Practise classifying organisms, quantifying biodiversity and evaluating conservation strategies from biological and field data.
Bears are several species of mammal in the family Ursidae.
Climate change and loss of habitats due to human activity have reduced the size of some bear populations in recent years.
The International Union for Conservation of Nature (IUCN) has a role in the conservation of species, such as species of bear.
Outline the role of the IUCN in the conservation of species.
Grizzly bears, Ursus arctos horribilis, and polar bears, Ursus maritimus, are found in North America.
Fig. 8.1 shows a grizzly bear and a polar bear.
Grizzly bears have:
- a varied diet that includes grasses, roots, berries, nuts, rodents, insects and fish
- a habitat of woodland or grassland
- a maximum mass of 270 kg .
Polar bears have:
- a diet that consists of other animals, such as seals
- a habitat of land and sea ice
- a maximum mass of 450 kg .
Climate change has caused populations of grizzly bears to spread further north and populations of polar bears to spread further south. In some areas there is habitat overlap and, on rare occasions, breeding between grizzly bears and polar bears has occurred.
The offspring of grizzly bears and polar bears are known as pizzly bears.
Pizzly bears can breed together in the wild.
Fig. 8.2 shows a pizzly bear.
Fig. 8.2
With reference to three different species concepts, discuss whether grizzly bears and polar bears should be classified as separate species.
The scientists calculated a D value of 0.833 for the undisturbed population.
Explain what is shown by the difference in the D values between the two populations of bear.
The natural ecosystem on Hawadax Island in Alaska was disrupted in the 1780s when brown rats, Rattus norvegicus, swam to the island from a sinking ship and then rapidly increased their population size.
The rats occupied a new niche on the island as predators. The rats ate the eggs and chicks of birds such as the black oystercatcher, Haematopus bachmani, and the glaucous-winged gull, Larus glaucescens. These birds make nests, lay eggs and rear their chicks on the beaches of the island.
Define the terms ecosystem and niche.
ecosystem
niche
Conservation ecologists carried out a project to try to restore the natural ecosystem of Hawadax Island. In 2008, they removed all rats from the island.
Before removing the rats, the ecologists measured the abundance of birds, invertebrates and seaweeds on eight of the island's beaches. Seaweeds are large algae that grow attached to rocks on the beach. The ecologists repeated these measurements in 2013 and in 2019, so that they could calculate the percentage change in abundance from 2008.
To measure the abundance of invertebrates and seaweeds, the ecologists used this method:
- They laid 30 m tapes from high-tide mark to low-tide mark on the beach.
- They placed quadrats at 5 metre intervals next to the tapes.
- They took a photograph of each quadrat.
- They analysed the photographs to calculate the percentage cover of seaweeds and the percentage cover of invertebrates such as mussels and sea snails.
State the name of the sampling technique used.
Biodiversity can be assessed at a number of different levels.
Identify the levels of biodiversity:
- that were assessed by this sampling technique
- that were not assessed by this sampling technique.
Table 2.1 shows the percentage change in abundance of some of the seaweeds, invertebrates and birds found on the beaches of Hawadax Island.
Table 2.1
Use Table 2.1 to state the genus name of one organism that has increased in abundance.
Seaweeds were once thought to be plants but are now classified in the kingdom Protoctista.
Outline the features of the kingdom Protoctista that are shown by seaweeds.
To evaluate the success of the Hawadax Island restoration project, the ecologists obtained data from other islands near to Hadawax Island.
- Some islands had never been occupied by rats (rat-free islands) and had a healthy ecosystem.
- Some islands were still occupied by rats (rat-occupied islands) and had a disrupted ecosystem.
Table 2.2 shows the percentage differences in the abundance of organisms in rat-free islands compared with rat-occupied islands.
Table 2.2
With reference to Table 2.1 and Table 2.2, suggest and explain how removing rats has restored the ecosystem on Hawadax Island.
The moose, Alces alces, is a large member of the deer family. It lives in temperate forests in North America and northern Europe, where snow is present for large parts of the year.
Fig. 10.1 shows an adult male moose feeding in a lake.
Fig. 10.1
The moose feeds on a plant in the lake called watermilfoil, Myriophyllum aquaticum.
The moose and the watermilfoil belong to the domain Eukarya, which includes the kingdoms Animalia and Plantae.
Describe the main differences between the kingdom Animalia and the kingdom Plantae.
Measurements of the surface temperature of land and oceans can be taken from locations around the world. The mean global surface temperature for land and ocean combined can be calculated for a fixed time period.
Scientists calculated:
- the mean global temperature for the twentieth century
- the mean global temperature for each decade (ten years) from 1880 to 2020.
The mean temperature for each decade was compared to the mean for the twentieth century. For each decade, the difference in temperature was calculated.
The calculated differences are shown in Fig. 10.2.
Fig. 10.2
Moose populations have decreased in North America since 1980.
Suggest and explain reasons for the decrease in moose populations.
Genetic technology uses many different enzymes and techniques.
Restriction endonucleases are used in genetic modification. These enzymes occur naturally in prokaryotic cells. More than 3500 different restriction endonucleases have been identified and it is thought there are many more to discover.
Name two domains that are a source of restriction endonucleases.