D3.1 Reproduction (plants)

Question 1

Why are there different strategies for reproducing in plants?

Answer 1

Because plants cannot move.

Question 2

What is sexual reproduction known as in plants?

Answer 2

Flowering plants or angiosperms

Question 3

What is hermaphrodites?

Answer 3

Many plants are hermaphrodites with flowers that contain both male and female parts.

Question 4

How do plants sexually reproduce with two parents?

Answer 4

However, in some species, this is not the case and there are male and female flowers on the same plant (e.g. hazel) or on different plants, e.g. kiwi and papaya.

Question 5

What do ovule contain? And what happens when that is fertilized?

Answer 5

An ovule contains an ovum as well as a store of nutrients. Once the ovum is fertilised it becomes a seed.

Question 6

What is the male reproductive cells in plants?

Answer 6

The male reproductive cells are pollen which travel to the female reproductive part in the same plant, or in another plant, carried by wind or insects.

Question 7

What is pollination

Answer 7

Pollination is the transfer of pollen from the anthers of one flower to the stigma of another. Multiple pollen grains land on the stigma.

Question 8

What happens when pollen lands on the stigma?

Answer 8

The pollen grain then germinates and the pollen nuclei travel through a pollen tube down the style, the ovary , the ovule and finally the ovum where fertilization occurs, producing an embryo.

Question 9

How does the pollen enter the ovule?

Answer 9

They enter the ovule through a tiny opening called the micropyle.

Question 10

What is double fertilization?

Answer 10

There are two male nuclei, one will fuse with the ovum nucleus in the embryo sac, forming a diploid zygote. The other nucleus fuses with another nucleus of the ovum, triggering the formation of the food store for the developing embryo. This is called ‘double fertilization’ and is unique to flowering plants.

Question 11

Where are the different parts of the flower found?

Answer 11

The different parts of the flower are found in rings or whorls attached to the swollen tip of the stalk which is called the receptacle.Not all the parts of a flower are always present, e.g. tulips lack sepals. If all the parts are present the flower is called a complete flower, otherwise it is an incomplete flower.

Question 12

Do all flower have all parts? What are they called if they do?

Answer 12

Not all the parts of a flower are always present, e.g. tulips lack sepals. If all the parts are present the flower is called a complete flower, otherwise it is an incomplete flower.

Question 13

What is cross pollination?

Answer 13

Cross pollination is favourable to flowering plants. In this method, pollen from one flower is transferred to a different plant of the same species.

Question 14

Are insect pollination plants only for insects?

Answer 14

No, also hummingbirds and bats.

Question 15

How do plants reproduce successfully?

Answer 15

For plants to reproduce successfully a lot of pollen needs to be transferred from the anthers to the stigma of a flower of the same species. Plants use a variety of strategies for this to happen and increase their chances of successful fertilization.

Question 16

How is cross-pollination achieved?

Answer 16

Cross-pollination is achieved by:
* the stamen and stigma maturing at different times
* the stigma and anthers at different heights in the same flower
* separate male and female flowers e.g. kiwi and papaya
* Self-incompatibility mechanisms which prevent hermaphrodite flowers from producing zygotes if self-pollinated

Question 17

What do self-pollination and cross-pollination result in?

Answer 17

Self-pollination results in inbreeding.
Cross-pollination results in outbreeding

Question 18

Why is cross-pollination more advantageous?

Answer 18

Advantage: variation and some genomes more successful than others - evolutionary advantage if there is selection pressure due to e.g. changes in the environment.

Question 19

What are the disadvantages of cross-pollination?

Answer 19

Disadvantage: pollen needs to land on the stigma of flowers of the same species which depends on an element of chance, especially in wind-pollinated flowers AND reduces variation, increasing the chance that two undesirable recessive alleles come together.

Question 20

What occurs when fertilization is successful?

Answer 20

When fertilization is successful a number of changes occur in the flower. The external whorls (sepals, petals and stamens) drop off. Inside the ovule, the zygote divides by mitosis to form an embryo and the triploid cell develops into the endosperm.

Question 21

What happen to the ovule after fertilisation?

Answer 21

The wall of the ovule hardens and becomes the seed coat or testa which protects the developing embryo and the endosperm.

Question 22

What happens after fertilisation to the ovary?

Answer 22

The ovary swells and forms the fruit (pericarp). The water content of the seed decreases and the seed enters a dormancy period.

Question 23

What is seed dispersal?

Answer 23

the carrying of seeds away from the parent plant

Question 24

What is germination? And what is cell called until germination?

Answer 24

Germination of the seed is the development of the seed from the moment it starts to take up water and results in the emergence of the radicle. It can only happen when the conditions for germination are favourable. Until that moment the seed remains in DORMANCY.