Bio 111Lake Tahoe Community College

Bio 111Lake Tahoe Community College

Winter QuarterInstructor: Sue Kloss

______

Evolution of Plants/Fungi

______

Intro – Forest Conservation – US citizens consume 50x more paper than LDC’s (Fig. 16.1)

I. Evolution of Plants

1. What is a plant ? multicellular, eukaryotes, make organic molecules through Ps; What about green algae, like Ulva? looks like a plant (Fig. 16.2)

1. algae adapted for aquatic life

a. algae have holdfast, anchors algae in substratum, but generally no rigid

supporting structure

b. whole algal body has access to water, all has capacity for Ps

2. plants adapted for terrestrial life

a. cuticle - waxy coating that helps retain water on aerial parts (which?)

b. CO2 and O2 diffuse in and out of stomata, tiny pores

c. body partly below ground, partly above, must be able to stand upright

d. obtains chemicals from both air and soil

1). chloroplasts - C from CO2 and light from sun

2. roots provide anchor - provide water and nutrients, mycorrhizae (Fig 16.3)

e. plant parts are analogous (not homologous) to algal parts (eg holdfast)

f. plants must be able to get photosynthate down and water and nutrients up -

vascular tissue (network of cells forming narrow tubes) (Fig. 16.4)

1). xylem

2). phloem

g. both plants and algae produce gametes in gametangia (protective jackets of

cells protecting gamete producing cells

1). egg remains in gametangia of female, fertilized there

2). sperm either swims to egg, or sperm producing cells conveyed close to egg by animals, where sperm is then produced

3). embryo develops inside female gametangium (Fig. 16.5)

1. most plants rely on wind or animals to disperse offspring (how?)

II. Plant Evolution and Diversity

A. Plants probably evolved from green algae called charophytes (Fig. 16.6)

1. some homologous features btn plants and algae

a. chloroplasts

b. cellulose

c. store carbos as starch

d. during cell division, cell plate comes from Golgi apparatus

2. algae probably were prolific about 50 mya; land masses were probably being flooded periodically; algae that were drought resistant probably selected for. Eventually, some

species may have accumulated enough adaptations to live permanently on land

3. green algae called charophytes probably ancestor of plants; evidence:

a. nucleic acid sequences

b. cell structure and reproduction

c. cell metabolism

4. early plants would have thrived on land- nothing to eat them, unlimited sunlight

a. Cooksonia - 415 million year old fossil

1). branched upright stem

2). primitive vascular tissues

3). lacked leaves

4). sporangium - bulbous structure on stem - produced spores

(haploid cell that can develop into a haploid multicelled adult without

fusing with another cell)

b. by 375 mya, plants with well developed leaves and roots were numerous and diverse

B. Plant diversity holds clues to evolution of plant kingdom (fig. 16.7)

1. 475 mya, lineage from charophytes arose - bryophytes (mosses and mosslike plants) (Fig. 16.8)

a. cuticle and embryo that develops in gametangia like other plants

b. lack vascular tissue (some have water conducting tubes)

c. lack internal support, no rigid structure of vascular tissue

d. mat of moss is actually numerous plants holding each other up; mat is spongy

and can retain water

e. flagellated sperm resemble green algae

f. sperm must swim to eggs, so fertilization requires a film of water

g. sporophyte and gametophyte (Fig. 16.9) – Alternation of Generations (Fig. 16.10)

C. Haploid and Diploid generations alternate in plant life cycles

1. Plant reproduction occurs asexually and sexually. Sexual reproduction can generate enormous amounts of genetic variation, providing a species with tools to contend with a variety of environmental conditions. Sexual reproduction occurs in plants during an alternation of generations.

2. Alternation of generations defined

a. sporophyte - literally, a "spore plant" - a structure that produces spores, produced itself

by diploid structure

b. gametophyte - literally, a "gamete plant" - a structure that produces gametes, produced

itself from haploid structures

c. spores - haploid structure produced by meiosis- can develop into a multicellular individual without fusing with another cell without

d. gametes - reproductive cells; haploid egg and sperm

3. vascular plants - 400 mya (Fig. 16.11)

a. xylem and phloem provide support

b. stand upright and grow tall

c. embryonic development within gametangia

d. seedless vascular plants - ferns and fern allies (horse tails)

1). well developed roots

2). rigid stems

3). fronds often sprout from stems along ground

4). flagellated sperm require film of water to reach eggs

5). some are woody (tree ferns)

4. seed plants 360 mya - embryo packaged with a food supply (fig. 16.13)

a. 90% of ~265K known species of plants are from seed plant lineage

b. alternation of generations revisited (Fig. 16. 14)

c. why are they so successful?

