Download Principles of Biology ______Lake Tahoe

Principles of Biology - Biology 102
Spring Quarter
Written by: Sue Kloss
Lake Tahoe Community College
Instructor: Ralph Sinibaldi
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Ch. 30 - Evolution of Seed Plants
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I. Reduced gametophytes of seed plants are protected involves and pollen grains
All seed plants have reduced gametophytes, heterospory, ovules, and pollen
A. Advantages of reduced gametophytes
1. mosses have more important gametophyte stages, where ferns and other plants have
sporophyte dominated life cycles
2. gametophytes of seed plants are mostly microscopic, gametophytes of seedless vascular
plants are visible to naked eye
3. advantage of this is that tiny gametophytes can develop from spores retained within parent
sporophyte
a. protection of delicate female (egg containing) gametophyte from enviro stresses
b. moist repro tissues of sporophyte shield gametophyte from drought conditions and
from UV radiation
c. dependent gametophyte can get nutrients from sporophyte
d. free living gametophytes of seedless plants must fend for themselves (fig. 30.2)
B. Heterospory
1. nearly all seedless plants are homosporous - produce only one kind of spore, which usually
gives rise to bisexual gametophyte
2. At some point, seed plants became heterosporous
a. megasporangia produce megaspores that give rise to female gametophytes
b. microsporangia produce microspores that give rise to male gametophytes
C. Ovules and production of eggs
1. seed plants retain megaspore within the parent sporophyte (Fig. 30.3)
2. integuments envelope and protect megasporangium
3. megasporangium, megaspore and integuments are called ovules
4. inside each ovule, a female gametophyte develops from a megaspore and produces eggs
D. Pollen and production of sperm
1. microspores develop into pollen grains, which contain male gametophytes of seed plants
2. pollen is protected by a tough coat
3. dispersed by wind or by being carried by an animal
4. transfer of pollen to part of seed plant containing ovule is called pollination
a. if the pollen grain germinates, it gives rise to a pollen tube that discharges two sperm
into female gametophyte within the ovule (Fig. 30.3b)
b. seedless plants- sperm swims to eggs in another plant; seed plants have protected
female gametes remain in sporophyte ovule, male gametes carried in durable structures
carried by wind or animals
c. sperm of some gymnosperms retain ancient flagellated condition, most gymnos have
lost flagella on sperm
d. sperm of seedplants don’t need motility, it does not depend on water, is carried by
wind or animals, and deposited into ovule
E. Evolutionary advantages of seeds
1. if sperm fertilizes egg of seed plant, the ovule becomes a seed = kid, coat, lunch box
a. seeds can resist harsh enviros and disperse offspring more widely
b. until seeds, spores were the only protective stage of a plant’s life cycle
1. eg. moss spores may survive even if enviro for plants becomes to hot cold, etc.
for plant itself to survive
c. spores were the way that mosses and other seedless plants spread themselves over
earth
d. seeds are more resistant and complex
1. may remain dormant for days, months, years.
2. may remain close to parent or be dispersed by wind or animal
3. germinate under favorable conditions
II. Gymnosperms bear “naked” seeds, typically on cones - not enclosed in an ovary
Conifers = cone-bearing; in contrast, angiosperm seeds are enclosed in fruit - ovary of sporophyte
A. Gymnosperm diversity (Fig. 30.4) and evolution
1. gymnosperms show up in fossil record from 360 mya, angiosperms did not show up till 200 my
after that
2. Lycophytes, horsetails and ferns dominated the Carboniferous; climate changed, got warmer
and drier, and favored spread of gymnos in Permian
3. gymnos were the main food supply of giant herbivorous dinosaurs
4. climate gradually cooled, and angios now dominate most terrestrial habitats
B. Pine Life Cycle (Fig. 30.6)
III. Reproductive adaptations of angiosperms include flowers and fruits; angio = Gr. vessel - ovary; most diverse
and widespread of all plants, w/250,000 spp.
