BIOLOGY

r o ject
P

NAME-
Disha Deshmukh
CLASS- XII ROLL NO-
SCHOOL- MIS INTERNATIONAL
SCHOOL
Topic
“To Study of
Dispersal of
Seeds by
Various
agencies”
 CERTIFICATE

This is to certify that Disha Sanket Deshmukh of class XII has

successfully completed her project on topic ‘To study of dispersal
of seeds by various agencies’ under the guidance of Mrs. Ashwini
Pandhare during the academic year 2024-25 as per the guidelines
issued by the CBSE

Teacher’s name : Student’s name:

_____________ __________

_________________
Principal’s Signature
(Ms. Monika Chhabra)
A big thank you to everyone who supported and aided me
during my project. Your contributions were invaluable.

I am extremely grateful to my Biology teacher

Ms. Ashwini Pandhare for their invaluable guidance,
supervision, and provision of essential project information.
Additionally, I extend my sincere appreciation to our
principal for affording me the opportunity to work on this
project.

With gratitude, I extend my heartfelt thanks to my parents,

friends, and team members whose unwavering support and
coordination have been pivotal to the success of this
project.
Sr.no Topic Pg.no Teacher ‘s sign
 Introduction-
About seed:
The seed is the part of a plant that grows from the ovules after
fertilisation. They're contained within the fruit that grows from the
fertilised ovary. Sexual reproduction produces seeds, which contain a
young embryo capable of growing into a new plant.
Structure of a Seed:
Although the anatomy of seeds from different plants may differ in many
ways, the underlying anatomy remains the same. The following are the
components of a typical seed:
1. Testa- Seed's outer coat that serves as a protective barrier for the
developing plant inside.
2. Micropyle- Little pore in the testa that's located on the opposite side
of the radical's tip. Before active germination, it allows water to
enter the embryo.
3. Hilum- A hilum is a scar created by the stalk that connected the
ovule to the ovary wall before it became a seed.
4. Cotyledon- This includes a lot of starch and serves as a food supply
for the developing embryo before germination in some plants; in
other plants, and endosperm serves in this role. There is just one
cotyledon in monocotyledons, but there are two in dicotyledons.
5. Radicle- The embryonic root will eventually develop into the plant's
major root. During germination, it is usually the first component of
the embryo to emerge from the seed.
6. Plumule- The embryonic shoot is known as a plumule. It appears as a
bud that will give rise to the shoot and the rest of the plant's
structures.
 7. Endosperm- In many plants, a distinct component called the
endosperm develops for starch storage. It can be found in both
maize and wheat.

Seed Dispersal:
The movement of the seed from one place to another is known as seed
dispersal. This movement generally occurs with the help of dispersal
vectors. Dispersal vectors can be biotic or abiotic components. Biotic
dispersal vectors include animals, bees, and other insects whereas abiotic
factors are wind and water.
Seed dispersal can be broadly classified into autochory and allochory.
Autochory refers to the dispersion of the diaspore without any help from
the external environment, whereas allochory refers to the dispersion of
seeds with the help of dispersal vectors.
Animals and birds disperse the seeds in different manners. Colourful fruits
attract animals and birds. When they eat these fruits only the pulpy part is
digested in their bodies and the seeds are excreted out by their systems in
the form of their dropping, which eventually gives birth to new plants.
Blackberry, cherry, tomato and apple seeds are usually dispersed in this way.

