Biology 102
Spring Quarter
Written by: Sue Kloss
Lake Tahoe Community College
Instructor: Ralph Sinibaldi
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Chapter 26 – Bio 102
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Read portion The sea around us
I.
Early earth and the origin of life
A. (Fig. 26.1a) Life began on a young earth
1. 3 billion yrs ago- earth bristles w/volcanoes, poisonous atmosphere;
2. greenish mats of prokaryotes line shore
3. O2 released from prokaryotes will change atmosphere forever
4. Formation and breakup of Pangaea had huge influence on diversity and distribution of life
5. Homo sapiens will alter the land air and sea, also; organisms and their environments interact
with, and change each other
6. It is thought that the universe is expanding, the result of a giant explosion 10 – 20 billion years
ago
7. The earth probably started as a swirling mass of dust that condensed
8. The core of earth is molten material, and there are layers of varying density
9. The outermost layer is the thin, solid crust of the earth
10. Early atmosphere of earth was composed of CO, CO2, N2, H2, H2S, and H20, w/ possibly some
methane and ammonia
11. First seas may have formed when earth cooled enough for water to condense as rain
12. Lightning, volcanic activity and UV radiation made early earth a pretty different place
13. In this environment, life began
14. Stromatolites are the fossilized mats of prokaryotes
B. How did life originate?
1. We think that life began in prokaryotic form about 3.6 billion yrs ago
2. Synthesis and accumulation of small organic molecules would have been a first step in formation
of life
3. 2nd, formation of polymers would have preceded formation of life
a. Origin of mechanism of polymer replication would have had to occur
4. Finally, aggregates of polymers must have had to have different chemical characteristics from
surroundings = “protobionts, surrounded by membrane
5. the origin of self replicating molecules that eventually made inheritance possible
C. Stanley Miller’s experiments
1. 1953 Miller showed that amino acids and other organic molecules could have been formed on
lifeless earth
2. Oparin and Haldane independently in the 1920’s, proposed that O2 (corrosive – disrupts
chemical bonds by extracting electrons) in atmosphere prevents spontaneous formation of
organic molecules, so that O2-free early earth’s atmosphere could have been a reducing
environment, where organic molecules could have formed from simple molecules
3. The early oceans would have been a solution of organic molecules, a “primitive soup” and early
earth’s atmosphere would have added electrons, encouraging formation of chemical bonds to
form more complex molecules
4. Miller showed this was possible
5. Fig. 26.2
a. tank of warm water = early sea
b. bulb of “atmosphere” = water vapor, H2, CH4, and NH3
c. electrodes in atmosphere discharged “lightning”
d. condensor cooled water vapor in gas mixture causing “rain”
e. dissolved substances along w/ rain fall into sea
6. After a week miller found a variety of organic molecules in the solution including amino acids
and lots of oily hydrocarbons
7. Since then researchers have been able to synthesize most amino acids as well as sugars,
lipids, nitrogenous bases of nucleotides of DNA and RNA, even ATP
8. It is unclear whether early atmosphere had methane and NH3 to reduce; but in localized
environments, (near vents and geothermal features) this would have been possible (Fig. 26.3)
D. Extraterrestrial sources of organic compounds
1. some organic compounds on earth may have come from space
2. some of the meteors that land on earth have carbon compounds
a. a 4.5 byo piece of rock that landed on earth sampled in 1969 contained more
than 80 amino acids, in proportions similar to Mller’s experiment
3. Amino acids that reached earth aboard meteors would have relatively small contributions
to the primitive soup
E. Abiotic synthesis of Polymers - The first polymers may have been formed on hot rocks or clay
1. after small organic molecules formed, the next step would have been polymerization – long
chains of small organic molecules to form one long molecule
2. polymers are formed by dehydration synthesis – a process that links two monomers (small
molecules) together in a process that results in formation of water – thus dehydration synth.
3. Normally, enzymes facilitate, but this can also be accomplished in lab settings where water is
vaporized and the monomers are concentrated; some spontaneously bond
4. Clay particles have electrically charged sites for binding monomers, so this could have
spontaneously occurred on clay surfaces.
