Vascular Plants- Alteration of Generations

Exam 1 - set 2

What are the advantages and disadvantages of Sexual reproduction?

Advantage: Produces genetic variation, which can help populations adapt to changing environments.

Disadvantage: Have to find mate, more time and energy, slower reproduction

What is sexual reproduction?

Reproduction involving two gametes (sperm + egg) that combine during fertilization to form a 2n zygote.

What is asexual reproduction?

Reproduction involving one parent that produces genetically similar or identical offspring.

What are the advantages and disadvantages of asexual reproduction?

Advantage: It is fast, energy-efficient, and does not require a mate.

Disadvantage: Produces little genetic variation, making populations potentially less adaptable to environmental changes or disease.

Explain the process of Alteration of Generations?

A life cycle that alternates between a haploid gametophyte (1n) and a diploid sporophyte (2n).

Remember: basic cycle

2n Sporophyte
↓ MEIOSIS
1n Spores
↓ MITOSIS
1n Gametophyte
↓ MITOSIS
1n Gametes
↓ FERTILIZATION
2n Zygote
↓ MITOSIS
2n Sporophyte

What is the ploidy of the gametophyte?

Haploid (1n)

What does the gametophyte produce?

Gametes (sperm and eggs).

How does a gametophyte produce gametes?

MITOSIS (⭐ Important: 1n gametophyte → mitosis → 1n gametes)

What happens when sperm fertilizes an egg?

The two 1n gametes combine → 2n zygote.

What is the ploidy of the sporophyte?

Diploid (2n)

What does the sporophyte produce?

Spores

How does the sporophyte produce spores?

MEIOSIS (⭐Important: 2n sporophyte → meiosis → 1n spores)

What happens to spores?

they germinate and undergo mitosis to develop into 1n gametophytes.

Which generation is dominant in mosses?

Gametophyte (1n)

Remember: For moss

1n Gametophyte
↓ produces gametes by MITOSIS
1n Sperm + 1n Egg
↓ FERTILIZATION
2n Zygote
↓ MITOSIS
2n Sporophyte
↓ MEIOSIS
1n Spores
↓ MITOSIS
1n Gametophyte

Remember: Ferns

2n Fern Sporophyte
↓ MEIOSIS
1n Spores
↓ MITOSIS
1n Gametophyte (prothallus)
↓ produces gametes by MITOSIS
1n Sperm + 1n Egg
↓ FERTILIZATION
2n Zygote
↓ MITOSIS
2n Fern Sporophyte

⭐ Ferns = sporophyte dominant

Which generation is dominant in gymnosperms?

Sporophyte (2n)

Remember for gymnosperms

2n Gymnosperm Sporophyte
↓ MEIOSIS
1n Microspores + 1n Megaspores
↓ MITOSIS
1n Male + Female Gametophytes
↓
1n Sperm + 1n Egg
↓ FERTILIZATION
2n Zygote
↓ MITOSIS
2n Sporophyte

⭐ Gymnosperm gametophytes are very small/reduced and dependent on the sporophyte.

Which generation is dominant in angiosperms?

Sporophyte (2n)

Remember for Angiosperms:

2n Flowering Plant (sporophyte)
↓ MEIOSIS
1n Microspores + 1n Megaspore
↓ MITOSIS
1n Pollen grain + 1n Female gametophyte
↓
1n Sperm + 1n Egg
↓ FERTILIZATION
2n Zygote
↓ MITOSIS
2n Embryo → 2n Adult plant

⭐ Angiosperms have very reduced gametophytes.

What process changes 2n → 1n?

MEIOSIS ⭐

What process changes 1n → more 1n cells?

MITOSIS

What process changes 1n + 1n → 2n?

FERTILIZATION