Practise IB Biology HL C4.1 by selecting sampling methods, interpreting growth and food-web data, and reasoning about interactions between species.
153 questions in this syllabus scope, with question parts counted together.
117 papers analysed · Tagging incomplete
The photograph shows Japanese knotweed, Reynoutria japonica, which is native to Japan, China and Korea. It has been introduced into other regions of the world and is now an invasive alien species in parts of Europe and North America. Dense groups of stems often develop with a height of up to 3 metres, which prevent other plants from growing.
State the biological term for a group of organisms of the same species living in an area.
To estimate the size of the turtle population, the Fish and Wildlife Research Institute (FWRI) conducted an annual survey along the coast of Florida from 1989 to 2021. They counted the number of turtle nests on selected beaches where turtles lay their eggs. The graphs show the results for the loggerhead turtle (Caretta caretta) and the green turtle (Chelonia mydas).
Suggest the limitations of only using nesting turtles to estimate the annual population.
An investigation was undertaken in Gåsbreen, Norway, in a freshly de-glaciated area to look at the organisms present at different times since the retreating glacier had exposed the land. A linear transect and quadrat were used starting at the edge of the retreating glacier. The first producers were recorded at a distance of 426 m from the glacier.
Outline how a transect and quadrats can be used in ecological fieldwork.
The diagram shows the relationship between commercial sea fishing activity and yield, and how this affects sustainability.
Explain how the population of fish in a pond could be estimated using the capture-mark-release-recapture method.
In an animal population, what could cause the exponential phase of population growth to level out to the plateau phase?
Increased species diversity
Increased resources
Increased natality
Increased predation
The elimination of wolves (Canis lupus) from Yellowstone National Park in 1926 and their reintroduction in 1995 provided the opportunity to examine ecological interactions with elk (Cervus elaphus). The National Park Service made efforts between the 1920s and 1968 to reduce the size of elk herds by culling (selective killing) because of concerns about overgrazing.
The graphs provide the trends for the numbers of wolves and elk in Yellowstone National Park from 1900 to 2004.
List two biotic factors, other than wolf predation or culling, that could affect the elk population.
1:
2:
Duckweed (Lemna gibba) is a plant that grows on the surface of water. It was grown in cultures and the percentage increase in total area covered per day was obtained. The graph shows the specific growth rates per day for duckweed measured over 22 days.
Suggest reasons for the slowing down of duckweed population growth after day 6.
Duckweed (Lemna aequinoctialis) is a small floating plant that sometimes forms a continuous cover over the surface of ponds. In an experiment, it was grown either in nutrient-rich medium or in sewage water for four weeks. The biomass obtained per square metre at different times is shown in the population growth curves.
Label two phases on the nutrient-rich medium population growth curve.
The pavement ant (Tetramorium caespitum) eats organic matter found within its territory. Individual ants leave their nest to forage for food. When they find a suitable source of food they return and communicate to other ants in the colony where the food can be found. The diagram shows the path of one ant when foraging for food and returning to the nest after finding food.
State one advantage to an insect of living in a colony.
Over time, the hull of a sunken ship may become colonized by a wide range of marine organisms. What term is used to describe all of the organisms living in and on a sunken ship?
A community
An ecological niche
A population
An ecosystem
Brandt's voles (Lasiopodomys brandtii) are small herbivorous rodents that live in the steppe grassland of Inner Mongolia. These mammals live in large family groups and feed on the roots, stems and leaves of a wide variety of plants that grow near their burrows. Their feeding activities have been found to have a large impact on the grassland vegetation. Researchers investigating the impact of these voles on the vegetation marked out plots of land and recorded how the biomass of two types of grasses, rhizome grasses and bunch grasses, changed in the presence and absence of voles from the years 2013 to 2017.
Key:
- voles
- no voles
The voles derive nutrition from only one type of the grasses. Deduce with a reason which type.
In a second study carried out from 2019 to 2020, researchers looked at how the presence of voles changed the plant volume of one type of bunch grass, Achnatherum splendens, in measured plots of land. This was done by measuring the change in plant volume of A. splendens in the plots.
Suggest a reason for the change in the plant volume of A. splendens in the plots over the period of this study.
In a final experiment, the researchers prepared plots containing varying levels of cover of A. splendens, as well as the plants the voles normally feed on. Shrikes were not excluded from the plots. The amount of time the voles spent feeding and the mortality rate of the voles was recorded over a 3 -week period.
Describe, with a reason, the condition that favours survival of the voles.
What describes a benefit of the relationship between coral and zooxanthellae?
Zooxanthellae receive carbon dioxide from the coral.
Zooxanthellae receive glucose from the coral.
Coral receives carbon dioxide from the zooxanthellae.
Coral receives protection from the zooxanthellae.
Discuss, giving an example, the possible effects of the introduction of an alien species into an ecosystem.
In South Korea, flocks of birds of the tit family (Paridae) forage together on trees for food. Researchers observed four species of Paridae to determine whether they shared the same habitat in the trees and whether their position on the tree depended on their size. The leafy part of the tree (crown) was divided into nine sections, three according to height from the ground and three according to the distance from the tree trunk. Observations were also made of birds foraging in the bushes surrounding the trunk and on the ground below the tree. The chart shows the relative use of each section of the habitat by the birds.
Discuss whether the results for the Varied Tit and Coal Tit indicate competitive exclusion.
A group of students used quadrat sampling and the chi-squared test to find out whether the distributions of two plant species were associated with each other or not. These two species were found in the ground vegetation in a woodland ecosystem.
Ground ivy (Glechoma hederacea)
Wood speedwell (Veronica montana)
The numbers of quadrats with one, both or neither species present were counted and recorded. The observed frequencies from 150 quadrats are shown in the following contingency table.
State the alternative hypothesis for this study.
To calculate chi-squared, expected values must first be calculated. Assuming that there is no association between the two species, calculate the expected number of quadrats in which both species would be present, showing your working.
State the number of degrees of freedom for this test to determine the critical value of chi-squared.
When the data in the table were used to calculate chi-squared, the calculated value was 0.056 . The critical value is 3.84 . Explain the conclusion that can be drawn from the calculated and critical values for chi-squared.
During the 1980s, a tiny invasive crustacean Bythotrephes cederstroemii entered the eastern Great Lakes from Europe (probably via freshwater or mud in the ballast water of merchant ships) and eventually colonized Lake Michigan. Bythotrephes reproduces very quickly and eats common zooplankton, disrupting the food web by directly competing with small juvenile resident fish. Bythotrephes avoids predation by larger fish through the timing of its activities which have been investigated in offshore waters of Lake Michigan at various depths during the day and night.
Explain the change in distribution of Bythotrephes between day and night in terms of its position in the lake food chain.
What is an example of a population control mechanism within a community?
Bottom-up control of herbivores by a top predator
Top-down control of grasses by consumers
Top-down control of a plant species by soil nutrient availability
Bottom-up control of dissolved oxygen by corals
The image shows mycorrhizal fungi growing between the cells of a recently germinated orchid plant.
Explain how a named plant can reduce competition by allelopathy.
The photograph shows Japanese knotweed, Reynoutria japonica, which is native to Japan, China and Korea. It has been introduced into other regions of the world and is now an invasive alien species in parts of Europe and North America. Dense groups of stems often develop with a height of up to 3 metres, which prevent other plants from growing.
State the biological term for a group of organisms of the same species living in an area.
Suggest two ways in which a plant such as Reynoutria japonica could prevent the growth of other plants.
