Short Answer
Evolution explains species extinction as a result of organisms failing to adapt to changing environmental conditions. When a species cannot survive or reproduce successfully, its population gradually declines.
Over time, factors such as environmental changes, competition, lack of adaptation, and natural selection can lead to the complete disappearance of a species. Extinction is a natural part of the evolutionary process.
Detailed Explanation :
Evolution and Species Extinction
Species extinction means the permanent disappearance of a species from Earth. Evolution explains extinction as a natural outcome when species are unable to cope with changes in their environment. Evolution works through adaptation and natural selection, but when these processes fail to support survival, extinction occurs.
Extinction is not sudden in most cases. It usually happens gradually over many generations as population size decreases. Evolutionary forces determine which species survive and which fail to continue.
Failure to Adapt to Environmental Changes
One of the main evolutionary reasons for extinction is failure to adapt.
Environmental changes may include:
- Climate change
- Habitat loss
- Change in food availability
- Natural disasters
Evolution favors species that develop useful traits. If a species lacks sufficient genetic variation or adaptive traits, it cannot survive these changes. As a result, its population declines and may become extinct.
Role of Natural Selection
Natural selection plays a major role in extinction.
Process:
- Environment changes
- Certain traits become disadvantageous
- Individuals with harmful traits survive less
- Reproduction decreases
If most individuals in a species have traits that are no longer suitable, natural selection removes them from the population. Over time, the species may disappear completely.
Lack of Genetic Variation
Genetic variation is essential for evolution and survival.
Problems occur when:
- Populations are small
- Inbreeding increases
- Genetic diversity is low
Without enough variation, species cannot adapt to new conditions. This increases the risk of extinction.
Competition with Other Species
Evolution explains extinction through competition.
Examples:
- New species may evolve with better adaptations
- Stronger competitors may replace weaker ones
When two species compete for the same resources, the better-adapted species survives. The weaker species may lose access to food, shelter, or breeding sites, leading to extinction.
Predation and Disease
Changes in predator–prey relationships can cause extinction.
Examples:
- New predators evolve better hunting abilities
- Prey species cannot evolve defenses fast enough
Similarly, diseases can spread rapidly. If a species lacks resistance, large numbers may die, leading to extinction.
Sudden Environmental Events
Some extinctions occur due to sudden events.
Examples:
- Volcanic eruptions
- Asteroid impacts
- Floods or droughts
Such events can wipe out large populations quickly. Species that cannot recover or adapt afterward may go extinct.
Evolutionary Trade-offs
Some adaptations may become harmful under new conditions.
Examples:
- Large body size may require more food
- Specialized diets may limit flexibility
Traits that were once useful can become disadvantages. Evolution explains extinction when past adaptations no longer support survival.
Mass Extinctions
Evolution also explains mass extinctions.
Mass extinctions occur when:
- Many species disappear in a short time
- Global environmental changes occur
After mass extinctions, evolution leads to:
- Survival of adaptable species
- Rapid evolution of new species
This shows that extinction and evolution are connected.
Human Impact and Evolution
Human activities have increased extinction rates.
Examples:
- Habitat destruction
- Pollution
- Overhunting
- Climate change
Evolution cannot always keep up with rapid human-caused changes. Species unable to adapt quickly face extinction.
Extinction as Part of Evolution
Extinction is not a failure of evolution.
Important points:
- Most species that ever lived are extinct
- Extinction makes space for new species
- Evolution continues through surviving species
Extinction helps shape biodiversity over time.
Balance Between Evolution and Extinction
Evolution maintains a balance:
- Some species evolve and survive
- Some fail and go extinct
This balance shapes the history of life on Earth.
Conclusion
Evolution explains species extinction as a natural result of failure to adapt to environmental changes, competition, lack of genetic variation, and natural selection. When species cannot survive or reproduce successfully under changing conditions, their populations decline and eventually disappear. Extinction is a normal part of evolutionary history and plays an important role in shaping biodiversity by allowing new species to evolve and occupy available ecological niches.