Methods of Studying Animal Behavior | Zoology Optional Notes for UPSC PDF Download

Introduction to Ethology

Ethology is the scientific study of animal behavior, aiming to understand the natural responses of animals to various environmental stimuli. It involves both laboratory and field studies, establishing strong connections with disciplines like ecology, environmental science, neurology, physiology, psychology, and evolution.

Pioneers of Modern Ethology

The origins of modern ethology can be traced back to the groundbreaking experimental and field studies conducted by notable figures such as Nikolas Tinbergen, Konrad Lorenz, and Karl von Frisch. Their collective contributions were honored with the Nobel Prize in 1973, marking a significant leap in the development of this emerging scientific field.

Laboratory Studies

Neuroanatomical Techniques

Understanding the relationship between specific brain regions and behavior is crucial. Techniques involve damaging brain areas to observe resulting behavioral changes. Examples include Broca's identification of the speech area and Carl Lashley's memory studies using rat brain ablation. Stereotaxic equipment and micropipettes enable precise brain injuries and chemical injections, respectively. Skinner boxes facilitate training animals for behavioral observation.

Neurophysiological Techniques

Physiological studies involve recording brain electrical activity through EEG, stimulating brain areas with electrodes, and categorizing waves like Alpha, Beta, Theta, and Delta. Each wave type indicates different states of the brain, such as relaxation, daily mental activity, emotional stress, and deep sleep.

Neurochemical Techniques

Stimulating brain parts with drugs like alcohol and hormones (e.g., estrogen, testosterone) alters animal behavior. Psychoactive drugs like tranquilizers and barbiturates impact the brain, while modern techniques like PET scans and MRI detect brain activity through glucose utilization.

Field Studies

Behavioral Sampling Methods

Focal Animal Sampling

Selecting an individual from a group for observation, Jane Goodall's chimpanzee studies exemplify this method. Unbiased data on various animal behaviors is obtained.

Ad Libitum Sampling

Observing a group without constraints, Diana Fossy's gorilla studies demonstrate this method. Results may be biased due to the observer's attention.

Instantaneous Sampling

Recording an individual's behavior at predetermined intervals provides data on the animal's state rather than events.

Continuous Sampling

Recording all activities during observation helps document the sequence of behaviors, such as courtship displays or fighting sequences.

Scan Sampling

Observing a group at fixed time intervals and recording selected behaviors provides insights into behavior distribution over time.

All Occurrence Sampling

Recording simultaneous behaviors as one event helps analyze behavior rates in a fixed time period.

Sequence Sampling

Focusing on interactions rather than individuals, this method records entire sequences, useful for studying social behaviors in primates and insects.

One-Zero Sampling

Recording activities as "Yes" or "No" with frequencies aids in studying specific behaviors like territorial attacks or infant-killing.

Tracking Animals in the Wild

Identifying animals in their natural environment involves natural marks, photographs, drawings, or capturing and marking them for easy tracking. GPS systems are used for continuous monitoring.

Kinship, Selfishness, and Altruism

Types of Interactions

Four types of interactions exist among individuals in a population: cooperation (mutualism), altruism, selfishness, and spite. These interactions shape the dynamics of animal populations and influence their evolutionary strategies.

Kinship & Altruism

Kinship in Social Animals

• Definition: Kinship is observed in social animals or closely knit populations that share genetic relations.
• Kin Selection: Operates in populations where traits leading to decreased personal fitness but increased survival and reproductive fitness of the species are favored by natural selection.
• Focus: Kin selection acts on genotypes rather than individuals.

Altruism in Colonies

• Evolution in Colonies: Altruism evolves in colonies with kinship where individuals help others, enhancing the fitness of their own genome.
• Example: Honey bee workers, despite being sterile females, choose to become sterile to ensure the survival of genetically identical sisters.
• Kin Selection's Impact: Leads to altruism in colonies, with fitness being direct when benefiting the individual and indirect when benefiting the colony or relatives.

Spread of Altruistic Genes

• Gene Spread: Altruistic genes spread when participants are related, and the cost to individuals is low compared to the benefit to recipients.
• Promotion of Altruism: Altruism is promoted by kin selection and close genetic kinship, fostering the spread of alleles that increase the indirect component of an individual's fitness.

