Biology by Bradford
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The subtopic in the middle and twelve tasks round it: label three diagrams, complete two tables, put a process in order and fill 55 gaps. Every standard level statement has a box; the three boxes for higher level only are dashed and badged HL, and drop off for an SL class. Type into the blanks and check them, or print it on A4, Letter or A3 with an answer key.
Emperor penguins raise their chicks on ice fixed to the Antarctic coast. If it breaks up , before the chicks have grown feathers, they drown or freeze. Arctic walruses rest on floating ice above shallow feeding grounds; as it shrinks, they crowd onto , far from their food.
As the climate warms, many species are shifting their ranges and . Birds of New Guinea's tropical mountains now live higher than they did in the 1960s, and those already near a summit have nowhere left to go. In North America many tree species' ranges are , while some are spreading .
Trees store carbon in their wood as they grow. Planting forest on land that has not recently been forested is ; letting cleared forest grow back is forest . Scientists still debate whether plantations of introduced trees or rewilding with species lock away more carbon. Restoring wetlands helps too: in soil, lack of oxygen stops dead plants decomposing fully, so their carbon builds up as .
| Population | Main cue | When spring is warmer |
|---|---|---|
| Arctic mouse-ear chickweed | grows and peaks sooner | |
| Migrating reindeer | arrive on the usual date, after the plants' peak | |
| Caterpillars in oak woods | reach peak biomass sooner | |
| Great tit | chicks hatch after the caterpillar peak, so survive |
Research into the timing of events such as budburst, flowering, migration and nesting is . Where two populations in one ecosystem respond to different cues, warming can break their .
Burning and clearing forests have raised carbon dioxide far above anything in the ice-core record, and cattle, rice paddies and landfill add . Antarctic ice cores show a correlation between CO₂ and temperature over 400 000 years. A correlation alone does not prove , but other evidence confirms that CO₂ warms the climate.
Corals build reefs from calcium carbonate. Dissolved CO₂ makes seawater more acidic, , leaving fewer carbonate ions, so is suppressed. Water that is too warm makes corals expel the living in their tissues, and they turn white: . Without them the corals starve, and the whole reef ecosystem can .
Shifting ocean currents change when and where cold, deep water reaches the surface. Warmer surface water, being less , floats on the cold water below and can stop it rising altogether. Then there is less at the surface, and less flows through marine food chains.
Warmer summers speed up the development of the spruce bark beetle, so more fit into one year: where there was one, there can now be . Its numbers can then climb much faster, and spruce trees weakened by resist attack poorly, so outbreaks kill trees over huge areas.
| Warming makes... | ...which adds to warming because |
|---|---|
| the deep ocean warm | warmer water holds dissolved CO₂, so it escapes to the air |
| snow and ice melt | darker land and water more solar radiation instead of reflecting it |
| permafrost thaw | and CO₂ escape from long-frozen organic matter |
| peat dry and warm | speeds up and releases its stored carbon |
| droughts more common | more forest burn, releasing carbon |
Each is a cycle: warming sets off a change that causes more warming.
Number the steps in order.
Once a boreal forest gives out more carbon than it takes in, it has passed a .
Tawny owls are grey or brown, and the colour is . In cold, snowy winters the grey ones survive better. As Finnish winters have brought less snow, the of the other colour has risen, and the proportion of owls has gone up: as a consequence of climate change.
123Burning fossil fuels and clearing forests have raised carbon dioxide far above anything in the ice-core record, and cattle, rice paddies and landfill add methane. Antarctic ice cores show a positive correlation between CO₂ and temperature over 400 000 years. A correlation alone does not prove causation, but other evidence confirms that CO₂ warms the climate.
| Warming makes... | ...which adds to warming because |
|---|---|
| the deep ocean warm | warmer water holds less dissolved CO₂, so it escapes to the air |
| snow and ice melt | darker land and water absorb more solar radiation instead of reflecting it |
| permafrost thaw | methane and CO₂ escape from long-frozen organic matter |
| peat dry and warm | decomposition speeds up and releases its stored carbon |
| droughts more common | more forest fires burn, releasing carbon |
Each is a positive feedback cycle: warming sets off a change that causes more warming.
Once a boreal forest gives out more carbon than it takes in, it has passed a tipping point.
Emperor penguins raise their chicks on ice fixed to the Antarctic coast. If it breaks up early, before the chicks have grown waterproof feathers, they drown or freeze. Arctic walruses rest on floating ice above shallow feeding grounds; as it shrinks, they crowd onto land, far from their food.
Shifting ocean currents change when and where cold, deep water reaches the surface. Warmer surface water, being less dense, floats on the cold water below and can stop it rising altogether. Then there is less primary production at the surface, and less energy flows through marine food chains.
As the climate warms, many species are shifting their ranges poleward and upslope. Birds of New Guinea's tropical mountains now live higher than they did in the 1960s, and those already near a summit have nowhere left to go. In North America many tree species' ranges are contracting, while some are spreading north.
Corals build reefs from calcium carbonate. Dissolved CO₂ makes seawater more acidic, ocean acidification, leaving fewer carbonate ions, so calcification is suppressed. Water that is too warm makes corals expel the zooxanthellae living in their tissues, and they turn white: bleaching. Without them the corals starve, and the whole reef ecosystem can collapse.
Trees store carbon in their wood as they grow. Planting forest on land that has not recently been forested is afforestation; letting cleared forest grow back is forest regeneration. Scientists still debate whether plantations of introduced trees or rewilding with native species lock away more carbon. Restoring wetlands helps too: in waterlogged soil, lack of oxygen stops dead plants decomposing fully, so their carbon builds up as peat.
| Population | Main cue | When spring is warmer |
|---|---|---|
| Arctic mouse-ear chickweed | temperature | grows and peaks sooner |
| Migrating reindeer | photoperiod | arrive on the usual date, after the plants' peak |
| Caterpillars in oak woods | temperature | reach peak biomass sooner |
| Great tit | photoperiod | chicks hatch after the caterpillar peak, so fewer survive |
Research into the timing of events such as budburst, flowering, migration and nesting is phenology. Where two populations in one ecosystem respond to different cues, warming can break their synchrony.
Warmer summers speed up the development of the spruce bark beetle, so more life cycles fit into one year: where there was one, there can now be two. Its numbers can then climb much faster, and spruce trees weakened by drought resist attack poorly, so outbreaks kill trees over huge areas.
Tawny owls are grey or brown, and the colour is heritable. In cold, snowy winters the grey ones survive better. As Finnish winters have brought less snow, the fitness of the other colour has risen, and the proportion of brown owls has gone up: evolution as a consequence of climate change.