Chapter 1
Earth Science
Course: Elementary Education Multiple Subjects 7001
Subject: Elementary Education Science Subtest 7005
Chapter: Life Science
Understanding the structure and function of living systems involves exploring how life is organized at different biological levels, from microscopic cells to complex organisms. Each level of organization contributes to essential life processes that sustain living organisms. Scientific study of living systems helps students grasp how internal and external structures relate to function, and how living things maintain balance, grow, and respond to their environments.
1. Characteristics of Living Things
All living organisms share fundamental traits that distinguish them from non-living things. These characteristics provide a framework for identifying and understanding life at all levels.
Key characteristics of living organisms include:
- Made of one or more cells: Cells are the smallest units capable of life. Unicellular organisms (e.g., bacteria) perform all life functions within a single cell, while multicellular organisms (e.g., humans, trees) have specialized cells working in coordination.
- Metabolism: All organisms undergo chemical reactions to obtain and use energy. Metabolism includes processes such as cellular respiration and photosynthesis.
- Growth and development: Organisms increase in size and undergo developmental changes determined by genetic information.
- Response to stimuli: Organisms can detect and respond to environmental changes (e.g., light, temperature, touch, sound).
- Reproduction: Organisms reproduce to pass on genetic material. Reproduction may be asexual (identical offspring) or sexual (genetically diverse offspring).
- Homeostasis: Organisms regulate internal conditions (e.g., temperature, hydration, pH) to maintain stability.
- Adaptation and evolution: Over generations, species adapt through natural selection, contributing to biodiversity and ecological resilience.