Chapter 1
Earth Science
Course: Elementary Education Multiple Subjects 5001
Subject: Elementary Education Science Subtest 5005
Chapter: Life Science
This section explains how all living things are alike in some ways (unity), how they are different (diversity), how they adapt to their environments, and how scientists group them through classification.
1. Unity of Life
Even though living things may appear very different from each other, they all share certain fundamental characteristics. These shared traits support the idea that all life on Earth has a common origin and operates through similar biological principles.
Basic characteristics shared by all living organisms:
- They are composed of one or more cells Single-celled organisms (like bacteria) perform all life functions in one cell. Multicellular organisms (like humans or trees) have many specialized cells.
- They use energy to carry out life functions Organisms must take in energy from food or sunlight and use it to grow, move, reproduce, and maintain internal balance.
- They respond to their environment All living things react to stimuli such as temperature, light, sound, or chemicals.
- They grow and develop Growth means increasing in size or number of cells. Development refers to changes in structure or function over time (e.g., a tadpole becoming a frog).
- They reproduce Organisms reproduce either asexually (with one parent) or sexually (with two parents), ensuring the continuation of their species.
- They contain genetic material (DNA or RNA) This genetic code carries the instructions for making proteins and passing traits to offspring.
- They maintain homeostasis Organisms regulate their internal conditions to keep them stable, such as temperature, water level, or blood sugar.