PBL 6: Alternations of Generations

Question 1

Haploid

Answer 1

1 set of complete chromosomes (1x)

Question 2

Diploid

Answer 2

2 sets of complete chromosomes (2x)

Question 3

Triploid

Answer 3

3 sets of complete chromosomes (3x)

Question 4

Polyploid

Answer 4

3+ sets of complete chromosomes
-x refers to sets of chromosomes
-n refers to generations, only up to 2 possible (n/2n)

Question 5

Meiosis

Answer 5

the process of a diploid cell undergoing cell division to form 4 haploid cells

Question 6

Fertilization/Syngamy

Answer 6

male gamete + female gamete= zygote

Question 7

Gametes

Answer 7

form from gametophytes

Question 8

Gametophytes

Answer 8

-Microgametophytes: male gametophyte (sperm cell). forms from microspores

-Megagametophytes: female gametophyte (egg cell). forms from megaspores

Question 9

Sporophytes

Answer 9

makes spores, undergoes mitosis and grows into an entire haploid plant (which is a gametophyte)

Question 10

Mitosis

Answer 10

The process by which a single parent cell divides to make two daughter cells (identical genetic material)

Question 11

Megasporangium

Answer 11

AKA ovule, structure in which megagametophytes are formed:
-place of meiosis + megaspore production

Question 12

Microsporangium

Answer 12

can be pollen sac, structure in which microgametophytes are formed:
-place of meiosis + microspore production

Question 13

Archegonium/megagamentangia

Answer 13

Place where eggs occur, contain female gamete

Question 14

Antheridia/microgamentangia

Answer 14

Place where sperms occur, contain male gamete

Question 15

Plant life cycle: MOSSES

Answer 15

1.) Start of sporophyte generation (diploid)
-Formation of zygote at the bottom of archegonium through fertilization
-Develops into an embryo which results in development of sporophytes (leaves of mosses)
-Sporophytes consist of a capsule (place of meiosis) and calyptra (protective cap that responds to humidity, close+open to receive+trap spores)

2.) Gametophyte generation (haploid)
-Mother cells in the capsule undergo meiosis & generate spores that are released
-Spores germinate and develop into a protonema
-Protonema produces apical meristem buds where moss gametophytes develop (differentiation of gametophytes to antheridia+archegonium)
-Fertilization occurs when sperm cells from antheridia land in archegonium and when it is sufficiently moist.

Question 16

Plant life cycle: MOSSES

Answer 16

1.) Start of sporophyte generation (diploid)
-Formation of zygote at the bottom of archegonium through fertilization
-Develops into an embryo which results in development of sporophytes (leaves of mosses)
-Sporophytes consist of a capsule (place of meiosis) and calyptra (protective cap that responds to humidity, close+open to receive+trap spores)

2.) Gametophyte generation (haploid)
-Mother cells in the capsule undergo meiosis & generate spores that are released
-Spores germinate and develop into a protonema
-Protonema produces apical meristem buds where moss gametophytes develop (differentiation of gametophytes to antheridia+archegonium)
-Fertilization occurs when sperm cells from antheridia land in archegonium and when it is sufficiently moist.

Question 17

Plant life cycle: FERNS

Answer 17

1.) Sporophyte generation (diploid)
-Formation of zygote through fertilisation, resulting in the development of the sporophyte (sporophyte forms leaves and roots from the prothallus)
-Mature sporophyte is the fern plant which has the rhizome as its base (thing that formed first)
-The leaf part of the fern (FROND) has clusters of sporangia cells (place of mother cells) on its underside (SORI)
-Mother cells undergo meiosis in sporangia

2.) Gametophyte generation (haploid)
-After meiosis, spores are produced and released from the sporangium (spores germinate and produce young gametophytes which have rhizoids (place of nutrients))
-On the underside of the gametophyte (protella) are both antheridia and archegonia
-In sufficient moist environment, antheridia release microgametophytes that swim to the archegonia and then fertilisation occurs.

Question 18

Plant life cycle: CONIFERS

Answer 18

Male cone: microsporangia+pollens
Female cone: outer integument

1.) Sporophyte generation
-Fertilization occurs in the scale of a female cone (seed cone) and the zygote feeds from the pollen tube.
-Zygote develops into an embryo and as it matures, it stays surrounded by the female gametophyte which acts as nutritive tissue for the embryo to feed on.

-Embryo develops into a mature seed and is then released from the female cone
-Under favourable conditions the seed can germinate, developing into a young sporophyte

2.) Gametophyte generation
-Mature sporophyte develops both male and female cones
-Female cone develops two ovules on each cone’s scale: each ovule contains 4 haploid megaspores where 1/4 develops into a female gametophyte
-Female gametophyte grows and produces archegonia (each containing an egg)
-Male cones produce 2 microsporangia on their scale: in the microsporangia: production of microspores by meiosis which develop into pollen grain (flagella)

-Via wind pollination the pollen grain lands near the opening of an ovule
(male gametophyte forms a pollen tube which penetrates through the tissue and grows towards the archegonium (antheridia is formed)
-Sperm cell+zygote