TOPIC 4: Biodiversity and Natural Resources Flashcards
Describe how aseptic techniques are used when handling bacterial cultures. (3)
- work near bunsen burner
- sterilise work surfaces
- sterilise equipment w/ heat
Explain the role of a placebo (2)
- provides a control group for comparison
- therefore ensuring that the drug is causing the effect
Explain the role of a double blind trial. (2)
- bcs neither doctors nor patients know who has received the actual drug
^ therefore, removing bias from trial
Explain why the agar plate was incubated at 25oC. (2)
- to allow bacteria to multiply
- without encouraging pathogenic organisms
Explain why bacteria are able to multiply in the bloodstream when they enter the body. (3)
- warm conditions
- suitable for bacterial enzymes
- glucose used for energy
Describe the structure of starch. (3)
- polysaccharide made from alpha glucose
- monomers in chains joined by 1,4 glycosidic bonds
- branches joined to chains via 1,6 glycosidic links
Describe how nitrate ions are transported from the root to the leaves. (2)
- through the xylem
- in water
Name the monomer that makes up cellulose
beta-glucose
Compare and contrast the structure of chitin and a cellulose molecule. (3)
similarities:
- both have glycosidic bonds
- every other monomer is inverted
differences:
- chitin contains nitrogen but cellulose doesn’t
Compare and contrast the structure of cellulose and amylopectin. (3)
similarities:
- both = polymers of glucose
- both contain 1,4 glycosidic bonds
differences:
- cellulose made of beta-glucose
amylopectin = alpha-glucose
Name the bond between adjacent cellulose molecules in a cellulose microfibril. (1)
hydrogen bond
Explain why a seedling needs a supply of magnesium ions. (2)
- needed to make chlorophyll
- which is required for photosynthesis
Name the plant tissue that has lignin in its cell walls
xylem
Explain the role of the middle lamella when a plant cell completes mitosis. (2)
- produced b/w adjacent new cells
- bcs middle lamella holds cell walls together
Explain the structure of the plasmodesma. (2)
- cytoplasmic connection
- which allows communication b/w cells
give 2 reasons why a sieve tube element doesn’t need a rER and ribosomes. (2)
- no transcription
- no proteins will be synthesised to be processed in ER
Define: tensile strength
the force the fibre can withstand before breaking
Explain how the structure and properties of starch are related to its function as a storage molecule. (3)
- contains glucose needed for respiration
- amylose is coiled, making starch compact
- amylopectin is branched -> rapidly hydrolysed
Describe the positions in the stem of those tissues that contain lignin. (2)
- sclerenchyma on outer side of vascular bundle
- xylem on inner side of vascular bundle
Describe arrangement of glucose monomers in a cellulose molecule. (2)
- monomers connected by 1,4 glycosidic bonds
- alternate monomers are inverted
Explain the relationship b/w the composition of starch and the rate of hydrolysis by enzymes. (4)
- the less amylose present, the greater the proportion of amylopectin
- amylose is unbranched
- amylopectin: 1,4 & 1,6 glycosidic bonds
- branches increase rate of hydrolysis
State why the Scottish wildcat is described as endemic. (1)
it’s only found in Scotland
The Scottish wildcat can successfully interbreed w/ domestic cats.
Explain the effect this could have on their genetic diversity. (2)
-increases genetic diversity
- bcs new alleles introduced
Define: allele
- alternative form of a gene
Define: endemic
found only in one geographical location
Explain how the primary structure of trypsin molecules can be used to produce a phylogenetic tree. (3)
- determine sequence of A.As
- determine number of differences in sequences of A.As b/w species
- the greater the number of differences, the less closely related the species
Explain why they are now classified as different species. (2)
- bcs populations have become reproductively isolated
- can no longer interbreed to produce fertile offspring
Describe how the Hardy-Weinberg equation can be used to provide evidence for changes in the elephant population in Mozambique. (2)
- calculate allele frequency
- regular sampling over a period of time
Describe how mutations can cause a population to become separate species. (4)
- mutations produce new alleles
- selection pressure causes alleles to be advantageous
- individuals w/ advantageous alleles more likely to survive & reproduce
- after time, population not able to reproduce with other species to produce fertile offspring
Define: species richness
measures number of species in a habitat
Define: heterozygosity index
a measure of genetic diversity within a species
Define: species
A group of organisms that can interbreed to produce fertile offspring
Explain how a Hardy-Weinberg can be used to show natural selection. (2)
- H.W equation shows allele frequency in a population
- if natural selection is occurring, there’d be a change in allele frequency over time
