Plants & Life Cycles

Chapter 12

Major groups of “plants”

Blue-green bacteriaAlgaeFungiMossesFerns and alliesGymnospermsAngiosperms

Generalized Plant Life Cycle

FERTILIZATION

zygote(2N)

SPOROPHYTE2N

spore mother cells

MEIOSIS

spore

GAMETOPHYTEN

diploid generation

haploid generation

antheridium

archegonium

sperm

egg

Life Cycle of a Flowering Plant

Homospory and Heterospory

Homospory• All spore are the same, with regard to size and

“gender”• Each is capable of make a hermaphroditic, male

or female gametophyte

Heterospory• The spore are different in size and gender

• Microspore = small, male• Megaspore = large, female

• Each spore makes a specific gendered gametophyte

Homosporous or Heterosporous?

Homosporous or Heterosporous?

Homosporous or Heterosporous?

Homosporous or Heterosporous?

Homosporous or Heterosporous?

Homosporous or Heterosporous?

Homosporous or Heterosporous?

Summary of spore types in free-sporing and seed plants

• Bryophytes: Mosses & Liverworts• Homosporous

• Ferns and allies• Homosporous & Heterosporous

• Seed Plants: gymnosperms & angiosperms• heterosporous

Generalized Plant Life Cycle

FERTILIZATION

zygote(2N)

SPOROPHYTE2N

Specialized diploidreproductive cells(spore mother cells)

MEIOSIS

spores

GAMETOPHYTE(male or female)

N

Gametes(egg & sperm)

cell division& growth

cell division& growth

diploid generation

haploid generation

1. What do the terms haploid and diploid refer to?

A. Cell numberB. Eye numberC. Number of chromosomesD. Number of chromosome setsE. Number of nuclei

2. A life cycle illustrates the reproductive stages for an organism. What process causes the haploid stage to become diploid?

A. meiosisB. mitosisC. fertilizationD. sterilizationE. germination

3. What process causes the diploid stage to become haploid?

A. meiosisB. mitosisC. fertilizationD. sterilizationE. germination

1. Zygotic Life Cycle

FERTILIZATION

zygote(2N)

MEIOSIS

Gametophyte (plant may act as gametes)

Zygote is the only diploid portion of the sporophyte generationPresumably the “original” life cycle

2. Gametic Life Cycle

FERTILIZATION

zygote(2N)

SPOROPHYTE2N

Specialized diploidreproductive cells

MEIOSIS

Gametes(egg or sperm)

cell division& growth

Gametes are the only haploid portion of the gametophyteZygote grows mitotically

3. Sporic Life Cycle

FERTILIZATION

zygote(2N)

SPOROPHYTE2N

Specialized diploidreproductive cells(spore mother cells)

MEIOSIS

spores

GAMETOPHYTE(male or female)

N

Gametes(egg or sperm)

cell division& growth

cell division& growth

Both generations (N and 2N) mitotic divisionsAlternation of generations (sporophyte & gametophyte)

4. What type of life cycle do most animals have (including humans)?

A. zygoticB. gameticC. sporic

Major Evolutionary Advances

• Flowers - 140 mya

5,000mya

4,000mya

3,000mya

2,000mya

1,000mya

EarthForms

ProkaryoticCells

EukaryoticCells

MulticellularPlants

Vascular

tissue

Seeds

Flowers

• Life - 3,800 mya• Prokaryotic cell/autotrophic

• Eukaryotic cell - 1,400 mya• Multicellar plants - 1,000 mya• Vascular tissue - 430 mya• Needed on land - why?

• Seeds - 350 mya

Place on the time scale, the following events:

1. Earth formation2. Prokaryotes3. Eukaryotes4. Multicellular life5. Vascular tissue6. Seeds7. Flowers