Common Challenges in Life
Biology 10; LPC, Ch. 24, Starr, 6th ed

I-Introduction
II-Challenges to Homeostasis
II-Homeostasis
III-Intracellular Signaling

I-Introduction

A. Levels of Organization

Cells
Specialized cells -> tissue with specialized function
Several tissues -> organ
Organs -> organ system

B. Form of organism a result of what works best for survival

C. Growth vs Development

All cells (& organisms) are small at first, then GROW to mature size.
Some specialization & organization as organisms increases in size = development. DEVELOPMENT is the succession of stages to reach mature form.

II-Challenges to Homeostasis

DIFFUSION = move down concentration gradient
ACTIVE TRANSPORT = more concentrated on one side than the other
Every activity coordinated for optimal homeostasis & survival via communication among cells

III-Homeostasis

A. Intro

Defn - maintaining organisms within life sustaining conditions
Responds to environment. Not static.

B. STIMULUS ) received by RECEPTOR and sent to INTEGRATOR which then sends appropriate response to maintain homeostasis to EFFECTOR.

C. Mechanisms

1. Negative feedback - Response stops condition

2. Positive feedback - Response increases condition

D. Plants

Respond to mechanical forces (gravity, sun, etc) and chemical conditions (nutrients, water)
No central integrator like spinal cord or brain

III-Intracellular Signaling

Cells need to respond to conditions outside themselves.
Signal from outside cell is received by cell’s surface. A chemical or electrical signal is TRANSDUCED to the inner part of the cell so that inside of cell can respond.