Early horses such as hyracotherium , which lived 55 million years ago, did have multiple toes, but they were much smaller animals. For taller animals ,excess weight at the end of their legs has a much bigger impact on their speed A recent study at harvard university, the USA, found that one broad hoof is almost as strong as multiple smaller toes , but much lighter . Natural selection has gradually discarded the horse's side toes and widened the middle one to increase running speed
•° WHY DO DOGS EAT GRASS?
A 2008 study found that 68% of dogs regularly eat grass but only 22% of them are sick afterwards, so it doesn't seem to be because the dog is ill . Wolves also eat grass, and it may be that this helps to purge intestines of parasites . Dog may have inherited this ancestral behaviour even though most pets are regularly dewormed .
•° WHY DO BEAVERS BUILD DAMS?
Dam-building is synonymous with beavers, the ultimate aquatic engineers . Using branches from trees they have felled , these large rodents dam lakes to create moat -like ponds of still water where they construct island known as ' conical lodges' out of timber , mud and rocks. The body of water surrounding the lodges provides protection from predators - resident beavers enter and exit their sophisticated homes incognito via water-filled tunnels leading from the lodges o the pond. The largest lodge, found in Alberta, Canada , measures over 500m in Length-though , contrary to a widely circulated myth , it is not visible from space! In deep or fast -moving water areas , beavers simply excavate into river banks and set up home there instead .
•° WHY DO DOGS WAG THEIR TAILS?
Dog 'talk' with their tails . The position of the tail can tell us a lot about how dog is feeling ; human low suggests fear and submission. Whereas held high is a sing of dominance and arousal . A wagging tail often conveys happiness and excitement , but neuroscience at the university of Trento in Italy have found that the speed and direction of wag is important in ascertaining if the dog is either negatively ( slow and to the left) or positively (fast and to the right) stimulation.
•° WHERE DOSE THE NITROGEN IN THE AIR COME FROM
Nitrogen makes up 78% of the air we breathe , and it's thought that most of it was initially trapped in the chunks of primordial rubble that formed the earth . When they smashed together , they coalesced and their nitrogen content has been seeping out along the molten cracks in the plants 's crust ever since . Nitrogen can only be used by living organisms after it has been 'fixed' into more reactive compounds such as ammonia or oxides of nitrogen . Nitrogen fixation is carried out by bacteria , algae and human activity , and onec organisms have benefited from it , some of the nitrogen compound break down and go back into the atmosphere as nitrogen gas . Along with top-ups from volcania eruptions , the 'nitrogen cycle' has kept the level pretty constant for at least 100 million years.
•° CAN A TREE GROW IN SPACE ?
Experiments on the ISS have shown that young sqruce tree seedlings do grow in microgravity , but they don't look quite the same . The seedling grow faster , and the pine needles don't point downward so much . DNA analysis shows that several plant genes are more active in space, but we're still waiting to find out the long -term effects on larger plants
•° IS IT POSSIBLE FOR CHICKENS TO LAY EGGS IN SPACE?
Only one bird has ever actually laid an egg in space . A quail aboard the russian soyuz TM- 10 spaceraft laid an egg while travelling to the mir space satation in 1990. It seems likely that other birds would be able to physically lay eggs in zero-g , but successfully including those eggs in much harder . experiments with both quail and chicken eggs in space show much higher rates of birth defects in the bird embryos.
•° WHY DO ANTS WALK IN A LINE?
Ants are highly social insects , thriving in colonies of millions of individuals that work as a team . Good communication skills lie at the heart of their success . They rely heavily on chemical scents , called 'Pheromones ' , information - form the location of food sources and nest sites , to the presence of predators . Each ant species has its own chemical vocabulary of up to 20 different pheromones that can be secreted to form specific scent trails . The tips of their antennae translate the chemical ' word' , thereby guiding the ants , in a line , to or from the desired destination .