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Showing posts with label feed. Show all posts

Whales Took an Evolutionary Leap Forward

Eons ago ancestors of whales made a major leap forward in evolution of their mouths. Whales living today can filter-feed in large amounts because the lower jaw is flexible in movement.

Ancient fossils such as Janjucetus hunderi do not have such a mobile lower jaw. The development of this attribute probably initially evolved to consume large living prey. It began with a wide upper jaw and normal teeth - no comb filters. Erich Fitzgerald from the Museum Victoria in Melbourne has created a family tree showing whale evolution.

The way whales feed is unique. It is believed that sucking when feeding still takes place, a left over from the days of the wide upper jaw.

A big question is why whales went back into the sea in the first place.
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Bull Ants Feed at Twilight

Bull ants do not feed during all daylight hours. Observation has shown that they feed at twilight. When the sun is brighter for longer, for example in summer or there is no cloud cover, they forage for food later in the day. When the sun is darker, earlier, they search for food sooner in the day. It was believed that all insects fed according to circadian rhythms, but this does not seem to be the case.

Activity in the nest was affected by cloud cover. But outside activity that involves feeding occurs at twilight. Obviously, they are feeding during these short intervals to avoid predators. Most animals that eat ants would be inactive at twilight.

Tests were done at ANU in Canberra. Bull ants were put in containers where diffused light was altered. It was found they only fed when the light was set at a particularly low level. Evolution does take some winding paths. This shows though that evolution develops in a rational way.
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