Behavior and Ecology - UNIT 8
43.1 Inheritance Influences Behavior
Learning outcomes
Explain key aspects of studies suggesting behavior has a genetic basis.
Describe body systems that influence behavior (nervous and endocrine).
Core idea: Nature via genetics and nurture via environment shape behavior
Behavior defined as any observable action or response.
“Nature vs. nurture” asks how genes and environment influence behavior; evidence supports a genetic basis for many behaviors because genes control neural/hormonal mechanisms that influence behavior.
Evidence that behavior has a genetic basis
Nest-building in lovebirds (Genetics influence behavior)
Fischer lovebirds (Agapornis fischeri) cut long nesting strips with bill and carry one at a time; peach-faced lovebirds (A. roseicollis) cut shorter strips and carry several by tucking them into rump feathers.
Hybrids show intermediate behavior: carry strips of intermediate length, but initially tuck them in rump feathers rather than bill, and strips often fall out during movement.
Hybrids learn to carry strips in bills after about 3 years, suggesting genetic control with learning modifying expression.
Food choice in garter snakes (Genetics influence prey preference)
Inland populations (aquatic; eat frogs/fish) vs coastal populations (terrestrial; eat slugs).
Crosses yield offspring with partial slug preference; tongue-flick rates to slug odor differ by population, indicating a physiological/neural basis for prey detection.
Hybrids show intermediate tongue-flick patterns, supporting a genetic component to sensory preference.
Twin studies in humans
Twins separated at birth show similar food preferences, activity patterns, and mate choices, supporting a genetic influence on some behaviors.
Animal studies: nervous and endocrine systems both influence behavior
Endocrine system can affect behavior patterns.
Egg-laying behavior in marine snail Aplysia
Egg-laying behavior involves a sequence of movements controlled by an egg-laying hormone (ELH).
ELH: a small protein of 36 amino acids that diffuses through the circulatory system to contract reproductive ducts.
ELH gene encodes a protein of 271 amino acids; cleavage can yield up to 11 products, with ELH being one.
Nurturing behavior in mice (fosB gene)
fosB alleles: presence promotes maternal nurturing behaviors (retrieving and crouching over young).
Absence of fosB alleles leads to lack of maternal nurturing; hypothalamus may fail to activate relevant enzymes/genes.
Females with fosB retrieve young more effectively; illustrated in Fig. 43.3.
Illustrative examples and takeaway
Nature provides a genetic basis for neural/hormonal pathways that shape behavior; environment can modulate expression, but many core behaviors have a genetic template.
Researchers use model organisms (lovebirds, garter snakes, mice, Aplysia) to demonstrate genetic components in behavior.
Check Your Progress (43.1)
Compare studies showing genetic basis for behavior.
Identify body systems influencing behavior.
43.2 The Environment Influences Behavior
Learning and environment interplay with genetics
Fixed action patterns (FAPs): once thought unmodifiable, elicited by sign stimuli; learning can modify many FAPs.
Example: stickleback fish respond aggressively to red-bellied models (sign stimulus); color acts as a cue for aggression.
Habituation and learning
Habituation: decreased response to a repeated, benign stimulus (e.g., deer ignored traffic).
Instinct and learning
Begging in laughing gull chicks considered partly instinctive but improves with learning; chicks become more accurate in pecking at a model bill over 2 days, showing motor-skill improvement aids instinct.
Imprinting and sensitive periods
Imprinting: young animals form an association with the first moving object during a sensitive period (2–3 days after hatching in many birds).
Lorenz classic studies: imprinting on the first moving object can be essential for species recognition and mate choice; in wild, imprinting on mother is crucial; in labs, imprinting can occur on a human or object if encountered during the sensitive period.
Social interactions during imprinting are important for normal imprinting (e.g., vocalizations by females during imprinting in mallards).
Social learning and cognitive approaches
Social learning: young white-crowned sparrows learn dialects from older birds; tapes alone during sensitive period can influence song, but tutor exposure yields stronger imitation.
Cognition and problem solving: observational learning, imitation, and insight.
Japanese macaques wash sweet potatoes by imitating others.
Ravens demonstrated insightful problem-solving with string and meat; some animals plan ahead (sea otter using a rock to crack clams; chimpanzees using leaves to extract termites).
Orientation, migration, and navigation
Migration requires orientation (directional travel) and navigation (ability to adjust course).
Birds use sun during the day and stars at night; biological clocks help compensate for sun movement.
Navigation can depend on Earth's magnetic field; experienced birds can correct flight paths, while inexperienced birds may deviate (as in starling migration experiments).
Proximate vs ultimate causes: proximate = environmental stimuli triggering travel; ultimate = survival/reproduction benefits of migration.
