plants and meiosis - BIO

Question 1

4 reasons why plants respond to stimuli?

Answer 1

to avoid stress
to avoid being eaten
enhance/ensure survival
to improve their chances of having offspring

Question 2

model answer for a plant growing upwards towards light using auxin:
auxin is a plant ? produced at the base of the ? of the plant/shoot. When light is directly ?, auxin ? evenly down the sides of the shoot. In a shoot, auxin promotes cell ? and ? elongation. Even distribution of ? causes even growth so the shoot grows ? evenly towards light. this is called ? phototropism

Answer 2

hormone, tip, above, diffuses, division, cell, Auxin, upwards, positive

Question 3

model answer for a plant bending diagonally towards light using auxin:
auxin is a plant ? produced at the base of the ? of the plant/shoot. When light is shining from one ?, auxin ? unevenly down the shaded side of the shoot (the side away from the ?). In a shoot, auxin promotes cell ? and ? elongation. Uneven distribution of ? causes uneven growth of the ? side so the shaded ? grows ? , causing it to bend towards ?. this is called ? phototropism

Answer 3

hormone, tip, side, diffuses, light, division, cell, Auxin, shaded, side, quicker, light, positive

Question 4

Model answer for negative geotropism (when the shoot lays sideways)

Answer 4

Auxin is a plant hormone produced at the base of the tip of a plant/shoot. When the shoot lays sideways, gravity causes the auxin to fall to the lower surface. In shoots, Auxin promotes cell division and cell elongation. As there is an uneven distribution of Auxin on the lower surface, there is uneven growth (the lower side grows more quickly than the upper side) and because of this the shoot grows upwards - against gravity - hence negative geotropism

Question 5

model answer for a root growing downwards towards gravity using auxin:

Answer 5

Auxin is a plant hormone produced in the base of the tip (in the shoot). When the shoot lays sideways, gravity causes Auxin to fall to the lower surface. IN roots, Auxin inhibits cell division and cell elongation. There is an uneven distribution of Auxin on the lower surface, so therefore there is uneven growth and the upper side/surface grows more quickly , so the root grows downwards , therefore positive geotropism.

Question 6

what 6 main things do plants respond to?

Answer 6

humidity, light, gravity, temperature, physical touch and water

Question 7

what is positive thigmotropism??

Answer 7

growth towards physical touch

Question 8

positive/negative geotropism?

Answer 8

growth with(towards)/against gravity

Question 9

positive/negative hydrotropism?

Answer 9

growth towards/away from water

Question 10

positive/negative phototropism?

Answer 10

growth towards/away from light

Question 11

plant germination required practical, key method points?

Answer 11

• collect 3 petri dishes,
• place 8 seedlings on cotton wool in each petri dish,
• put each dish in a different type of light - one in full light (eg: the window), one is partial light (eg: in a box with a hole cut in it), and one in darkness (eg: a closet/cupboard),
• measure the height of each seedling beforehand and record this in a table,
• then leave the petri dishes in their appropriate areas for 5 days, - - once this time is up - measure the new heights and record these in the same table.

Question 12

plant germination required practical, results/hypothesis points?

Answer 12

• ones in full sunlight should grow the most and grow upwards - positive phototropism
• ones in partial sunlight should grow more diagonally towards the light source and slightly less so - positive phototropism
• ones in no sunlight should initially grow due to their energy source - and they naturally grow to search for light, but will then die when there is no light

Question 13

plant germination required practical, key analysis points?

Answer 13

• draw a table of heights before and after and calculate the height difference between these two
• calculate a mean of change in height for each petri dish
• maybe also repeat experiment for increased accuracy
• draw a graph to show and compare results (maybe a bar chart) with change in height on the y axis and the light condition on the x axis

Question 14

plant germination required practical, key variables points?

Answer 14

• control variables: same amount of seedlings, same amount of dampness and water, same light intensity, same type of seedlings
• independent variable : type of sunlight - full, partial, or none
• dependent variable(s) : change in height, how many plants have grown, direction of growth

Question 15

3 ways that Auxin can help commercial farming??

Answer 15

can grow plant clones by adding an Auxin growth medium, can grow cuttings using rooting powder (which contains Auxin), can use Auxin in weedkillers as it can disrupt the plant’s growth patterns

Question 16

3 ways that Giberrellins can help commercial farming??

Answer 16

can expose plants to it to induce germination as it controls plant dormancy ( allowing farmers to grow mutliple crops per year and at better times), can make more or bigger flowers, and can make fruit especially seedless ones grow bigger fruit

Question 17

ways that Ethene can help commercial farming??

Answer 17

it can control the ripening process, so people pick the fruit before it’s ripe, so it doesn’t decompose while travelling and then expose to ethene with big Ethene chambers. However plants can often produce their own ethene so they block this by chilling it or blocking with a chemical inhibitor.

Question 18

what happens in interphase?

Answer 18

the organelles duplicate, as well as the DNA - so there are 4 chromatids (but still 2 chromosomes - one mother, one father)

Question 19

what happens in prophase?

Answer 19

each chromosome is made of 2 sister chromatids, nuclear membrane disappears and spindles start to form

Question 20

what happens in metaphase?

Answer 20

homologous chromosomes line up on equator of cell, and spindle fibres attach to chromosomes

Question 21

what happens in anaphase?

