Plant and Animal Cells

In this lesson, students compare plant and animal cells, connecting the presence of specific internal structures with the way in which an organism gets energy.

• All living things are made up of cells, which themselves are made up of atoms and molecules. Cells are the smallest unit of life, and they are made from many thousands of molecules (two or more atoms joined together). 
• All cells share certain structures because all cells need to be able to perform basic life functions. A structure is the way in which parts are put together to form a whole. 
• Plants and animals have many similar organelles, but they also have a few different organelles that allow them to survive. 
  
  

• Why are cells matter?
• What is the relationship between cells and the organism they are part of?
• How does a cell function as a system?
• Why is it important that a cell’s organelles be connected in some way to each other?
• What would happen to the cell if the nucleus stopped working?
• How does the cell membrane help the cell?
• How is the cell able to get energy from food?
• What would happen to the cell, and the organism, if the mitochondria stopped functioning?
• What happens to food and water that isn’t used immediately in a cell?
• Why is the structure of an animal cell slightly different from the structure of a plant cell?
• Why do plants have chloroplasts?
• How do animals get energy without chloroplasts?
  
  

Misconception: An organism is not a system.

Fact: Ecosystems are systems, made up of smaller interacting parts. Both the living and nonliving parts of an ecosystem influence the overall ecosystem.

Animal : a living thing that eats other organisms for energy, breathes oxygen, and undergoes growth and reproduction

Cell :  the smallest unit of life

Function :  the normal action of something or how something works

Nutrients :  chemicals that organisms need for the growth and maintenance of cells

Organic :  anything that is living or was once living (e.g., fallen leaves and animal remains)

Organism :  a complete living thing

Plant :  a living thing that captures energy from sunlight for growth and development

Structure :  the way in which parts are put together to form a whole

Life in a Pond

On its surface, a pond looks quiet and still. Ponds are small bodies of freshwater that are shallow enough for sunlight to reach the bottom and for rooted plants to grow.

However, ponds are full of activity. They are filled with living things, some so tiny they cannot be seen with the human eye. These tiny living things are called microscopic. For example, a single drop of pond water can hold millions of microscopic bacteria.

Many different kinds of plants and animals also make their home in ponds. Plants are living things that capture energy from sunlight for growth and development. Water lilies are common plants found in ponds.

Animals are living things that eat other organisms for energy and undergo growth and reproduction. An organism is a complete living thing. Frogs, insects, and fish are common animals that live in ponds.

Living Things Are Made of Cells

All organisms, from the microscopic bacteria to the croaking frog, have something in common. They are all made of cells. A cell is the smallest unit of life. Cells are made up of molecules, which are two or more atoms joined together. Living things take in new molecules from air, food, and liquids. These molecules get into the cells and help them function. Some living things, such as bacteria, are made up of just one cell. These organisms are called single-celled organisms.

Other organisms are made up of many cells. These organisms are multi-celled organisms. Plants and animals are both kinds of multi-celled organisms.

Cells are alive because they use energy to carry out life functions. Life functions include growing, developing, and getting energy from food. Energy is required because it powers all of these actions. Plant and animal cells have different structures that help them carry out their life functions. A structure is the way in which parts are put together to form a whole.

The internal structures of a plant or animal cell are called organelles. Each organelle has a specific function. Function is the normal action of something or how something works.

The Parts of a Cell

All cells are filled with a jelly-like liquid. This liquid is called cytoplasm, and it surrounds all of the organelles. The cell membrane surrounds the cell and selects what molecules can enter and exit the cell. The cell membrane is flexible. This is why cells can be many different shapes.

The control center of plant and animal cells is the nucleus. It tells all of the other organelles what to do. This is possible because the nucleus contains the cell’s DNA. DNA is an instruction manual for how the cell should look and what it should do.

The workers that power the cell are the mitochondria. Mitochondria are organelles that break down food into usable energy.

The storage centers of the cell are the vacuoles. Vacuoles are large sacs that store water and food for the cell. Plant cells contain a larger central vacuole than animal cells. Ninety percent of a plant cell is taken up by the central vacuole. A plant wilts if its cells lose water in their central vacuoles.

In this lesson, students create plant and animal cell models to compare and contrast the internal structures of plants and animals. They use the cell models to observe relationships between the cell’s functions and its different structures. Students compare their plant and animal cell models with other student teams, and then use their observations to analyze the cell from a systems perspective, describing relationships among the various parts of the cell.