L-Systems Preparation

Overview

We’re now going to be focusing on a specific dynamic of life: growth. How do multi-cellular organisms grow in such complex and organized ways without top-down control? We’ll start by considering a set of systems that isolate and capture the dynamic of growth: L-systems.

AI Policy

As a reminder, you are not allowed to use genAI to summarize or produce your reading check responses. These checks are for you to engage with the material and start thinking about things before class. It’s okay if you don’t understand everything ahead of time!

Basic Learning Objectives

Before class, you should be able to:

• Explain how L-systems relate to organism growth
• Demonstrate the expansion process of an L-system string

Advanced Learning Objectives

After class, you should be able to:

• Implement an L-system to capture organism growth dynamics

Reading

Read the following:

• Biological Bits Section 4.2 Lindenmayer systems

Checks

Submit answers to the following on Moodle:

• Consider the following L-system grammar and write out the full string for iterations 0, 1, and 2:
  • Axiom ‘A’
  • Rules:
    • A -> F[+A][-A]
    • F -> FF

• There is a brown seaweed species called Bladderwrack that grows by an active tip splitting equally into two identical growing tips, forming a symmetrical Y structure. The older stem segments don’t stretch further after forming, i.e. growth only occurs at those active tip sections. Here is a picture:

  

  By User Stemonitis on en.wikipedia - Taken by Stemonitis, CC BY-SA 2.5, Link

  Write the starting axiom and rules that would capture this growth pattern in an L system. Hint, you’ll want two rules, though one is fairly simple.