Topic 16 (Reproduction in plants)

Question 1

What is asexual reproduction?

Answer 1

Asexual reproduction is the process that produces genetically identical offspring from one parent, without
the fusion of gametes (reproductive cells).

Question 2

What are some examples of asexual reproduction?

Answer 2

1. Stem tuber
2. Rhizome
3. Runner

Question 3

What are the advantages of asexual reproduction?

Answer 3

Advantages:
*Only one parent is required.
*Fusion of gametes is not required.
*All the beneficial qualities are passed on to
the offspring.
*This method of producing offspring is faster
than sexual reproduction.
*Since organisms are already in a suitable
habitat, they can colonize the area rapidly.

Question 4

What are the disadvantages of asexual reproduction?

Answer 4

Disadvantages:
There is no genetic variation in offspring. Hence,
species are not well adapted to changes in the
environment.

Question 5

What are the advantages of
asexual reproduction in plants?

Answer 5

Advantages:
*In the wild, when plants are dispersed to a new habitat, they can rapidly colonize the area.
*In crop production, several methods are used to propagate plants with desirable qualities.

Question 6

What are the disadvantages of
asexual reproduction in plants?

Answer 6

Disadvantages:
*In the wild and in crop production, it may be a disadvantage to have no genetic variation.
*Rapid colonization could lead to overcrowding and competition for light, water and nutrients.

Question 7

What is sexual reproduction?

Answer 7

Sexual reproduction is a process involving the fusion of two gametes to form a zygote . It produces genetically
dissimilar offspring.

Question 8

What are the advantages of sexual reproduction?

Answer 8

Advantages:
*Offspring may inherit beneficial qualities from
both parents.
*There is genetic variation in the offspring,
leading to species that are better adapted to
changes in the environment.

Question 9

What are the disadvantages of sexual reproduction?

Answer 9

Disadvantages:
*Two parents are required (except in plants
with bisexual flowers).
*Fusion of gametes is required.
*This method of producing offspring is slower
than asexual reproduction.

Question 10

What are the advantages of
sexual reproduction in plants?

Answer 10

Advantages:
In crop production, plants can be selectively bred to produce offspring with desirable qualities.
These plants may
*grow and mature faster, which reduces harvesting time;
*have resistance to diseases;
*result in higher yield of crop;
*have resistance to unfavorable environmental conditions, such as a rise in environmental
temperature or
*changes in soil pH.

Question 11

What are the disadvantages of
sexual reproduction in plants?

Answer 11

Disadvantages:
*Due to genetic variation, some offspring may be less well adapted to changes in the environment.
*The reproduction process is slower than asexual reproduction. It also has to depend on external
factors such as insects and wind for cross pollination.
*There will be wastage of pollen and energy. Pollen grains contain the male gametes that are
required for sexual reproduction. A large amount of pollen needs to be produced to offset the loss
of pollen.

Question 12

Compare asexual reproduction and sexual reproduction.

Answer 12

Asexual reproduction:
Does not involve the fusion of gametes
Only one parent required
Offspring are genetically identical
Relatively quicker method

Sexual reproduction:
Involves the fusion of a male gamete with a female gamete to form a zygote
Requires two parents (except for plants with bisexual flowers)
Offspring are genetically different
Slower method

Question 13

What is a complete flower?

Answer 13

A complete flower consists of a flower stalk sepals , petals , stamens and a carpel

Question 14

What is pollination?

Answer 14

Pollination is the transfer of pollen grains from the anther to the stigma.
*There are two types of pollination self pollination and cross pollination.

Question 15

What is self-pollination?

Answer 15

Self pollination is the transfer of pollen grains from the anther to the stigma of the same flower or of a
different flower on the same plant.

Question 16

What are the features favoring self pollination?

Answer 16

*Flowers are bisexual with anthers and stigmas
maturing at the same time.
*Stigma is situated directly below the anthers.
*In certain plants, some bisexual flowers never
open. Only self pollination can occur.

Question 17

What are the advantages of self-pollination?

Answer 17

Advantages:
*Only one parent plant is required.
*The offspring inherits its genes from the parent
plant. Hence, beneficial qualities are more likely to be passed on to the offspring.
*It does not depend on external factors such as insects or wind for pollination.
*Since the anthers are close to the stigmas of the
same flower, there is a higher probability that pollination will occur, as compared with cross-pollination.
*Less pollen and energy is wasted in self-pollination
as compared with cross-pollination.

Question 18

What are the disadvantages of self-pollination?

