Ecology and Animal Behaviors

Unit 8: Ecology

• Animal Behaviors

• Energy flow through ecosystems

• Population Ecology

• Effect of density on populations

• Community ecology

• Biodiversity

• Disruptions in ecosystems

What is Ecology?

• Definition:

  • Ecology is the study of the interactions between organisms and the environment.

• Organism's environment includes a wide range of:

  • Biotic factors: Living (or once living) components such as plants, animals, fungi, bacteria, etc.

  • Abiotic factors: Nonliving components that include temperature, water, light, nutrients, and soil types.

Ecological Levels of Organization

• Levels of ecological organization:

  • Organism: A living thing, including plants, animals, fungi, and microorganisms.

  • Population: A group of individuals of the same species living together in the same geographic area.

  • Community: Groups of populations of different species that inhabit a particular area.

  • Ecosystem: All abiotic factors and the entire community of species in a specific area.

  • Biosphere: The entire planet and all ecosystems found on Earth.

Habitat and Niche

• Habitat:

  • Definition: The place or part of an ecosystem that an organism occupies.

  • Example: The habitat of a tropical tree lizard includes the forests where they are found and the specific environments within those forests that they occupy.

• Niche:

  • Definition: The role of an organism within its ecosystem, encompassing interactions with biotic and abiotic factors.

  • Example: The niche of a tropical tree lizard includes the temperature ranges tolerated, size of branches perched on, activity times, and types of insects eaten.

Niche Types: Fundamental vs Realized

• Fundamental niche: The complete set of conditions under which an animal (population, species) can survive and reproduce.

• Realized niche: The set of conditions actually used by a given animal (population, species), considering interactions with other species (predation and competition).

Ethology

• Ethology: The study of animal behaviors and their evolutionary origins.

  • Behaviors: Encompasses everything an animal does and how it does it.

  • Organisms respond to environmental changes through behavioral and physiological mechanisms.

  • Organisms communicate with one another in response to internal changes and external cues, which can alter behavior.

Types of Behaviors

• Innate Behavior:

  • Definition: Inherited, instinctive, fixed action patterns that are automatic and consistent.

  • Benefits: All individuals exhibit the behavior regardless of environment; no learning curve.

  • Example: Birds chirping for food.

• Learned Behavior:

  • Definition: Ability to learn is inherited, with behaviors developing through the animal's lifetime.

  • Benefits: Variable and changeable, enabling adaptation to complex or changing environments.

Innate Behaviors

• Migration:

  • Definition: Cyclic movement of animals over long distances according to seasonal changes.

  • Example: Monarch butterfly migration.

• Imprinting:

  • Definition: Learning to form social attachments during a critical period.

  • Example: Work by Konrad Lorenz.

• Kinesis:

  • Definition: Change in the rate of random, undirected movement until a favorable environment is reached.

• Taxis:

  • Definition: Movement in a specific direction, either toward or away from a particular stimulus.

Learned Behaviors

• Associative Learning:

  • Definition: Learning to associate a stimulus with a consequence.

  • Operant Conditioning:

  • Definition: Trial-and-error learning where behaviors are trained through rewards or punishments.

  • Classical Conditioning:

  • Definition: Associating a neutral stimulus with a significant stimulus (e.g., Pavlov's dogs).

• Habituation:

  • Definition: Loss of responsiveness to unimportant stimuli (e.g., becoming accustomed to background noise).

• Observational Learning:

  • Definition: Learning how to do something by watching others.

  • Example: Apollo 12 astronaut training observed by spider monkeys.

• Insight Learning:

  • Definition: Ability to solve a problem the first time, requiring reasoning ability without prior experience.

Social Behaviors

• Definition: Interactions among two or more animals, typically of the same species.

• Cooperation:

  • Definition: Working together allows individuals to perform behaviors more effectively than alone.

• Communication:

  • Definition: Species-specific songs often used for mating or alerting to danger.

• Agonistic Behavior:

  • Definition: Threatening and submissive rituals; usually symbolic with no harm.

  • Example: Territoriality and competitor aggression.

• Dominance Hierarchy:

  • Definition: Social ranking within a group often referred to as a “pecking order.”

• Foraging:

  • Definition: The feeding behavior of individuals.

• Altruistic Behavior:

  • Definition: Actions that reduce individual fitness but increase the fitness of others.