Reciprocal Altruism Without Kinship

• Theory of Group Selection: Championed by Wynne-Edwards (1962), altruism evolves among related individuals through kin selection.
• Reciprocal Altruism: Altruistic acts toward non-kin are possible if the recipient is likely to reciprocate in a 'Tit for Tat' manner.
• Conditions for Development: Reciprocal altruism can develop under specific conditions, including prolonged interactions, high frequency of altruistic attempts, equal costs and benefits, and punishment for selfish individuals.
• Examples: Seen in monkeys, baboons, chimpanzees, and humans, where mutual dependence in defense, foraging, and territoriality fosters reciprocal altruism.
• Coexistence with Kin Selection: Group selection and kin selection may coexist, making it challenging to distinguish or measure them independently.

Trophallaxis

• Definition: The exchange of food between individuals, even if not offspring of the donor.
• Common in Social Insects: Notable in social insects where specialized workers feed the colony.
• Example: Vampire bats (Desmodus rotundus) demonstrate altruistic behavior by regurgitating and sharing blood meals, crucial for the species' survival.
• Reciprocal Altruism: Bats regurgitate more frequently to relatives, indicating reciprocal altruism.

Cost of Selfishness

• Advantages of Group Living: Individuals in groups gain protection from predators, shared prey, and assistance in hunting.
• Favorable Conditions: Favors individuals who faithfully contribute to the group's well-being.
• Punishment for Selfishness: Selfish individuals are selected out and eliminated from the population.
• Examples: Lions killing cubs in prides, protocooperation (e.g., suckerfish and sharks), and the demand for faithfulness to society.

Orientation, Navigation And Homing

Orientation

• Definition: The position of an animal with reference to gravity or resources.
• Positional Orientation: Maintaining an upright posture against gravity using structures like the membranous labyrinth.
• Object Orientation: Approaching objects, such as food or water.
• Aquatic Animals: Exhibit strato-orientation in ponds or lakes; zonal orientation when moving between grasslands, forests, deserts, or mountains.
• Migratory Animals: Possess topographical or geographical orientation for long-distance migration.

Kinesis

• Movement Response: Movement in response to stimuli, which may be oriented or undirected.
• Klinokinesis: Change of direction during movement, alternating right and left movements to gain correct orientation.
• Orthokinesis: Whole-body involvement, influenced by the intensity of the stimulus.
• Examples: Ammocoete larvae burrowing away from light, cockroaches moving from brightness to darkness.
• Types of Kinesis: Hygrokinesis (humidity), photokinesis (light gradient), chemokinesis (chemical stimuli).

Taxis

• Definition: Orientation of the animal with reference to the direction of a stimulus in space.
• Types of Taxis: Hygrotaxis (humidity), geotaxis (gravity), chemotaxis (taste or odor), thermotaxis (temperature), anemotaxis (air current), rheotaxis (water current), phototaxis (light intensity), phonotaxis (sound waves), astrotaxis (sun, moon, and stars), menotaxis (angle to the stimulus), mnemotaxis (memory).
• Klinotaxis: Single-receptor animals comparing intensity through alternate lateral movements.
• Tropotaxis: Animals with paired receptors moving towards or away from light.
• Telotaxis: Animals making choices based on a constant angle relative to the stimulus.

Mnemotaxis

• Definition: Orientation based on memory.
• Example: Digger wasps creating memory maps of their nests for accurate orientation.
• Zonal Orientation: Involves distance, direction, and landmarks, aiding in homing to the nest.

Navigation & Homing

• Migratory Animals: Possess extraordinary capabilities to navigate oceans, deserts, forests, and mountains.
• Guidance: Guided by the sun, moon, stars, and topography of the area to follow accurate routes.
• Examples: Monarch butterflies migrating thousands of kilometers and returning accurately to the same place.

Fish Navigation

Orientation in the Sea

• Mystery of Navigation: Fishes navigate vast expanses of the sea, covering thousands of kilometers.
• Guiding Elements: Believe to orient by the positions of stars and moon at night and the sun during the day.
• Utilization of Environmental Factors: Temperature gradients and ocean currents are utilized for both swimming and navigation.
• Evidence from Experiments: A.S. Hasler's experiments confirm that salmons, during the return journey, are guided by the odor of their parent stream imprinted in their brains as larvae.

Olfactory Navigation in Eels

• Odor Maps: Eels, similar to salmons, use odor maps for migration, imprinting them as larvae.
• Challenges in Understanding: The mystery lies in how eel larvae, leptocephali, find their way back to river mouths across vast stretches of the Atlantic Sea.
• Possible Explanation: Speculation suggests parents leaving odor trails during their journey might guide the larvae.