Answer 21

chromatids are pulled to opposite poles by the spindle fibres

Question 22

what happens in telephase?

Answer 22

nuclear envelope reforms around each new nuclei, each chromosome still had two chromatids - end of mitosis

Question 23

what happens after mitosis and what is it called?

Answer 23

cytokinesis - the membrane divides to give 2 genetically identical daughter cells, chromosome number stays the same, and cytoplasm and cell membrane divides!

Question 24

what main thing happens at meiosis and why?

Answer 24

4 genetically different gametes are produced from 1parent cell - with half the number of chromosomes - this is because two gametes fuse together in fertilisation so if they fused with a full amount of chromosomes they would have 92 chromosomes which is too much and would lead to an increased risk of miscarriage in human sexual reproduction.

Question 25

what happens if a cell has a chromosome from both the maternal and paternal cell?

Answer 25

the cell is diploid

Question 26

examples of homologous chromosomes?

Answer 26

the maternal and paternal genes that code for the same genes

Question 27

what happens in meiosis after cytokinesis 1

Answer 27

this forms two haploid daughter cells - only one chromosome! prophase 2 : the nuclear envelope disappears and spindle fibres reform

Question 28

what happens in meiosis after prophase 2

Answer 28

metaphase 2 - chromosomes line up on equator

Question 29

what happens in meiosis after metaphase 2

Answer 29

anaphase 2 -chromatids are pulled to opposite poles by the spindle fibres

Question 30

what happens in meiosis after anaphase 2

Answer 30

telophase and cytokinetis 2 - nuclear membranes reform around the chromosomes. then cytokinesis occurs to form 4 granddaughter cells

Question 31

what does cytokinesis make?

Answer 31

4 haploid daughter cells which are genetically different from one another and the parent cell - and only have 23 chromosomes

Question 32

what is different in the first anaphase inmitosis compared to meiosis

Answer 32

in mitosis - the chromatids are pulled to the poles by the spindle fibres but in meiosis the pairs of chromosomes are pulled to the poles by the spindle fibres

Question 33

2 ways meiosis creates genetically different daughter cells by creating variation?

Answer 33

• recombination/cross over where there is an exchange of DNA between chromatids from homologous - so chromosomes are no longer genetically identical
• random fertilisation where an sperm could fertilise any egg and so therefore random combinations of genetic material

Question 34

purpose of mitosis vs meiosis

Answer 34

to repair body cells, to form gametes

Question 35

how many chromosomes are in a daughter cell comapred to a parent cell?
1. mitosis
2. meiosis

Answer 35

1. same - 46
2. half - 23

Question 36

Sexual reproduction :
- Involves ? to form the gametes - egg and ?
- At ? , the gametes (sex ? ) fuse - each gamete has ? a set of genetic information - so they are ?
- After fertilisation, the embryo divides by ?
- This requires ? parents
- Variation is introduced by crossing ? and due to ? fertilisation - producing genetically ? offspring

Answer 36

meiosis, sperm
fertilisation, cells, half, haploid
mitosis
two
over, random, different

Question 37

Asexual reproduction:
- Involves ? only
- Only needs ? parent
- No fusing of sex ?
- Offspring are ? identical to parent ?

Answer 37

mitosis
one
cells
genetically, CLONES

Question 38

2 main pros of sexual reproduction?

Answer 38

• variation - means some offspring are likely/ able to survive environmental changes : evolution
• new variation means some offspring can colonise (and survive in) new location

Question 39

3 main cons of sexual reproduction?

Answer 39

• variation could lead to some offspring being less able to survive certain conditions
• 2 parents - means it is time consuming or energy inefficient to find a mate
• energy costly to make gametes

Question 40

5 main pros of asexual reproduction?

Answer 40

• 1 parent - so no time or energy wasted finding a mate
• faster (as mitosis has one division whereas meiosis has two)
• not making gametes - so easier
• lots of identical offspring produced in favourable conditions
• clones could have economic benefits

Question 41

main con of asexual reproduction?

Answer 41

no variation - so if all offspring are identical they may all be at risk to new environmental changes

Question 42

what 4 organisms can carry out both sexual and asexual reproduction?

Answer 42

plasmodium, fungi, strawberry, daffodils

Question 43

what is plasmodium?

Answer 43

the parasite involved in malaria

Question 44

when does the parasite plasmodium divide asexually and when does it divide sexually?

Answer 44

• asexually - when it’s in the human host (mitosis)
• sexually - when it’s in the vector/mosquito (meiosis)

Question 45

when does fungi divide asexually and when does it divide sexually?

Answer 45

• in favorable conditions, fungi produce spores via asexual reproduction- and these spores are spread by wind or water - which colonize areas and matured to give adult fungi

Question 46

when does the strawberry divide asexually and when does it divide sexually?

Answer 46

• reproduces sexually via pollination
• reproduces asexually when strawberry plants produce runners and new genetically identical strawberry plants form along them

Question 47

when does the daffodils divide asexually and when does it divide sexually?

Answer 47

• reproduce sexually via pollution
• reproduce asexually (mitosis) - when new genetically identical bulbs form on the older bud and these bulbs can be divided and replanted!

Question 48

why may there be variation in organisms produced by asexual reproduction?

Answer 48

as although they are genetically identical, there may be variation due to the environment, eg: lack of water, nutrients in soil like ions, light intensity, humidity and space!!!