Extinction
Biology: Cambridge International A Level, topic 17.3.4
Extinction
Extinction is a normal part of macroevolution and has occurred throughout the Earth's history. Ecological stress and human activity can accelerate extinction events.
Extinction
- Extinction happens when there are no individuals of a species left in the world.
- A change in abiotic (physical) or biotic (relating to organisms) factors can cause an extinction if a species cannot adapt or move to another environment.
- Extinction can be seen to be in balance with speciation.
- As new species are formed through speciation, some species are lost through extinction.
- This equilibrium between extinction and speciation is in constant flux.
Dangers of extinction
- Accelerated extinction rates accompanied by the loss of tens of thousands of species and the collapse of ecosystems can affect human welfare.
- With respect to health, many medicines, including aspirin, codeine, and vincristine, are derived from plants.
- Agricultural diversity is a requirement for food security, and the loss of wild relatives to crops threatens our ability to create new varieties that can grow in areas with previously impossible climates and soil conditions.
Humans & extinction
- Human activity can cause changes in ecosystems and accelerate rates of extinction.
- Human population growth and the unsustainable removable of resources from the environment threatens many species with extinction.
- For example, a major cause of species extinction—climate change—is becoming increasingly more significant.
- The burning of fossil fuels raises levels of carbon dioxide in the atmosphere, and this “greenhouse effect” results in global climate change.
- The rising global temperatures lead to habitat destruction.
Humans & extinction 2
- Humans can also lead to the extinction of species through killing animals. This may be through hunting for food or poaching.
- For example, northern white rhinos are now endangered following extended periods of poaching.
Other causes of extinction
- Species can also become extinct due to competition.
- This may be competition for food, habitats, or mates.
- Many canine species have become extinct through competition for resources.
Test yourself on Extinction
Suggest why the dinosaurs that survived the immediate impact of the meteorite during this mass extinction also died off?
Which of the following provides the best explanation as to why eating less meat could preserve the diversity of plant species on Earth?