Hummingbirds eat flower nectar and small insects. To which nutritional group do they belong?

The diagram shows the food web for an aquatic ecosystem in which letters R–Z represent individual species. Which organism is a tertiary consumer?

Which organisms produce methane in anaerobic environments such as waterlogged soils?

In an ecosystem, in the transfer of carbon from producers to consumers, what is carbon transferred as?

I. Carbon dioxide

II. Protein

III. Hydrogencarbonate ions

The Silver Springs feed into the Silver River in Florida. The diagram shows a pyramid of energy for the Silver Springs ecosystem. The units are kJ m^–2 y^–1. What do level I and level III represent in the pyramid of energy?

Which is not essential in a viable mesocosm?

The diagram shows interactions between food chains in an ecosystem in the African savannah. Which arrows indicate the flow of chemical energy?

The Australian pitcher plant (Cephalotus follicularis) is a green plant that traps and feeds on flies and other live insects. What is this plant’s mode of nutrition?

In 1789 Gilbert White, a naturalist, observed eight breeding pairs of swifts (Apus apus) in the English village of Selborne. On average, each pair of swifts produces two offspring per year. This would allow the population to rise to 1030 swifts over 200 years. A bird survey carried out in 1983 revealed only 12 breeding pairs in this village.

What could have prevented the numbers rising to 1030?

I. The number of nesting sites remained the same.

II. The food supply of the swifts remained constant.

III. Predatory birds in the area were exterminated.

Limpets are molluscs with conical shells that cling tightly to rocks on seashores. In a study of two species of limpets found on rocks along the Oregon coast, 30 randomly placed quadrats were used to determine how often the two species occurred together. The table shows the data that were collected.

Which statistical method will determine whether these two species occur together by chance or by some kind of interaction?

Animals in the highest trophic level of a food chain will often be the largest in body size but will be few in numbers. What accounts for the small numbers?

Which conditions favour peat formation?

In addition to carbon dioxide, which of these greenhouse gases is the most significant?

The image shows a food web. Which organism in the food web is assigned to its method of nutrition?

The Venus flytrap (Dionaea muscipula) is a photosynthetic plant. It obtains nitrogen but not energy by digesting captured insects.

Which term describes this plant?

What describes a possible cause of a negative carbon flux in the atmosphere due to processes occurring in a forest ecosystem?

The diagram shows the carbon cycle. Which two processes correspond to the labelled arrows?

Euglena is a unicellular organism that feeds on bacteria and uses CO₂ as a carbon source. Which describes the nutrition of this organism?

Which characteristic of water vapour classifies it as a greenhouse gas?

What is lost between trophic levels in ecosystems and cannot be recycled?

By which mechanism do greenhouse gases contribute to global warming?

The image shows a transect through a stream and a field.

Which calculation would test for the association between two species of plants from quadrat data from section A and section B of the field?

Native oyster populations are decreasing where rivers meet the ocean along the northwest coast of North America. These oyster populations are being attacked by a gastropod. It is known that oysters and gastropods have hard parts composed of calcium carbonate and that ocean acidification is increasing. Studies were carried out using juvenile oysters and gastropods to investigate the effects of acidification on the decrease in the population of oysters.

The first step was to raise oysters in two different mesocosms. One had seawater at a normal concentration of CO₂ and the other had sea water with a high concentration of CO₂. Gastropods were raised in two further mesocosms with normal and high CO₂ concentrations respectively. How could acidified sea water affect the shells of the oyster?

What is the classification of an organism that is able to make organic compounds from inorganic nutrients?

What restricts the length of a food chain?

Image I shows a spotted hyena (Crocuta crocuta) and image II shows a leopard tortoise (Geochelone pardalis). Based on their diet, the feces of spotted hyenas appear white because of high calcium content. Leopard tortoises eat hyena feces. What would explain such tortoise behaviour?