Navigation in Birds

• Methods of Bird Navigation: Birds employ celestial navigation, menotaxis, detecting ultraviolet radiation emitted by the sun.
• Experiments in Planetarium: Night migrant birds orient themselves using the position of stars in the night sky.
• Coriolis Force Sensitivity: Some birds are sensitive to the Coriolis force resulting from the deflection of winds in the northern hemisphere due to the Earth's rotation.

Landmarks and Sensory Perception

• Use of Topographical Landmarks: Diurnal birds utilize landmarks such as mountains, river valleys, and forests.
• Infrasound Detection: Birds, especially seabirds, identify destinations by detecting infrasounds, including low-frequency sounds produced by ocean waves.
• Internal Compass and Biological Clock: Many birds possess an instinct, internal compass, or biological clock guiding them through migration routes, with young birds exhibiting inherent navigational abilities.
• Echolocation: Some birds, like oil birds and Himalayan cave swifts, possess echolocation for navigation.

Magnetic Sensitivity

• Sensitivity to Earth's Magnetic Field: Pigeons, for instance, are sensitive to changes in the Earth's magnetic field due to the presence of magnetite in their head and neck muscles.
• Iron Oxide Crystals and Cryptochromes: Researchers find tiny iron oxide crystals in the skin lining of pigeons' upper beaks, potentially helping sense the Earth's magnetic field. Cryptochromes in migratory birds' retinas may aid in navigation by changing their chemistry in the presence of a magnetic field.

Infrasound and Additional Navigation

• Infrasound Detection: Birds can hear infrasounds, which travel farther than ordinary sounds, and may possess this additional navigational capability.
• Various Natural Sources: Infrasounds come from ocean waves, surf, winds, storms, earthquakes, and other geologic events.

Courtship Behaviour and Animals

Evolution and Purpose of Courtship

• Definition: Courtship is a social behavior involving interactions between male and female members leading to mating and reproduction.
• Evolutionary Origin: Evolved due to the competition among sperms as large numbers are produced, and few must fertilize limited ova.
• Sexual Selection: Male-male competition and female choice emerged from gametic selection, leading to courtship behavior.

Drosophila Courtship

• Behavior Description: Courtship behavior in vinegar flies (Drosophila) involves circling, wing vibration, touching with front tarsi, and genitalia licking.
• Importance of Wing Vibration: Male's wing vibration produces sound and air currents, stimulating the female.
• Mating Success: Successful mating occurs after specific courtship rituals, and wingless males' courtship is not accepted by females.

3-Spined Stickleback Fish Courtship

• Species Description: Three-spined stickleback fish exhibit courtship behavior for mating.
• Male's Territory and Nest: Male builds a nest in the sandy bottom with weeds, defending the territory.
• Female Invitation: Male invites females by swimming near the nest's surface, aggressively chasing away other males.
• Mating Process: Involves stabbing the female with the dorsal spine, swimming in zig-zag fashion, and laying eggs in the nest.
• Multiple Mating Events: Male can lure up to five females to lay eggs in his nest.

Bird Courtship

• Evolved Complexity: Birds exhibit sophisticated courtship behaviors involving auditory and visual displays.
• Singing: Male birds in dense forests use singing as auditory stimuli to attract females.
• Mimicry: Some birds imitate other animals to impress females, showcasing extraordinary capabilities.
• Nest Building: Visual stimulus involving nest construction used by male weaver birds and bower birds.
• Feather Displays: Display of feathers, size, and brilliance in species like birds of paradise, peacocks, pheasants, and grouse.
• Dancing: Many bird species use dancing as a stimulus for courtship, with various tactics observed in peacocks and birds of paradise.
• Aerial Displays: Pigeons, kites, buzzards, and doves engage in aerial displays and aerobatics during courtship.
• Lek Birds: Grouse and other lek birds clear arenas in forests for dancing and feather displays, with females observing passively.
• Species-Specific Displays: Unique courtship displays in species like Jackson’s whydah involve clearing grasses, dancing, and frequent jumps.

Social Life in Primates

Evolution of Social Behavior in Primates

• Primitive Origins: Primates, initially non-social, evolved from primitive insectivore ancestors in the Palaeocene epoch.
• Development of Social Interactions: Over time, primates became gregarious, leading to the establishment of complex social structures resembling human societies.

