Unity and diversityIB Biology HL: Topic test

20 questions, 54 marks

IB Biology HL

Unity and diversity topic test

Total 54 marks

Name

Class

Date

1
A biologist compares the energy cost of locomotion in water and in air at 20 °C. Water has a viscosity about 55 times that of air and a density about 800 times that of air. Water also has a much higher specific heat capacity than air. A rainbow trout (Oncorhynchus mykiss) swims through water using undulating body movements, while a barn swallow (Hirundo rustica) flies through air using flapping flight.
(a)
Which property of water explains why the trout must expend more energy overcoming resistance per metre travelled than the swallow does in air?
[1 mark]
AWater's much higher viscosity and density increase resistance to movement compared with air
BWater's higher specific heat capacity slows the trout's muscle contractions
CWater's higher thermal conductivity directly reduces the trout's swimming speed
DWater's lower buoyancy makes swimming more difficult than flying
(b)
Compared with the swallow, which additional energetic cost does the trout avoid because of water's high buoyancy?
[1 mark]
AThe cost of generating heat to maintain a constant body temperature
BThe cost of supporting its body weight against gravity, since water's density is close to that of the fish's tissues
CThe cost of osmoregulation in a hypotonic environment
DThe cost of overcoming viscosity while swimming
(c)
Water molecules form hydrogen bonds because of their polarity. Explain how hydrogen bonding between water molecules contributes to water's high specific heat capacity, and state one consequence of this property for aquatic organisms such as the trout.
[2 marks]
Total for question 1: 4 marks
2
A student extracts nucleic acid from a sample of animal liver tissue and hydrolyses it into its component nucleotides. The first extract contains four types of nitrogenous base and forms two strands running in opposite 5' to 3' directions, held together by hydrogen bonds between paired bases. A second extraction from the same tissue yields a single-stranded nucleic acid containing a different pentose sugar and a different fourth base, and this second extract is rapidly degraded by ribonuclease enzymes while the first is not.
(a)
Which molecule is the first extract?
[1 mark]
AA phospholipid
BRNA
CDNA
DA protein
(b)
Which feature identifies the two strands of the first extract as antiparallel?
[1 mark]
AOne strand contains only bases A and G, the other only C and T
BBoth strands run in the same 5' to 3' direction
CThe strands are joined only at their 5' ends
DThe two strands run in opposite directions, one 5' to 3' and the other 3' to 5'
(c)
Explain two structural differences between the second extract and the first extract that would allow them to be distinguished chemically.
[2 marks]
Total for question 2: 4 marks
3
A researcher compares two cells viewed with an electron microscope: a Gram-positive bacterial cell about 2 µm long, and a liver cell from a mammal about 20 µm across. The bacterial cell shows a cell wall, a plasma membrane, cytoplasm with ribosomes, and a single loop of DNA in a nucleoid region with no surrounding membrane. The liver cell shows a nucleus bound by a double membrane with pores, numerous mitochondria, extensive rough and smooth endoplasmic reticulum, a Golgi apparatus, and a cytoskeleton of microtubules and microfilaments, but no cell wall or chloroplasts.
(a)
Identify three structural features, other than size, that distinguish the liver cell as eukaryotic rather than prokaryotic, using the description given.
[3 marks]
(b)
Explain, using the description, why the liver cell can carry out a wider variety of internal chemical processes at the same time than the bacterial cell.
[4 marks]
Total for question 3: 7 marks
4
Two populations of an originally single freshwater fish species became separated when a new waterfall formed 50,000 years ago, blocking migration between the upper and lower sections of a river. Today, individuals from the upper population have a different courtship display and a different body shape from the lower population. When researchers artificially mixed gametes from both populations in the laboratory, fertilisation occurred, but almost all of the resulting embryos died before hatching.
(a)
Using the information given, explain how the waterfall could have led to the formation of two separate species over 50,000 years.
[6 marks]
(b)
Discuss whether the upper and lower populations should be classified as two separate species, referring to the biological species concept and its limitations.
[6 marks]
Total for question 4: 12 marks
5
Bacteriophage lambda infects Escherichia coli. In the lytic cycle, the phage injects its DNA into the bacterial cell, which is then used to direct the production of new phage particles that are released when the cell lyses. In the lysogenic cycle, the phage DNA instead becomes inserted into the bacterial chromosome and is replicated along with the host DNA for many generations before a trigger causes it to enter the lytic cycle.
(a)
Which feature is shared by all viruses, including bacteriophage lambda?
[1 mark]
AA capsid made of protein enclosing their genetic material
BA cytoplasm containing ribosomes for translating their own proteins
CA plasma membrane derived from the host cell in every case
DA double-stranded DNA genome
(b)
During the lysogenic cycle, what happens to the phage DNA?
[1 mark]
AIt is degraded immediately by host restriction enzymes
BIt is inserted into the host chromosome and replicated along with it for many generations
CIt remains free in the cytoplasm and is translated immediately into capsid proteins
DIt directs immediate lysis of the host cell
(c)
Explain why bacteriophage lambda relies entirely on its host bacterium to complete its life cycle.
[2 marks]
Total for question 5: 4 marks
6
A biologist compares base sequences of one gene from four related species, W, X, Y and Z, together with an outgroup species known to have diverged before any of the four. Using parsimony analysis, the cladogram that best fits the data groups X and Y as most closely related at one node, with W joining this group at an earlier node, and Z branching off earliest of the four.
(a)
In a cladogram, what does a node represent?
[1 mark]
AA living species used to root the tree
BThe total number of sequence differences between two species
CA hypothetical common ancestor of the lineages that branch from it
DA single mutation event
(b)
Why is parsimony analysis used to select between competing cladograms?
[1 mark]
AIt selects the cladogram with the largest number of species
BIt selects the cladogram based only on morphological similarity
CIt selects the cladogram that matches the traditional Linnaean hierarchy
DIt selects the cladogram requiring the smallest number of sequence changes to account for the observed variation
(c)
Explain why base sequence data is considered more objective evidence than morphological traits for placing species W, X, Y and Z into clades.
[2 marks]
Total for question 6: 4 marks
7
Researchers studying the origin of life propose that self-replicating RNA molecules acted as both genetic material and catalysts in the earliest protocells, before fatty acid membranes enclosed these molecules into separate compartments. Separately, conservationists studying a coral reef ecosystem estimate that overfishing, coastal development and rising sea temperatures have together reduced live coral cover from 45% to 12% over 30 years, and they must decide how to prioritise limited conservation funding among several affected reef species.
(a)
Explain why RNA, rather than protein, is thought to have been the first genetic material of early protocells.
[3 marks]
(b)
Using the information given, discuss which approach(es) to conservation would be most appropriate for the coral reef, and explain why several approaches are usually needed together to conserve biodiversity.
[4 marks]
Total for question 7: 7 marks
8
Mitochondria isolated from a eukaryotic cell are compared with a sample of free-living aerobic bacteria. Both structures are found to contain naked circular DNA, 70S ribosomes, and a double membrane, and both are capable of dividing independently by a process resembling bacterial binary fission. In contrast, structures isolated from the same eukaryotic cell's rough endoplasmic reticulum contain no DNA and cannot divide independently.
(a)
Using the evidence given, explain how the endosymbiotic theory accounts for the origin of mitochondria in eukaryotic cells.
[6 marks]
(b)
The rough endoplasmic reticulum structures described contain no DNA and cannot divide independently. Explain why this evidence suggests that the endoplasmic reticulum did not arise by endosymbiosis, and outline how the strength of the endosymbiotic theory for mitochondria comes from the range of observations it explains.
[6 marks]
Total for question 8: 12 marks

End of questions