Practise IB Biology HL D4.1 by interpreting selection evidence, tracing allele-frequency change and applying Hardy-Weinberg calculations to populations.
120 questions in this syllabus scope, with question parts counted together.
117 papers analysed · Tagging incomplete
The willie wagtail (Rhipidura leucophrys) is a common species of bird found in New Guinea and Australia. It feeds by foraging for a diverse selection of prey, including arthropods and lizards. When a willie wagtail catches prey, it either eats it or flies back to the nest to feed a young nestling bird. Researchers studied the feces of the birds to determine the size of prey eaten by the adults and the nestlings. The results are shown in the chart.
Explain how the foraging behaviour shown in the graph could have evolved in willie wagtails.
What would restrict evolution by natural selection, if a species only reproduced by cloning?
Too few offspring would be produced.
Mutations could not occur.
The offspring would show a lack of variation.
The offspring would be the same sex as the parent.
What promotes natural selection?
I. Overpopulation
II. Competition
III. Variation
I and II only
I and III only
II and III only
I, II and III
White clover (Trifolium repens) is native to Eurasia but is now a common plant found worldwide in lawns, next to roads, in pastures and similar habitats.
Some T. repens plants are able to produce the toxin hydrogen cyanide (HCN) by cyanogenesis. A study at 128 sites ( 2509 plants) in Toronto (Canada) looked at the proportion of T. repens plants producing HCN. The sites were at regular intervals from the city centre towards rural areas.
The researchers then investigated a possible correlation between cyanogenesis and exposure to freezing conditions. It had been proposed that when a cyanogenic plant freezes, its cells burst, releasing HCN which is toxic to the plant. Snow can insulate the ground and plants from freezing temperatures. However, snow is more likely to melt in cities, which then exposes plants to freezing temperatures.
All four of the cities studied receive below freezing temperatures and winter snowfall. Researchers looked at the number of days below freezing that did not have snow cover in these cities.
Using all of the data so far, suggest whether exposure to freezing temperatures in the four cities is supported as a reason for the differences in HCN production in T. repens.
Mandible (mouthpart) size is variable in the male broadhorned flour beetle (Gnatocerus cornutus).
In a laboratory experiment, scientists investigated how natural selection by predation on flour beetles by the larger assassin bug (Amphibolus venator) affected male mandible size. The graph shows the mean and standard deviation (SD) male mandible size over seven generations in three replicate experiments. Control populations were not subjected to predation.
Explain how natural selection by predation affects male mandible size in flour beetles.
Coho salmon, Oncorhynchus kisutch, displays two distinct male phenotypes commonly referred to as "jack" and "hooknose". Females will spawn with both male phenotypes. Hooknose males are larger, have greater fat reserves and have more strongly developed secondary sex characteristics.
jack male
hooknose male
The reproductive behaviour of the two phenotypes is different. Jack males prefer a less aggressive approach to females while hooknose males display a more threatening, aggressive approach.
In the presence of a male (hooknose or jack), females display digging and egg-laying behaviour. Digging involves making one or more holes in the riverbed to receive the eggs. The occurrence of digging behaviour and the time spent laying eggs were recorded over two mating seasons.
Suggest an evolutionary advantage for the presence of stable populations of jack and hooknose males in coho salmon populations.
John Endler experimented on populations of guppies (Poecilia reticulata) with different colouration. A male guppy fish is shown with large spots, which makes the fish more attractive to females, but more visible to predators.
The table shows the male colouration of guppy fish and number of predators in three different ponds.
What can be concluded from the data?
There is a positive correlation between numbers of predator X and size of spots.
Predator Y has least influence on colouration.
There is a negative correlation between number of predators and size of spots.
There is no sexual selection.
Cystic fibrosis (CF) is caused by a mutation of a human gene which codes for a chloride channel. The frequency of the CF allele is much higher in Europe than expected for an allele that causes a harmful condition. It has been suggested that individuals who are heterozygous for this allele may be protected against an infectious disease such as cholera or typhoid. This could cause both the CF allele and the normal allele of the chloride channel gene to persist in the population.
Using CF as an example, distinguish between allele frequency and gene pool.
The ability to digest lactose in adulthood appeared due to a mutation in the lactase gene. The frequency of the lactase persistence allele was recorded as 0.8 in present-day European populations and as 0.05 in fossils from populations of their prehistoric ancestors.
What could have caused the change in the allele frequency?
Drinking more milk caused the mutation to occur.
There was a strong positive selection for the lactase persistence allele.
Lactase persistence was transferred to humans from cows.
Prehistoric milk did not contain lactose.
What is an outcome of selection?
Directional selection increases the size of the gene pool.
Stabilizing selection increases allele frequencies of phenotypic extremes.
Disruptive selection increases genetic variance in a population.
Sexual selection leads to allopatric speciation.
The Hardy-Weinberg equation, used to calculate expected genotype frequencies in a population in genetic equilibrium, is:
The length of the mouthparts in an insect population is controlled by a gene with two alleles: long mouthparts (dominant) and short mouthparts (recessive). The frequency of the allele for long mouthparts is 0.72 .
What is the expected genotype frequency of individuals with short mouthparts?
0.52
0.40
0.28
0.08
Which of these conditions is/are necessary for genotype frequencies to fit the Hardy-Weinberg equation?
I. Homozygous recessive phenotypes have lower survival.
II. Mating is random.
III. The population is small.
I only
II only
II and III only
I, II and III
Which is an example of evolution by selective breeding?
Selection of prey animals that can run faster than their predators
The variation in the size of different breeds of dogs
The tendency, during breeding, for birds to produce more offspring than will survive
Some female spiders only breeding with males which make the right signals