Types of Seed Dispersal

● Seed Dispersal by Wind

● Seed Dispersal by Water
● Seed Dispersal by Animals and Birds
● Seed Dispersal by Gravity
● Seed Dispersal by Explosion
● Dispersal by Animals:

Dispersal by the animal is termed as zoochory.Based on the way of carrying

the diaspore zoochory can be classified as endozoochory, epizoochory, and
synzoochory.
1. Endozoochory- It is the condition when seeds are carried within the
dispersal vectors, which are animals in this case.In this type seed is
generally inside the fruit, animals that perform dispersion eat the
fruit surrounding the seed and discard the seed at a distant location,
thus performing dispersion. Animal helps in plant survival by allowing
it to grow in various locations, thus both the species mutually
benefited from the seed dispersal by animals.
2. Epizoochory- It is the condition when an animal carries the diaspore
outside its body. This condition arises in the case of accidental
dispersion of the seed by animals. When animals or birds pass by the
seed some of the seed might get attached to the body of the animal
and move along with it, diaspore than generally falls at a distant
location from the parental plant.
3. Synzoochory- It is a condition when the diaspore seed has not
completely entered the alimentary canal of animals rather they carry
the seed in their mouth. Synzoochory is often seen in seed dispersal
by squirrels. It is also done by rodents and birds. Synzoochory has a
characteristic feature, the seed is generally a nut that is used as a
food source by the animals.

Diplochory is also considered as a type of synzoochory where it is

indirect or two-step dispersion by an animal, this occurs when the
 nut is the food source of more than one species. It is a highly
effective way of dispersion.

● Seed Dispersal by Water-

In this mode of seed dispersal, seeds float away from their parent plant in
rivers or ponds due to their light weight. Plants which grow near water
bodies usually rely on water to transport their seeds to different places. The
seeds of such plants are light in weight and thus float, or there may be fluff
that helps buoyancy.
This method of dispersal is mainly seen in those plants which are found in
water or nearby the water bodies like sea shores, lakes, ponds etc.
Characteristics of Seed Dispersal by Water:

There are some characteristic features of hydrochory they are as follows,

1. Diaspore must be lightweight and hollow

2. Diaspora can swim
3. They generally have long filaments
4. They generally do not produce nectar
5. They are not usually very colorful
6. They must have the property of hygrochasy, that is seed can
germinate in moist weather.
● Seed Dispersal by Wind-
This process of dispersal is mainly seen in those plants which bear
very light seeds. The seeds of the orchid plant, dandelions, swan
plants, cottonwood tree, hornbeam, ash, cattail, puya, willow herb,
are all examples of plants whose seed are dispersed by the wind.
● Seed Dispersal by Water-
In this method of seed dispersal, seeds float away from their parent
plant. These are mainly seen in those plant which lives in water or
nearby the water bodies like beaches, lakes, ponds etc. Coconut,
palm, mangroves, water lily, water mint, are a few examples of plants
whose seed are dispersed by the water.
● Seed Dispersal by Gravity-
Gravity is a force of attraction that exists among all the objects in
the universe. As the fruits from the tree fall on the ground due to the
force of attraction, they sometimes roll down to some smaller
distance, get buried in the soil after a few days and germinate into a
new plant. In certain cases, fruits which do not have very hard seed
coat may crack and open after falling down from a height, which
leads to a better dispersion of seeds.In some cases, the fallen fruit is
carried by other agents like water, wind, birds or animal and helps in
the dispersion of seeds.
Apples, Commelina, canna, coconuts, calabash, passion fruit are a
few examples of plants whose seeds are dispersed by Gravity – A
force of attraction.
● Seed Dispersal by Explosion-
Explosions in fruits literally refer to bursting with all its energy. In
this case, as the fruits get ripened, it shoots out its seeds into the
external environment. This type of seed dispersal is mainly seen in
those plants having pods.
Okra, Lupins, gorse, and broom are a few examples of plants whose
seeds are dispersed by Explosions. Pea and bean plants also have
pods and the seeds burst out when they ripen and pod has dried.
Examples of specific plants and how their seeds are dispersed-

