1. Plants have developed various mechanisms to disperse seeds away from the parent plant including wind, animal, water, and mechanical dispersal. 2. Wind dispersal uses light seeds with wings or hairs to catch wind currents. Animal dispersal relies on fruit storing food so animals eat and disperse the seeds through their digestive tracts. Water dispersal allows fruits to float so seeds can drift long distances in water. Mechanical dispersal uses dry fruits that eject seeds explosively when opening. 3. These dispersal mechanisms ensure seeds are spread to new habitats with less competition around the parent plant to support survival of the plant species.

1. FRUIT AND SEED DISPERSAL
http://en.wikipedia.org/wiki/Fruit
http://www.school.net.th/library/create-web
/10000/science/10000-6605/pic1.jpeg
http://waynesword.palomar.edu/plfeb99
.htm#parachutes
http://wildlifeofhawaii.com/flowers/category/view-
plants/hawaiian-fruit-or-cones/
INTRODUCTION
ANIMAL
DISPERSAL
WIND
DISPERSAL
MECHANICAL
DISPERSAL
WATER
DISPERSAL
SUMMARY
MODULE 4 UNIT 13 LESSON 5
MENU

2. X
INTRODUCTION
 Plants need to find new habitats in
which to grow their new generation, in
order to avoid competition with each
other, especially between parents and
offspring, for all the necessities of life. In
this way, the new generation is able to
continue the life cycle of the plant that
produced it/them.
Dispersal enables this to happen!
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3. X
OBJECTIVES
When you finish, you should be able to:
 explain the need for/importance of
seed dispersal.
 list the main agents of dispersal.
 describe the structural modifications of
fruits to facilitate various methods of
seed dispersal.
(Source of pictures >> http://waynesword.palomar.edu/index.htm )
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4. X
WHY SHOULD SEEDS BE DISPERSED?
 A seed contains an embryo in which is
all of the genetic information needed
for it to develop into an entire plant.
 If it is to give rise to the next generation
of its species, it must somehow get out
of the protective casing – the fruit – and
find a suitable habitat, e.g. away from
its parent plants, in which to grow and
develop. Each fruit is structured to
ensure dispersal of its seed/s.
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5. X
THINK AND TELL:
www.tntisland.com/fruits.html
Both fruits have a fleshy, food-storing pericarp that
smells and tastes good and is attractive to animals
as food, so they eat the fruit wall and discard the
seed, thus helping with its dispersal.
CHECK
A mango and an avocado pear have a similar structure
that adapts them to disperse their seed in a similar way.
What is this similarity?
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6. X
THINK AND TELL:
Talk about these different fruits below. Are their seeds
dispersed in the same way? Why do you say so?
http://lh4.ggpht.com/_6LWjP0sZ22w?SXig-27Qbvl/AAAAAAAADGE/nPr1YccAPo8/S
CHECK
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7. X
FEEDBACK
The seeds from the two different fruits would be
dispersed in different ways. The fruit on the left has
fine hairs, so is likely to be blown from place to place
by wind.
The other fruits (right) have bright red, food-storing
walls, likely to attract birds and other animals who
would eat them and either discard the seeds or pass
them out unharmed in their faeces.
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8. X
THINK AND TELL:
Look at how buoyant in sea water
these seeds of the Asian Coral tree
are! They belong to a group that
we call ‘drift seeds’.
How do you think they are
dispersed?
By water.
The chart (next slide) shows
various seed dispersal
methods.
Discuss it with your teacher.
CHECK
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9. X
EXAMPLES OF DISPERSAL METHODS
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10. X
DIAGRAM OF THE PARTS OF A ‘TYPICAL’,
SIMPLE FLESHY FRUIT
The wall of various fruits become modified to enable
the fruit to carry out seed dispersal.
Pericarp or
fruit wall
http://academic.kellogg.edu/herbrandsonc/bio111/seeds_fruits_flowers.htm
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11. X
A. DISPERSED BY ANIMALS
1. Discuss the structural
adaptations for dispersal of
the seed/s shown by the
fruits on the following slides.
2. Examine actual samples
similar to those in the slides
and discuss the
adaptations with your
teacher.
http://www.picturesof.net/pages/100313-133371-955053.html
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12. X
STRUCTURAL AIDS TO DISPERSAL BY ANIMALS
1. The outer pericarp (skin) may develop
bright colours (apples, Tomatoes, guavas)
and distinct odours, both of which serve
to attract various animals looking for food.
http://www.tradewindsfruit.com/guava.htm
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13. X
STRUCTURAL AIDS TO DISPERSAL BY ANIMALS
2. The middle fruit-wall layer may become
fleshy with stored foods and changes colour
when ripe.
For more information, click open this site: http://jbworld.jbs.st-
louis.mo.us/science/resources/flower/fruit1.html
www.tntisland.com/fruits.html
Paw-paw has a
sweet (sugars),
succulent, edible
pericarp with small
seeds in the centre.
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14. X
STRUCTURAL AIDS TO DISPERSAL BY ANIMALS
Citrus fruits e.g. orange, have juice-filled hairs
http://visual.merriam-webster.com/food-kitchen/food/fruits/citrus-fruits_1.php
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15. X
STRUCTURAL AIDS TO DISPERSAL BY ANIMALS
Some fruits store nutrients other than sugars. Their
seeds are very small and abundant. The whole fruit
with its seeds are often eaten as ‘vegetables’ and
seeds defaecated. L – R: Egg plant, Tomato, Pepper
http://www.fotosearch.com/goodsh
oot/fruits-vegetables/GSH126/2/
http://www.freeclipartpictures.com/clipart/
food77.htm
http://www.fotosearch.com/GSH126/gs016078/
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16. X
ADAPTATIONS FOR DISPERSAL
Brightly coloured wall of Cherries (Left) attract
animals who eat the fruits and seeds.
Undigested Cherry ‘pits’ (seeds with hard
testa) pass out in animal droppings (Right).
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17. X
STRUCTURAL AIDS TO DISPERSAL BY ANIMALS
17
Birds eat fleshy fruit and distribute
the seeds with their waste. The hard
testa protects the embryo in the
seed while it is inside the animal.
Cerasee fruit – bitter-
sweet, seedy pulp is
eaten by birds when
the ripe fruit splits open.
http://mrcsclass.com/mcdougaltext/397_404.pdf

