REPRODUCTION IN PLANTS

Question 1

What are the advantages of asexual reproduction?

Answer 1

Only one parent is required.
Gamete fusion is unrequired.
All the beneficial qualities are passed onto the off spring.
Faster method of producing offspring as compared with sexual reproduction.
Since organisms are already in a suitable habitat, they can colonise the area rapidly.

Question 2

What is a disadvantages of asexual repro?

Answer 2

No genetic variation in the offspring. Hence species are not well adapted to changes in the environment.

Question 3

What are the advantages of sexual reproduction?

Answer 3

Offspring may inherit beneficial qualities from both parents.
There is better genetic variation in offspring, leading to a species that are better adapted to changes in the environment.
Provides means of survival of species in unfavourable conditions.

Question 4

What are the disadvantages of sexual reproduction?

Answer 4

1. 2 parents are required
2. Fusion of gametes is required
3. Slower method of producing offspring as compared with asexual reproduction.

Question 5

What does a complete flower consist of?

Answer 5

Pedicel
Receptacle
Sepals
Petals
Stamens
Carpels

Question 6

What are stamens consist of? What are the functions?

Answer 6

ANTHER- Consists of 2 lobes. Each lobe contains 2 pollen sacs. In the pollen sacs are the pollen grains. The anther produces pollen grains, when it is mature, it splits open to release the pollen grains
FILAMENT- stalk that holds the anther in a suitable position to disperse the protein

Question 7

What are pollen grains?

Answer 7

Pollen grains are produced by meiosis {haploid}. Each pollen grain contains a male gamete.

Question 8

What does the carpel consist of? What are the functions?

Answer 8

An ovary
Style above the ovary
one or more stigma

Question 9

What are the functions of the ovary, ovules, ovum?
(Plants)

Answer 9

The ovary is the structure that will develop into a fruit after fertilisation. It produces and protects one or more ovules.
The ovule is the structure that will develop into a seed after fertilisation. It produces a female gamete or ovum by meiosis. The ovum is therefore haploid. The ovule is attached to a region in the ovary called the placenta, by the stalk the funicle.

Question 10

What is the function of the stigma?

Answer 10

Swollen structure at the end of the style. It receives the pollen grains. The mature stigma secretes a sugary fluid that stimulate the pollen grains to germinate.

Question 11

What are the features favouring self pollination?

Answer 11

Flowers are bisexual with anthers and stigmas maturing at the same time.
The stigma is situated directly below the anthers
In certain plants with bisexual flowers, some flowers never open, thus only self pollination can occur in these flowers.

Question 12

What are the advantages of self pollination?

Answer 12

1. Only one parent plant is required
2. The offspring inherits genes from the parent plant thus favourable genes are more likely to be passed down.
3. It may not depend on external factors such as insects/wind for pollination.
4. Since the anthers are close to the stigmas of the same flower, there is a higher probability that pollination occurs as compared with cross pollination.
5. Less pollen and energy is wasted in self pollination as compared with cross pollination

Question 13

What are the disadvantages of self pollination?

Answer 13

1. Less genetic variation in the offspring as compared with cross-pollination. Species is less well adapted to changes in the environment.
2. The probability of harmful recessive allele is higher as compared to cross-polli
3. Continued self pollination may lead to the offspring becoming weaker, smaller and less resistant to diseases.

Question 14

What are the features favouring cross-pollination?

Answer 14

1. Dioecious plants (bear either male or female flowers, cannot undergo self pollination.)
2. In many plants with bisexual flowers, the anthers and stigmas may mature at different times.
3. The stigmas of plants with bisexual flowers may be situated some distance away from the anthers so self-pollination is unlikely.
4. OR SELF STERILITY

Question 15

What are the advantages of cross pollination?

Answer 15

Offspring produced may have inherited beneficial qualities from both parents.
More varieties of offspring are produced (greater genetic v. leads to higher chance of species surviving changes in environment)
Increased probability of offspring being heterozygous. Hence, the likelihood of harmful recessive alleles being expressed in offspring is lower as compared with self-pollination.
More viable seeds are produced. Such seeds are capable of surviving longer before germination.

Question 16

What are the disadvantages of cross pollination?

Answer 16

2 parent plants are required
It depends on external factors such as wind or insects 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 of pollination as compared with self pollination.
More energy and pollen are wasted as compared with self pollination.

Question 17

What characteristic of the clitoria flower petal helps in its insect pollination?

Answer 17

The petals has lines on it that guide insects to where the nectar is located- nectar guides

Question 18

What are the features of clitoria that benefit insect pollination?

Answer 18

The filaments of 9 stamens are fused along most of their length to form a trough, enclosing the carpel. Nectar secreted by the flower collects at the bottom, so only bees and butterflies with long proboscis can reach it.
The tenth stamen is free.

Question 19

What are the characteristics of insect pollinated flowers?

Answer 19

Flowers are usually large with brightly coloured petals to attract insects
Nectar is present
Flowers are fragrant or sweet smelling
Stigmas are usually small, compact and do not protrude out of the flower.
Pollen is fairly abundant, larger with rough surfacees so that they can readily cling to the body of insects.
Nectar guide may be present on petals to guide insects towards the nectar

Question 20

What is the characteristic of wind pollinated flowers?

Answer 20

Flowers are usually small and dull coloured without petals
Nectar is absent
Flowers are odourless
Stigmas are large, feathery and usually protrude out of the flower to provide a large surface area to trap pollen
Stamens have long pendulous filaments and protruding anthers. Pollen grains are easily shaken out from the anthers
Pollen is more abundant, Pollen grains have smooth surfaces and are tiny and light so they are easily blown about the wind.
Nectar guide absent.

Question 21

How does fertilisation take place in plants?

Answer 21

After pollination, the pollen grain germinates after it comes into contact with the stigma, in response to the sugary fluid secreted by mature stigma.
A pollen tube grows out from each pollen grain.
As the pollen tube grows, it secretes enzymes to digest the surrounding tissues of the stigma and style. Thus the pollen tube grows down the style into the ovary.
The pollen tube enters the ovule through an opening in the ovule wall (micropyle)
Within the ovule, the tip of the pollen tube absorbs sap and bursts, releasing 2 male gametes.
The nucleus one one male gamete fuses with the nucleus of the ovum to form the zygote. This is fertilisation.