Copyright © Rebecca Rehder Wingerden

Lecture Presentations for

Biology Eighth Edition

Neil Campbell and Jane Reece

Pearson Education, Inc., publishing as Person Benjamin Cummings College Board, AP Biology Curriculum Framework 2012-2013

Many biological processes involved in growth, reproduction and dynamic homeostases include temporal regulation and coordination. (2.E.2)

Big Idea 2: Cellular Processes

38.1, 39.2, 39.3, 24.1, 11.1

Timing and coordination of physiological events are regulated by multiple mechanisms. (2.E.2)

a. In plants, physiological events involve interactions between environmental stimuli and internal molecular signals.

1. Phototropism, or the response to the presence of lights (2.C.2)

Auxins are produced in the cells which are located on the dark side of the shoot, auxin stimulates stem elongation which bends the stem toward light source.

Phototropism. Growth of a plant shoot toward (positive) or away (negative) from light.

Auxins. A class of plant hormones which stimulate plant growth.

Copyright © 2012 Rebecca Rehder Wingerden

Timing and coordination of physiological events are regulated by multiple mechanisms. (2.E.2)

2. Photoperiodism, or the response to change in length of the night, that results in flowering in long-day and short-day plants (2.C.2)

Plant must be able to anticipate seasons in order to flower at the correct time of year. To determine whether it is the correct season for flowering plants have evolved a way to determine the length of day and to respond correctly.

Long Day Plants (LDP) flower when the day exceeds the critical value and fails when it does not.

Short Day Plants (SDP) flower when the day is shorter than the critical length and when the night is longer than the critical length.

Phytochrome is a pigment that fundamentally alters plant behavior. It has two interconvertible forms: Pr and Pfr. Each form elicits a different responses.

Copyright © 2012 Rebecca Rehder Wingerden

Timing and coordination of physiological events are regulated by multiple mechanisms. (2.E.2)

b. In animals, internal and external signals regulate a variety of physiological responses that synchronize with environmental cycles and cues.

Human Circadian Biological Clock

Jet lag in humans.

• Circadian rhythms, or the physiological cycle of about 24 hours that is present in all eukaryotes and persists even in the absence of external cues

The primary circadian “clock” in mammals is located in the suprachiasmatic nucleus (SCN), a pair of distinct groups of cells located in the hypothalamus. The SCN receives light information through the eyes. This information is then passed on to the the pineal gland which secretes the hormone melatonin. Secretion of melatonin peaks at night and ebbs during the day.

Copyright © 2012 Rebecca Rehder Wingerden

Timing and coordination of physiological events are regulated by multiple mechanisms. (2.E.2)

Hibernation - is a state of inactivity and metabolic depression in animals, characterized by lower body temperature, slower breathing, and/or lower metabolic rate. Hibernating animals conserve energy, especially during winter months when food supplies are limited.

European hedgehog

Obligate Hibernators

ground squirrel

Obligate hibernators are “true hibernators” arousals are driven by internal mechanisms, and external stimuli often fail to wake them

Facultative Hibernation

bears

bat

Facultative hibernators can be aroused by external stimuli but unless so alarmed, they are able to sleep for the entire winter.

Torpor

hummingbirdTorpor is known as temporary hibernation, it is a state of decreased physiological activity characterized by a reduced body temperature and rate of metabolism.

Copyright © 2012 Rebecca Rehder Wingerden Copyright © 2012 Rebecca Rehder Wingerden

Timing and coordination of physiological events are regulated by multiple mechanisms. (2.E.2)

c. In fungi, protists and bacteria, internal and external signals regulate a variety of physiological responses that synchronize with environmental cycles and cues. • Fruiting body formation in fungi

A fruiting body is a specialized spore-producing structure, often referred to as a mushroom. When ripe, the spores fall downwards and are carried away form the mushroom on air currents. A spore that lands on a moist surface with nutrients can form a new fungal colony, but must mate with another colony of the same species before a new mushroom can be produced.

Bird’s nest fungi (Nidularlaceae) fruiting bodies resemble tiny egg-filled birds’ nests. Fruiting body formations influenced by external factors such as season (temperature and air humidity), nutrients and light.

Timing and coordination of physiological events are regulated by multiple mechanisms. (2.E.2)

Quorum sensing is a system of stimulus and response correlated to population density. Many species of bacterial use quorum sensing to coordinate gene expression (signal transduction pathways) according to the density of their local population, and therefore the behavior of the entire community. The evolution of quorum sensing system in bacteria could have been one of the early steps in the development of multicellularity.

Quorum sensing was first observed in Vibrio fischeri, a bioluminescent bacterium that lives as a mutualistic symbiont in the photophore (light-producing organ) of the Hawaiian bobtail squid.

Quorum sensing bacteria produce and release chemical signal molecules called autoinducers that increase in concentration as a function of cell density. Bacteria use quorum sensing to coordinate certain behaviors based on the local density of the bacterial population; such as symbiosis, virulence, conjugation, motility, sporulation, and biofilm formation.

Positive Feedback Loop

Copyright © 2012 Rebecca Rehder Wingerden

Timing and coordination of physiological events are regulated by multiple mechanisms. (2.E.2)

Bozeman Biology: Mechanisms of Timing and Control (10:00 min.) http://www.bozemanscience.com/025-mechanisms-of-timing-and-control

Bozeman Biology: Signal Transduction Pathways (10:00 min.) http://www.bozemanscience.com/038-signal-transduction-pathways

Bozeman Biology: Evolutionary Significance of Cell Communication (8:00 min.) http://www.bozemanscience.com/036-evolutinary-significance-of-cell-communication

Bozeman Biology: Fungi (10:00 min.) http://www.bozemanscience.com/fungi

Copyright © 2012 Rebecca Rehder Wingerden