Life Functions Lesson: What Makes Living Things Alive

Lesson Overview

• Characteristics of Living Organisms
• Cells: The Building Blocks of Life
• Homeostasis: Keeping the Body Balanced
• Metabolism: All the Chemical Reactions in the Body
• Reproduction: Making More Living Things
• Symbiotic Relationships: Living Together
• Biotic and Abiotic Factors in Ecosystems
• Decomposition: Nature's Recycling
• Stimuli and Responses
• Cell Differentiation: Specialized Cells for Specific Jobs
• Adaptation and Evolution
• Negative and Positive Feedback Loops

Every living thing-from tiny bacteria to large animals like whales-has special traits and processes that help it survive, grow, and respond to its environment. These are called life functions. 

Life functions are what separate living things from non-living things. In this lesson, we'll explore these important processes, how the human body and plants carry them out, and why they are necessary for life.

Characteristics of Living Organisms

All living things share common features, or characteristics, that make them different from non-living objects. These include:

• Made of cells: All living things are built from one or more cells.
  
• Grow and develop: Organisms increase in size and change over time.
  
• Respond to stimuli: They react to things in their environment, like light, heat, or sound.
  
• Reproduce: Living things make more of their kind.
  
• Use energy: Every living thing needs energy to move, grow, and live.
  
• Maintain homeostasis: They keep their internal environment stable.
  
• Carry out metabolism: This includes all the chemical activities inside their body.
  

Each of these characteristics helps organisms stay alive and function properly.

Cells: The Building Blocks of Life

All living organisms are made up of cells. Some organisms, like bacteria, have only one cell (unicellular), while others, like humans, have many cells (multicellular).

Inside cells are parts called organelles, and each has a special job. One very important organelle is the mitochondrion (plural: mitochondria). This is known as the "powerhouse" of the cell.

• The mitochondria produce energy through a process called cellular respiration.
  
• They take in nutrients from food and change them into a form of energy called ATP, which powers the cell's activities.
  

Without mitochondria, your cells wouldn't have energy to work.

Homeostasis: Keeping the Body Balanced

Homeostasis is the ability of an organism to maintain a stable internal environment even when the outside world changes.

Examples of homeostasis in humans:

• Sweating cools the body down when it's too hot.
  
• Shivering warms the body up when it's cold.
  
• Releasing insulin helps control blood sugar after eating.
  

Homeostasis helps your body function properly and stay healthy. It's like having a built-in thermostat that adjusts as needed.

Metabolism: All the Chemical Reactions in the Body

Metabolism is the total of all the chemical reactions that happen in your body to keep you alive. These include:

• Breaking down food to make energy
  
• Building body tissues
  
• Repairing cells
  

Metabolism helps your body grow, move, heal, and stay alive. Every cell in your body takes part in metabolic processes.

Reproduction: Making More Living Things

All living things can reproduce, which means they create new individuals of the same kind. There are two main types of reproduction:

Bacteria reproduce asexually by splitting in half. Humans, animals, and flowering plants reproduce sexually.

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Test Yourself: Life Functions Quiz

Symbiotic Relationships: Living Together

Organisms often live in close relationships with other organisms. These are called symbiotic relationships. One important type is mutualism, where both organisms benefit.

Examples of mutualism:

• Bees and flowers: Bees get nectar; flowers get pollinated.
  
• Cleaner fish and big fish: Cleaner fish eat parasites; big fish stay healthy.
  

Other types of symbiosis include:

• Parasitism: One benefits, the other is harmed (like a tick on a dog)
  
• Commensalism: One benefits, the other is unaffected (like a bird nesting in a tree)
  

Biotic and Abiotic Factors in Ecosystems

In an ecosystem, everything is connected. The parts of an ecosystem can be:

• Biotic: Living things like plants, animals, fungi, and bacteria
  
• Abiotic: Non-living things like sunlight, water, air, and temperature
  

Sunlight is an abiotic factor that helps plants carry out photosynthesis, which supports the whole food chain.

Knowing the difference between biotic and abiotic helps us understand how ecosystems work.

Decomposition: Nature's Recycling

When plants and animals die, their bodies break down. This process is called decomposition.

• Decomposers, like bacteria and fungi, break down dead matter into nutrients.
  
• These nutrients return to the soil and help new plants grow.
  

Decomposition is important because it recycles materials and keeps ecosystems healthy.

Stimuli and Responses

Living things respond to stimuli-anything that causes a reaction.

Examples:

• You blink when something flies at your eye.
  
• A plant bends toward sunlight.
  
• A dog salivates when it smells food.
  

This response to stimuli helps organisms survive and adapt to their surroundings.

Cell Differentiation: Specialized Cells for Specific Jobs

In multicellular organisms like humans and plants, cells develop into different types with special jobs. This is called cell differentiation.

Examples:

• Muscle cells contract to move your body.
  
• Red blood cells carry oxygen.
  
• Root cells in plants absorb water.
  

Differentiation is not part of homeostasis, but it is essential for growth and development.

Adaptation and Evolution

Adaptation is when a living thing changes over time to better survive in its environment.

• Camels have humps to store fat.
  
• Arctic foxes have thick fur to stay warm.
  

Evolution is a process where changes happen to entire species over many generations, often due to adaptations passed down.

Negative and Positive Feedback Loops

Your body uses feedback loops to help maintain homeostasis.

• A negative feedback loop works to reverse a change and return the body to normal. Example: Shivering increases body temperature when you're cold.
  
• A positive feedback loop increases a change. Example: Releasing a hormone to cause more contractions during childbirth.
  

Negative feedback is more common in maintaining daily balance.