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saturday 26 april 2025
Automatically translated from Basque, translation may contain errors. More information here. Elhuyarren itzultzaile automatikoaren logoa

Nola eboluzionatzen du ugaztunen tamainak?

Joxerra Aizpurua Sarasola
07 February 2012

Monash Unibertsitateko (AEB) Alistair Evans ikerlariaren lantaldeak aztertu egin du ugaztunen tamainaren eboluzioa azken 70 milioi urteetan, eta datu interesgarriak argitaratu ditu. Adibidez, errazagoa da lehorreko ugaztun batentzat txikiagoa izatea handiagoa izatea baino, eta itsasoko ugaztunen handitze abiadura handiagoa da lurtarrena baino.

Hona hemen datu batzuk: lehorreko ugaztun batek tamaina 100 aldiz handitzeko 1,6 milioi belaunaldi behar dira, tamaina 1.000 aldiz handitzeko bost milioi belaunaldi, eta hamar milioi belaunaldi tamaina 5.000 aldiz handitzeko. Adibidez, saguen tamaina elefanteenaren adinekoa izateko 24 milioi belaunaldi behar dira. Aldiz, ugaztunen txikitzea askoz ere astiroago gertatzen omen da: ugaztun bat nano bihurtzeko 100.000 urte baino ez dira behar.

Baina nola liteke ugaztun batek txikitzeko joera izatea? Batez ere lurralde mugatuetan, irletan adibidez, gertatzen da hori. Janari gutxiago dagoenez, egoera horretara moldatzeko txikiagotzen dira animaliak, eta aldi berean ugaltze-tasa handitzen dute.
 

ASTEKARIA
2310. zenbakia
2012ko otsailaren 12a
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