1). seeds - survival packets for life on land

2). don’t require water layer for fertilization - no sperm; instead, pollen

carries nonflagellated sperm forming cells to female parts of plant by wind

or animals. pollination- arrival of pollen to female; fertilization occurs sometime

after pollination (fig. 16.16)

d. first seed plants - gymnosperms (gymno = naked, sperma = seed); not contained

in a fruit. A gymnosperm seed has a thin protective coating- part of the seed itself

1). 200 million yrs - gymnos coexisted with ferns and other seedless plants,

dominated the landscape (fig. 16.15)

2). conifers - cone bearing plants- are the largest group of

gymnosperms

4. 130 mya split in the lineage of seed plants –

a. Flowering plants - rise of angiosperms (angeion =

vessel, sperma= seed), the flowering plants. Flowers are complex reproductive structures

that develop seeds within protective chambers. The great majority of modern plants - 235 k

species - are angiosperms (fig. 16.17)

b. angiosperm life cycle (Fig. 16.18)

c. fruits and seed dispersal (fig. 16.19)

d. angiosperms and agriculture- all crop plants are angios

5. summary - 4 major adaptations for life on land mark main lineages in plant kingdom

a. gametangia- present in all plants: protect gametes, zygotes and embryos from

drying out

b. vascular tissues- transport materials; provide structure

c. seeds

d. flowers - angiosperm lineage, dominant group of seed plants

D. Plant Diversity as nonrenewable resource (table 16.1)

E. Comparison of life cycles for algae, bryophytes, vascular plants (fig 25.2 starr and taggart)

1. Evolutionary trend toward diploid dominance during colonization of land

II More Details of Plant Group Life Cycles

A. Life Cycle of Polytrichum, a Species of Moss

1. Gametophytes are the dominant part of moss life cycle; gametangia produce sperm, egg.

2. flagellated sperm require film of water to swim to egg

3.zygote remains in female gametangium, develops into sporophyte

4. Sporophytes remain attached to the gametophytes; sporangium produce spores by meiosis

5. spores released, develop into gametophyte

E. Ferns have a dominant sporophyte

1. sporophyte grows out of gametophyte (fern fronds are sporophyte)

2. spores released and develop into gametophyte by mitosis

3. gametophyte produce flagellated sperm and egg

4. like mosses, fern zygotes remain in female gametangium and develop into adult sporophytes;

sporophyte takes over

5. sporangia in clusters on fern’s underside produce haploid spores- meiosis

6. spores dispersed by wind- grow into small, heart shaped gametophytes - mitosis

F. Seedless plants formed “coal forests”

1. tropical swamp forests- as plants died they fell into stagnant wetlands and didn’t decay completely

2. remains formed peat

3. swamps were covered by marine sediments, pressure formed coal

4. coal- black sedimentary rock made up of fossilized plant material

G. Life Cycle of Ponderosa Pine

1. Sporophyte is the dominant portion of the vascular plant life cycle

2. Pine trees and other conifers illustrate how drastically the relative roles of the haploid and diploid generations changed as plants evolved on land.

3. The gametophyte generation consists of microscopic stages that grow on the cone scales.

4. Each of the female cone scales bears a spore, which develops into the ovule; in the ovule,

gametophyte is formed by meiosis

5. Male cones produce many haploid spores. Pollen grains, the gametophytes, develop inside these spore cells. Pollen is wind dispersed in pines, lands near an egg. Pollen tube grows

toward the egg

6. months later, pollen tube releases a nonflagellated sperm into the egg that has formed in the ovule -

fertilization.

7. Seed formation - the zygote develops into a sporophyte embryo, and the whole ovule transforms into a seed. The seed contains the embryo, food supply and a tough seed coat (the integument).

8. Summary: All the reproductive stages of conifers are housed in cones borne on the sporophytes.

H. Conifers dominate northern regions but angiosperms dominate most other landscapes

1. conifers- adapeted to harsh winter storms, branches readily shed snow

needle like leaves resist drying- little surface area; thick cuticle

2. angiosperms- flat, efficiently Psing leaves; vascular tissue with stronger, thicker cell walls;

flowers and fruits

I. Angiosperms is a sporophyte with gametophytes in its flowers

1. flowers- short stems with modified leaves: sepals - protect flower buds; petals to attract insects and

animal pollinators; stamens- male repro parts (contain anthers, where pollen develops); carpels -female

repro parts (stigma to trap pollen, ovary- contains ovule to bear eggs which become fruit

2. flowers protect all microscopic reproductive structures; sporangia, male and female gametophytes,

and zygotes

3. anthers- meiosis - haploid spores develop into male gametophytes - (pollen grains)

4. meiosis in ovules leads to haploid spores- mitosis- develop into gametophytes, -produce eggs in ovule

5. pollination - wind/insects, - pollen lands on stigma

6. pollen grows into nucleus and delivers one nucleus (nonflagellated sperm) ; fertilization = 12 hrs later