Answer 18

Disadvantages:
*Less genetic variation in the offspring as
compared with cross pollination. The
species is less well adapted to changes in
the environment.
*The probability of harmful recessive
alleles being expressed in the offspring is
higher as compared with cross
pollination.
*Continued self pollination may lead to the
offspring becoming weaker, smaller and
less resistant to diseases.

Question 19

What is cross-pollination?

Answer 19

Cross pollination is the transfer of pollen grains from one plant to the stigma of a flower in another plant of
the same species.

Question 20

What are the features favoring cross-pollination?

Answer 20

*Dioecious plants, such as papaya, bear either
male or female flowers.
*In many plants with bisexual flowers, the anthers
and the stigmas may mature at different times.
*The stigmas of plants with bisexual flowers may
be situated some distance away from the
anthers so that self pollination is unlikely to
occur.

Question 21

What are the advantages of cross-pollination?

Answer 21

Advantages:
*The offspring produced may inherit beneficial
qualities from both parents.
*More varieties of offspring can be produced,
that is, there is greater genetic variation (gene
combination from two parents).
*There is an increased probability of the
offspring being heterozygous.
*More viable seeds are produced. Such seeds
are capable of surviving longer, before
germination.

Question 22

What are the disadvantages of cross-pollination?

Answer 22

*Two parent plants are required.
*It depends on external factors such as insects
or wind for pollination.
*Since the pollen grains have to be transferred
from the anther of one plant to the stigma of
another plant, there is a lower probability that
pollination will occur, as compared with self-pollination.
*More energy and pollen are wasted as
compared with self-pollination.

Question 23

What are the differences between insect-pollinated and wind-pollinated flowers? (Flowers, nectar, and scent)

Answer 23

INSECT-POLLINATED:-
Petals: Flowers are usually large with brightly
colored petals to attract insects.
Nectar: Nectar is present.
Scent: Flowers are fragrant or sweet
smelling.

WIND-POLLINATED:-
Petals: Flowers are usually small and dull
colored, without petals.
Nectar: Nectar is absent.
Scent: Flowers are odorless .

Question 24

What are the difference between insect-pollinated
and wind-pollinated flowers? (Stigma, stamen, pollen, and nectar guide)

Answer 24

INSECT-POLLINATED:-
Stigma: Stigmas are usually small and compact, and
do not protrude out of the flower.
Stamen: Stamens are not pendulous and usually do
not protrude out of the flower.
Pollen: Pollen is fairly abundant. Pollen grains are
usually larger with rough surfaces so that
they can readily cling onto the body of
insects.
Nectar guide: Nectar guide may be present on the petals
to guide insects towards the nectar.

WIND-POLLINATED:-
Stigma: Stigmas are large and feathery, and usually
protrude out of the flower to provide a large
surface area to trap pollen.
Stamen: Stamens have long pendulous filaments and
protruding anthers. Pollen grains are easily
shaken out from the anthers.
Pollen: Pollen is more abundant. Pollen grains have
smooth surfaces and are tiny and light so
that they are easily blown about by the wind.
Nectar guide: Nectar guide is absent.

Question 25

How does fertilisation take place?

Answer 25

1) The first step is pollination, where a pollen grain must land on the stigma.
2) Next, a pollen tube grows out of the pollen grain and down through the stigma and the style.
3) The pollen tube enters the ovary via a micropyle.
4) The male gamete then passes down the pollen tube and enters the ovary. This is when it fertilises the female gamete cell (egg cell).
5) Once fertilised, the zygote (fertilised egg cell) develops into a seed, while the ovule wall becomes the seed coat, and the ovary becomes the fruit.

Question 26

What is fertilisation?

Answer 26

Fertilisation is the fusion of nucleus of male gamete with the nucleus of the female gamete to form a zygote.

Question 27

What happens after fertilisation?

Answer 27

*the ovary becomes the fruit;
*the ovule becomes the seed;
*the zygote becomes the embryo. The embryo consists of the embryonic shoot, the embryonic root and the cotyledons;
*the petals, the style and stigma, and the anthers wither and drop off.

Question 28

What are the conditions necessary for seeds to germinate?

Answer 28

Water - causes the seed to swell, and activates the enzymes required for growth.
Oxygen - required for aerobic respiration, which provides the energy needed for the plant to grow.
Warmth (suitable temperature) - increases the rate of enzyme activity, which in turn increases the rate of growth. However, very high temperatures can denature enzymes and so may slow or stop its growth.