SEXUAL REPRODUCTION IN PLANTS

Question 1

What occurs during subsequent development? (4)

Answer 1

• zygote develops a embryo plant, embryonic root (radical) and embryonic shoot (plumule)
  -primary endosperm cell forms a mass of food tissue (endosperm)
  -embryo sac develops into a seed
  -wall of ovary develops into a fruit

Question 2

what happens when the pollen tube reaches the ovule? (2)

Answer 2

the pollen tube grows through the micropyle and into the embryo sac; the pollen tube then breaks down and the tube nucleus degenerates, male gametes move into embryo sac and double fertilisation occurs.

Question 3

what is the function of the pollen tube nucleus? (1)

Answer 3

controls growth of the tube (this is possible because it digests the recipients plant tissue as it moves through the style)

Question 4

what is the function of the generative nucleus? (1)

Answer 4

follows the pollen tube nucleus down the pollen tube, it divides by mitosis to produce 2 haploid nuclei (male gametes)

Question 5

what is the nucellus? (1)

Answer 5

a central mass of tissue containing the diploid megaspore mother cell surrounded by two layers of cells called the integuments.

Question 6

where are the reproductive organs in plants? (1)

Answer 6

in their flowers or inflorescences.

Question 7

what are the male reproductive structures known as? (1)

Answer 7

known as stamens each stamen consists of an anther and a filament.

Question 8

what is meant by hermaphrodite? (1)

Answer 8

a multicellular organism that possess both male and female reproductive structures.

Question 9

what is a stigma? (1)

Answer 9

a platform on which pollen grains may land, a style that supports the stigma and an ovary.

Question 10

where are the female gametes contained? (1)

Answer 10

inside the ovary contains the ovule contains female gametes.

Question 11

what are the female reproductive structures known as? (1)

Answer 11

known as carpels which consists of a stigma.

Question 12

where are the male gametes contained? (1)

Answer 12

the anther produces pollen grains that contain the male gametes.

Question 13

what happens during double fertilisation? (2)

Answer 13

-one male nucleus fuses with the female gamete forming a diploid zygote.
-the other male nucleus fuse with the polar nuclei to form a triploid primary endosperm cell.

Question 14

what are the stages of the formation of female gametes? (2)

Answer 14

-megasporogenesis
-megagametogenesis

Question 15

what happens in megasporogenesis? (3)

Answer 15

-a cell in the ovule differentiates into a megaspore mother cell (diploid)
-this megaspore mother cell undergoes meiosis to form 4 (haploid) megaspores
-3 of the 4 megaspores degenerate and only one megaspore is left in each ovule.

Question 16

what happens in megagametogenesis? (4)

Answer 16

-megaspore nucleus mow begins to divide mitotically to form 8 nuclei
-6 of the 8 migrate to opposing poles while two nuclei remain at the centre (known as polar nuclei)
-these polar nuclei fuse to form the secondary nucleus
-megaspore matures into an embryo sac

Question 17

what are the stages of the formation of male gametes? (2)

Answer 17

-microsporogenesis
-microgametogenesis

Question 18

what does pollen grain in germinate depend on? (2)

Answer 18

pollen grains have shapes and surface protrusions that are unique to each plant species, a plant must have a stigma with complimentary patterns to allow a pollen grain to germinate.

Question 19

what happens in microgametogenesis? (4)

Answer 19

-pollen grain (haploid) has 2 layers the outer exine layer which is derived from the tapetum and the inner layer (intine). exine is present everywhere apart from the pollen tube (Pollination).
-pollen grain divides in 2 (small generative nucleus and larger vegetative nucleus)
-generative nucleus gives rise to 2 male nuclei; whereas the vegetative nucleus gives rise to the pollen tube.

Question 20

what is cross pollination? (1)

Answer 20

occurs when pollen is transferred from the anther of one plant to the stigma of another plant.

Question 21

how pollen carried in cross pollination? (2)

Answer 21

-by insects or other animals
-the wind

Question 22

what happens in microsporogenesis? (4)

Answer 22

-the anther is automatically divided into lobes which further divide into chambers (microsporgonia) (pollen presents there)
-the archesporial cell (pollen development cell) divides into outer and inner layers (inner layer forms sporogenous tissue or cell that forms pollen cell)
-sporogenious tissue provides nourishment to pollen cell present in sporogenous tissue.
-mother cell divides mitotically to form haploid pollen.

Question 23

what is the micropyle? (1)

Answer 23

as the integuments grow they almost enclose the nucellus leaving only a tiny hole (the micropyle)

Question 24

how is fertilisation achieved? (1)

Answer 24

the male gamete within the pollen grain must fuse with the female gamete in the embryo sac.

Question 25

what is pollination? (1)

Answer 25

transfer of pollen from an anther to a stigma.

Question 26

what is self pollination? (1)

Answer 26

occurs when the pollen is transferred from the anther of the same plant to the stigma.

Question 27

what is the 1st stage of yeast budding? (1)

Answer 27

spindle body pole duplication and bud emergence.

Question 28

what is the 2nd stage of yeast budding? (1)

Answer 28

DNA replication

Question 29

what is the 3rd stage of yeast budding? (1)

Answer 29

nuclear mitigation (migration)

Question 30

what is the 4th stage of yeast budding? (1)

Answer 30

spindle formation

Question 31

what is the 5th stage of yeast budding? (1)

Answer 31

chromosome segregation (Nuclear division)

Question 32

what is the 6th stage of yeast budding? (1)

Answer 32

cytokinesis is new bud formed

Question 33

what are the stages of binary fission? (4)

Answer 33

-DNA replicates
-DNA goes to separate ends of the cells (plasmids to this too)
-cell membranes pinch in the middle
-cell divides into two identical daughter cells.

Question 34

what is fragmentation? (1)

Answer 34

when an organism can be divided into multiple fragments and each fragment can develop into a new independent organism.

Question 35

what is regeneration? (1)

Answer 35

the process of renewal, restoration and tissue growth that makes genomes, cells, organisms and ecosystems resilient to natural fluctuations.

Question 36

what is sporulation? (1)

Answer 36

the generation of spores from vegetative cells in the presence of unfavourable environmental conditions.

Question 37

what organisms reproduce by binary fission? (2)

Answer 37

common among prokaryotes and certain protozoans

Question 38

what is binary fission? (1)

Answer 38

where a parent cell divides resulting in two identical daughter cells.

Question 39

what are the types of mitotic asexual reproduction? (4)

Answer 39

-binary fission
-sporulation
-regeneration
-fragmentation