Plant Evolution & Plant Evolution & Diversity – Ch. 22-25Diversity – Ch. 22-25

Kingdom Protista: Algae & Protozoa

• Organisms in this Kingdom don’t fit clearly into what we call plant, animal, or fungi.

• Most diverse eukaryotic Kingdom (>60,000 species).

• We are interested in this Kingdom because of the Chlorophytes & Charophyceans - green algae.

The line between Kingdom Protista and Kingdom Plantae is still being discussed……

Fig 29.4

Origin of Plants

Characteristics of Green Algae - Chlorophytes

• .• Can live symbiotically with fungi as lichens

Fig 28.30

Volvox - freshwater

Caulerpa - intertidal

Ulva – sea lettuce

Characteristics of Green Algae - Charophyceans• fresh water ponds• They are considered to be the closest ancestors of

true plants. Evidence:

Plants

• So how are they different from Charophyceans??

What challenges did plants face when they “moved” onto land?

Adaptation to life on Land:

1. .

2. .

3. .

4. Multicellular gametangia

5. Multicellular, dependent embryos

1. Apical Meristems –

2. Alternation of Generations

• 2 multicellular life stages:1. Sporophyte:

• Diploid• Divides by meiosis to form spores• Spores – haploid cells that can grow into a

new, multicellular, haploid organism (the gametophyte) without fusing to another cell.

2. Gametophyte: • Haploid• Divides by mitosis to form the gametes (egg

and sperm)• Egg & sperm fuse to form the diploid zygote,

which divides by mitosis to form the sporophyte

3. Spores produced in sporangia

• Sporangia =

• diploid cells within the sporangia divide by meiosis to form the haploid spores

sporocytes

4. Multicellular gametangia

• Gametangia =

• 2 types of gametangia:

1. Archegonia –

2. Antheridia – • Sperm travel to the egg, fertilizing it within the

archegonia.

5. Multicelluar, dependent embryos

• Zygote divides by mitosis to become the sporophyte.

Other examples of adaptations to life on land: (not all plants have the following):

1. Cuticle –

2. Secondary compounds –

3. Roots –

4. Shoots - stems and leaves to make food. 5. Stomata – openings in the leaf surface to allow gas exchange

for photosynthesis and to regulate water loss.

More Adaptations

4. .

5. A vascular system that transports food & water from roots to shoots and vice versa.

Fig 29.7

Nonvascular Land Plants: Bryophytes

• Earliest land plants• 3 Phyla:

1. Hepatophyta – 2. Anthocerophyta – 3. Bryophyta -

• .

• Peat moss (sphagnum): doesn’t decay rapidly, stores 400 bil tons of carbon

• Gametophyte is the dominant generation:

Fig 29.8

Moss life cycle

Phylum Hepatophyta – liverworts

Phylum Anthocerophyta – hornworts

Phylum bryophyta - mosses

Peat bogs – sphagnum

moss

Fig 29.10

Vascular Plants

• Vascular tissue:– Xylem = water & mineral transport– Phloem = food (carbohydrates) transport

• .

Seedless Vascular Land Plants

-Egg & sperm need moist environment to fertilize (similar to bryophytes)

Two phyla of seedless vascular plants:

1. Phylum Lycophyta (Club Mosses)

- flammable spore clouds- were tree-like in the Carboniferous period

Phylum Lycophyta: clubmosses, spikemosses, quillwarts

2. Phylum Pterophyta

a) Whisk ferns –

b) Horsetails –

c) Ferns – produce clusters (sori) of sporangia on underside of leaves (fronds)

Phylum Pterophyta: ferns, horsetails, whisk ferns

Fig 29.12 Life cycle of a fern

Forests of the Carboniferous period (290-360 mil years ago):

• Heat + pressure + time ----> coal

• Pulled lots of CO2 out of atmosphere, cooling the earth & forming glaciers

• Larger species died out when climate became drier

Terrestrial Adaptations of Seed Plants

1. Seeds replace spores as main means of dispersal.• Why?

2. Gametophytes became reduced and retained within reproductive tissue of the sporophyte

3. Heterospory –

4. Zygote develops into an embryo packaged with a food supply within a protective seed coat.

5. Pollen & Pollination - freed plants from the requirement of water for fertilization.

1. Seeds replace spores as main means of dispersal.

• old way (ferns & mosses) =

• new way: the sporophyte RETAINS its spores within the sporangia & the tiny gametophyte develops within the spore.