A. Flowers - structure for sexual reproduction
1. pollination is usually by animal; some wind pollinated, esp. in dense pops - eg grasses
2. flower - specialized shoot w/ up to 4 whorls of modified leaves a. sepals - enclose bud
b. petals - attract animal
c. stamens - male or microsporophylls - produce pollen - usually more than one
d. carpels - female or megasporophylls - produce eggs; may have one or more
3. receptacle - special part of stem all are attached to
B. Fruits - mature ovary, may include other floral parts
1. as seed develops, ovary thickens into fruit
2. fruit devel. caused by hormonal changes that cause ovary to grow
3. pericarp - wall of ovary that becomes thickened fruit wall
a. fruits can be fleshy - orange
b. or dry = nuts, grains etc.
4. fruits help dispersal (Fig. 30.9)
a. seeds eaten along w. fruits usually pass thru digestive system and get deposited
elsewhere in fertilizer
C. Angiosperm Life cycle (Fig. 30.10) - double fertilization - synchronize food source w. embryo devel.
D. Angiosperm diversity - (fig. 30.12) 1. Monocots - one seedleaf, called a cotyledon
2. dicots- 2 cotyledons
E. Evolutionary links between angiosperms and animals
1. animals exert huge selective pressure on plants
2. coevolution - reciprocal genetic influence on both partners in an evolutionary relationship
a. pollinators and plants (Fig. 30.13)
3. most relationships are less specific - many insects may pollinate a particular plant sp.
4. expansion of grasslands in past 65 million years due to decline in atmos. CO2 increased
diversity of grazing animals (C4 photosynthesis)
IV. Human welfare depends greatly on seed plants
A. Products from seed plants
1. food for humans and live stock
2. non food consumables - spices, tea, coffee
3. wood, pulp, wood products
4. pharmaceuticals - (Table 30.1)
B. Threats to plant diversity
1. deforestation in the tropics - area size of WA state each year; in 25 yrs, forests will be gone
2. fewer than 5000 spp have been studied for potential medicines,
3. most food crops come from 2 dozen species of seed plants
Ch. 30 Objectives
1. Name five terrestrial adaptations that contributed to the success of seed plants.
2. Compare the size and independence of the gametophytes of bryophytes with those of seed plants.
3. Describe the ovule of a seed plant.
4. Contrast the male gametophytes of bryophytes with those of seed plants.
5. Explain why pollen grains were an important adaptation for successful reproduction on land.
6. Explain how a seed can be said to include contributions from three distinct generations.
7. Compare spores with seeds as dispersal stages in plant life cycles.
8. List and distinguish among the four phyla of gymnosperms.
9. Describe the life history of a pine. Indicate which structures are part of the gametophyte generation and which are
part of the sporophyte generation.
10. Identify the following floral structures and describe a function for each:
a. sepal
f. anther
b. petal
g. stigma
c. stamen
h. style
d. carpel
i. ovary
e. filament
j. ovule
11. Define fruit. Explain how fruits may be adapted to disperse seeds.
12. Explain why a cereal grain is a fruit rather than a seed.
13. Diagram the generalized life cycle of an angiosperm. Indicate which structures are part of the gametophyte
generation and which are part of the sporophyte generation.
