Exam 1: Plants- Bio 2

synapomorphy

defining characteristic or trait of an evolutionary group

three domains

• bacteria- prokaryotes (cells w/o nuclei and peptidoglycan in cell walls, 1 RNA pol)

  • typcially has motion

• archaea- prokaryotes (cells w/o nuclei or peptidoglycan in cell walls, 3 RNA pol)

  • cell wall is different from baceteria

  • don’t really see them, volcanoes, thermal vents

  • nearest living relatives to all eukaryotes

• Eukarya- eukaryotes (cells with nuclei and 3 RNA polyerase)

photosynthesis

-harvests light energy and uses this to synthesize high-energy molecules

-chemiosmotic theory- protein gradient that was established by protein transport in light reactions can be used to synthesize ATP, concentration gradient

• Used to convert CO2 into sugars

6CO2 + 6H20 —> glucose + O2

cyanobacteria

-Ubiquitous photosynthetic prokaryotes (no nucleus, circular chromosomes, etc.)

-These were the first organisms to do oxygenic photosynthesis (typical carbon-fixing type prevalent today

-can also “fix” nitrogen gas from the atmosphere

-N2 (gas) → NH4 , NO2 & NO3

• Ammonia, nitrite, nitrate = fertilizer.

• Needed for synthesis of amino acids (proteins) and nucleic acid (DNA, RNA)

origin of photosynthesis

-Oxygenic photosynthesis drastically influenced the course of evolutionary history on earth.

-Oxygen rich atmosphere favored organisms that could withstand and utilize oxygen.

-Set the stage for the rise and diversification of the eukaryotes.

primary endosymbiosis- need to know

-All chloroplasts can be traced back to one cyanobacteria

- A eukaryotic host cell directly engulfs a free-living prokaryotic organism (like a bacterium or cyanobacterium) instead of digesting it

-The eukaryotic chloroplast originated from symbiotic cyanobacteria. It has membranes similar to both cyanobacteria and eukaryotes. Chloroplasts are now considered an “organelle” within photosynthetic eukaryotic cells.

-the domestication of cyanobacterial cells occurred in an ancestor of red algae, green algae and land plants

secondary endosymbiosis- need to know

-three chloroplast membranes

-occurs when a living eukaryotic cell (a complex cell with a nucleus) engulfs and retains another eukaryotic cell that already contains a photosynthetic organelle

tertiary endosymbiosis

-an evolutionary event where a eukaryotic host cell engulfs a different eukaryotic alga that already carries a secondary plastid

-ex. dinoflagellates (red tide)

what is a plant

Plantae- that clade of eukaryotic life with chloroplasts derived from primary endosymbiosis

-Most of the earliest splits in this tree have led to aquatic lineages (marine or freshwater): ALGAE

phragmoplasts- need to know

-thought to help algae grow 3-dimesntionally- create cell plates with plasmodesmata

• serves as a scaffold of cell plate assembly

• assemble perpendicular to the plane of the future cell plate so that new cells can grow outwards

red algae

-vary from single-celled to elaboratey branced multicellular organisms

• cell walls- cellulose

• photosynthetic pigment- chlorophyll

• red color- phycoerythrin pigments that absorb green and blue light

-”corraline” red algae represent one of the earlist lineages of eukaryotes that we can see in the rock record

• improtant as reef builders, food for reef organisms

plasmodesmata- need to know

-channels that penetrate the cell walls of adjacent cells

-most streptophtes have plasmodesmata

parenchyma

-the basic tissue type in the streptophyes with cells linked by plasmodesmata

isogamy vs oogamy need to know

oogamy- fusing gametes are very different in size and mobility

• egg is large and does not move, sperm is small and mobile

isogamy- fusion of two gametes that look identical in size and shape

• same size, strucute, and form. they cannot be called male of female

streptophte

-plant group that includes all land plants (embryophytes) and several classes of freshwater and terrestrial green algae

glaucophytes

-rare group of microscopic, single celled freshwater algae that provide vital clues about the evolutionary origin of plant chloroplasts

-archaeplastida

evolutionary changes that not all streptophytes have

-oogamy, plasmodesmata, and apical growth

-many other green algae may be single cleed or filamentous multicellular without branched structure

-isogamy and no plasmodesmata

key adaptations permitted plants to colonize land

-they had to

• adapt to dry, high-light conditions

• develop transport systems for water and nutrients

• develop structural support

  • ex. redwood trees

• find new ways to disperse reproductive cells and progeny (offspring)

  • prior to this it had been water. land plants had to get creative.

specific physical adaptations to plants

-cuticle- a waxy coating that slows water loss on the surface of everything above ground

-spores- with thick walls containing sporopollenin for desiccation resistance (halts their metabolism during droughts and revives when water returns)

-stomata- closable openings that regulate gas exchange; when the stomata are open, there is almost no resistance to airflow. When they close, they resist transpiration

-pigments- protect against UV radiation; anthocyanins absorb UV light and remit it as blue or purple light

-relationship with fungi (mycorrhizae)- promotes nutrient uptake from the soil

cross section of a leaf (need to know and what parts each does)

-carbon dioxide gets stored is spongy mesophyll

-palisade layer holds the chloroplasts, where photosynthesis happens

-stomata- closes and opens for gas exchange, controlled by guard cells

• allows CO2 to enter and H20 to exit

-cutilce- prevents evaportation across the epidermis

spores and sporopollenin wall

-protects spores against drying out and decay

-swimming spore and spore blown in wind

-spores protected against desiccation and decay

guard cells and stomata

-when guard cells are flaccid (soft) they are open

-when guard cells are sturgid (filled with water) they are closed

accessory photosynthetic pigments

-in the streptophytes chlorophyll b evolved

-they absorb light in different wavelengths then chlorophyll a

-can help increase photosynthetic efficiency

-flavonoids protect from uv exposure

-involved in pollination

• flowers produce nectar to attract animals for pollination

• pigments can serve as a private communicating channel with pollinators

mycorrhizae

-fungi associated with underground plant parts (roots)

• have biochemical enzymes that enable the release of phosphate that is tightly bonded to soil particles, then will bring to roots

- vesicular-arbuscular mycorrhizal fungi- grow into root cells and exchange water and nutrients, invade the root and kill a small …-

-ectomycorrhizal fungi- have cillia that grow between the cell walls, increasing surface area for water and mineral absorption

land plants have alternation of genertions

-there are both haploid and diploid multicellular stages

-this life cycle is a synapomorphy for the land plant clade

alternation of generations

-spores grow via mitosis to produce haploid multicellular gametophytes which make gametes in gametangia

• two types of gametangia- antheridia (make sperm) and archegonia (make eggs)

-eggs are fertilized by sperm to form diploid zygotes

-the diploid zygote develops by mitosis into a multicellular embryo, which eventually grows into a mature diploid plant (sporophyte).

• forms spore producing sporangia

• cells in sporoangia produce haploid spores by meiosis

gametangia

-organs that enclose gametes and prevent them from drying out

-two kinds

• archegonium- produces egg cell; houses embryo after fertilization

• antheridium- produces motile sperm

embryos

-young plants contained within a protective structure

-found in all land plants, and the land plant clade is called “Embryophyta”

-early growth of diploud, sporophyte generation, protected by archegonium