18. X
DISPERSED BY ANIMALS
Most herbivores cannot crack
the hard Calabash shell.
But, horses use their mouth
to break them open, then
they eat the sweet, pulpy
mass of seeds and disperse
seeds in their dung.
http://waynesword.palomar.edu/ww0503.htm
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19. X
STRUCTURAL AIDS TO DISPERSAL BY ANIMALS
Seeds (peanuts (Left), corn grains, sun-flower and
pumpkin) may also store nutrients in their
cotyledons or endosperm which attract animals
as a food source.
19
http://waynesword.palomar.edu/termfr1.htm#baobab
http://www.featurepics.com/photos-images/corn+grains.htm

20. X
STRUCTURAL AIDS TO DISPERSAL BY ANIMALS
http://www.bulkfoods.com/nuts.asp
Any nuts store fats/oils, starches and proteins and attract not
just humans but many insects and rodents who eat them and
help disperse them.
(L – R Cashew, pecans, almonds, brazil nuts)
(
Peas/beans store protein and can be
dispersed by humans.
http://visual.merriam-webster.com/food-kitchen/food/legumes/peas.php
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21. X
A sweet-tasting, fleshy layer may develop around
the seed (L –R pomegranate, guinep) which is
then sucked off and the seeds discarded
elsewhere.
http://jugalbandi.info/2009/07/mamoncillo-guinep-chenet/http://waynesword.palomar.edu/termfr4.htm
STRUCTURAL AIDS TO DISPERSAL BY ANIMALS
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22. X
STRUCTURAL AIDS TO DISPERSAL BY ANIMALS
The fleshy Cashew ‘apple’ is the swollen
succulent stalk/pedicel and base. The
‘nut’ is a dry fruit. Both parts can be
eaten.
22www.fao.org/.../vlibrary/ac306e/ac306e04.htm slog.thestranger.com/2008/04/new_fruit

23. X
STRUCTURAL AIDS TO DISPERSAL
 Ripe, food-storing fruits/vegetables with seeds
are eaten by humans, cows, dogs, rats, various
insects, also birds, etc. The fruit wall or else the
seeds have a hard layer that protects the
seeds inside so that they are not damaged as
they pass through the animal’s gut.
 The seeds are passed out in faeces, often at
some distance from the plant from which the
ripe fruit came.
See the next two slides for other means of animal
dispersal of seeds.
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24. X
DISPERSED BY ANIMALS
3. Desmodium fruit breaks into little flattened
sections that stick to clothing e.g. socks, or to
an animal’s fur.
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25. X
DISPERSED BY ANIMALS
25
http://mrcsclass.com/mcdougaltext/397_404.pdf
4.The burrs in this
horse’s mane are
dry fruit that
contain seeds.

