Understanding Global Warming and Its Biological Impact Revision Notes | GCSE OCR Foundation Biology

What this lesson covers

Explore how increasing levels of carbon dioxide and methane in the atmosphere contribute to global warming, and examine the various biological consequen...

• Explain how increased levels of carbon dioxide and methane contribute to global warming
• Describe the biological consequences of global warming on ecosystems and species
• Evaluate the impact of human activities on atmospheric greenhouse gas concentrations
• Apply knowledge of global warming to predict effects on biodiversity and food chains

Key ideas to keep in view

Use this lesson to stay inside B6.1 Monitoring and maintaining the environment while connecting the detail back to the wider B6: Global challenges topic.

• B6: Global challenges
• B6.1 Monitoring and maintaining the environment
• GCSE OCR Foundation Biology

Lesson notes preview

Read the core explanations from Understanding Global Warming and Its Biological Impact before testing yourself from memory.

• 1. The Greenhouse Effect and Rising Gas Levels
• Picture Earth wrapped in an invisible blanket. This blanket - our atmosphere - keeps us warm enough for life to exist. But we're making this blanket thicker every year, and that's causing problems.
• A greenhouse gas produced by burning fossil fuels, deforestation, and respiration. Current atmospheric levels are the highest in 3 million years.
• A greenhouse gas about 25 times more potent than CO₂ over a 100-year period, produced by livestock, rice farming, and landfill sites. Levels have tripled since pre-industrial times.
• Here's the key point: both gases are increasing rapidly due to human activities. CO₂ levels have risen from 280 parts per million in 1880 to over 420 ppm today. Methane concentrations have more than doubled in the same period.
• These gases trap heat that would normally escape to space. More greenhouse gases mean more trapped heat, leading to global warming. This sounds simple, but the biological consequences are complex and far-reaching.
• Global average temperatures have risen by approximately 1.1°C since pre-industrial times. This might sound small, but it's huge in climate terms. During the last ice age, global temperatures were only 6°C cooler than today.
• This warming isn't uniform across the planet. The Arctic is warming twice as fast as the global average - a phenomenon called Arctic amplification. Polar ice reflects sunlight back to space, but as ice melts, darker ocean water absorbs more heat, accelerating warming further.
• Rising temperatures cause immediate physical changes: glaciers retreat, ice caps shrink, and sea levels rise due to thermal expansion of seawater and melting ice. These changes set the stage for biological impacts.
• Now we reach the heart of the biological impact. Global warming affects living organisms in several key ways, and these effects cascade through entire ecosystems.

Continue through the topic

Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.