Evolution is the process by which living organisms change over generations. It explains the incredible diversity of life we see today.
Sexual vs Asexual Reproduction
Many organisms need a male and female to reproduce. Their offspring inherit DNA from both parents, producing new combinations of traits.
Other organisms reproduce by cloning (asexual reproduction), like bacteria. In this case, offspring are nearly identical to their parent. However, DNA replication isn’t perfect, and random errors can create mutations — small changes in traits.
Note: These mutations are usually small but are the raw material for evolution.
Random Mutations and Natural Selection
Mutations introduce variation. The environment acts as a filter:
- If a mutation makes an organism less likely to survive, it won’t pass its traits on.
Organism dies fast and it does not have living offspring to carry its DNA.
- If a mutation makes an organism more likely to survive and reproduce, its traits can spread through the population over generations.
Example: Giraffe Necks
- Variation: Some giraffes are born with slightly longer necks.
- Pressure: Taller giraffes reach more leaves.
- Result: Taller giraffes survive and reproduce more.
- Outcome: Over many generations, the population’s average neck length increases.
Why Evolution Takes Time
Evolution is gradual. Mutations are small, and beneficial traits accumulate slowly. The environment selects traits, favoring some and disadvantaging others. This “filtering” happens over many generations.
Advantages and Disadvantages of Reproduction Types
Asexual reproduction:
- Fast and efficient.
- Produces little genetic diversity, making populations vulnerable to environmental changes.
Sexual reproduction:
- Slower, but introduces genetic diversity.
- Provides a more robust mechanism for adaptation, especially in changing environments.
While large populations of asexual organisms can increase the likelihood of beneficial mutations, the lack of recombination limits adaptability. Sexual reproduction overcomes this by mixing DNA, creating traits that might survive environmental shifts.
Key Takeaways
- Evolution is driven by mutation, selection, and reproduction.
- Small genetic changes accumulate over time.
- Sexual reproduction increases diversity and long-term survival.
- Asexual reproduction is efficient but risky in changing environments.