Week 4

Question 1

Advantages of AS

Answer 1

1. Allows needed traits to be produced quickly and effectively.
2. Creates the potential for added profitability.
3. Creation of crops with a higher yield
4. Production of crops with a shorter harvest time
5. Creation of crops with higher resistance to pests and diseases
6. Creation of new plant and animal varieties

Question 2

Disadvantages of AS

Answer 2

1. There can be unanticipated consequences of encouraging a specific trait.
2. It lessens the amount of variation that exists in a gene pool.
3. The quality of life of the organism being breed is often reduced
4. poor traits also have the potential to be transferred because mutations are
   spontaneous.

Question 3

Angiosperms

Answer 3

• Angiosperms are flowering plants
  that have flowers and produce seeds
  enclosed within a carpel.
• The carpel is the female
  reproductive organ of a flower,
  consisting of an ovary, a stigma, and
  usually a style.

Question 4

Spore

Answer 4

A dormant, reproductive cell formed by certain organisms..

Question 5

Megasporangium

Answer 5

(female sporangia): produce megasporocytes that yield
megaspores.

Question 6

Microsporangium

Answer 6

(male sporangia): produce microsporocytes that yield
microspores.

Question 7

Sporophyte

Answer 7

A phase in the life cycle of certain plants and algae that starts
with the union of gametes. It is an asexual and usually diploid phase,
producing spores from which the gametophyte arises. It is the dominant
form in vascular plants, e.g., the frond of a fern.

Question 8

Sporangium

Answer 8

The capsule structure belonging to many plants and fungi, in
which the reproductive spores are produced and stored

Question 9

Alternation of Generations

Answer 9

• Alternation of generations is a type of life cycle in which subsequent generations of plants
  alternate between diploid and haploid organisms.
• The generations alternate between the sporophytes capable of creating spores and the
  gametophytes, capable of creating gametes.
• This type of life cycle is found in terrestrial plants and some algae.

Question 10

Gametogenesis

Answer 10

as the biological process in which the formation of
gametes take place.

Question 11

Male Gamete Formation in the Anther

Answer 11

• The formation of male gametes consist of two stages:
• Microsporogenesis
• Microgametogenesis

Question 12

Gametogenesis in the Anther

Answer 12

Stamens are the male reproductive
organs of the flower.
* Stamen has two components: anther
and filament.
* The anther contains microsporangia.
* Each microsporangium contains
microspore mother cells or
microsporocytes.

Question 13

Microsporogenesis

Answer 13

• Occurs in the microsporangium
• Microsporocytes (mother cells) are diploid cells
• Microsporocytes undergo meiosis to produce a tetrad of four haploid
  microspores.

Question 14

Microgametogenesis

Answer 14

• The single nucleus of each
  microspore divides once by
  mitosis and one of the two
  daughter nuclei becomes a
  generative nucleus and
  accumulates little cytoplasm,
  while the other becomes a
  tube nucleus.
• The generative nucleus
  undergoes a single mitotic
  division and forms two male
  gametes or sperm cells.
• These microspores form the pollen grain/ a
  mature microgametophyte.
• Pollens or microspores are very tiny round
  structures.
• After the formation, microspores or pollen grains
  dry up and become powdery. The anther
  becomes a dry structure and pollens are
  liberated from the anther to the environment by
  dehiscence of the anther.
• Each pollen grain has two nuclei; one generative
  nucleus and one tube nucleus

Question 15

Megasporogenesis

Answer 15

• Megasporangium (the ovule) contains
  megaspore mother cells.
• Megaspore mother cells are diploid cells
  (2n cells). These mother cells divide by
  meiosis to produce haploid cells (n cells).
• One mother cell divides by meiosis and
  creates four haploid megaspores. This
  process is known as megasporogenesis.
• Megasporogenesis takes place within
  the ovule.
• In most plants, only one megaspore
  develops into the megagametophyte and
  the other three megaspores disintegrate.

Question 16

Megagametogenesis

Answer 16

The surviving megaspore divides into eight nuclei
by consecutive mitotic divisions and produces
eight haploid daughter cells inside of the embryo
sac.
* 6 of the 8 nuclei migrate to opposing poles (3
each) while two nuclei remain at the center.
* The nuclei that remain at the center are known as
polar nuclei. These polar nuclei fuse to form the
secondary nucleus.
* The embryo sac with these eight nuclei represent
the mature megagametophyte.

Question 17

Pollination

Answer 17

• Pollen a is powdery substance that serves to
  move plant sperm to an egg.
• A pollen grain has two cells: a tube cell and
  a generative cell. The entire pollen grain is the
  male gametophyte.
• Pollination is the placement of pollen on the
  stigma of the carpel. This pollen transfer can be
  accomplished by:
  o Wind
  o Insects
  o Built in mechanical discharge
  o Other animals, including man

Question 18

What happens after Pollination

Answer 18

• Once the pollen lands on the stigma, a
  series of chemical reactions takes place
  allowing the pollen grain’s tube
  nucleus to begin producing a structure
  called the pollen tube
• The pollen tube digests its way down
  the style toward the egg.
• The pollen tube will work its way
  through the style of the carpel and
  touch the micropyle of the ovule.

Question 19

Double Fertilization

Answer 19

• After penetrating the degenerated synergid, the pollen tube releases the two sperm into
  the embryo sac
• One sperm fuses with the egg and forms a zygote and the other fuses with the two polar
  nuclei of the central cell and forms a triple fusion or endosperm, nucleus.
• This is called double fertilization because the true fertilization (fusion of a sperm with an
  egg) is accompanied by another fusion process (that of a sperm with the polar nuclei)
  that resembles fertilization.
• Fertilization can be defined as the fusion of the male gametes (pollen) with the female
  gametes (ovum) to form a diploid zygote.
• Double fertilization of this type is unique to angiosperms.
• The zygote now has a full complement of
  chromosomes (i.e., it is diploid)
• The endosperm nucleus has three sets of
  chromosomes (triploid).
• The endosperm nucleus divides mitotically to
  form the endosperm of the seed, which is a
  food-storage tissue utilized by the developing
  embryo and the subsequent germinating seed.
• The zygote undergoes a series of mitotic
  divisions to form a multicellular,
  undifferentiated embryo.

Question 20

Seed

Answer 20

• An angiosperm seed consists of the:
  1. embryo (2N) – this is the
  immature sporophyte
  2. endosperm (3N) which serves as
  stored nutrients.
  3. seed coat which protects the seed
• The micropyle is the only opening into
  the seed. It is through here that the
  water will enter to start germination.
• The seed contains stored food in the
  form of seed leaves (cotyledons). Some
  seeds contain one (monocots) while
  others contain two seed leaves (dicots).