Social Structures in Prosimians

Solitary Prosimians

• Nocturnal and Arboreal: Prosimians like tarsiers, bush babies, and lorises are mostly nocturnal and highly arboreal.
• Solitary Living: Males are often solitary or in pairs with breeding females. Females stay with infants until independence.
• Defensive Strategies: Shy and predominantly hiding in foliage, rarely descending from trees. The nocturnal Aye-aye lives singly or in pairs.

Monogamous Prosimians

• Tree Shrews: Primitive primates like tree shrews (Tupaia species) in Southeast Asia live singly or in pairs, forming nuclear families.
• Territorial Aggression: Highly territorial, males mark territories with urine and defend them through threat-calls and tail-flicking. Nuclear families include male, female, and juveniles.
• Lemurs and Tamarins: Lemurs in Madagascar and Tamarins in South America are also monogamous, forming family units with male, female, and offspring.

Single Male Bisexual Groups

• Group Dynamics: Some monkeys, including hanuman langur, howler monkey, red-tailed monkey, and blue monkey, live in groups led by a single dominant male with a harem of females.
• All-Male Groups: Young males form all-male groups outside the dominant male's harem. Constant aggression involves attempts to unseat the dominant male.

Multimale Bisexual Groups

• Baboons: Terrestrial primates like baboons form large groups with several small units. Each unit consists of one male and several females with offspring.
• Group Defense: Collective defense against predators, with all males uniting to attack threats like leopards. Hierarchy maintained for female access to the dominant male.
• Rhesus Monkeys: Similar multimale bisexual groups, forming foraging units with bonded females. Large groups formed for foraging and defense.

Social Structures in Apes

Solitary Apes

• Orang-Utan: Arboreal ape in Sumatra and Borneo, with solitary males seeking females for mating. No shared family responsibilities. Females are found with only one young, and nests are made in trees for sleeping.

Monogamous Apes

• Gibbons: White-handed gibbon and hoolock gibbon in eastern India, China, and Burma. Highly arboreal, living in family units with male, female, and up to 4 young. Communication through loud hooting calls. Shared family responsibilities.

Multimale Bisexual Apes

• Gorillas: Largest ape found in dense forests of Africa. Group living with dominant silverback males, females, and young. Hierarchy observed during feeding, drinking, and female access.

Diffused Social Apes

• Chimpanzees: Form diffused social groups of up to 50 individuals. Hierarchy among males and females, but females accept several males without conflict. Omnivorous, hunting, and sharing meat. Defend group collectively.

Cryptic Strategies in Nature

Crypsis Overview

• Evolutionary Dynamics: Co-evolution of predator and prey results in deceptive strategies for survival.
• Prey's Deception: Crypsis involves mimicking non-living objects and surroundings for protection.

Protective Coloration

• Matching Background: Majority of animals match their color to their background for camouflage. Examples include earth-colored hares, green grasshoppers, and beach crabs resembling pebbles.
• Counter-Shading: Dorsal dark and ventral light shading helps neutralize sunlight effects. Some animals press against the ground, eliminating shadows.

Disruptive Coloration

• Outline Obliteration: Spots, patches, or stripes break body outline, enhancing camouflage effectiveness. Examples include salamanders, deers, leopards, and fishes.

Protective Resemblance

• Complete Camouflage: Resembling both color and structure of the habitat for complete inconspicuousness. Examples include caterpillars resembling twigs, sea horses among seaweeds, and stick insects on grass.

Aggressive Resemblance

• Predator Ambush: Predators use crypsis to ambush prey. Examples include tigers with stripes in tall grasses and slow-moving predators resembling plants.

Cryptic Actions

• Feigning Death or Injury: Beetles, opossums, echidnas, hedgehogs, and porcupines feign death or curl up for defense.
• Misdirecting Attack: Swallowtail butterflies expose bright tails, misdirecting predators. Some birds feign injuries to distract predators from nests.

Dymantism

• Bright Flash Display: Butterflies and birds expose bright colors during flight, momentarily frightening predators and providing an escape opportunity.

Aposematism

• Bright Warning Colors: Protected species sport bright colors to advertise danger, warning predators. Examples include wasps and unpalatable butterflies.

Cryptic Organs for Misdirection

• Misdirected Attacks: Swallowtail butterflies have brightly colored tails, drawing attention away from vital body parts. Lantern butterflies have false heads to misdirect bird attacks.

