BIOL 1450 Exam 1 Review Session

What is homeostasis?

abilitiy to maintian internal conditions, adjust internal conditions to adjust to external environments and conditions

What are some internal conditions an individual must keep to maintain homeostasis?

• body tempeture

• pH level

• blood sugar/blood pressure

• metabolism

• (plants) water content

Do internal conditions fluctuate or stay constant?

Fluctuate

List reasons external conditions could change? Interal?

• External: environment, stressers, temperature, food

• Interal: Body temp will range, stomata will close in plants with lack of water, body will burn energy depending on how you consume food, etc.

What four steps does our body go through to be able to maintain homeostasis?

Sense, communicate, interpret and integrate, respond

Can you recall any of the processes that affect plant homeostasis?

• Drought stress

• disease, systemic acquired resistance

• Apical dominance

• Gravity, gravitropism

• photoperiodism

• Phototropism

What are hormones?

Chemical communicate over long distances in human and plants

What are the 5 basic steps of transmission of hormones?

1. Signal (stimulus) sensed by specific cells

2. Cause specific hormone(s) to be produced and released

3. Hormone travels throughout plant via vascular tissue fluid

4. Hormone signal detected by certain cells- causes cells to change their function

5. Changes in cell functions determine overall response of the plant

Explain the role of each of the following:

• leaves

• stomata

• roots

• vascular tissue

• leaves: absorb sunlight, light energy required for photosynthesis

• stomata: takes in CO2, lets in and out water and oxygen

• Roots: absorbs water and nutrients

• Vascular tissue: transports water and nutreints, chemical that signals other molcules: horomones

Where does growth occur?

very tip of roots and shoots

what is apical dominance?

Growth occurs on apical bud, lateral buds are inhibtited, apical bud overpowers growth of lateral buds

why does apical domiance occur?

outcompete other plants, get as close as it can to the sun/energy source, to keep growing taller

What hormone is involved in the signaling in apical dominance?

Auxin

What is systemic acquired resistance?

When a plant gets a virus/infection, the second time it gets it is resistant, the virus in a certain area will get distrubuted to the rest of the plant so the whole plant is resistant next time

What triggers SAR?

Infections, pathogen infection, viral infection

What is the primary signaling molecule for SAR?

Salicylic acid

How does the signal for SAR travel through the plant?

vascular tissue

What are the benefits of SAR?

A systemic effect on plant so no matter where infected, the whole plant as immunity

what is the difference between permanent defenses and induced defenses?

• Permanent: permanently there, not triggered by anything (ex. thorns)

• Induced: triggered by stimulus (SAR)

What is drought stress?

plants not having enough water

how do plants respond to drough conditions?

close stomata

What hormone is involved in signaling when there isn’t enough water content in the soil?

ABA

ABA stands for

abscisic acid

What sense takes up water, what sense drought?

a. leaves

b. stomata

c. roots

d. all of the above

e. a and b

f. b and c

c. Roots

how does the signaling hormone ABA travel through the cell?

vascular tissue

What is a photoperiodism?

flowering response due to the length of day and night, darkness is responsible

what hormone is suspected to play a role in photoperiodism?

Florigen

Explain what short-day (long-night), long-day (short-night), and day neutral means for plants.

• Short-day (long-night): needs more than its critical period to flower

• Long-day (short-night): needs less than its critical period to flower

• Day Neutral: plant isnt affected by photoperiod, can flower at certain time of year or life

What is a critical period?

The amount of darkness required for a flower to bloom

Explain the role of phytochrome in regards to flowering in the presence of red and far red light.

Photoreceptor (molecule that absorbs and responds to specific wavelengths of light) allows plants to sense red and far-red light

Whar are the two subtypes of tropisms

• phototropism

• Gravitropism

What makes a tropism a tropism?

Growth response that grows away or to the stimulus

What hormone plays a role in both tropisms?

auxin

In shoot cells, what response does auxin have?

• promotes growth

• more concentrated on side farther away from the light

In root cells, what response does auxin have?

• inhibits growth

• auxin is abundant on bottom of root, the top of the root needs to grow more if the root is sideways, making it harder to grow

Where is auxin more abundant in shoot cells? Root cells?

• Shoot: dark side

• Root: bottom side

gravity-sensing cells contain starch filled sacks

statoliths