2E - BIOLOGY COORDINATES WITH TIME

Essential knowledge 2.E.1:Timing and coordination of specific events are necessary for the normal development of an organism, and these events are regulated by a variety of mechanisms.

Observable cell differentiation results from the expression of genes for tissue-specific proteins.

Induction of transcription factors during development results in sequential gene expression.

Evidence of student learning is a demonstrated understanding of each of the following:

1. Homeotic genes are involved in developmental patterns and sequences.

2. Embryonic induction in development results in the correct timing of events.

3. Temperature and the availability of water determine seed germination in most plants.

4. Genetic mutations can result in abnormal development.

5. Genetic transplantation experiments support the link between gene expression and normal development.

6. Genetic regulation by microRNAs plays an important role in the development of organisms and the control of cellular functions.

Programmed cell death (apoptosis) plays a role in the normal development and differentiation.

Students should be able to demonstrate understanding of the above concept by using an illustrative example such as:

• • • •

Morphogenesis of fingers and toes Immune function C. elegans development Flower development

✘✘ Names of the specific stages of embryonic development are beyond the scope of the course and the AP Exam.

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Essential knowledge 2.E.2:Timing and coordination of physiological events are regulated by multiple mechanisms

In plants, physiological events involve interactions between environmental stimuli and internal molecular signals. [See also 2.C.2]

Evidence of student learning is a demonstrated understanding of each of the following:

1. Phototropism, or the response to the presence of light

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

✘✘ Memorization of the names, molecular structures and specific effects of all plant hormones are beyond the scope of the course and the AP Exam.

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

To foster student understanding of this concept, instructors can choose an illustrative example such as:
• 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

• Diurnal/nocturnal and sleep/awake cycles

• Jet lag in humans

• Seasonal responses, such as hibernation, estivation and migration

• Release and reaction to pheromones • Visual displays in the reproductive cycle

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

To foster student understanding of this concept, instructors can choose an illustrative example such as:

• Fruiting body formation in fungi, slime molds and certain types of bacteria

• Quorum sensing in bacteria

✘✘ Memorization of the names, molecular structures and specific effects of hormones or features of the brain responsible for these physiological phenomena is beyond the scope of the course and the AP Exam.

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Essential knowledge 2.E.3:Timing and coordination of behavior are regulated by various mechanisms and are important in natural selection.

a. Individuals can act on information and communicate it to others.

Evidence of student learning is a demonstrated understanding of each of the following:

1. Innate behaviors are behaviors that are inherited.
2. Learning occurs through interactions with the environment and other organisms.
Responses to information and communication of information are vital to natural selection. 
Evidence of student learning is a demonstrated understanding of each of the following:

1. In phototropism in plants, changes in the light source lead to differential growth, resulting in maximum exposure of leaves to light for photosynthesis.

2. In photoperiodism in plants, changes in the length of night regulate flowering and preparation for winter.

3. Behaviors in animals are triggered by environmental cues and are vital to reproduction, natural selection and survival.
Students should be able to demonstrate understanding of the above concept by using an illustrative example such as:
• Hibernation 
• Estivation 
• Migration 
• Courtship

4. Cooperative behavior within or between populations contributes to the survival of the populations.
Students should be able to demonstrate understanding of the above concept by using an illustrative example such as:

• Availability of resources leading to fruiting body formation in fungi and certain types of bacteria
• Niche and resource partitioning
• Mutualistic relationships (lichens; bacteria in digestive tracts of animals; mycorrhizae)
• Biology of pollination

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