BISC208 Mini Exam 1 (University of Delaware, Dr. DeVito)

Characteristics of life

Reproduction, growth and development, responds to stimuli, and homeostasis

What was the atmosphere like in early earth?

A reducing environment that promoted the synthesis of organic compounds. Required input of energy (lightning and UV)

Oxidation

Losing electrons

Separation of two molecules

Reduction

Gaining electrons

Joining of two molecules

Oparin & Haldane

The Oparin and Haldane hypothesis states that early oceans were a "prebiotic soup" of organic molecules. Early earth was a reducing environment.

Miller & Urey

They said that the synthesis of organic compounds is possible, although the "atmosphere" affects the outcome.

Stages in the Origin of Life

1. Synthesis of small organic molecules

2. Polymerization

3. Protocells

4. Self- Replication

Desiccation

Dry-out

Plasmodesmata

Pores between cells used for communication

Stoma

Allows CO2 in and O2 out, surrounded by two guard cells which open and close by expanding

Uptake of solutes causes water to be drawn in by osmosis. The guard cells swells and opens the stomata. Releasing solutes causes the stomata to close.

Sexual reproduction

Alters between haploid and diploid multicellular stages

What are the major challenges to moving to land?

No constant access to water, potential for competition for sunlight

They may not have all the inputs they need to constantly photosynthesize

Dermal tissue system

Outermost layer of cells

Protect in shoots & absorb in roots

Epidermis and endodermis

Endodermis

Dermal Tissue

Layer of cells that surround the stele; contains waxy strip that forces incoming water to filter through a selectively permeable membrane before it gets to the xylem.

This is where the plant switches from diffusion to bulk flow (movement due to pressure gradient)

Upper Epidermis

Dermal Tissue

The waxy cuticle minimizes water loss

Dry environments where the plants need to store all their water

Lower Epidermis

Dermal Tissue

Allow gas exchange between the air and the plant

Thinner cuticle or no cuticle

Contains stoma

Ground tissue system

Storage, support, photosynthesis

Parenchyma/Collenchyma/Sclerenchyma

Mesophyll

Collenchyma

Ground tissue

Shoot support

Sclerenchyma

Ground tissue

Fibers and Sclereids

esophyll

Ground tissue

They're on top of the leaf to get the best exposure to light possible, since their main function is light absorption for photosynthesis

They are densely packed

Spongy mesophyll

They are loosely packed for efficient gas exchange.

In what environments may this be favored?

Vascular tissue system

Transport to all plant organs (Thick cells walls)

Vascular bundles with Xylem and Phloem

Xylem

Vascular tissue in bundles

Moves water and dissolved minerals; water enters/exits through the pits

Tracheids and vessel elements

Tracheids

Vascular tissue in xylem

Product of single cell

Vessel elements

Vascular tissue in xylem

Conduct water more efficiently then tracheids

Phloem

Vascular tissue in bundles

Moves food (photosynthate)

Sieve-tube elements and companion cells

Sieve-tube elements

Vascular tissue in phloem

Transporting sugars and nutrients

Compainion cell

Vascular tissue in phloem

Provides materials to maintain sieve-tube elements

Vascular bundles

Vascular tissue

Contains xylem and phloem

Meristematic tissue

meristems, location of growth

Apical meristem

Length

Lateral meristem

Width

Intercalary meristem

Where the leaf meets the stem

Intermediate growth

Cell growth is localized to specific regions called meristems

Diffusion

The net movement of anything from a higher concentration → lower concentration

Osmosis

The movement of water molecules to a concentration where there is less free water

Passive

Solute potential

Transpiration

Water moves from the roots to the shoots to replace H2O lost during evaporation in stomata

Root pressure and capillary action

Root pressure

Involved in transpiration

Diffusion of H2O creates pressure (pressure potential, lower when dry & hot)

Capillary action

Involved in transpiration

Cohesion and adhesion

Hydrogen bonds

Cohesion

Partial charges between H2O (surface tension)

Adhesion

Water & hydrophilic surfaces (i.e. inner walls of tracheids in xylem)

Translocation

Movement of sugar between plant cells in the phloem

Sources

Points of translocation

Sugar enters the phloem

Sinks

Points of translocation

Sugar exits phloem

Growing season sinks and sources

Leaves have excess sugar (sources), sugar moves to meristems, developing leaves/seeds/fruits, and storage (sinks)

Early growing season sinks and sources

Storage (sources) moves to growing areas (sinks)

Oleander Habitat

Endures long seasons of drought & inundation of winter rains

Thicker/more spongy mesophyll for water storage through the drought

Water Lily

Sits in the water

Stomata on the top of the leaf

Nanoparticles

Penetratesthe waxy cuticle, the epidermis, and the ground tissue to reach the phloem in the centerleaves & deliver nutrients to crops, made of plant phospholipids

More nutritious crops provide more nutrients for humans to be healthy

Auxin

Hormone that prevents abscission, produced in shoot tips, blue light signal

Gravitropism and phototropism

Tropism

Response resulting in curvature of organs towards or away from a stimulus

Phototropism

Any directional plant movement in response to light

Red & Blue wavelengths: drives germination

Far-red wavelengths: indicates shade

Blue wavelengths

Phototropins are phosphorylated causing photosynthesis (move chloroplast to optimise light absorption inside leaf cells and their stoma opens in response to blue light) and plants to bend through elongation

Cytokinins

Hormone that promotes cell division

Apical Dominance

The interplay of auxin and cytokinins communicates to axillary buds when conditions are right for the growth of new branches

Auxin greatest at top of tree, Cytokinins greatest at bottom of tree → tree symmetry

Gibberellins (GAs)

Hormones that stimulate growth in plants and fungi

Abscisic Acid (ABA)

Hormone that inhibits growth by stimulating stomatal closure

Ethylene

Hormone that causes senescence

Leaf Abscission at high levels of ethylene and low levels of auxin

Senescence

Regulated process of aging and death

Pathogens enter plants through...

the cuticle of the epidermis is the first line of defense

Plant reactions to pathogens

Close stomata

Plug Xylem: can cause Vascular Wilt Disease

Hypersensitive response: creates barrier of dead tissue to prevent spreading

Plants can isolate certain portions of the infected plants and send chemical signals to uninfected regions to increase defense and resistance

Vascular Wilt Disease

In some cases, the leaf will block its entire vascular system, causing its own death

Biotrophic pathogens

Eating live material (viral, bacterial, fungal)

Necrotrophic pathogens

Eating dead material Kills cells before colonizing them (bacterial, fungal)

How can bacteria and fungi be more effective

Vascular system allows pathogens to travel long distances

Can secrete a chemical that prevents the stomata from closing and secrete enzymes that weaken the cell wall