group
• So samples are used as models for the whole population

Question 19

Random Sampling

Answer 19

• Important that sample data accurately represents the whole population and that any patterns observed are tested to make sure they’re not due to chance
• To make sure sample isn’t biased, it should be random
• A sample is biased if it doesn’t represent the population as a whole
• Could be done by dividing grid using a random number generator to select coordinates
• To ensure variation observed isn’t due to chance, should analyse results statistically (can use mean and S.D to measure variation in a sample)

Question 20

Mean

Answer 20

• Average of the values collected in a sample
• Can be used to tell if their is variation between samples
• Most samples will include values either side of the mean, so you end up with a bell-shaped graph- called normal distribution
• A normal distribution is symmetrical about the mean

Question 21

Standard Deviation

Answer 21

• Tells you how much the values in a single sample vary
• Measure of spread of values about the mean ( 9 +- 3 means 9 is mean and the 3 is S.D, so most of the values are spread between 6 and 12
• Values with a larger standard deviation show greater variation
• S.D is one way of calculating the dispersion of data

Question 22

Another method of calculating dispersion?

Answer 22

• Looking at range- difference between highest and lowest figures
• S.D is more useful than range because it takes into account all values in the data set, whereas the range only use 2
• Makes range more likely to be affected by an anomalous result

Question 23

Using standard deviation to draw error bars

Answer 23

• Error bars extend one S.D above and one S.D below the mean (total length of an error bar is twice the S.D)
• The longer the bar, the larger the standard deviation and the more spread out the sample data is from the mean
• The smaller the error bars, the smaller the standard deviation and the less the data in the sample varies

Question 24

Ecosystem diversity

Answer 24

Range of different habitats

Question 25

Biodiversity

Answer 25

Variety of living organisms in an area

Question 26

Habitat

Answer 26

Place where an organism lives

Question 27

Community

Answer 27

All populations of different species in a habitat

Question 28

Local biodiversity

Answer 28

Variety of different species living in a small habitat that’s local to you (some habitats will be more diverse than others)

Question 29

Global biodiversity

Answer 29

Consider variety of species on earth (biodiversity varies in different parts of the world- greatest at equator)

Question 30

How can you measure biodiversity?

Answer 30

Species richness or an index of diversity

Question 31

Species diversity

Answer 31

Number of species in a community and the abundance of each species

Question 32

Species Richness

Answer 32

• Measure of number of different species in a community (simple measure for biodiversity)
• Can be worked out by taking random samples of a community and counting the number of different species
• Population sizes of species affects biodiversity
• Species that are in a community in very small numbers shouldn’t be treated the same as those with bigger populations

Question 33

Index of Diversity

Answer 33

The higher the number, the more diverse the area is (if all individuals are of the same species, the index is 1 beacuse no biodiversity)

Question 34

Index of Diversity table

Answer 34

Question 35

Conservation Techniques

Answer 35

• Maintain hedgerows at beneficial height
• Plant hedges rather than fences as boundaries
• Maintain existing ponds, if possible create new ones
• Leave wet corners of fields rather than draining them
• Reduce use of pesticides (organic fertilisers)(use biological control)
• Use intercropping rather than herbicides to control weeds and other pests
• Leave cutting of verges and field edges until after flowering and when seeds have dispersed
• Use crop rotation (nitrogen-fixing crop) rather than fertilisers to improve soil fertility

Question 36

The impact of agriculture on biodiversity

Answer 36

• Farmers try to maximise the amount of food they can produce from a given area of land (but many of the methods they use reduce biodiversity)
• Woodland clearance is done to increase the area of farmland
• It reduces the number of trees and sometimes the number of different tree species
• It also destroys habitats, so some species could lose their shelter and food source
• Means that species will die or be forced to migrate to another suitable area, further reducing biodiversity
• Hedgerow removal is also done to increase the area of farmland by turning lots of small fields into fewer large fields (reduces biodiversity for same reasons as woodland clearance)
• Pesticides are chemicals that kill organisms (pests) that feed on crops (reduces diversity by directly killing pests)
• Any species that feed on the pests will lose a food source, so their numbers could decrease too
• Herbicides are chemicals that kill unwanted plants (reduces plant diversity and could reduce the number of organisms that feed on the weeds)
• Monoculture is when farmers have fields containing only one type of plant
• A single type of plant reduces biodiversity and will support fewer organisms (reducing biodiversity further)

Question 37

Consevation Schemes

Answer 37

• Agriculture is one way of producing the resources we need from the environment- we need it to produce food and fibres for clothing, as well as some medicines and fuels
• Biodiversity helps maintain environment
• Provides us with new sources of food and medicines, and it benefits agriculture
• Needs to be a balance between agriculture and biodiversity
• Conservationists try to achieve this through conservation schemes

Question 38

Analysing effect of agriculture on biodiversity

Answer 38

• If you need to work out whether there’s a correlation between 2 variables or not, you can calculate the spearman’s rank correlation coefficient (r>s)
• This is a type of correlation coefficient and an example of a statistical test
• Rexult of the test is a muber between -1 and +1
• If -1, then there is a perfect negative correlation between 2 variables
• If +1, then there’s a perfect positive correlation
• Closer to 0, weaker the correlation

Question 39

What to do to find out if a result is statistically significant or not?

Answer 39

• First come up with null hypothesis
• Result of spearman’s rank test allows you to decide whether the null hypothesis can be rejected (to find out, consult a table of critical values)
• Result is compared to the critical value 0.05, which corresponds to data your looking at
• Value represents point at which the correlation your investigating would occur (5% chance correlation is down to chance)
• Can reject null hypothesis if the result of your test is higher than the value
• If result is negative, ignore minus
• If result is not statistically significant, it could be down to chance