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WonderEvolutionary design fact

Convergent evolution happens when unrelated organisms independently evolve similar traits, such as streamlined bodies in sharks, dolphins and extinct ichthyosaurs.

Convergent evolution

EvolutionBiologyDesignScience

The story behind the card

Sharks are fish, dolphins are mammals and ichthyosaurs were marine reptiles, yet all three evolved a similar streamlined, fin-driven body built for fast swimming. The same pattern shows up elsewhere: camera-like eyes, with a lens that focuses light onto a retina, evolved independently in both vertebrates and octopuses, and the extinct Australian thylacine looked strikingly like a wolf despite being a marsupial with no close relation to dogs. Convergent evolution does not mean life is aiming for a fixed set of designs. Natural selection simply favours whatever body plan works best under a given set of physical pressures, so unrelated lineages can arrive at strikingly similar answers.

Türkçe oku
Yakınsak evrim, akraba olmayan canlıların benzer özellikleri birbirinden bağımsız olarak geliştirmesidir. Köpek balıklarının, yunusların ve soyu tükenmiş ihtiyozorların aynı akıcı gövde biçimine sahip olması buna bir örnektir.

Köpek balığı bir balık, yunus bir memeli, ihtiyozor ise bir deniz sürüngeniydi. Yine de üçü de birbirinden bağımsız olarak hızlı yüzmeye uygun, yüzgeçli, akıcı bir gövde geliştirdi. Aynı durum başka örneklerde de görülür: ışığı bir mercekle ağ tabakaya odaklayan, fotoğraf makinesine benzer gözler hem omurgalılarda hem ahtapotlarda ayrı ayrı ortaya çıktı. Soyu tükenmiş Tazmanya kaplanı (keseli kurt) kesesi olan bir hayvandı ve köpeklerle yakın akrabalığı yoktu; yine de görünüşü şaşırtıcı ölçüde kurda benziyordu. Yakınsak evrim, canlılığın önceden belirlenmiş tasarımlara doğru ilerlediği anlamına gelmez. Doğal seçilim, belli koşullarda en iyi işleyen beden yapısını öne çıkarır; bu yüzden akraba olmayan soylar çoğu zaman birbirine çok benzeyen çözümlere varır.

Sources and further reading

Background reading: Convergent evolution
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