Cognitive learning and language-like capabilities
Humans' language ability exceeds other animals; nonhuman primates can learn symbolic communication but struggle with grammar.
Clickable example: migratory orientation and navigation illustrated by starling experiments (Holland, Switzerland relocation trials; results show navigational learning in experienced birds).
Check Your Progress (43.2)
Describe the sequence of events for classical and operant conditioning.
Identify examples of how environment influences behavior.
Discuss evidence for environmental influence on behavior.
43.3 Animal Communication
Communication overview
Communication is an action by a sender that may influence a receiver’s behavior; can be intentional or incidental.
Examples: echolocation in bats, moths hearing bat pulses and evading them.
Chemical communication
Pheromones are chemical signals used within species; effective day and night.
Examples: moths secrete pheromones for mate finding; ants/termites mark trails with pheromones; cheetahs mark territories with urine/feces; honeybees use pheromones for social organization.
The vomeronasal organ (VNO) in some animals detects pheromones; signals from VNO can influence hypothalamic hormone release.
Researchers investigate pheromones’ roles in parental care, aggression, and mating.
Auditory communication
Advantages: fast, effective day/night; can vary in loudness, pattern, duration, repetition.
Examples: crickets calls; birds songs (distinct calls for distress, courtship, territory); humpback whale songs with six basic themes; dolphins have complex communication; vervet monkeys have alarm calls for different predators; human language is highly complex and capable of grammar.
Visual communication
Visual signals: displays during courtship and defense; conspicuous plumage or displays (e.g., Raggiana Bird of Paradise); fireflies flash patterns for species-specific mating signals.
Visual cues can replace auditory/chemical messages in many contexts; body language (e.g., human classroom signals) reflects internal states.
Threat displays (e.g., male baboon full threat display) establish dominance without fighting; hippos use mouth displays.
Tactile communication
Touch conveys information and bonds social groups; grooming strengthens social ties in primates.
Waggle dances in honeybees combine tactile and spatial cues; bees also use sun compass aided by the clock gene period to calibrate the dance direction.
Do animals have emotions?
Nature of Science discussion explores whether animals experience emotions (fear, joy, grief) and links this to behavior and brain chemistry (e.g., dopamine's role in reward and emotion).
This area is debated; evidence suggests emotional states influence behavior in many species.
Bee communication specifics
Waggle dance: distance/direction of food; outside hive, straight run points to food; inside hive, angle relative to gravity matches food source relative to sun; sun compass relies on clock gene period.
Auditory and visual examples
Vervet alarm calls differentiate eagles vs leopards; different calls produce different responses.
Check Your Progress (43.3)
Describe how communication affects receiver behavior.
List advantages/disadvantages of chemical, auditory, visual, tactile communication.
Identify human receptors for each communication type.
43.4 Behaviors That Increase Fitness
Behavioral ecology and fitness
Natural selection shapes behavior; many behaviors increase survival and reproductive success (territoriality, foraging efficiency, reproductive strategies, social behaviors, altruism).
Territoriality and fitness
Home range vs territory: defended area used exclusively for access to resources and mating.
Gibbons: monogamous, territorial; territories defended by dawn songs; male injuries indicate defense efforts. Territory size must balance resource access with defense costs.
Examples: cheetahs require large territories; hummingbirds defend small patches; seabirds have large ocean ranges but defend nesting territories during reproduction.
Foraging and energy optimization
Foraging theory: optimal foraging model—maximize net energy gained per unit time; energy intake must exceed energy expenditure of foraging.
Example: shore crabs prefer intermediate-size mussels because net energy gain (yield minus cost) is highest for that size; larger mussels cost more energy to crack than the energy they provide.
Reproductive strategies and sexual selection
In many primates, females invest heavily in offspring; male strategies include displays and competition to access females.
Monogamy: gibbons are monogamous; many primates are not.
Sexual selection: traits that increase mating success but may incur survival costs (e.g., elaborate tails in peacocks).
Zebra finch imprinting example shows female choice can be influenced by artificial ornaments.
Male courtship displays and female choice (bowers)
Bowerbirds build elaborate bowers and decorate with objects to attract females; females choose males based on bower quality and displays.
Robotic female experiment (fempots) shows males adjust display intensity in response to female crouching; better-adjusting males have higher courtship success and startle females less often.
Conclusion: female signals influence male displays; sexual selection favors males who can read female signals and adjust accordingly.
Societies, kin selection, and altruism
Inclusive fitness: an individual’s fitness includes its own offspring plus related offspring (kin selection).
Queen-centric eusocial systems (bees/wasps/ants): workers are related; sterile workers help raise sisters; high relatedness (e.g., 75% for sisters when queen has single mate) can favor helping over direct reproduction.
