Seed Dispersal8SCIENCE Thurs. March 24, 2011

Review: Seed Plants

• What are the two types of seed plants?– Gymnosperms– Angiosperms

• What is the difference?– Gymnosperms have cones– Angiosperms rely on pollination

• Today we will learn about how seeds formed in gymnosperms or angiosperms are dispersed (spread)

Seed Dispersal

• Seeds need to get from where they are formed to the ground to grow into a new plant

• How do seeds get to the ground?– Gravity

• What abiotic/biotic factors help to spread seeds?– Animals– Water – Wind

Animal dispersal

• Some seeds are eaten in fruits and dispersed as animals move around

• ‘Hitchhiking’– Attaching to animal fur/skin/clothing can help to

disperse seeds• Ex: apple seeds, burs

Water dispersal• Rain may cause seeds to fall out of a fruit or

cone• Rivers/oceans may carry seeds to new

locations– Some seeds float• Ex: Coconut palm seed

Wind dispersal• Some seeds have special structures that allow

them to be carried by the wind• If seeds are very small they may be carried far

on the windEx. Dandelion seeds

How does the seed structure relate to how it is dispersed?