Levels of Analysis in Ethology

Transcription

1 Levels of Analysis in Ethology Ethology: the study of animal behavior Example: Why do male monkeys fight? Niko Tinbergen 1963 On Aims and Methods in Ethology Answer questions about WHY behaviors occur Four levels of analysis Proximate Causal Developmental Evolutionary Phylogenetic Functional Not mutually exclusive

2 Evolutionary Levels of Analysis: Over many generations of lifetimes Phylogenetic Level Understanding a behavior/trait by examining relationships with other species over evolutionary time Functional Level Understanding how a behavior/ trait was designed by natural selection to facilitate reproduction

3 Functional Level of Analysis Was the behavior/trait designed by natural selection to facilitate reproduction in the ancestral past? What is the function of the trait/behavior? Is the trait an adaptation?

4 Adaptations An adaptation is a trait with a functional role in the life trajectory of an organism that evolved by natural selection. Adaptations transform their surroundings in specific ways that facilitate the reproduction of the genes that made those traits. Adaptations can be structural or behavioral. Structural adaptations are physical features of an organism (shape, body covering, armament; and also the internal organization). Behavioral adaptations are include instincts and/or the ability to learn. Examples include searching for food, mating, fight-or-flight, and vocalizations.

5 Linking adaptations and behavior the BRAIN!

6 Neurons = Brain Cells with lots of arms (arms are called dendrites and axons )

7 Neural circuits process electrochemical information that produce thought/feelings/behavior (materialism!)

8 Movement, the Brain, and Behavior The brain is connected to the spinal cord; spinal cord connected to nerves; nerves send impulses between brain and body s other tissues to create movement behavior is movement in the body guided by the brain think sea squirts: only need brains in motile phase of life; when done moving around, they reabsorb their own brains!

9 Sea Squirt

10 Functional mechanisms solve specific problems.

11 Functional mechanisms have specific design features that solve specific problems. Most configurations will not solve the problem.

12 What kinds of functional mechanisms are selected? Those that facilitated reproduction, both directly (uteruses) and indirectly (hearts), in an organism s ancestral past. These functional mechanisms are called adaptations. An organism can be thought of an integrated set of adaptations. Adaptations show evidence of design: a strong, though not necessarily perfect, fit between the mechanism and the reproductive problem it was selected to solve natural selection is more of a tinkerer than a goaldirected engineer. (Bad backbones, etc.)

13 Adaptation/Functionality How do you identify an adaptation? (1) Design Analysis (2)!Compara+ve!method!

14 Analysis of Design Harvey dissected the heart and learned that the heart functions to pump blood by examining what he saw: chambers, strong muscles that expand and contract the chambers, arteries through which blood leaves a chamber and gets to other tissues in the body, valves to keep it from flowing backwards, etc.

15 Analysis of Design Adaptations show evidence of: Precision Economy Efficiency Constancy Complexity Reliability George!Williams!

16 Analysis of Design Problems: It is subjective but let s be reasonable Adaptations are not always perfectly-designed, hindering our ability to see, for sure, what their functions are (human spine) The function of an adaptation is not always obvious, even though we KNOW they are adaptations (e.g., human bipedalism)

17 The Comparative Method icthyosaur Marlin Dolphin