Threats, conservation, invasive species and assisted reproduction

Last time

Before we start: last time, in Sampling, biodiversity and Simpson's index, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.

Losing species faster than we name them

Species have always gone extinct, but humans are now speeding the rate up enormously. Habitat loss, climate change, over exploitation and invasive species are the main causes. The exam asks why each one matters, how conservation can slow the loss, and how zoos and breeding programmes help. We start with the threats.

Threats to biodiversity

Habitat loss is the biggest threat. Forests are cleared for farming and palm oil, and wetlands are drained. Species lose their food, shelter and breeding sites. Over exploitation by hunting, fishing and trade can reduce a population faster than it breeds. Pollution damages ecosystems, and climate change shifts the conditions species need. Invasive alien species compete with, prey on, or bring disease to native species.

Climate change and carbon dioxide

Carbon dioxide is a greenhouse gas. It traps heat, raising global temperatures, melting ice, raising sea level and changing rainfall. If the concentration rises from 280 to 410 parts per million, the increase is 130, which is 46 percent of the original. Always calculate a percentage change from the starting value.

A past-paper example

May June 2024, Paper 43, question 9. A graph shows how the global atmospheric carbon dioxide concentration changed over 800 000 years. Calculate the percentage increase between point A and the year 2020. Read the two values, subtract to find the increase, divide by the starting value, and multiply by one hundred. Show the working. Give the answer to the number of decimal places asked.