Animal Behavior

Key Behavioral Terms

Animal behavior encompasses a range of genetically programmed and learned responses to environmental stimuli. Understanding these behaviors is essential for studying how animals interact with their environment and each other.

• Ecotourism: Conservation approach where tourism in natural areas funds conservation and supports local economies.

• Instinctive Behavior: Genetically programmed actions that do not require prior experience.

• Imprinting: Learning the identity of a caretaker or key features during a restricted developmental stage.

• Classical Conditioning: Association formed between two unrelated phenomena (e.g., Pavlov's dogs).

• Operant Conditioning: Linking a voluntary activity with a reward.

• Habituation: Decreased responsiveness to repeated, non-reinforced stimuli, conserving energy and attention.

• Migration: Seasonal movement between birth and distant locations, often returning to the original site.

• Waypoint: A specific location along a migration route.

• Kinesis: Change in movement rate or turning frequency in response to environmental stimuli.

• Taxis: Directed movement toward or away from a stimulus.

Instinctive vs. Learned Behaviors

• Instinctive Behaviors: Do not depend on prior experience; differences may reflect genetic variation.

• Learned Behaviors: Depend on experience during development.

• Most behaviors are a combination of both instinct and learning.

Types of Conditioning

• Classical Conditioning: Association between two unrelated stimuli.

• Operant Conditioning: Association between a voluntary action and its consequence (reward or punishment).

Movement Behaviors

• Piloting: Using familiar landmarks to guide movement.

• Compass Orientation: Moving in a specific direction using cues like polarized light or Earth's magnetic field.

• Navigation: Combining compass orientation with a mental map to reach a specific destination.

• Benefits of Migration: Access to seasonal food and avoidance of harsh climates.

Habitat Selection and Defense

• Habitat Selection: Assumed to be adaptive and genetically influenced by natural selection; may involve kinesis or taxis.

• Territorial Defense: Costly due to risk of injury but provides access to resources and mating opportunities.

Evolutionary Processes

Microevolution vs. Macroevolution

Darwin's Observations and Natural Selection

• Populations would grow exponentially if unchecked, but resources are limited.

• Competition for resources leads to changes in population characteristics over generations.

• Natural Selection: Occurs when:

  • There is variation in a character within a population.

  • The character is heritable.

  • Some variants have higher survival and reproduction rates.

Genetic Variation

• Qualitative Variation: Trait exists in discrete states (e.g., flower color: red or white).

• Quantitative Variation: Trait exists along a continuum (e.g., height, weight).

• Evolutionary forces act only on traits with a genetic basis.

Population Genetics

Key Terms

• Population: Localized group of interbreeding individuals.

• Gene: DNA region encoding a specific product.

• Allele: Alternate version of a gene (e.g., B or b).

• Genotype: Genetic makeup (e.g., BB, Bb, bb).

• Phenotype: Observable characteristics resulting from genotype.

• Genotype Frequency: Proportion of individuals with a specific genotype.

• Allele Frequency: Proportion of a specific allele among all alleles at a locus.

• Dominant: Allele expressed in heterozygotes (B).

• Recessive: Allele expressed only in homozygotes (b).

• Incomplete Dominance: Heterozygote shows a blend of traits.

• Co-Dominance: Both alleles are fully expressed in the phenotype.

Hardy-Weinberg Principle

The Hardy-Weinberg equilibrium describes how allele and genotype frequencies remain constant in a non-evolving population.

• Assumptions:

  • No evolution (no mutation, migration, selection, or drift)

  • Population is closed to migration

  • Large population size

  • All genotypes have equal survival and reproduction

• Equations:

  • Allele frequencies:

  • Genotype frequencies:

  • Frequency of homozygous dominant:

  • Frequency of heterozygotes:

  • Frequency of homozygous recessive:

Causes of Evolution

1. Mutation: Changes in DNA sequence, source of new alleles.

2. Gene Flow: Movement of alleles between populations.

3. Non-random Mating: Mating based on phenotype or relatedness.

4. Genetic Drift: Random changes in allele frequencies, especially in small populations.

5. Natural Selection: Differential survival and reproduction of individuals with certain traits.

Types of Natural Selection

Other Evolutionary Forces

Mutation

• Source of new genetic variation.

• Only mutations in germ cells are heritable in multicellular organisms.

• Most mutations are neutral or harmful to reproductive success.

Genetic Drift

• Random changes in allele frequencies due to chance events.

• Founder Effect: Small group starts a new population with limited genetic variation.