  • Kin Selection:

  • Definition: Helping relatives increase survival, leading to the perpetuation of shared genes.

  • Coefficient of Relatedness:

  • Definition: The closer the genetic relationship between two organisms, the more likely they are to act altruistically.

  • Example: Belding ground squirrel behavior.

• Pheromones:

  • Definition: Chemical signals that elicit responses from other individuals (e.g., alarm pheromones or sexual pheromones).

  • Example: Female lions using pheromones and behavior to attract males.

Population Ecology

• Population: A group of individuals of the same species in the same area at the same time.

  • Populations rely on shared resources and interact with each other.

• Properties of Populations:

  • N: Size; total number of individuals.

  • Density: Number of individuals per unit area.

Measuring Population Density

• Methods for estimating population density include:

  • Counting individuals directly (often impractical).

  • Estimating by sampling a few areas.

  • Counting indirect signs like nests, burrows, tracks, or droppings.

  • Mark and Recapture Method:

  • Formula: N = rac{( ext{# marked in 1st catch}) imes ( ext{total # in 2nd catch})}{ ext{# of marked recaptures}}

  • Conditions: Sufficient time for remixing must be allowed.

Dispersion Patterns

• Dispersion: Pattern of spacing of individuals in an area consisting of:

  • Clumped Dispersion: Organisms grouped together (e.g., fish schools for safety).

  • Uniform Dispersion: Even spacing of organisms (e.g., plants producing toxins to compete).

  • Random Dispersion: No specific attraction or repulsion (e.g., trees spaced randomly in forests).

Survivorship Curves or Mortality Curves

• Purpose: Show the size and composition of a population.

• Survivorship curve types:

  • Type I: Low mortality in young and middle ages, high mortality in old age (e.g., humans).

  • Type II: Constant death rate throughout lifespan (e.g., Hydra, reptiles, some rodents).

  • Type III: High mortality among the young, with survival improving after a certain age (e.g., fish and invertebrates).

Age Structure Diagrams

• Purpose: Illustrate the relative numbers of individuals at each age.

• Categories:

  • Rapid growth: Example - Zambia.

  • Slow growth: Example - United States.

  • No growth: Example - Italy.

Population Growth

• Biotic Potential: Maximum rate at which a population could increase under ideal conditions influenced by various factors, including:

  • Age of reproduction initiation.

  • Lifespan with reproductive capability.

  • Number of reproductive periods.

  • Number of offspring produced.

Population Growth Equations

• Population Growth Rate:

  • Equation: $rac{dN}{dt} = B - D$

  • Where:

  • $dN$ = Change in population size.

  • $dt$ = Change in time.

  • $B$ = Birth rate.

  • $D$ = Death rate.

• Exponential Growth:

  • Equation: $rac{dN_{ ext{max}}}{dt} = rN$

  • Characteristics: J-shaped growth curve, common in newly introduced populations, limited by no predation, parasitism, or environmental restrictions.

Logistic Growth

• Definition: As $N$ approaches $K$ (carrying capacity), growth rate slows, stabilizing around a fluctuating population size near $K$.

External Factors Affecting Population Growth

• Carrying Capacity (K): The maximum number of individuals the environment can sustain.

• Limiting Factors: Factors that restrict population growth:

  • Density-Dependent: Increase in impact as population density increases (e.g., competition, predation, disease).

  • Density-Independent: Unrelated to population density (e.g., natural disasters, temperature fluctuations).

Introduced/Invasive Species

• Non-Native Species:

  • Definition: Populations that grow exponentially when introduced to a new area, often outcompeting native species due to the absence of natural predators.

  • Consequence: Reduction in biodiversity.

  • Examples:

  • Purple Loosestrife

  • Zebra Mussels

  • Spotted Lanternfly

Reproductive Strategies

• K-selected:

  • Definition: Characterized by later reproduction, fewer offspring, and significant parental investment leading to stable populations (e.g., humans).

• R-selected:

  • Definition: Characterized by early reproduction, many offspring, and little parental care allowing for rapid population growth (e.g., insects).

Understanding Population Data

• Mortality Rate Calculation:

  • Example calculation for population changes through years.

• Mortality Rate Example: If 50 fish are born in year 1, there are 36 left in year 2 and 22 left in year 3, calculate the mortality rate.

• Rate of Population Growth Example: Given birth rate and death rate, calculate per capita growth rate and determine if the population is increasing or decreasing.