Sr.no Plant species Seed/Fruit Seed Mechanism Ecological Impact

Image Characteris of
tics Dispersal
Dandelion Light seeds Wind Rapid colonization
1 (Taraxacum with catches of new areas, often
officinale) parachute- pappus and in disturbed soils
like pappus carries
seeds away
Maple (Acer Wing-like Samaras Spreads seeds
2 spp.) structures spin and across large areas,
(samaras) are carried aiding in
by wind biodiversity
Coconut Buoyant, Floats on Establishes on
3 (Cocos fibrous water until coastal areas and
nucifera) husk reaching a tropical islands
new shore
Lotus Buoyant, Floats on Spreads across
(Nelumbo fibrous water aquatic
4 nucifera) husk surface to environments,
new enhancing
locations biodiversity
Holly (Ilex Bright, Eaten by Mutualistic
5 spp.) attractive birds and relationship aiding
berries excreted seed dispersal and
elsewhere bird nutrition
Burdock Hooked Attach to Wide dispersal
(Arctium structures animal fur along animal paths
6 spp.) and are and in wildlife
carried habitats
away
Apple (Malus Heavy, falls Gravity Seeds may
domestica) from tree pulls fruit germinate near the
7 to the parent or be further
ground dispersed by
animals
Horse Large seeds Falls Secondary dispersal
Chestnut (conkers) directly by animals or water
8 (Aesculus under the
hippocastan parent tree
um)
Seed pods Seeds are Reduces
Touch-me-
burst open flung away competition among
not
9 from the seedlings by wide
(Impatiens
parent dispersal
spp.)
plant
Squirting Builds Seeds are Rapid colonization
Cucumber internal squirted of new areas
10 (Ecballium pressure out
elaterium) forcefully
 Conclusion-
Seed dispersal is a vital process for the survival and propagation of plant species.
The various methods of seed dispersal—wind, water, animals, gravity, and
explosive mechanisms—each play a crucial role in ensuring that seeds are spread
over wide areas. This dispersion reduces competition among seedlings and the
parent plant, enables plants to colonize new environments, and helps maintain
genetic diversity within plant populations.

Importance of Seed Dispersal:

1. Plant Biodiversity: By enabling seeds to travel to different locations,
seed dispersal helps in the establishment of plants in varied habitats,
contributing to overall plant biodiversity. Each method of dispersal is
adapted to specific environmental conditions, ensuring that plants
can thrive in diverse ecosystems.
2. Ecosystem Health: Seed dispersal supports ecosystem resilience by
promoting a variety of plant species within an area. Diverse plant
communities can better withstand environmental changes, pests,
and diseases. Moreover, plants form the basis of most food webs,
and their health directly impacts the broader ecosystem, including
animals and other organisms that depend on them.
Impact of Human Activities:
Human activities significantly influence seed dispersal processes, both
positively and negatively:
1. Habitat Destruction: Urbanization, deforestation, and agricultural
expansion can destroy habitats and disrupt natural seed dispersal
mechanisms. For example, the removal of animal species that
participate in zoochory can lead to reduced seed dispersal and lower
plant diversity.
2. Pollution: Pollution can affect the viability of seeds and the health of
dispersal agents. Air pollution can hinder wind dispersal, while water
pollution can reduce the effectiveness of hydrochory.
3. Climate Change: Changes in climate patterns can alter the
effectiveness of various seed dispersal methods. For instance, shifts
in wind patterns or water currents can impact where and how far
seeds are dispersed.
4. Conservation Efforts: On the positive side, conservation initiatives
that protect natural habitats and wildlife can support natural seed
dispersal processes. Reforestation and habitat restoration projects
often rely on understanding and leveraging seed dispersal
mechanisms to re-establish plant communities.
Summary:
Seed dispersal is fundamental to the survival of plant species and the health of
ecosystems. Understanding the various dispersal mechanisms and their ecological
roles highlights the importance of conserving natural habitats and mitigating the
adverse impacts of human activities. By protecting the processes that facilitate
seed dispersal, we can support biodiversity and the resilience of ecosystems for
future generations.
For successfully completing this project I had
taken the help of these websites-
www.google.com
www.wikipedia.com
Books- Class 12 Biology Labmaual
Biology Ncert Class 12
www.sciencedirect.com