F. Protobionts - molecular cooperatives enclosed by membranes
1. protobiont - abiotically produced molecules surrounded by a membrane
2. exhibit some of the chars of life, but are not livinga. diff’t internal chem environment
b. simple metabolism
3. liposomes - membrane bound droplets when dropped in H2O have hydrophobic molecules
that self assemble into bilayer at surface of droplet, much like plasma membrane (Fig. 26.4)
a. semipermeable, so liposomes swell and shrink in solutions
b. some store energy as membrane potential
G. RNA and natural selection
1. The first genetic materials may have been RNA, which in lab settings has been known to
spontaneously assemble
2. this process could occur a number of times, resulting in replication of genetic information
3. Life requires a great number of complex organic molecules and the molecules must interact
and cooperate in precise ways
4. Ribozymes are some RNAs can also carry out enzyme-like functions (fig. 26.5)
5. this process could occur a number of times, resulting in replication of genetic information
6. Experiments have shown that in aqueous environment, certain organic molecules(including
lipids and proteins) self assemble into spheres filled w/fluid; these have a semipermeable
membrane
7. these are cell-like, but not truly living.
8. if these were likely to grow and replicate more efficiently than other collections of coops, they
would have been favored by natural selection
II. Fossil Record Chronicles life on earth
A. How Rocks and Fossils are dated
1. most fossils are found in sedimentary rocks
2. trapping of dead organisms in sediments freezes them in time, they are a record of life
that existed when the rocks were formed
3. Strata at one location are correlated with strata at other location via similar fossils known
as index fossils (Fig. 26.6) such as brachiopods
4. to determine the ages of fossils, use radiometric dating.
a. some elements have isotopes (diff’t number of neutrons)
b. some isotopes decay radioactively
c. as these elements decay, they form “daughter” isotopes (Fig. 26.7)
d. each isotopes decays at a particular rate - C14 has a half life of 5730, and is
useful for dating fossils up to 75,000 yrs old, while uranium 238 has a halflife of 4.5
billion yrs.
5. you can also use the ratio of C14 to C12 (the most common isotope) to date organisms,
because the ratio changes over evolutionary time
6. Magnetism of rocks can also provide info
a. iron particles in rocks align themselves magnetically as rock is forming, then are
“frozen” in that position
b. earth’s magnetic poles have reversed themselves repeatedly over time, and
these magnetic reversals (which affect the entire planet) can be matched with
corresponding patterns elsewhere allowing rocks to be dated when other methods
are not available
B. Geologic Record (Table 26.1)
1. Eons- Archaean and Proterozoic lasted 4 billion yrs - collectively called Precambrian era
2 eons divided into eras- Paleozoic, Mesozoic and Cenozoic
3. boundaries of eras correlate with mass extinctions (Fig. 26.8) when many forms of life
disappeared and were replaced by other forms
a. Permian mass extinction claimed about 96% of all marine animal species; these
extinctions occurred in less than 5 million yrs.; emormous volcanic explosions in
Siberia
b. another mass extinction event happened at the end of the Cretaceous between
Mesozoic and Cenozoic eras (Fig. 26.9) extinction of dinos; adaptive radiation
4. Clock analogy and life on earth (Fig. 26.10)
III. Prokaryotes Evolved and exploited and changed early earth
A. stromatolites many layers of bacteria and sediments (fig. 26.11)
1. evidence that life evolved when earth was relatively young (3.5 bya).
2. prokaryotes (auto and heterotrophs) were the only inhabitants of earth from 3.5 to 2 bya
B. Electron transport systems
1. common to all 3 domains
2. must have evolved before common ancestor of all life, with no O2 in atmosphere
C. Ps and O2
1. most O2 in our atmosphere is of biological origin; accumulated slowly from 2.7 to 2.2
bya, then shot up
2. O2 is corrosive, can inhibit enzymes and damage cells
a. probably sent into extinction many prokaryote groups
b. anaerobic envs. today still have descendants - obligate anaerobes
c. survivors had adaptations to the “poison” - O2 e.g. cellular respiration
IV. Eukaryotic cells arose from symbioses and genetic exchanges btwn proks
A. endosymbiosis probably led to mitochondria and plastids (including chloroplasts)
1. undigested prey or internal parasites
2. all euks have mitochondria or genetic remnants of them, not all have plastids
3. serial endosymbiosis (Fig. 26.13).