7. zygote develops into embryonic sporophyte (seed) and ovary becomes fruit

8. seed dispersal by wind or animals, germination in favorable conditions

1. coevolution of plants and pollinators

J. Fruit function (seed dispersal) is reflected in structure

K. Interaction with animals has profoundly influenced angiosperm evolution

III. Fungi

A. Fungi and plants moved to land together - Mycorrhizae helped make colonization of land possible

1. fungi heterotrophic, external food sources required; food supply was plants, as plants moved

onto land so did fungi (Fig. 16.20)

2. Fungi found in terrestrial and aquatic environments

3. many fungi are parasites of plants, many mutualist relationships too

4. unique adaptations for trapping food

5. decomposition of dead organisms, organic molecules; some can break down pesticide

residues and cancer causing chemicals

B. nutrition - fungi absorb food after digesting outside body

1. heterotrophic eukaryotes

2. cannot make food by Ps; how does it do its job?

3. cell walls of chitin

4. spore production

5. absence of motile stages

6. usually multicellular, but bodies, mycelia composed of networks of hyphae (filamentous units)

7. hyphae grow into the cells of leaves and digest cytoplasm

8. mycelium can add up to a kilometer of hyphae/day, which extend rapidly to food source and

excrete digestive enzymes. the hyphae then absorb the nutrients

9. some fungi produce mushrooms, external reproductive structures composed of packed hyphae

C. Many fungi- three phases in life cycle

1. nucleus forms spores that grow into hyphae

2. If 2 discrete kinds of hyphae (mating types) grow together, dikarytotic - unique to fungi

mating types must be sexually compatible

3. fertilization of one nucleus by another in mushroom produces diploid zygotes. Held in terminal

cells of hyphae in mushroom. meiosis of zygote produces haploid nuclei that form spores

4. haploid spores shed from fruiting body (mushroom)

5. dikaryotic mycelia are among world’s oldest and largest organisms, one in Michigan ~ 30 ac.,

scientists estimate it is about 1500 years old (humongous fungus)

6. some fungi are very simple - yeasts are single celled and mostly reproduce by mitosis

D. Lichens consist of fungi living mutualistically with algae or other photosynthetic organisms (Fig. 16.25)

1. lichens consist of associations of green algae or cyanobacteria in fungal hyphae

2. fungus- food from partner

3. algae receives housing, water and minerals trapped by fungal network

4. asexual reproduction occurs in both; dispersal of both together occurs, they set up shop

someplace new

5. lichens can survive in habitats where neither can grow alone but they are susceptible

to air pollution

6. some lichen are important in soil formation and as part of food chain

E. Parasitic fungi harm plants and animals (Fig. 16.22)

1. 100k known species; .33 parasitic, .33 mutualistic as mycchorizae and lichen, .33

decomposers

2. parasitic fungi - plant pests, esp. nonnative parasites - e.g. dutch elm disease, corn smut,

armillarea in forest trees

3. some fungi cause disease in humans - some serious, like yeast infection of lung, which can be

fatal; we also have fungi that hang around moist, warm places, like our sweaty feet and

lockerrooms - not to mentions the absolute pests that cause jock itch for the boys and vaginal

yeast infections in the girls of our species

F. Fungi also very important (fig. 16.23)

1. decomposers

2. food - mushrooms

3. yeast used in making many of our foods

4. commercial sources for antibiotics - Penicilliium(Fig 16.24)

5. evidence that fungi evolved from the same lineage as animals

Web Resources

As you are surfing the web later on today, pop these web addresses into your browser for some extra scoop on alternation of generations.

- life cycle of the angiosperm (flowering plant)

- alternation of generations in mosses

- plant reproduction

- Hundreds of botanical images put together by University of Wisconsin Botany Department. Many of meiosis, mitosis, plant life cycles.

ch 16 Homework Questions/Lesson Objectives

1. Explain importance of micorrhizae to plant health.
2. Compare structure of multicellular algae and plants. Explain how plants are adapted to life on land.
3. Explain how the first terrestrial plants evolved. Describe the structure of Cooksonia.
4. Distinguish between bryophytes, seedless vascular plants, gymnosperms and angiosperms.
5. Describe the 4 key adaptations for life on land that evolved the plants.
6. Describe alternations of generations life cycle. Explain why this cycle seems to have evolved separately in different groups of plants.
7. Describe key events of moss and fern life cycles.
8. Explain how coal formed.
9. Describe the conditions in which gymnosperms became dominant.
10. Describe the stages of the pine tree life cycle.
11. Describe parts of a flower and list their functions.
12. Describe stages of the angiosperm life cycle
13. Describe examples of adaptations that promote seed dispersal.
14. Explain how flowers attract pollinators.
15. Describe various roles of fungi in natural systems, and how mutualism with plants allowed colonization of land.
16. Describe main traits of fungi.
17. Describe the most common life cycle of fungi.
18. Describe structure and characteristic of lichen
19. Explain how parasitic fungi harm plants and animals.