14. Describe the role of the generative cell and the tube cell within the angiosperm pollen grain.
15. Explain the process and function of double fertilization.
16. Distinguish between monocots and eudicots.
17. Explain how animals may have influenced the evolution of terrestrial plants and vice versa.
18. Name the six angiosperms that are most important in the diet of the human species.
19. Describe the current threat to plant diversity caused by human population growth.
Ch. 31 - Fungi
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Intro - Armillaria in Oregon - single enormous mushroom 2200 ac., weighs hundreds of tons, has been growing for
2600+ yrs. Fungi are hugely diverse; an organism we know little about. 100k spp. described, may be as many as
1.5 million spp. some are single celled, most are multicelled and colonized just about every known habitat
I. Fungi are heterotrophs that feed by absorption
A. Nutrition and Fungal life styles
1. heterotrophs
2. digest food outside bodies by secreting powerful enzymes (exoenzymes), then absorb it
3. there are decomposers (saprobes), parasites and mutualists
B. Body structure
1. single celled fungi are known as yeast
2. bodies of multicelled fungi are hyphae
a. tubular cell walls surround plasma membrane
b. cell walls contain chitin, a nitrogen containing polysaccharide also in insects
c. hyphae form an interwoven mass called mycelium that surrounds and infiltrates food
d. 1 cm3 may contain 1 km of hyphae - lots of surface area - 300cm2 interface w/ soil
e. fungal energy goes to increasing hyphal length and overall absorptive surface area
f. hyphae are nonmotile; but they grow into new areas
g. hyphae are divided into cells by crosswalls called septa
h. septa have pores large enough for ribosomes, mitochondria, etc to flow from cell to cell
1. some fungi lack septa, consist of continuous cytoplasmic mass w/ hundreds
or thousands of nuclei = coenocytic fungi
2. comes from repeated division of nuclei without cytoplasmic division
I. some hyphae specialized for feeding on live animals (Fig. 31.4)
j. some specialized for relationships with plant cells - haustoria - parasites or mutualists
1. ectomycorrhiza - penetrate between plant cells
2. endomycorrhiza - penetrate actual cells
II. Fungi produce spores through sexual or asexual life cycles - fungi produce vast numbers of spores, either
sexually or asexually. e.g. puffballs release trillions of spores in bursts, carried by wind/water; (Fig. 31.5). Most
fungi reproduce both sexually and asexually; others, one or the other
A. Sexual reproduction
1. nuclei of fungal hyphae and spores are haploid, except for transient diploid stages during
sexual reproduction
2. sex begins when 2 distinct mycelia release pheromones - signal molecules
3. if mycelia are from different mating types, pheromones from each partner bind to receptors on
surface of other, hyphae then extend toward source of pheromones
4. when they meet, they fuse; this “compatibility test” increases genetic variation
5. Union of cytoplasm of 2 parent mycelia is known as plasmogamy
6. Haploid nuclei may not fuse right away; parts of the mycelia contain coexisting, genetically
different nuclei - heterokaryon
a. some fungi keep nuclei separate, in different areas of mycelium;
b. others fuse nuclei and may exchange chromosomes and genes
c. in some, one nucleus from each parent pairs off, 2 to a cell - dikaryotic
7. hours, days, centuries may pass before the next stage of sexual life cycle occurs - karyogamy
8. karyogamy - nuclei fuse and produce diploid cells; only diploid stage in fungi
9. meiosis restores haploid condition
10. this process produces extensive g.v., and the heterokaryotic condition offers 2 sets of genes
to offset mutations that may exist
B. Asexual reproduction
1. clones produced by mitosis via spores, spread by air or water
2. some spp. only reproduce asexually
3. some fungi that reproduce asexually grow as mold, some molds can also reproduce sexually if
they come in contact w/ another mating type; molds look like fuzzy carpets (Fig. 31.6)
4. some fungi that reproduce asexually grow as yeast, which grow in liquid environments
including plant saps and animal tissues (Fig. 31.7)
a. no spores in yeasts - they pinch off small “bud cells” form parent or cell division
b. some yeasts can also reproduce sexually
5. Some fungi have no know sexual life stage - deuteromycetes or imperfect fungi
6. if sexual stage is discovered, organisms is then classified depending on sexual structures
III. Fungi have radiated into a diverse set of lineages - (Fig. 31.9)
A. Chytrids - ubiquitous in lakes and soils
1. may be parasites, saprobes
2. earliest to evolve - walls of chitin and certain proteins and metabolic pathways
3. chytrids are classed based on zoospores - flagellated spores (Fig. 31.10)