V. Multicellularity evolved several times in Eukaryotes - multiple Kingdoms forming e.g. sponges, protist (algae)
Ch. 26 Lesson Objectives
1. Describe the four stages of the hypothesis for the origin of life on Earth by chemical evolution.
2. Describe the contributions that A. I. Oparin, J.B.S. Haldane, and Stanley Miller made toward developing a
model for the abiotic synthesis of organic molecules. Describe the conditions and locations where most of these
chemical reactions probably occurred on Earth.
3. Describe the evidence that suggests that RNA was the first genetic material. Explain the significance of the
discovery of ribozymes.
4. Describe how natural selection may have worked in an early RNA world.
5. Describe how natural selection may have favored the proliferation of stable protobionts with self-replicating,
catalytic RNA
6. Explain how the histories of Earth and life are inseparable.
7. Explain how index fossils can be used to determine the relative age of fossil-bearing rock strata. Explain how
radiometric dating can be used to determine the absolute age of rock strata. Explain how magnetism can be
used to date rock strata.
8. Describe the major events in Earth’s history from its origin until 2 billion years ago. In particular, note when
Earth first formed, when life first evolved, and what forms of life existed in each eon.
9. Describe the mass extinctions of the Permian and Cretaceous periods. Discuss a hypothesis that accounts for
each of these mass extinctions.
10. Describe how chemiosmotic ATP production may have arisen.
11. Describe the timing and significance of the evolution of oxygenic photosynthesis.
12. Explain the endosymbiotic theory for the evolution of the eukaryotic cell. Describe the evidence that supports
this theory.
Evolution of Plants/Fungi
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I. Evolution of Plants
A. What is a plant ? multicellular, eukaryotes, make organic molecules through Ps; What about green
algae,
like Ulva? looks like a plant
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 – multicellular organisms 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
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)
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
h. 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 29.3)
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 both in nucleus and chloroplast
b. cell structure –
1) arrays of proteins in plasma membrane for constructing cellulose are
rosette shaped (Fig. 29.2); in noncharophyceans they are linear
2) cell walls have a higher percent of cellulose than noncharophyceans
c. cell metabolism
1) peroxisomes of both have enzymes to prevent loss of organic products due to
photorespiration
d. reproduction – certain details of cell division happen only in charophyceans and plants,
not algae
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
c. derived traits of plants
1. cuticle – protection from microbes, prevent water loss
2. secondary compounds
a. terpenes, alkaloids, tannins – bitter taste. Odor to prevent herbivory
b. flavonoids – absorb harmful UV rays
c. phenols – deter attack by pathogens
d. some helpful to humans e.g. alkaloid called quinine deters malaria
3. Fig. 29.5 – apical meristems
b. alternation of generations
c. walled spores produced in sporangia
d. multicellular gametangia
e. multicellular dependent embryos
5. exact age of plants evolution is unknown, somewhere btn 400 – 700 mya
B. Plant diversity holds clues to evolution of plant kingdom (Table 29.1 – 10 extant phyla.
(fig. 29.4) (debate ongoing about taxonomy)
1. 475 mya, lineage from charophytes arose - bryophytes (mosses and mosslike plants)
Including
Phylum Hepatophyta, Anthocerophyta, Bryophyta
a. cuticle (polymers of polyester and waxes) 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
2. vascular plants - 400 mya – Lycophytes and Pterophyta – about 93 % of all plant species
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)
3. seed plants 360 mya - embryo packaged with a food supply
a. 90% of ~265K known species of plants are from seed plant lineage
b. 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
c. 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
2). conifers - cone bearing plants- are the largest group of gymnosperms
d. 130 mya split in the lineage of seed 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
4. 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
III. Altermation of generation/plant life cycles
A. 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
3. sporophyte - literally, a "spore plant" - a structure that produces spores, produced itself
by diploid structure
4. gametophyte - literally, a "gamete plant" - a structure that produces gametes, produced itself from
haploid structures
5. spores - haploid structure produced by meiosis- can develop into a multicellular individual without
fusing with another cell without
6. gametes - reproductive cells; haploid egg and sperm
B. Review generalized diagram of alternation of generations (handout)
1. Fertilization marks the beginning of the diploid part of the life cycle
2. Meiosis begins the haploid phase of the life cycle
C. 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
D. Life Cycle of Polytrichum, a Species of Moss (29.8)
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. Bryophyte Diversity (Fig. 29.9)
1. liverworts – Phylum Hepatophyta – liver shaped gametophytes
2. Hornworts- Phylum Anthocerophyta – horn shaped sporophyte
3. Mosses – Phylum Bryophyta- grow more vertically than horizontally; leaves gen’ly 1 cell thick
4. Ecological and Economic importance
a. habitats for tiny animals
b. important in many ecosystems – mountaintops, tundra, desert (can survive loss of fluids,
rehydrate later
c. peat – very imp. For carbon reservoirs, and as fuel source.
