Levels of Organization and Causation PSC 113 Jeff Schank

Outline Levels of Organization – Composition – Interactions Time Scale – Composition – Interactions Complex Systems Complexity and Levels of Organization Scientific Perspectives and Organization Causation – Aristotle’s Four Causes – A Reformulation of Aristotle’s Four Causes Army Ants

First an Example Fall Webworms

Levels of Composition A thing X is at a higher level of composition than a thing Y if X is composed of Ys (and possibly other things) For example, – A brain is at a higher level of composition than a neuron because brains are composed of neurons (among other things) – A cell is at a higher level of composition than DNA molecules, because among other subcellular structures, cells are composed of DNA

Levels of Composition

Interactions Levels of composition do not reveal how the components at a level interact to produce the patterns of organization

Interactions

Levels of Organization Organization often emerges from simple interactions of components as we saw with fall webworms and as see saw with army Another meaning of Levels (i.e., levels of organization) is the number, strength, and kinds of interactions among components at a level of composition Flocking Boids

Levels of Organization

Time Scale and Levels of Composition

Time Scale and Interactions

Complexity and Levels of Organization Complex systems are not limited to interactions among components at only one level of composition Oxytocin is a peptide hormone Oxytocin – It is involved in the process of birth and nursing in mammalsbirth and nursing in mammals – It is also involved in social behaviorsocial behavior E.g., attachment, social recognition and aggression Vasopressin is also a peptide hormone Vasopressin – Regulates kidney function Regulates kidney function – It is also involved in social behaviorsocial behavior E.g., aggression and pair-bond formation, and mediating anxiety

Complexity and Levels of Organization

Scientific Perspectives and Level of Organization

Scientific Perspectives × Levels of Organization

Causation Our ordinary meaning of causation is a relationship between events: cause and effect such that certain conditions that bring about certain effects Causation in this sense is proximate, which means that the conditions bringing about an effect are near their effects in space, time, and typically at the same level of organization

Aristotle He thought of causes as reasons or factors explaining the objects and processes that exist in the world. For Aristotle there were four basic causes 1.Material Cause: The material of which a thing is made. 2.Efficient Cause: The conditions that combine to produce an effect from acause. 3.Formal Cause: The shape, configuration or type of thing something is. 4.Final Cause: The purpose or end of a thing or process.

Aristotelian Causation

Works well for explaining artifacts that we build Does not work well for explaining biological systems from an evolutionary-developmental view No corresponding sense formal cause in biological systems No corresponding sense of final cause in biological systems

A Reinterpretation of Aristotle’s four causes 1.Composition corresponds closely to Aristotle’s notion of material cause. It is the components, entities and processes that compose a system at some level of organization 2.Proximate Cause corresponds closely to Aristotle’s notion of efficient cause. These are the causal conditions specified in mechanisms for how things work, such as the firing of a neuron, or hormonal factors that modulate reproduction and maternal care of young 3.Organization is somewhat related to one aspect of Aristotle’s notion of formal cause, namely the idea of configuration. Organization is configuration or pattern of interactions that emerge from the interactions among components of a systems 4.Function: The notion of function is the biggest departure from Aristotle’s system. In biology and psychology we replace Aristotle’s notion a.System function: This is the role of a component in a system. For example, a function of a neuron is to modulate action potentials. A function the heart is to circulate blood b.Evolutionary adaptive function: This is the role of a component in the survival and reproduction of a system in a larger ecosystem or environment. Typically, adaptive functions are ascribed to components and characteristic of individuals, but they may apply to entities at other levels of organization such as groups, ecosystems, and species

Army Ants Army ants are an interesting example of the complex organization that illustrate different kinds of causes operating during development. T. C. Schneirla studied army ants throughout the 1940s T. C. Schneirla army ants Army ants are nomadic foraging social insects. Unlike many other social ants, wasps and bees they do not build permanent nests (video1, video2)video1video2 One of the more remarkable aspects of army ant social behavior is that individual development is highly coupled with social behavior and individual development drives social behavior.

Cycles of Behavior Army ants exhibit daily or diurnal cycles of functional activity. Functional activity includes daytime foraging (when light, temperature and humidity are best), thermoregulation and climate control in the bivouac These functional cycles are largely under external control of the daily light cycle, temperature and humidity conditions. These are external Zeitgebers. They go through Nomadic and Statary phases of colony behavior that are tightly coupled with development of offspring Interestingly, these cycles are not driven by external Zeitgebers but emerge from the individual interactions of workers, new workers and pupae. Colony Functional Cycle refers to the functions performed by the colony such as foraging and incubation, care and feeding of the next generation on a daily basis Brood Cycle is a much longer cycle lasting more than 30 days during which the colony produces a new brood

Cycles of Behavior

Brood Cycle

How are these cycle produced? External Zeitgebers? No Internal biological clocks? No The queen running the colony? No Local interactions among old works, new workers, and larva? Yes – Newly eclosed brood (first spike above threshold) of workers increase the activity levels of old workers due to chemical signals they (new workers release) – Developing larvae (the second more gradual rise) release larva pheromones and nutritive secretions that the workers ingest, which increases the worker’s activity and spreads throughout the colony

Army Ants and Causation 1.Composition: queen, old workers, new workers, larva, pupa, chemicals for signaling 2.Proximate Cause: licking and grooming, physical contact, release of chemical signals 3.Organization: colony functional cycle, brood cycle, raiding patterns, bivouac formation 4.Function: a.System function: forage for food, care for larva, pupa, and queen b.Evolutionary adaptive function: produce members of the colony and, in particular, reproductive males and females to found new colonies