d) Different lines of finches developed different beak types because they needed them in order to obtain the available food. Gaia: -A complex entity which involves the biosphere, atmosphere, oceans, and soils of the earth.

All the finches in the different islands share a common ancestor, which is a group of finches that initially migrated into the islands and conquered the different islands. Due to the different ecologies in the different islands, adaptive radiation of the finches occurred and hence allopatric speciation.

However, the finches showed wide variations in their size, beaks and claws from island to island. For example, their beaks were different depending on the local food source. Darwin concluded that because the islands are so far from the mainland, the finches that had arrived there had changed over time.

Which statement about evolution in the Galápagos finches is true? Natural selection on beak size and shape is driven by available food. According to Lamarck’s hypothesis, an organism could change parts of its genotype and pass those changes to its offspring.

The avian palaeontologist David Steadman argued, based on morphological and behavioural similarities (1982), that the blue-back grassquit Volatinia jacarina, a small tropical bird common throughout much of Central and South America, was the most likely direct ancestor of the Galápagos finches.

Species Overview. Darwin’s finches, named after Charles Darwin, are small land birds, 13 of which are endemic to the Galapagos Islands. The 14th finch is the Cocos finch which is found on Cocos island, Costa Rica. They are not actually true finches – they belong to the tanager family.

Song and appearance both play a role in keeping different species from mating. So when populations of the same species are separated, changes in these traits set the stage for the formation of new species. The Grants have shown that both geography and ecology are keys to the evolution of the Galápagos finches.

They are far too genetically incompatible to produce a fertile egg. If offspring are produced and they survive they are often sterile and would never be able to breed with any other finch no matter which species they attempt to mate with.

The most likely explanation is that many years ago a single mainland flinch species migrated to the islands and with time food scarcity and availability led to the evolution of different species ina bid for adaptation and survival. 2. Different finch species have beaks of different shapes and sizes.

This indicates that the species have continued to interbreed or hybridise, after diversifying when they first arrived on the islands. “It’s been observed that the species of Darwin’s finches sometimes hybridise – Peter and Rosemary Grant have seen that during their fieldwork,” Prof Andersson told the BBC.

Enough time has passed for species to become physically distinct, adapted to the unique niches of their home islands. Not enough time has passed, however, for interbreeding to become impossible. Yet finch species often keep to themselves, even when winds or migratory impulses carry them between islands.

All 18 species of Darwin’s finches derived from a single ancestral species that colonized the Galápagos about one to two million years ago. The finches have since diversified into different species, and changes in beak shape and size have allowed different species to utilize different food sources on the Galápagos.

New species arise through a process called speciation. In speciation, an ancestral species splits into two or more descendant species that are genetically different from one another and can no longer interbreed. Darwin envisioned speciation as a branching event.