Component 2 - Plant reproduction

Question 1

What are the four sets of modified leaves in flowers?

Answer 1

Sepals, petals, stamens and carpels

Question 2

What is the swollen end of the stem called and its function?

Answer 2

The receptacle
Provides structural support

Question 3

Label the structure of a flower

Answer 3

Question 4

What is the petal and its function?

Answer 4

The inner whorl of a flower, often colourful to attract insects

Question 5

What is meant by the corolla?

Answer 5

A collective term for all the petals

Question 6

What are sepals and its function?

Answer 6

The outermost ring of a flower, usually green
Protect the flower when it is in bud

Question 7

What is meant by the calyx?

Answer 7

A collective term for all the sepals

Question 8

What is the receptacle and its function?

Answer 8

The basal portion of a flower to which all floral parts are attached

Question 9

What does the male reproductive structure of a flower consist of?

Answer 9

The stamen:
The anther
The filament

Question 10

What is the function of the anther?

Answer 10

The part in which pollen is produced (usually meiosis) usually consisting of 4 pollen sacs. They eventually split to release the pollen

Question 11

What is the function of the filament?

Answer 11

Contains vascular tissue that supports the anther
It also transports sucrose and amino acids necessary for the formation of the pollen grains

Question 12

What does the female reproductive structure of a flower consist of?

Answer 12

The carpel:
Stigma
Style
Ovary

Question 13

What is the function of the stigma?

Answer 13

Receives the pollen from the anther

Question 14

What is the function of the style?

Answer 14

Holds the stigma to receive the pollen
Pollen produces a tube which grows down through the style to the ovule

Question 15

What is the function of the ovary?

Answer 15

Contains the ovules and develops into the fruit
Meiosis occurs in the ovary to produce haploid ovules

Question 16

Where is the ovule made and what is it’s function?

Answer 16

Made inside the ovary and contains an egg cell formed by a process involving meiosis
After fertilisation, the ovules eventually form the seeds
Site of meiosis

Question 17

Describe the structure of the anther

Answer 17

A cross section of the developing anther displays four chambers called pollen sacs
Each sac is enclosed by protective epidermis fibrous layer
Inside the fibrous layer is the tapetum (food store and provide energy for divisions)

Question 18

Describe the development of a pollen grain within the pollen sac of an anther

Answer 18

Each pollen sac is filled with large numbers of diploid pollen mother cells
These cells are called microspores
Each one of these microspores become a pollen grain
Inside the pollen grain the haploid nucleus undergoes mitosis to produce two nuclei, a generative nucleus and a tube nucleus

Question 19

What happens during ovule production?

Answer 19

A mother diploid cell divides by meiosis to form 4 haploid cells (megaspores)
3 of these cells degenerate and one megaspore survives

Question 20

What happens to the surviving megaspore which does not degenerate?

Answer 20

Undergoes three mitotic divisions
Eight haploid nuclei are now present
3 antipodal cells at the top
2 polar nuclei in the center which fuse to produce the diploid polar nucleus
2 synergids either side of the haploid female gamete next to the micropyle

Question 21

Describe the ovule structure

Answer 21

Each ovary contains one or more ovules
The integuments are the 2 walls of the ovule
There is a small opening in the walls called a micropyle (where pollen tube enters)
The nucellus contains cells that provide nutrients for growth

Question 22

What is pollination?

Answer 22

The transfer of pollen from the anther to the stigma

Question 23

What are insect pollinated flowers and how are they adapted?

Answer 23

Adapted to attract insects to them to enable transfer of pollen
Adaptations such as:
Pollen has barbs for hooking onto insect fur
Nectar and scent present
Anther positioned to rub pollen onto insects
Brightly coloured petals
Sticky stigma to collect pollen

Question 24

What are wind pollinated flowers and how are they adapted?