• ovule =

• after fertilization, the ovule becomes the seed• seed = sporophyte embryo + food supply (mature ovule

tissues)

2. Reduction of the gametophyte:

Similar to Fig 30.2

3. Separate male & female gametophytes

• Old way: sporangia spores bisexual gametophyte (antheridia sperm, archegonia -> eggs)

• New way:

• Microsporangia microspores male gametophyte sperm

4. Ovules and seed production

• Ovule =

• After fertilization, embryo develops, ovule becomes a seed

Fig 30.3

5. Pollen & Pollination

• Microsporangia microspores male gametophyte sperm

• Pollen =• Pollination =

• Pollen tube brings sperm to egg within the ovule

Two types of seed plants:

1. Gymnosperms •Evolved first•“naked seed” –

• 2. Angiosperms

•Evolved from gymnosperms

Gymnosperms

• Four phyla:1. Ginkophyta – 2. Cycadophyta – 3. Gnetophyta – 4. Coniferophyta –

Dominate forests of the N. hemisphere Most are evergreen Needle-shaped leaves to reduce water loss

during drought

Phylum Cycadophyta

Phylum Ginkophyta

Phylum Gnetophyta

Phylum Coniferophyta

Fig 30.6

Angiosperms

• One phylum: Anthophyta

• 2 classes: monocots & dicots.1. Monocots

2. Eudicots

Evolutionary success of Angiosperms due to:

1. .

2. Flowers – attract pollinators

3. Fruits – many forms for variety of dispersal mechanisms

Fig 30.3

Notice the triploid stage!•Each pollen grain (male gametophyte) produces two sperm•Sperm travel down the pollen tube & into the ovule.•Double fertilization –

•Ovule matures into the seed – contains sporophyte embryo & endosperm (food).•Ovary (female sporangium tissues) matures into the fruit.

Ch. 9: flowers, fruits: Ch. 9: flowers, fruits: Angiosperm ReproductionAngiosperm Reproduction

Flower parts occur in 4 sections:1. Sepals –

The parts of a flower are typically attached to the:pedicel – the stalk of a single flower. It attaches the flower to the plant.

2. Petals – a typically colored or white, delicate structure. Petals function to attract pollinators.

3. Each male flower part is called a stamen.

The stamen is composed of:1. Filament –

2. Anther – a collection of pollen sacs that sits on top of the filament.

Each female part is called a pistil.

Pistil = the female reproductive organ, consisting of:1. Stigma –

2. Style –

3. Ovary – the base of the pistil, contains the ovules. (Mature ovules are seeds and mature ovary is the fruit)

The Angiosperm Life Cycle

• Male gametophyte =

• Female gametophyte = embryo sac, develops in the ovule of the ovary. Produces egg

Development of Male Gametophyte (Pollen)

• Anther is composed of pollen sacs (sporangium).

• Each microspore divides by mitosis to make 2 cells:

1. Generative cell –

2. Tube cell – will make pollen tube• The 2 cells enclosed in thick wall => pollen grain

Development of the Female Gametophyte (Embryo Sac)

• Ovule = female sporangium

• Only one megaspore survives and divides by mitosis 3 times to make 8 haploid nuclei.

Embryo Sac = female gametophyte

Antipodal cells

2 polar nuclei

EggSynergid cells

Fig 38.4

Angiosperm Reproduction

1. Pollen grain lands on stigma (= pollination)2. .

3. .

4. Sperm travel down pollen tube and enter embryo sac5. Double fertilization –

• Egg + sperm zygote• 2 polar nuclei + sperm 3n nucleus that becomes

the endosperm

Fig 38.6

Double fertilization

Maturation

• Endosperm begins to divide to form structure that provides nutrients to developing embryo

• Ovule is now a seed – dehydrates & becomes dormant (low metabolism, no growth).

• Ovary tissues divide & mature into fruit

Complete flower =

Incomplete flower = lacks one of the above parts

Flowers are diverse…….

Inflorescence types:

Inflorescence = the entire flowering part of a plant

1. Spike =

2. Raceme = single flowers on pedicels along the rachis3. Panicle = a much-branched inflorescence4. Solitary flower5. Many more!!

Fruit types

Fruit =

.*the primary function of a fruit is seed dispersal