Living Organisms Lesson: Characteristics, Functions, and Life Processes

Lesson Overview

• The Characteristics of Life
• The Chemicals of Life
• Types of Organisms
• Scientific Thinking and Variables
• The Importance of Reproduction and Genetic Variation

Living organisms are all around us-plants, animals, fungi, bacteria, and even microscopic creatures too small to be seen with the naked eye. Every living thing, no matter how simple or complex, follows a set of rules that define life. These rules help scientists separate living things from non-living things and understand how they survive, grow, and reproduce.

The Characteristics of Life

Every living organism shares a common set of traits, which scientists call the characteristics of life. These characteristics help biologists identify and classify living things.

Made of Cells

All living organisms are made up of one or more cells. These are the smallest units of life. Some organisms, like bacteria, are unicellular, meaning they are made up of just one cell. Others, like humans, trees, and dogs, are multicellular, meaning they consist of many cells working together.

Use of Energy (Metabolism)

Living organisms need energy to survive. They get energy in different ways: animals eat food, while green plants make their own food through a process called photosynthesis. This energy is used in all life activities, including movement, repair, growth, and reproduction. The chemical processes that occur in the body to build up or break down substances are collectively known as metabolism.

Growth and Development

All living things grow and develop. Growth refers to an increase in size or number of cells. Development involves changes in form or function as the organism matures. For example, a tadpole developing into a frog is development, while getting taller is a form of growth.

Response to the Environment

Organisms can respond to changes in their environment, such as temperature, light, or danger. These changes are called stimuli, and the reaction is a response. This allows organisms to stay safe, find food, or reproduce.

Reproduction

Living organisms have the ability to reproduce and make new organisms like themselves. There are two main types:

• Asexual reproduction: A single parent produces an offspring. The new organism is genetically identical to the parent.
• Sexual reproduction: Two parents combine their genetic materials to produce offspring. The result is genetic diversity, meaning the offspring are different from the parents.

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Living Organisms Trivia: MCQ Quiz!

Homeostasis

Homeostasis is the ability of an organism to maintain stable internal conditions even when the external environment changes. For example, humans sweat to cool down when they get too hot, and birds fluff their feathers to trap heat in the cold.

The Chemicals of Life

Living organisms are made up of specific chemicals that are essential for life processes. These chemicals include:

• Water: Most of a living cell is made up of water. It is vital for all chemical reactions inside the body.
• Carbohydrates: Provide energy and help form cell structures. Sugars and starches are common carbohydrates.
• Proteins: Important for building cell parts and carrying out life functions. They make up enzymes, which speed up chemical reactions.
• Lipids (Fats): Store energy and form cell membranes.
• Nucleic Acids: DNA and RNA store and pass on genetic information that tells the body how to grow and function.

Minerals, though important for health, are not considered primary chemicals of life because they are inorganic and not involved in life processes like the chemicals listed above.

Types of Organisms

Organisms are categorized in several ways depending on their structure and how they get their energy.

Autotrophs vs. Heterotrophs

• Autotrophs are organisms that make their own food. Green plants are a perfect example. They use sunlight, water, and carbon dioxide in photosynthesis to create glucose, a type of sugar.
• Heterotrophs cannot make their own food and must consume other organisms for energy. Animals, fungi, and most bacteria fall into this category.

Unicellular vs. Multicellular

• Unicellular organisms consist of a single cell. Even with just one cell, they can perform all the necessary functions of life.
• Multicellular organisms have many cells that are often specialized. Each type of cell has a job, such as nerve cells for communication or blood cells for transporting oxygen.

Scientific Thinking and Variables

In science, when performing experiments, it's important to understand how to control and measure changes

• The manipulated variable (independent variable) is the one thing that is purposely changed to test a hypothesis.
• The responding variable (dependent variable) is what is measured to see the effect of the manipulated variable.
• Controlled variables are all the other factors in the experiment that must remain the same so that the results are reliable.

Understanding these terms helps young scientists plan better experiments and analyze results accurately.

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Living Organisms & Their Environment

The Importance of Reproduction and Genetic Variation

Reproduction is not just about creating new individuals. In sexual reproduction, the offspring receive genes from both parents. These combinations of genes lead to genetic variation, which is the reason we all look different from one another, even within the same family.

Genetic variation is essential for the survival of a species. It allows populations to adapt to changing environments. Some traits that are passed on may give individuals an advantage, such as better resistance to disease.

Understanding living organisms means understanding life itself. From the smallest bacterium to the largest animal, all life shares basic characteristics like metabolism, reproduction, growth, and response to the environment. These concepts give us insight into how life functions and how all organisms, including humans, fit into the web of life.

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Lesson 1: What is Life?