Drive and Learning in Animal Behavior

Drive Theories

• Woodworth's Concept: Drive introduced by Woodworth (1918) as a motivational concept.
• Biological Needs: Animals experience drive related to biological needs like eating and drinking, influencing their behavior.
• Freud and Hull: Sigmund Freud (1915) and Clark Hull (1943) later contributed to drive theories.
• Freudian Drive Theory: Based on recurring conditions causing energy build-up and psychological discomfort, resulting in restlessness.
  • Principles:
    1. Drive from bodily needs.
    2. Drive energizes behavior due to restlessness.
    3. Reduction of drive by satisfying needs leads to learning.

Lorenz's Psycho-hydraulic Model

• Proposed Model: Konrad Lorenz (1950) introduced the Psycho-hydraulic or Flush Toilet model.
• Three Steps:
  1. Drive causes action-specific energy accumulation, leading to increased restlessness.
  2. Consummatory behavior begins after achieving the goal, releasing accumulated energy.
  3. Refractory behavior follows, with a quiescent period as accumulated energy is released.

Specific Drives

Hunger and Thirst Drive

• Control Centers: Lateral hypothalamus and ventro-median nucleus regulate hunger drive.
  • Stimulation: Lateral hypothalamus stimulated by epinephrine.
• Inhibition: Glucocorticoids inhibit hunger drive.
• Dependence: Hunger and thirst drives depend on hours of feeding deprivation on dry food.

Hoarding Drive

• Occurrence: Found in mammals like male gerbils and squirrels during lean seasons.
• Stimulation: Low estrogen and testosterone levels stimulate hoarding drive.
• Castration Effect: Castrated individuals show increased hoarding drive, reducible with testosterone treatment.

Migratory Drive

• Occurrence: Present in fishes and birds, can be seasonal or related to reproduction.
• Factors: Pineal glands affected by daylight hours influence migration in birds.
• Examples: Warblers influenced by pituitary gland, stickleback fish migrating with thyroxin injection.

Aggression Drive

• Control Centers: Amygdala and posterior hypothalamus control aggression.
• Testosterone Effect: Testosterone increases aggression in most male mammals.
• Estrogen Effect: High estrogen levels reduce aggression in females.
• Hormones: Hydrocortisone increases aggression, hydroxydione decreases it.

Territorial Drive

• Territorial Marking: Vertebrates mark and defend territories.
• Examples: Dogs, hyenas, and prosimians mark territories with urine.
• Hormone Dependence: Territorial behavior influenced by hormones. Yahr & Thiessen (1972) identified 11 hormones influencing territorial behavior.

Hormones in Sexual Drive

• Courtship Behavior: Involves singing, dancing, or fighting in birds, frogs, and vertebrates.
• Breeding Season: Hormonal levels increase during the breeding season.
• Effects of Castration: Castrated individuals show no sexual behavior.
• Testosterone Influence: Testosterone injections elicit sexual behavior.
• Female Attractiveness: Estrogen enhances female attractiveness and receptivity.
• Releasing Factors: Hypothalamic Releasing Factor (LH-RF) and ACTH influence copulatory behavior.

Parental Care Drive

• Gonadotropin Secretion: Pituitary gland secretion causes courtship display and parental care in birds.
• Progesterone Effect: In pigeons, prolactin secretion from the pituitary causes crop enlargement and pigeon-milk production for chicks.
• Learning and Hormones: Learning during the growing period influences parental care behaviors.

Learning in Animals

Definition

• W.H. Thorpe's Definition: Learning is an internal change causing adaptive changes in behavior.
• N.E. Miller's Definition: Learning is a permanent tendency for a stimulus to elicit a response, reversible by training.
• S.A. Barnett's Definition: Learning is any adaptive change in behavior due to repeated stimuli.

Types of Learning

Instinct

• Innate Behavior: Instinct is the innate behavior, a heritable characteristic.
• Species Memory: Also known as species memory, learned by all members through generations.
• Advantages: Advantageous for species with short lifespans and no time for learning.

Imprinting

• Control by Genes: Imprinting strongly controlled by genes.
• Types:
  1. Filial Imprinting: Learned from parents in early life stages. Examples include hunting in big cats.
  2. Sexual Imprinting: Recognition of opposite sex during adulthood.
  3. Social Imprinting: Influences behavior towards others for the rest of life.