B. Zygomycetes - about 1000 known spp.
1. includes both fast growing molds that rot produce, parasites or commensal symbionts of
animals
2. Rhizopus (Black bread mold) (Fig. 31.12) is typical
a. hyphae coenocytic - no septa except where repro cells are formed
b. bulbous black sporangia found at tips of hyphae
c. in each sporangium, hundreds of haploid spores develop
d. some zygomycetes can actually “aim” spores toward a good food source (Fig. 31.13)
3. if environmental conditions deteriorate, zygomycetes may reproduce sexually
a. plasmogamy produces a structure called zygosporangium 1. karyogamy and then meiosis occur
b. a zygosporangium is a multinucleated structure - 1st, heterokaryotic then with many
diploid nuclei after karyogamy
c. zygosporangium are resistant to drying and frying and freezing, metabolically inactive
d. when conditions improve, zygosporangium undergoes meiosis, germinates into
sporangium and releases a genetically diverse haploid spores that may colonize
new substrate
4. microsporidia - unicellular parasites of animals and protists - often used in biocontrol
a. don’t normally infect humans, but may be problems for HIV
b. do not have conventional mitochondria, but organelles derived from them
C. Glomeromycetes - only 160 spp. - all are endomycorrhizae called arbuscular (tree-like)
endomycorrhizae (fig.31.15)
D. Ascomycetes - 32k spp. - marine, freshwater and terrestrial habitats
1. defining feature is asci- saclike structure for producing sexual spores; aka sac fungi
2. most ascomycetes bear sexual stage in fruiting bodies, or ascocarps - micro or macroscopic
a. spore forming asci found in ascocarps
3. ascomycetes vary in size and complexity (fig. 31.16)
a. some are saprobes
b. some are devastating plant pathogens
4. more than 40% of all ascomycetes live symbiotically w/ green algae in lichen
5. some are mycorrhizal
6. some live in mesophyll of leaves. secrete compounds to protect leaves from herbivores
7. common elements of reproduction (Fig. 31.17)
a. produce enormous numbers of asexual spores called conidia
1. conidia not produced in sporangia but in tips of specialized hyphae called
conidiophores, dispersed by wind
2. conidia of diff/’t mating types may reproduce sexually
E. Basidiomycetes - approximately 30k spp. including mushroom and shelf fungi (Fig. 31.18)
1. includes molds, mutualists, parasites
2. basidium - cell for sexual reproduction that is club shaped - aka club fungus
3. important decomposers of wood and plants
4. life cycle includes long lived dikaryotic mycelium - opportunities for many genetic
recombinations to occur
5. in response to environmental cues, mycelium reproduces sexually by producing basidiocarps
e.g. mushrooms are a type
6. by concentrating growth in hyphae of mushrooms, a mycelium can erect fruiting body in a
couple of hours, as water and cytoplasm stream in; a ring of mushrooms can appear over nite
(Fig. 31.10)
7. Numerous basidia in a basidiocarp release sexual spores (basidiospores)
a. mushroom cap protects and supports numerous large surface area of basidia on gills
b. a common store bought white mushroom may release a billion basidiospores which
drop from bottom of cap and blow away
c. asexual repro much less common in basidiomycetes than ascomycetes
V. Fungal impacts
A. Decomposers = can decompose almost and carbon containing substance - eg. jet fuel, house paint
great recyclers
B. Symbionts
a. mycorrhizae (Fig. 31.21)
b. fungus animal symbiosis - leafcutter ants (Fig. 31.22)
c. lichens (Fig. 31.23)
d. pathogens (Fig. 31.25)
C. practical uses - antibiotics
Ch. 31 – Fungi Learning Objectives
1. List the characteristics that distinguish fungi from members of other multicellular kingdoms.
2. Explain how fungi acquire their nutrients.
3. Describe the basic body plan of a fungus.
4. Describe the processes of plasmogamy and karyogamy in fungi.
5. Explain the significance of heterokaryotic stages in fungal life cycles.
6. Describe the evidence that suggests that Fungi and Animalia are sister kingdoms.
7. Explain the possible significance of the flagellated spores of members of the phylum Chytridiomycota.
8. Describe the life cycle of the black bread mold, Rhizopus stolonifer.
9. Describe importance of the microsporidia.
10. Distinguish between ectomycorrhizae and endomycorrhizae.
11. Distinguish among the Zygomycota, Ascomycota, and Basidiomycota. Include a description of the sexual
structure that characterizes each group and list some common examples of each group.
12. Describe some of the roles of fungi in ecosystems.
13. Describe the structure of a lichen. Explain the roles of the fungal component of the lichen.
14. Explain how lichens may act as pioneers on newly burned soil or volcanic rock.
15. Describe the role of fungi as agricultural pests.
16. Define mycosis, and describe some human mycoses.
17. Describe three commercial roles played by fungi