Answer 24

Rely on wind to be pollinated
Adaptations:
Pollen grains are very small and light (large numbers)
Anthers are exposed to the wind so that pollen can easily be blown away
Stigma are feathery to catch pollen carried on wind
Petals are small and green as there is no need to attract insects
No scent or nectary

Question 25

What is cross pollination and how does it help them survive?

Answer 25

When pollen travels from one flower to a different flower Desirable in plants as it promotes variation

Question 26

What is self-pollination? Name some +ves and -ves

Answer 26

Occurs when pollen falls from the anther onto the stigma of the same flower Disadvantages: Self-pollination is not desirable - reduces genetic variation Also a greater chance of two undesirable recessive alleles being brought together Advantages: It can preserve good genomes which may be suited to a stable environment

Question 27

How do flowers prevent self-pollination?

Answer 27

Having stigma above stamen so pollen cannot fall onto stigma By having stamen and stigma mature at different times

Question 28

What are some ways to encourage cross pollination?

Answer 28

Genetic incompatibility - pollen cannot germinate on the stigma of the flower which produced it Male and female flowers on the same plant - maize Separate male and female plants - holly

Question 30

Describe the whole process of fertilisation

Answer 30

On the stigma of a plant of the same species, the stigma produces a sugar solution in which pollen grain germinates into pollen tube Pollen tube secrets hydrolase enzymes as it grows, digesting its way through the tissue of the style, gaining nutrients Pollen tube grows down style following a gradient of chemoattractants Behind tube nucleus, the generative nucleus divides by mitosis to produce two male haploid nuclei at tip of pollen tube (3 now) When pollen tube reaches ovary, it enters the ovule through the micropyle. The tube nucleus disintegrates and the tip of the pollen tube bursts. Two male gametes are released into embryo sac One male gamete fuses with egg nucleus to form a diploid zygote Other male gamete fuses with both polar nuclei to form a triploid endosperm nucleus at the centre of the embryo sac

Question 31

What occurs after fertilisation?

Answer 31

Petals, stamen and sepals fall of Fertilised ovule turns into a seed Fertilised egg divides by mitosis to become embryo Ovary develops into the fruit The integuments become the testa, which still contains the micropyle as a pore

Question 32

What is the embryo?

Answer 32

Essential living part of seed Consists of a radicle, gives rise to the root And a plumule, the growing part of a young shoot

Question 33

What is the food-store?

Answer 33

Reserve of food which supplies the embryo and growing plant until it is able to make its own good Food-store may be in the cotyledons or in endosperm

Question 34

What is the testa/seed-coat?

Answer 34

Tough protective outer covering the seed Often has outgrowths which help in dispersal of seed

Question 35

What are the two types of seed in which flowering plants are divided into?

Answer 35

Monocotyledons - only one cotyledon Dicotyledons - they have 2 cotyledons

Question 37

What is the example of a dicot fruit and what are some of the properties?

Answer 37

Broad bean Ovary wall of a bean is the bean pod

Question 38

What are the 4 main ways in which seeds can be dispersed?

Answer 38

Wind Water Mechanical Animals

Question 39

What are the conditions needed for the germination of Vicia faba?

Answer 39

Water - nutrients in the dry tissue of the seed need to be rehydrated - also cracks the seed coat so roots can grow out and allow hydrolytic enzymes to work Oxygen - aerobic respiration is very important for germination as so much ATP is required for metabolism and growth Temperature - the optimum temperature for germination is the optimum for the enzymes involved in the process of germination (depending on the time of year)

Question 40

How does gibberellin aid seed germination?

Answer 40

Water is imbibed through the micropyle Cotyledons well, testa splits open to allow entry of oxygen for aerobic respiration Rehydration activated a gene in the embryo that coded for gibberellin synthesis The gibberellin diffuses into the aleurone layer which contains protein It induces the synthesis of hydrolytic enzymes The amylase produced breaks down starch in the endosperm into maltose The maltose diffuses to the embryo where it is used in aerobic respiration and growth of the radicle and plumule

Question 41

Add numbers 1-5 of the order in which this process occurs

Answer 41