Habituation

• Decreased Responsiveness: Decrease in responsiveness upon repeated exposure to a stimulus.
• Stimulus-Specific: Specific decline in response due to repeated stimulation.
• Urban Example: Animals in urban areas habituate to vehicular traffic noise.

Sensitization

• Increased Responsiveness: Opposite of habituation, increased responsiveness to a repeated stimulus.
• Example: Frog's skin touch with a needle leads to increased response intensity with each touch.

Conditioning

Definition

• Flexible Learning: Conditioning involves flexible learning where a stimulus elicits a specific response from the animal.

Pavlov's Experiments

• Pavlov's Dog Experiment (1927): Dog associated the gong of a bell with food and salivated.
• Conditioned Response: The dog salivated at the sound of the bell even without the presence of food.
• Choice Conditioning: Animals conditioned to choose the best option from two or more stimuli.
• Example: Birds choosing edible butterflies over unpleasant ones.

Sign Stimuli

Definition

• Releasers: Sign stimuli, also called releasers or key stimuli, release Fixed Action Pattern (FAP) or consummatory behavior.
• Territorial Behavior Example: Lehrman's study on male doves courting a stuffed female model in the absence of a living female.

Konrad Lorenz and Sign Stimuli

• Identification: Konrad Lorenz (1972) identified sign stimuli, calling them key stimuli.
• Innate Release Mechanism: Lorenz proposed the Innate Release Mechanism triggered by sign stimuli.
• Niko Tinbergen's Experiment: Stickleback fish responding to the red color of the belly and neck as a sign stimulus.

Types of Sign Stimuli

• Visual Releasers: Morphological characters like feather display in birds or nuptial coloration in fish.
• Auditory Releasers: Auditory signals, e.g., songs in birds and humming sounds in insects.
• Chemical Releasers: Pheromones, with sex pheromones in insects and alarm pheromones in fishes.

Examples of Sign Stimuli

• Visual Releaser Example: Three-spined stickleback fish exhibiting bright red coloration during the breeding season.
• Auditory Releaser Example: Co-qui calls in tree frogs and the singing behavior of birds like cuckoos.
• Chemical Releaser Example: Sex pheromones in insects, like Copulin secreted by females in estrus.

Importance of Sign Stimuli

• Responsiveness: Sign stimuli induce responsiveness in target individuals, leading to consummatory behavior.
• Diminishing Responsiveness: Responsiveness diminishes as consumption proceeds and energy is released.

Sensory Filtering

Definition

• Selective Brain Activity: Sensory filtering occurs as the brain selectively processes and filters out unnecessary information.
• Multiple Levels: Filtering occurs at the level of sense organs, nerves, and different parts of the brain.

Filtering Process

• Sense Organs Filtering: Limitations of sense organs result in filtering out specific information.
• Peripheral Filtering: Receptors, highly specialized, respond to specific stimuli, e.g., caloreceptors and frigidireceptors.
• CNS Filtering: Different parts of the brain perform filtering through selective attention or underdevelopment.
• Perception: Interpretation of sensory information by the brain in light of previous experiences.
• Reticular Activating System: Located in the medulla oblongata, inactivation stops numerous nerve impulses.

Specific Filtering Examples

• Visual Filtering Example: Human eyes filtering out ultraviolet and infrared rays from the spectrum.
• Peripheral Filtering Example: Bats perceiving ultrasonic sounds for echolocation, unlike other mammals.
• CNS Filtering Example: Epithalamus acting as a central switchboard, selecting and sending necessary nerve impulses.

Müller's Law of Specific Nerve Energies

• Principle: Sensation perception depends on the part of the nervous system activated, not the stimulated sense organ.
• Examples: Male tree frog (Eleutherodactylus coqui) producing co-qui call for attraction and repulsion. Olfactory cells on the antennae of male moths perceiving specific pheromones.

Biological Rhythms

Definition

• Natural Cycles: Biological rhythms are self-sustaining natural cycles in animal life, independent of environmental factors.
• Driven by Biochemical Mechanisms: Innate biological clocks driven by biochemical mechanisms.

Circannual Rhythms

• One-Year Periodicity: Animals reproducing once a year, flowering in plants, hibernation cycles, and migrations.
• Examples: Monarch butterflies' migration, beetles hibernating in the Himalayas, and Arctic/Antarctic animals' annual activity cycles.

