Transcript Lesson Overview

Lesson Overview
24.2 Fruits and Seeds
Lesson Overview
Fruits and Seeds
Seed and Fruit Development
• Once fertilization is complete, nutrients
flow into the flower tissue and support the
development of the growing embryo
within the seed
• A fruit is a matured angiosperm ovary,
usually containing seeds.
Lesson Overview
Fruits and Seeds
Seed and Fruit Development
• The term fruit applies to the
sweet things we usually think
of as fruits, such as apples
and strawberries.
• However, foods such as peas,
corn, rice, and tomatoes,
which we commonly call
vegetables, are also “fruits”
Lesson Overview
Fruits and Seeds
Seed and Fruit Development
• The ovary wall surrounding a fruit may be
fleshy, as it is in grapes and tomatoes, or
tough and dry, like the shell that surrounds
peanuts. (The peanuts themselves are the
seeds.)
Lesson Overview
Fruits and Seeds
Dispersal by Animals
• The seeds encased in sweet, fleshy fruits,
are often eaten by animals.
• The seeds are covered with tough
coatings, allowing them to pass through an
animal’s digestive system unharmed.
Lesson Overview
Fruits and Seeds
Dispersal by Animals
• The seeds then sprout in the
feces eliminated from the animal.
• These fruits provide nutrition for
the animal and also help the plant
disperse its seeds—often to
areas where there is less
competition with the parent
plants.
Lesson Overview
Fruits and Seeds
Dispersal by Animals
• Animals also disperse dry
fruits, but not by eating them.
• Dry fruits have burrs or hooks
that catch in an animal’s fur,
enabling them to be carried
many miles from the parent
plant.
Lesson Overview
Fruits and Seeds
Dispersal by Wind and Water
• Seeds dispersed by wind or water are
typically contained in lightweight fruits that
allow them to be carried in the air or in
buoyant fruits that allow them to float on
the surface of the water.
Lesson Overview
Fruits and Seeds
Dispersal by Wind and Water
• Dandelion seed = dry fruit that
has a parachute-like structure,
allowing the seed to glide
considerable distances away
from the parent plant
• Coconut fruits = buoyant
enough to float in seawater for
many weeks, enabling the
seeds to reach and colonize
even remote islands
Lesson Overview
Fruits and Seeds
Seed Dormancy and Germination
• Dormancy = a period during which the embryo is
alive but not growing
o Many seeds will not grow when they first mature.
o Environmental factors such as temperature and
moisture can cause a seed to end dormancy and
germinate.
• Germination = the resumption of growth of the
plant embryo
Lesson Overview
Fruits and Seeds
Advantages of Dormancy
• Allow for long-distance dispersal
• Seeds germinate under ideal growth conditions
• Sometimes, only extreme environmental
conditions (hot/cold) can end seed dormancy.
Lesson Overview
Fruits and Seeds
Advantages of Dormancy
• Some pine trees, for example,
produce seeds in cones that
remain sealed until the high
temperatures generated by forest
fires cause the cones to open.
• The high temperature both
activates and releases the seeds,
allowing the plants to reclaim the
forest quickly after a fire.