26. X
B. WIND DISPERSAL
Each fruit/seed has been modified in some way.
26
http://www.cas.vanderbilt.edu/bioimages/pages/fruit-
seed-dispersal.htm
Papery-thin winged
seeds (Jacaranda)
flutter and spin as
wind currents carry
them away.
Silky hairs on fruits
help them to be
blown in the wind.
Winged seeds
spin like helicopter
blades.

27. X
STRUCTURAL AIDS TO WIND DISPERSAL
In many fruits, the pericarp becomes dry
and hard and may grow hairs, hooks, wings
(e.g. Jacaranda, Left), prickles or other
extensions which aid dispersal or else
provide protection for the seeds while
the fruit is being dispersed.
http://jbworld.jbs.st-louis.mo.us/science/resources/flower/fruit3.html
http://www.classzone.com/books/ml_science_share/vis_
sim/dltm05_pg112_seed/dltm05_pg112_seed.html
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28. X
DID YOU KNOW?
‘Tumbleweeds’ are blown about by the
wind and scatter seeds as they move!
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29. X
C. MECHANICAL DISPERSAL
Dry, dehiscent pod is composed of one
carpel; splits open when mature along
two lines of weakness. Then the two
halves curl back, flicking out the seeds
that are inside in an explosive manner,
scattering them away from he plant.
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30. X
MECHANICAL DISPERSAL
http://visual.merriam-webster.com/plants-gardening/plants/fruits/dry-fruits_2.php
30

31. X
MECHANICAL DISPERSAL
Dry fruit that has two carpels separated
by a seed-bearing septum; splits open
releasing seeds.
31
http://visual.merriam-webster.com/plants-gardening/plants/fruits/dry-fruits_2.php

32. X
MECHANICAL DISPERSAL
Capsule -The carpels
were originally fused
together to form the
gynoecium.
The carpels separate
to expose the seeds
which can be flung
out of the capsule.
An example is ackee.
Flesh is eaten, seed
discarded, and so is
dispersed.
www.jamaica-beach-villa.com/ackee.htm
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33. X
MECHANICAL DISPERSAL
Sandbox flower (top, red) and exploding fruit.
seeddry fruit wall
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34. X
D. WATER DISPERSAL
 Coconut trees and
mangroves have their
natural habitat near
water.
 Their fruits/seeds are
water dispersed. To do
so, the fruits and seeds
must be adapted to be
light and buoyant and
must be able to drift in
water currents.
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35. X
WATER DISPERSAL
35
http://www2.estrellamount
ain.edu/faculty/farabee/bi
obk/BioBookflowersII.html
#Double Fertilization
Air is trapped
between the fibrous
coir and causes the
fruit to be bouyant,
so it can float in
water for long
distances. The hard
endocarp/shell
protects the seed
with its embryo
inside.

36. X
WATER DISPERSAL
Viviparous seedling of the red mangrove – has
germinated while still in the fruit that is
attached to the parent.
Note the elongated hypocotyl
or embryonic root. When the
seedling drops into water,
it floats with the root still
pointed downward. If it hits
soft mud, the tap root grows
in the soft mud and quickly
establishes the plant.
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37. X
DID YOU KNOW?
This map shows the distances over which
water-dispersed ‘drift seeds’ can travel!
http://waynesword.palomar.edu/pldec398.htm
37

38. X
WATER DISPERSAL
38
Drift fruits and seeds of Beach bean

39. X
DID YOU KNOW?
Many plants are killed off when a fire
becomes extremely fierce and hot (
high intensity), but some plants in the
Australian bush are very reliant on fire for
their seed to be dispersed. An example
is a plant called ‘Old Man Baksia’. This
plant is killed by fire but uses the fire to
trigger the seed dispersal mechanism.
39
http://www.zephyrus.co.uk/firedispersal.html

40. X
SUMMARY
1. Wind Dispersal
-- Small, light seeds with wings/hairs for mobility.
2. Animal Dispersal
 Fruit stores food so is eaten; seeds pass through
digestive tract unharmed or are seed/s
discarded.
 Fruits and seeds have hooks
that in catch in fur/hair, or clothing.
3. Water Dispersal
 Some fruits have trapped air so can float.
4. Mechanical Ejection of Seeds as fruit dries
and explodes open.
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http://www.zephyrus.co.uk/seeddispersal1.html

41. X
SUMMARY
1. All structural modifications of the fruit
wall and of physiological processes
are developed to ensure that the
seed/s are dispersed away from the
parent plant, to ensure survival of that
plant species.
2. Do the quiz at this website:
http://www.classzone.com/books/ml_science_share/
vis_sim/dltm05_pg112_seed/dltm05_pg112_seed.html
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