Circalunar Rhythms

• Synchronization with Moon Phases: Periodicity aligns with the 28-day phases of the moon.
• Examples: Palolo worm swimming to the surface in Fiji, sea hare (Aplysia) periodicity.

Tidal Rhythms

• Synchronization with Tidal Movements: Tidal rhythms follow the periodic rise and fall in sea levels.
• Daily Tides: Daily tides due to the Earth's rotation. Spring and neap tides explained.

Circaszygic Rhythms and Circatidal Rhythms

• Fortnightly Cycles: Circaszygic rhythms follow a fortnightly cycle related to high tide after new or full moons.
• Circatidal Rhythms: 12.4 or 24.8-hour cycles synchronized with low and high tides.
• Examples: Mollusks exhibiting egg-laying behavior, periwinkles emerging during high tides, and grunion fish spawning at high tides.

Circadian Rhythms

Definition and Classification

• Cycle Length: Circadian rhythms follow a 24-hour cycle synchronized with light and darkness.
• Classification: Animals classified as nocturnal, diurnal, or crepuscular.
  • Nocturnal: Active during the night (e.g., bats).
  • Diurnal: Active during the day (e.g., birds).
  • Crepuscular: Active at sunrise and sunset.

Synchronization and Examples

• Metabolism and Hormones: Body metabolism and hormone release synchronized with the 24-hour cycle.
• Examples:
  • Nocturnal Example: Bats finding their way using echolocation.
  • Jet Lag: Human circadian rhythm disturbance during air travel.

Specific Examples and Influencing Factors

• Wuchereria bancrofti larvae: Move to peripheral blood at night, synchronized with Culex mosquito's blood-sucking habit.
• Brady's Hypothesis (1969): Optic lobes in cockroaches, corpora allata, and corpora cardiaca release hormones influencing circadian rhythms.
• Biochemical Events: Involvement of cyclic AMP and serotonin in controlling circadian oscillations.
• Neural Connections: In vertebrates, retina-hypothalamus connections, with a possible pacemaker in the ventromedian nucleus of the hypothalamus.
• Photoperiodism Regulation: Pineal and parietal bodies' regulation in amniotes.

Designing An Experiment

Importance and Objectives

• Experiment Definition: Imposing an action treatment on objects or subjects to observe reactions.
• Validity Importance: Validity depends on planning and execution; hence, experimental design crucial.

Experimental Units and Biostatisticians

• Experimental Units: Objects or subjects (e.g., populations with a specific illness).
• Biostatisticians Role: Study and analyze data from experiments; plan experiments for valid and clear results.

Experimental Design Principles

• Planning Process: Process of planning, designing, and analyzing experiments.
• Understanding Data: Clear understanding of the data needed and expected results before conducting experiments.
• Precision Improvement: Designing crucial to improve precision of answers.

Historical Development

• James Lind's Experiment (1747): Experiment on scurvy, dividing 12 men into groups to test different remedies.
• Missing Element: Lind lacked randomization, essential in modern experiments.

Principles of Experimental Design

• Ronald A. Fisher's Contribution (1935): Proposed a methodology in "The Design of Experiments."
• Randomization: Assigns treatments randomly to groups to reduce bias.
• Replication: Repeatedly running parts of the experiment under varying conditions for more accurate estimates and decreased error.
• Blocking: Arranging experimental units into blocks of similar entities to reduce deviations and enhance precision.

Steps for Designing an Experiment

1. Recognition of the Problem: Clearly define the problem based on evidence.
2. Selection of Response Variable: Choose a variable providing useful information about the problem.
3. Selection of Factors: Identify factors influencing experiment performance, including controllable, uncontrollable, and noise factors.
4. Selection of Experiment Design: Consider inferences from statistics and sequential analysis; design must be randomized.
5. Performing the Experiment: Execute the experiment smoothly; record and analyze results.
6. Statistical Analysis of Data: Analyze recorded data statistically for valid conclusions.
7. Final Conclusions and Recommendations: Make recommendations based on statistical analysis conclusions.

Applications of Experimental Design

• Agricultural Origin: Initially for agricultural needs but expanded to various scientific and engineering fields.
• Widespread Usage: Found in science, engineering, business, finance, and government operations.
• Reliability of Statistical Methods: Statistical analyses crucial for reliable results.
• Recent Trends: Increasing use in service sectors beyond traditional applications.