SWBAT: Explain how timing and coordination of physiological and behavioral events are regulated by multiple mechanisms and involve interactions between environmental stimuli and internal molecular signals.

How do each of these events or processes help the organism to maintain homeostasis?

What is the stimulus, receptor, response?

How do homeostasis, and these coordinated events in particular, relate to natural selection?

We are talking about innate physiological responses and behaviors, NOT learned ones.

Plants must respond to things such as • Available light• Passage of time (day/night, seasons)

Their response cannot be movement, so instead, they often respond with changes in their growth and development

Plants responses include

•Phototropism

•Photoperiodism

= growth toward (positive phototropism) or away from (negative phototropism) light

Controlled by auxins•plant hormones that cause cells to lengthen by “loosening” the cell wall

Auxin, produced in the apical meristem, always moves away from light so the cells farthest from the light source lengthen

The elongation of the cells is made possible by the activation of proton pumps

Acidifies and thereby “loosens” the cell wall allow more water to enter

The cell wall is “stretched” in this way

The response of an organism to the length of exposure to light throughout the day; length of day vs. night.

Phytochrome – a protein in plants that changes shape when it absorbs light.

PR PFR (named for the absorption spectrum)

The amount of PR vs. PFR , relates to the amount of light a plant has been exposed to over the day.

This in turn, tells the plant what season it is and whether it is time to bloom (reproduce)

Poinsettia- long night, short day (winter)

Lettuce- long day, short night (summer)

SURVIVAL!

Gibberellins = • Work with auxins to elongate.• Signal seeds to germinate

Abscisic acid =• Slows growth• Promotes dormancy• Conserves water by closing stomata

Ethylene =• Apoptosis –leaf shedding• Fruit ripening

Animals, especially humans, also respond to light and the amount of light stimulates in us a 24 hour “clock”.

Light eyes pineal gland releases melatonin (mostly in the dark)

Plants- phototropism and photoperiodism

Animals- circadian rhythms

Bacteria- quorum sensing

A way that bacteria can communicate with others in their species or even other species

Autoinducers= proteins given off by bacteria that simply say “I’m here”

More bacteria = more autoinducers

Behaviors related to density of population (and therefore autoinducers)• Symbiosis• Increased virulence• Motility• Biofilms

Physiological events

Behavioral events

Remember. . . These are innate behaviors NOT learned behaviors.

SURVIVAL!

Hibernation= A physiological state in which metabolism decreases, the heart and respiratory system slow down, and body temperature is maintained at a lower level than normal. Cold

Estivation= hot dry

Migration= a regular long-distance change in location

Courtship routines

Resource partitioning =•The differentiation of niches that enables similar species to coexist in a community

Mutualistic relationships•Lichens- a symbiotic association of a

fungus and photosynthetic microorganism•Bacteria in the digestive tract•Pollination

All timed coordinated events•Require communication within cells, between cells, or even between organisms.

•They are innate, NOT learned•They help to maintain homeostasis•They increase survival

SWBAT: Explain how timing and coordination of physiological and behavioral events are regulated by multiple mechanisms and involve interactions between environmental stimuli and internal molecular signals.