d. may form bogs where acidic conditions may preserve bodies (Fig. 29.10)
F. Ferns life cycle – they are vascular plants and have a dominant sporophyte (29.11)
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
7. xylem, phloem, lignin in water conducting tissues- allows greater height growth
8. Roots anchor plant and allow water/nutrient absorption
9. Leaves- increase surface area for Ps
a. microphylls - in lycophytes – small spine shaped leaves with single vein
b. megaphylls- all other vascular plants- leaves with branched veins
G. Seedless Vascular plant diversity (Fig 29.14)
1. Phy. Lycophyta- Upright stems with many small leaves
2. Phylum Pterophyta – whisk ferns, horsetails, ferns
H. 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
5. removed much CO2 from atmosphere
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.
http://home.thezone.net/~gosse/asperm.html - life cycle of the angiosperm (flowering plant)
http://curriculum.calstatela.edu/courses/builders/lessons/less/les8/altgen.html - alternation of generations in
mosses
http://curriculum.calstatela.edu/courses/builders/lessons/less/les8/pollen.html - plant reproduction
http://www.wisc.edu/botit/img/bot/130/ - Hundreds of botanical images put together by University of Wisconsin
Botany Department. Many of meiosis, mitosis, plant life cycles.
Objectives Ch. 29
1. Describe four shared derived homologies that link charophyceans and land plants.
2. Distinguish among the kingdoms Plantae, Streptophyta, and Viridiplantae. Note which of these is used in the
textbook.
3. Describe five characteristics that distinguish land plants from charophycean algae. Explain how these
features are adaptive for life on land.
4. Define and distinguish among the stages of the alternation of generations life cycle
5. Describe evidence that suggests that plants arose roughly 475 million years ago
6. List and distinguish among the three phyla of bryophytes. Briefly describe the characteristics of each group.
7. Distinguish between the phylum Bryophyta and the bryophytes.
8. Explain why bryophyte rhizoids are not considered roots.
9. Explain why most bryophytes grow close to the ground.
10. Diagram the life cycle of a bryophyte. Label the gametophyte and sporophyte stages and the locations of
gamete production, fertilization, and spore production.
11. Describe the ecological and economic significance of bryophytes.
12. Describe the five traits that characterize modern vascular plants. Explain how these characteristics have
contributed to their success on land.
13. Distinguish between microphylls and megaphylls.
14. Distinguish between the homosporous and heterosporous condition.
15. Explain why seedless vascular plants are most commonly found in damp habitats.
16. Name the two clades of living seedless vascular plants.
17. Explain how vascular plants differ from bryophytes.
18. Distinguish between giant and small lycophytes.
19. Explain why whisk ferns are no longer considered to be “living fossils.”
20. Describe the production and dispersal of fern spores.
These areas are often problems for students
1. Many students have difficulty in understanding the significance of derived characters that are shared between
two extant groups. Just as many members of the general public have the mistaken notion that humans evolved
from chimpanzees, some students will think that charophyceans are in some sense ancestral to plants or that
charophyceans are identical to the last common ancestor that plants and charophyceans shared.
2. It is important to make sure that your students understand alternation of generations in bryophytes and
seedless vascular plants. Plant life cycles are challenging for all students. Without a good understanding of the
life cycles of plants with recognizable gametophytes and sporophytes, students will have great difficulty with
gymnosperm and angiosperm life cycles.
3. Students tend to think of derived traits as “advanced.” Be careful to avoid this term. Point out that organisms
have a combination of primitive and derived traits, and that all living organisms have an equally long
evolutionary history, dating back to the origin of life on Earth.
4. Many students are not very familiar with or knowledgeable about plants. Some of the terminology of plant life
cycles can be confusing to such students. Clarify for students the meaning of these pairs of terms:
a. homosporous and heterosporous
b. bryophyte and phylum Bryophyta
c. rhizoid and root