Biology Unit 2: Meiosis + Flowers

Front 1

When is Meiosis involved?

Back 1

During:

1. Crossing Over

2. Production of Gametes.

Front 2

The pollen tube grows from the pollen grain to the micropyle. Suggest onestimulus, other than water, that causes the pollen tube to grow towards themicropyle.

Back 2

Chemical, air, gravity, light.

Front 3

The tip of the growing pollen tube releases digestive enzymes into the style.Suggest the role of these digestive enzymes in the growth of the pollen tube.

Back 3

1. idea of {breakdown / digestion / eq} of style ;2. (breaks down) protein / pectin / middlelamella

3. reference to hydrolysis /

4. easier for pollen tube to grow / reducedresistance

5. supplies {nutrients / named nutrient / energy}for (pollen tube) growth

Front 4

Give three roles of water in a plant other than for pollen tube growth.

Back 4

1. Photosynthesis.

2. Water as a solvent.

3. Water as a transport medium.

4. Role in structural support.

5. Involvement in hydrolysis.

6. Thermogredulation.

Front 5

In the second fertilisation, the other male gamete nucleus fuses with twopolar nuclei forming a triploid structure. Name the triploid structure formed

Back 5

Endosperm nucleus.

Front 6

Suggest the advantages to flowering plants of increased pollen tube growth.

Back 6

1. more likely to reach the ovule

2. fertilisation more likely to occur

3. idea of fertilisation in shorter time period

Front 7

Name the type of cell division required for asexual reproduction.

Back 7

Mitosis

Front 8

Describe and explain why asexual reproduction results in low genetic diversity.

Back 8

1. low genetic diversity is less different alleles in the gene pool.

2. (asexual reproduction leads to) all offspring being{genetically identical / clones / same genotype / samealleles

3. no meiosis/ no recombination of genetic material

4. idea of variation only possible as a result of mutation

Front 9

Explain the function of the pollen tube in fertilisation in flowering plants.

Back 9

1. idea of {forms a pathway/ grows down through thestyle

2. grows towards { ovary / ovule / micropyle / egg cell

3. reference to digestive enzymes;

4. transports {generative nucleus / haploid nuclei / malegametes /

5. fuses with embryo sac (membrane) / tip breaks downwhen it enters the micropyle / allows male nuclei toenter embryo sac

Front 10

Describe what happens to each of these two male nuclei.

Back 10

1. One (nucleus) fuses with the {egg nucleus / femalegamete }

2. one (nucleus) fuses with the (two) polar nuclei

Front 11

Explain how Meiosis gives rise to genetic variation in gametes.

Back 11

1. Both independent /random assortment and {crossing-over/chiasma(ta)

2. Independent assortment gives riseto new / different combinations of (paternal andmaternal) chromosomes

3. crossing over involves swapping of{sections / eq} of {chromatids/chromosomes} ;

Front 12

Describe the process of fertilisation that takes place in flowering plants.

Back 12

1. Idea that generative nucleus dividesto form two male gametes

2. by mitosis

3. pollen tube fuses with embryo sac

4. reference to double fertilisation

5. (one) male { gamete / nucleus }fuses with egg (cell) nucleus

6. to produce diploid zygote

7. other male nucleus fuses with twopolar nuclei

8. to produce triploid endosperm

Front 13

Explain how meiosis produces genetic variation in gametes.

Back 13

1. Independent /random } assortment and {crossing-over/chiasma(ta) }

2. Independent assortment gives riseto {new / different / eq}combinations of (paternal andmaternal) chromosomes

3. crossing over involves swapping of{sections / eq} of {chromatids/chromosomes

Front 14

Explain the importance of meiosis in the production of gametes.

Back 14

1. Halves the chromosome number

2. to produce a haploid nucleus

3. so that at fertilisation the {fullcomplement / diploid number ofchromosomes is restored / eq 4. allows genetic variation (in gametes)

5. through independent assortment /

6. through crossing over

Front 15

Explain how the pollen tubes grow through the style of the flower.

Back 15

1. idea of enzymes being {produced / released / secreted

2. idea of these enzymes being used to {digest / break down /eq} (tissues of style)

3. idea of forming a pathway

Front 16

Describe how the structure of a pollen grain differs from that of a sperm cell.

Back 16

1. pollen grain does not possess flagellum

2. pollen grain does not have an acrosome

3. idea of {more / 2 / 3} nuclei in pollen grain

4. idea of difference in outer boundary e.g. exine in pollengrains

Front 17

Explain how meiosis can give rise to genetic variation in the gametesproduced.

Back 17

1. Crossing over and { independent/ random} assortment

2. description of crossing over as swapping over sections of{ chromatid / DNA }

3. description of independent assortment of maternal andpaternal chromosomes

4. consequence described e.g. produces recombinants ornew combinations of alleles