5. Give reasons for the following.
a) Seeds of burdock have hook-like structures on them.
Answers
Answer:
Plants such as burdock have hooks to which the seed is attached. These hooks easily get caught in the fur of mammals as they pass by the plant. At some point the seed will fall, often a considerable distance from the parent. If conditions are right the seed will germinate and grow into a new plant.
burdock.jpg (225968 bytes) burdock_hook.jpg (146716 bytes)
Burdock Seed head.
Note the hooks.
A close up of one of the hooks, shown with the tip of a pencil.
Hooks are not the only way by which plant seeds are distributed. Many plants produce fruits which animals such as birds and mammals eat.
In the autumn blackberries are a common sight in British woodlands and hedgerows. The berries are eaten by birds such as blackbirds and pigeons. Mice, deer and even foxes eat also eat them.
The small hard seed is hidden inside the fruit and passes through the gut of the animal as it can not be digested. The seeds are therefore expelled in the droppings of the animal. Some seeds dispersed in this way cannot germinate unless they have passed through the digestive system of an animal.