• Population Bottleneck: Drastic reduction in population size reduces genetic diversity.

• Often eliminates rare alleles and can make populations genetically distinct.

Gene Flow

• Movement of alleles between populations via migration or gamete transfer.

• Can introduce beneficial, neutral, or harmful alleles.

Sexual Selection (Non-random Mating)

• Selection of mates based on phenotype.

• Explains evolution of sexual dimorphism (differences between sexes).

• Intrasexual Selection: Competition within one sex (often males).

• Intersexual Selection: Mate choice, often by females.

Speciation

Species Concepts

Reproductive Isolation Mechanisms

• Prezygotic Barriers: Prevent fertilization

  • Ecological Isolation: Different habitats

  • Temporal Isolation: Different breeding times

  • Behavioral Isolation: Different mating signals

  • Mechanical Isolation: Incompatible reproductive structures

  • Gametic Isolation: Incompatible gametes

• Postzygotic Barriers: After fertilization

  • Hybrid Inviability: Offspring do not develop fully

  • Hybrid Sterility: Offspring are sterile

  • Hybrid Breakdown: Reduced survival or fertility in later generations

Types of Speciation

• Polyploidy: Extra chromosome sets prevent interbreeding with parent species (common in plants).

• Habitat Differentiation: Subpopulations exploit different resources or habitats.

• Sexual Selection: Mate preferences reduce gene flow between subpopulations.

Macroevolution and the History of Life

Fossils and Dating

• Fossils: Preserved remains, impressions, or traces of ancient organisms.

• Paleogenetics: Extraction of DNA from fossils for classification and dating.

• Limitations: Fossilization is rare, favors hard parts and abundant species, and geological processes can destroy fossils.

• Principle of Stratigraphy: Deeper rock layers contain older fossils.

• Radiometric Dating: Uses decay of radioactive isotopes to estimate age.

• Key Concepts:

  • Isotopes: Atoms with different numbers of neutrons.

  • Radioisotopes: Unstable isotopes that decay at a predictable rate (half-life).

  • Half-life: Time for half of a parent isotope to decay to a daughter isotope.

  • Example: , half-life = 5,730 years.

Continental Drift and Plate Tectonics

• Plate Tectonics: Earth's crust is divided into plates that move over the mantle.

• Continental Drift: Movement of plates alters climate, geography, and can cause mass speciation events.

• Supercontinents: Landmasses have merged and split multiple times (e.g., Pangaea).

Major Events in Earth's History

• Earth formed ~4.6 billion years ago.

• First oceans formed ~4 billion years ago.

• First fossil evidence of bacteria ~3.5 billion years ago.

• Prokaryotes: Unicellular, no nucleus, reproduce by binary fission, rapid adaptation.

• Stromatolites: Layered rocks formed by prokaryotes binding sediment.

• Photosynthesis: Evolved in prokaryotes, oxygenated oceans and atmosphere.

• Oxygen was initially toxic to many prokaryotes; survivors adapted or found anaerobic niches.

• Endosymbiosis: Origin of eukaryotes by engulfing prokaryotes (mitochondria, plastids).

• Multicellularity: Evolved after eukaryotes, leading to more complex life forms.

• Mass Extinctions: Five major events have drastically reduced biodiversity.

Systematics and Phylogeny

Systematics and Taxonomy

• Systematics: Study of biological diversity and evolutionary relationships.

• Taxonomy: Formal system for naming and classifying organisms.

• Binomial Nomenclature: Two-part Latinized name (genus and species).

• Taxon: Group of organisms forming a unit in classification.

Phylogenetic Trees and Cladistics

• Phylogenetic Tree: Diagram showing evolutionary relationships.

• Cladistics: Classification based on common ancestry.

• Principle of Parsimony: The simplest explanation (fewest evolutionary changes) is preferred.

• Homology: Similarity due to shared ancestry.

• Analogy (Homoplasy): Similarity due to convergent evolution, not shared ancestry.

Constructing Phylogenies

1. Identify heritable traits that vary among species.

2. Select an outgroup for comparison.

3. Determine which traits are ancestral or derived.

4. Construct the tree, minimizing the number of evolutionary changes.

Types of Groups in Cladistics

Ancestral vs. Derived Traits

• Shared Ancestral Trait: Originated in an ancestor of the group.

• Apomorphy: Derived trait unique to a single taxon.

• Synapomorphy: Derived trait shared by two or more taxa, indicating a recent common ancestor.