ancestral sea-run stickleback populations live exclusively fresh water Stickleback lab answers

1. how did some ancestral sea-run stickleback populations come to live exclusively in fresh water?

Answer:

The correct answer is "some stickleback populations come to live exclusively in fresh water they became trapped in lakes that formed at the end of the last ice age".

Explanation:

There are different types of speciation. Allopatric speciation consists of the geographic separation of a continuous genetic background so that it can give place to two or more new geographically isolated populations. Some barriers might impede the genetic interchange or genetic flux, making a place to two new populations that are separated and can not get together to mate anymore. Glaciation is one of the most important drivers of speciation and production of different phylogeographic structures by vicariance. Glacials originate isolated gene-pools that accumulate differences that end in reproductive isolation. Melting of the ice also generated divergence and speciation, as land appearance acted as a barrier for some populations.  

During the last glaciation, stickleback fishes were able to reach certain new places or areas that provided better conditions to inhabit. There were fewer predators and more available food sources that made these new areas to be a better choice. These new grounds were lakes and were the product of ice melting. But at a certain point, as ice melting increased, the land started to show up again and became a barrier for this species. Animals that were living in lakes could not go back to the sea, they were trapped so they had to adapt to living exclusively in lakes. This species diverged and suffered speciation.

How did the stickleback adapt to freshwater living?

The bodies of threespine stickleback fish in certain populations evolved as they adapted from living in the ocean to a life exclusively in freshwater environments. One adaptation was the loss of pelvic spines, which are homologous to the hind limbs of four-legged animals.

How did ancestral population of ocean dwelling fish come to live in freshwater lakes?

How did ancestral populations of ocean-dwelling dish come to live in freshwater lakes? Sea-run stickleback fish got trapped in postglacial lakes.

How did marine stickleback fish become trapped in freshwater lakes?

Sticklebacks started out as saltwater fish. As the glaciers of the last Ice Age receded 10,000 years ago, some of these fish swam inland, and many became trapped in lakes left behind by the glacial melt.

How do sticklebacks fish adapt to their environment?

Researchers at the Friedrich Miescher Laboratory are studying stickleback fish to unravel the genetic changes which allow organisms to adapt and speciate in new environments. Marine sticklebacks have undergone an adaptive radiation with freshwater forms evolving repeatedly and independently at many different places.

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