23/02/2017
Life Science - Grade 11
SIGNIFICANCE OF SEEDS ESSAY
Write an essay in which you discuss why
seeds have made the spermatophytes the
most successful plants on Earth. Discuss
the importance of seeds as a food source
and how seed banks have helped to
maintain biodiversity of Earth.
Facts: 17
Synthesis: 3
WHY SEEDS HAVE MADE THE
SPERMATOPHYTES THE MOST
SUCCESSFUL
• The seeds can remain dormant (inactive
but alive) and can survive harsh weather
conditions for a very long time
• The seed becomes active when the
conditions are favourable for germination
• The testa and cotyledons protect the
embryo during the early stages of
development
• The cotyledons contain stored food to
nourish the embryo in the early stages of
development until the seedling (young
plant) can photosynthesis for itself
• Dispersal is significant because the
seeds are spread away from the parent
plant and from each other, which reduces
competition
• The seed is a product of sexual
reproduction and therefore every seed is
genetically different, which increases its
chances of survival in changing environ
mental conditions
THE IMPORTANCE OF SEEDS AS A FOOD
SOURCE
• Seeds, which develop from fertilized
ovules, are a valuable source of food for
humans and animals
• Seeds that are cultivated and harvested
for food for humans include rice, coffee,
cacao, peas, soya beans and maize
(mealies)
• Some of these form the staple diet, eg
rice, mealies, potatoes, wheat of people
om different countries
• When the crops fail, because of drought
or flooding, this often causes starvation
and death in a population, especially in
poorer countries
SEED BANKS AND BIODIVERSITY
• A seed bank is a facility to store seeds
of different crop plants and wild plants,
so that biodiversity can be maintained
• The reason for maintaining a seed back
include: the crop could be wiped out if
attacked by a disease, eg especially if all
the plants are of the same variety
• In a seed back, samples of all the
variations of a crop are preserved so the
hardier the crop that is resistant to
disease may be grown
• A seed bank also preserves unusual and
rare crop varieties that are not
commercially farmed, to maintain
biodiversity
• There are approximated 150 crops that
make up the majority of the food grown
and consumed by humans
• Farmers cultivate crops that will
increase desirable traits (eg drought
resistance) at the expense of genetic
variation
• The crops with these desirable traits are
in**ed to maintain only the desirable
traits, which leads to loss of genetic
variation
• The genetic variety of food crops needs
to be maintained to safeguard food
security
LIFE SCIENCE – GRADE 11
