This worksheet will help you understand the key characteristics that define living organisms. We'll explore each characteristic in detail, providing examples and opportunities for you to test your knowledge.
What Makes Something Alive?
All living things share several fundamental characteristics. These characteristics, when considered together, help us distinguish between living and non-living things. Let's delve into each one:
1. Organization: From Cells to Ecosystems
What it is: Living things are highly organized, starting at the cellular level. Cells are the basic units of life. Multicellular organisms are made up of many cells organized into tissues, organs, and organ systems. These organisms, in turn, interact with each other and their environment to form ecosystems.
Example: A human is composed of trillions of cells organized into various tissues (like muscle tissue and nervous tissue), organs (like the heart and brain), and organ systems (like the circulatory system and nervous system).
Activity: Can you name three different levels of organization within a plant? (Think cells, tissues, organs, etc.)
2. Metabolism: Energy and Matter Transformation
What it is: Metabolism encompasses all the chemical reactions that occur within an organism. These reactions allow organisms to acquire and use energy to grow, repair, and reproduce. This includes processes like photosynthesis (in plants) and cellular respiration (in both plants and animals).
Example: A plant uses sunlight to convert carbon dioxide and water into glucose (a sugar) through photosynthesis. This glucose provides energy for the plant's growth and other life processes.
Activity: Explain how a human uses the energy obtained from food.
3. Growth and Development: Increasing in Size and Complexity
What it is: Living things increase in size (growth) and change in form (development) over their lifespan. Growth involves an increase in the number of cells or the size of cells. Development involves changes in the organism's structure and function as it matures.
Example: A seed germinates, grows into a seedling, and eventually develops into a mature plant capable of reproduction.
Activity: Describe the stages of development of a butterfly.
4. Adaptation: Responding to the Environment
What it is: Living things possess adaptations, which are traits that enhance their survival and reproduction in their specific environment. These adaptations can be physical structures, behaviors, or physiological processes.
Example: A cactus has spines to reduce water loss in a desert environment. A chameleon changes its skin color to camouflage itself from predators.
Activity: Identify an adaptation of a polar bear and explain how it helps the bear survive in its environment.
5. Response to Stimuli: Interaction with the Surroundings
What it is: Living things react to changes in their internal or external environment. These changes, known as stimuli, can include light, temperature, touch, or chemicals. The response can be a movement, a change in behavior, or a physiological adjustment.
Example: A plant bends towards a light source (phototropism). A person pulls their hand away from a hot stove.
Activity: Describe how a plant responds to gravity (gravitropism).
6. Reproduction: Passing on Genetic Information
What it is: Living things reproduce, creating new organisms similar to themselves. This involves the transmission of genetic information (DNA) from one generation to the next. Reproduction can be asexual (involving a single parent) or sexual (involving two parents).
Example: A bacterium divides to create two identical daughter cells (asexual reproduction). Humans reproduce sexually, with each parent contributing half of the genetic material to the offspring.
Activity: Explain the difference between asexual and sexual reproduction.
7. Homeostasis: Maintaining Internal Balance
What it is: Living things maintain a stable internal environment despite changes in their external environment. This process is called homeostasis. This includes regulating temperature, water balance, and blood sugar levels.
Example: Humans sweat to cool down when they are overheated.
Activity: Describe how the human body maintains a relatively constant body temperature.
By understanding these seven characteristics, you can confidently differentiate between living and non-living things. Remember that these characteristics are interconnected and work together to maintain life.
