Practise IB Biology HL D4.1 by interpreting selection evidence, tracing allele-frequency change and applying Hardy-Weinberg calculations to populations.
Explain how evolution may happen in response to environmental change with evidence from examples.
Variation in genetically inherited characteristics is the basis for evolution.
Explain how genetic variation between the individuals in a species can be generated.
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.
In a natural population, what is a feature of individuals that are better adapted?
They start to produce offspring at a younger age than less well adapted individuals.
They produce identical offspring by cloning that are also better adapted.
They tend to produce more offspring during their lifetime than less well adapted individuals.
They do not produce more offspring than the environment can support.
Male eastern bluebirds (Sialia sialis) display brilliant UV-blue feathers on their heads, backs, wings and tails. The brightness index of the male was calculated; the larger the score, the brighter the blue feathers. A brightness value of 0 indicates normal male brightness, so birds with negative scores are less bright than normal.
In an experiment to see the mating behaviour of bluebirds, scientists separated pairs of males and females and then allowed females to choose new partners.
The graph shows the relationship between male brightness index and choice of mate by females in eastern bluebirds.
Evaluate the hypothesis that females prefer to mate with males whose feathers are a brighter blue.
Explain how natural selection can cause mate selection behaviour patterns to develop in a species such as eastern bluebirds.
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.
Define gene pool.
If a wild population of cats contained both curled ears and normal ears, explain how the proportion of these two phenotypes could change in the population.
Male and female human skeletons obtained from different archaeological sites in Greece were studied in order to find trends in human height evolution in Europe. The box-and-whisker plots show heights of skeletons dating from two historical periods: Neolithic (6500-3000 BC) and Roman (146-324 AD).
Phenotypic variation allows natural selection within populations. Compare and contrast directional and disruptive selection.
In fruit flies (Drosophila melanogaster) the allele for long wings is dominant to the allele for short (vestigial) wings. In a laboratory population of 200 flies there were 168 with long wings. Using the Hardy-Weinberg equation, calculate the percentage of flies that would be heterozygous for this characteristic. Show your working.
State two assumptions made when using the Hardy-Weinberg equation to calculate allele frequencies.
Dogs are descended from the grey wolf, Canis lupus, by selective breeding and are thought to be first domesticated about 30000 years ago. What is a result of this selective breeding?
Many different species of dogs exist.
The legs of different breeds of dogs show discrete variation.
Dogs have a variety of phenotypes.
The tails of dogs are analogous structures.