Question

Discuss the order in which seed dispersal mechanisms could have evolved. Which do you think was most effective in which era and which is most effective today? Give reasons for your hypothesis.

Answer 1

In the evolution of plants the first plants that lived on land needed to be by the water. Their 'seeds' were spores that needed to swim through a film of water in order for fertilization to occur. These were primitive plants such as mosses and ferns and they are limited in where they can grow since they need to be in moist environments.

The next important type of plant was the gymnosperm. Their seed dispersal mechanism is pollen which is transported by the wind so water was no longer needed. Gymnosperm means naked seed so their seeds were not surrounded by a fleshy fruit, just a hard seed coat which protected the embryo. Therefore they were not attractive to animals.

Finally, the most successful plants are the Angiosperms, the flowering plants, which are the majority of the plants around today. Their pollen is dispersed by wind and well as insect pollinators who are attracted to the flowers. Once the seed is fertilized it develops a fleshy fruit which attracts animals to eat it. Once the animals eat the fruit they poop out the seed. Therefore the seed can be dispersed farther distances by animals. When the animals poop out the seed this essentially proves fertilizer for the seed and the possibly the right conditions for germination.