Indirect selection (kin selection): relatives sharing genes can make helping advantageous.
Examples of inclusive fitness and kin selection: bees, ants; chimpanzee group dynamics; meerkats provide babysitting for kin; red deer social dynamics with male/female competition.
Reciprocal altruism
Behavior where individuals help others with the expectation of future reciprocation; cheaters are punished or excluded.
Vampire bats: sharing blood meals; failure to share can lead to exclusion from future sharing.
Group living: benefits and costs
Benefits: predator avoidance, cooperative foraging, shared information.
Costs: competition for resources, disease spread, dominance hierarchies.
Check Your Progress (43.4)
Explain how territoriality relates to foraging.
Compare and contrast reproductive strategies and forms of sexual selection.
Describe examples of altruistic behaviors increasing fitness.
Big Ideas connections
BIG IDEA 2: Ecosystems and environments influence behavior cycles (migration, circadian rhythms, taxis, kinesis) and are shaped by natural selection.
BIG IDEA 3: Information storage, transmission, and response—communication signals alter behavior for sender/receiver advantages and influence evolutionary trajectories.
BIG IDEA 4 (implied in intro): Biological systems interact to create complex properties; ecosystems rely on interactions among producers, consumers, and recyclers to sustain the biosphere.
Relevance to AP Biology foundations:
Innate vs. learned behaviors, genetic basis of behavior, environmental modulation, communication, sociality, and fitness.
Role of natural selection in shaping behavior with examples across species.
Important numerical values and formulas
ELH in Aplysia: 36 amino acids (ELH) and a gene product of 271 amino acids; ELH can be cleaved into up to 11 products.
Imprinting sensitive period: 2–3 days after hatching.
Inclusive fitness example: sister workers in haplodiploid bees/ants share on average 75% of genes due to their relatedness from the queen’s single mating.
Net energy gain concept in foraging: Net energy = Energy yield − Energy costs; organisms optimize foraging to maximize this net gain over time.
Bee waggle dance geometry: outside hive, straight run points toward food; inside hive, the angle of the straight run relative to gravity equals the angle from the food to the sun, leveraging the sun as a compass; clock gene period modulates timing to compensate for sun’s movement: period gene involvement.
Ethical and practical implications
Understanding animal emotions and cognition can inform debates on captivity and welfare.
Human implications of animal communication studies and interpretation of animal minds.
Conservation relevance: knowledge of mating systems, territory, and cooperative behaviors informs management of wildlife populations.
AP exam prep cues
Be able to classify behaviors as innate or learned; explain genetic/hormonal mechanisms; cite specific studies (lovebirds, garter snakes, Aplysia, fosB mice).
Explain FAPs, sign stimuli, imprinting, and conditioning; describe proximate vs ultimate causes of behaviors such as migration.
Compare communication modalities (chemical, auditory, visual, tactile) and give concrete examples.
Discuss how territoriality, foraging strategies, and sexual selection contribute to fitness; explain inclusive/reciprocal altruism and kin selection.
Connections to prior/future material
Links to Chapter 16 (social behavior; communication) and Chapter 43 outline (in this unit, behavior, populations, communities, biosphere-level organization).
Foundational biology concepts: gene expression, neural/hormonal control, sensory systems, evolution by natural selection, and energy flow in ecosystems.
Appendix: Quick reference figures and concepts mentioned
Fig. 43.1a/b: Nest-building behavior in Fischer vs peach-faced lovebirds; hybrid intermediate behavior.
Fig. 43.2: Tongue-flicks in inland vs coastal garter snakes; relation to slug detection.
Fig. 43.3: fosB in maternal care in mice; presence vs absence alleles.
Fig. 43.4: Gull chick begging behavior; imprinting and learning interaction.
Fig. 43.5: Pavlovian classical conditioning diagram and setup.
Fig. 43.6: Starling migratory navigation experiment (experienced vs inexperienced birds).
Fig. 43.7: Use of pheromones and signaling in social interactions.
Fig. 43.8: Vervet alarm calls and species-specific signals.
Fig. 43.9: Threat display in baboons.
Fig. 43.10: Fireflies visual signaling via flash patterns.
Fig. 43.11: Bee waggle dance inside and outside hive showing directional encoding relative to sun.
Fig. 43.12: Bee waggle dance and sun compass.
Fig. 43.13: Foraging energy optimization in shore crabs (net energy gain vs mussel size).
Fig. 43.14–43.16: Examples of social structures, mating strategies, and inclusive fitness in primates and insects (baboons, ants, meerkats, queen/worker dynamics).
Fig. 43.17: Inclusive fitness illustration in meerkats.
Fig. 43.6–43.9: Starling navigational experiments; various animal communication visuals across sections.